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1

Interactive Molecular Orbital Diagrams  

NSDL National Science Digital Library

Here is an application for constructing the molecular orbital electron configurations of heteronuclear diatomic molecules. Energy level diagrams are given for the two different cases encountered in heteronuclear diatomics of the first short period (Li2 - Ne2). This is a useful tool for having students explore questions of bond order, magnetic properties and numbers of unpaired electrons.

2

Visualization of Molecular Orbitals: Formaldehyde  

ERIC Educational Resources Information Center

Describes a computer program that plots a solid" representation of molecular orbital charge density which can be used to analyze wave functions of molecules. Illustrated with diagrams for formaldehyde. (AL)

Olcott, Richard J.

1972-01-01

3

Near Earth Objects Program: Orbit Diagrams  

NSDL National Science Digital Library

This page provides access to diagrams of the orbits of a very large number of objects in the asteroid belt as well as comets that cross Earth's orbit. The collection is searchable by object name or designation and users can also browse through an extensive list of potentially hazardous asteroids.

Program, Nasa J.; Nasa

4

Interactive Molecular Orbitals  

NSDL National Science Digital Library

The majority of Introductory Chemistry texts provide students with an adequate introduction to the visual aspects of the molecular orbital model for homonuclear diatomic molecules. The treatment of heteronuclear diatomic and polyatomic molecules is less uniform. Heteronuclear diatomics, when mentioned, are invariably treated as being derived from homonuclear diatomics. While the atomic orbital energy level differences in heteronuclear diatomics is sometimes pictured, the consequences of those differences for the resultant molecular orbitals are rarely discussed. The discussion of polyatomic molecular orbitals in these texts is limited to showing that parallel p-orbitals produce delocalized pi molecular orbitals. The molecules typically mentioned in this context are benzene, nitrate ion and carbonate ion. However, It is rarely pointed out that the six p-orbitals in benzene would form 6 pi molecular orbitals, and that only one of these orbitals would look like the picture in the text.These interactive modules are designed to clarify this subject.

5

ISS EPS Orbital Replacement Unit Block Diagrams  

NASA Technical Reports Server (NTRS)

The attached documents are being provided to Switching Power Magazine for information purposes. This magazine is writing a feature article on the International Space Station Electrical Power System, focusing on the switching power processors. These units include the DC-DC Converter Unit (DDCU), the Bi-directional Charge/Discharge Unit (BCDU), and the Sequential Shunt Unit (SSU). These diagrams are high-level schematics/block diagrams depicting the overall functionality of each unit.

Schmitz, Gregory V.

2001-01-01

6

Heteronuclear Diatomic Molecular Orbital Formation  

NSDL National Science Digital Library

Here is a set of movies that demonstrates heteronuclear diatomic molecular orbital formation. The orbitals start at a distance where there is little or no interatomic interaction and move to the appropriate bond distance. Orbital phase is shown by the different colors.

7

Pseudosymmetry analysis of molecular orbitals.  

PubMed

We introduce a pseudosymmetry analysis of molecular orbitals by means of the newly proposed irreducible representation measures. To do that we define first what we consider as molecular pseudosymmetry and the relationships of this concept with those of approximate symmetry and quasisymmetry. We develop a general algorithm to quantify the pseudosymmetry content of a given object within the framework of the finite group algebra. The obtained mathematical expressions are able to decompose molecular orbitals by means of the irreducible representations of any reference symmetry point group. The implementation and usefulness of the pseudosymmetry analysis of molecular orbitals is demonstrated in the study of ? and ? orbitals in planar and nonplanar polycyclic aromatic hydrocarbons and the t2 g and eg character of the d-orbitals in the [FeH6](3-) anion in its high spin state along the Bailar twist pathway. PMID:23436743

Casanova, David; Alemany, Pere; Falceto, Andrés; Carreras, Abel; Alvarez, Santiago

2013-06-01

8

Tribochemistry of ZDDP in molecular orbital calculations  

Microsoft Academic Search

The molecular orbital parameters of zinc dialkyldithiophosphate (ZDDP) and several metal-atom-cluster models were calculated. The nature and the strength of the interactions between the ZDDP molecules and different metal surfaces are analysed and discussed with the use of frontier orbital theory. By comparing the highest occupied molecular orbital energy (EHOMO) and the lowest unoccupied molecular orbital energy (ELUMO) of the

Yuanqiang Tan; Weijiu Huang; Xueye Wang

2004-01-01

9

Some Observations on Molecular Orbital Theory  

ERIC Educational Resources Information Center

A few flawed predictions in the context of homonuclear diatomic molecules are presented in order to introduce students to molecular orbital (MO) theory. A common misrepresentation of the relationship between the energy of an atomic orbital and the energy of the MO associated with the atomic orbital is illustrated.

Journal of Chemical Education, 2005

2005-01-01

10

How Different Variants of Orbit Diagrams Influence Student Explanations of the Seasons  

ERIC Educational Resources Information Center

The cause of the seasons is often associated with a very particular alternative conception: That the earth's orbit around the sun is highly elongated, and the differences in distance result in variations in temperature. It has been suggested that the standard diagrams used to depict the earth's orbit may be in some way responsible for the initial…

Lee, Victor R.

2010-01-01

11

Molecular crystal global phase diagrams. I. Method of construction.  

PubMed

A method is described to produce global phase diagrams for single-component molecular crystals with separable internal and external modes. The phase diagrams present the equilibrium crystalline phase as a function of the coefficients of a general intermolecular potential based on rotational symmetry-adapted basis functions. It is assumed that phase transitions are driven by orientational ordering of molecules with a fixed time-averaged shape. The mean-field approximation is utilized and the process begins in a high-temperature disordered reference state, then spontaneous symmetry-breaking phase transitions and phase structure information at lower temperature are sought. The information is mapped onto phase diagrams using the intermolecular expansion coefficients as independent variables. This is illustrated by global phase diagrams for molecules having tetrahedral symmetry (e.g. carbon tetrachloride, adamantane and white phosphorus). Uses of global phase diagrams include crystal structure data mining, guidance for crystal design and enumeration of likely or missing polymorphic structures. PMID:15507746

Mettes, Jonathan A; Keith, J Brandon; McClurg, Richard B

2004-11-01

12

Molecular Electronic Terms and Molecular Orbital Configurations.  

ERIC Educational Resources Information Center

Discussed are the molecular electronic terms which can arise from a given electronic configuration. Considered are simple cases, molecular states, direct products, closed shells, and open shells. Two examples are provided. (CW)

Mazo, R. M.

1990-01-01

13

Spin-orbit interaction mediated molecular dissociation  

NASA Astrophysics Data System (ADS)

The effect of the spin-orbit interaction to photofragmentation is investigated in the mercury(II) bromide (HgBr2) molecule. Changes in the fragmentation between the two spin-orbit components of Hg 5d photoionization, as well as within the molecular-field-splitted levels of these components are observed. Dissociation subsequent to photoionization is studied with synchrotron radiation and photoelectron-photoion coincidence spectroscopy. The experimental results are accompanied by relativistic ab initio analysis of the photoelectron spectrum.

Kokkonen, E.; Löytynoja, T.; Jänkälä, K.; Kettunen, J. A.; Heinäsmäki, S.; Karpenko, A.; Huttula, M.

2014-05-01

14

Relativistic Molecular Orbital Calculations for Diatomic Molecules  

Microsoft Academic Search

The relativistic molecular orbital calculations have been made for diatomic molecules by the use of the discrete variational Xa method. The validity of the method has been tested for CO mole- cule and good agreement is obtained between the relativistic and nonrelativistic calculations. The relativistic results for UO molecule are compared with the nonrelativistic ones and the importance of the

Takeshi MUKOYAMA; Hirohiko ADACHI

15

Phase diagram of a three-orbital model for high-Tc cuprate superconductors.  

PubMed

We study the phase diagram of an effective three-orbital model of the cuprates using variational Monte Carlo calculations on asymptotically large lattices and exact diagonalization on a 24-site cluster. States with ordered orbital current loops (LC), itinerant antiferromagnetism, d-wave superconductivity, and the Fermi liquid are investigated using appropriate Slater determinants refined by Jastrow functions for on-site and intersite correlations. We find an LC state stable in the thermodynamic limit for a range of parameters compatible with the Fermi surface of a typical hole doped superconductor provided the transfer integrals between the oxygen atoms have signs determined by the effects of indirect transfer through the Cu-4s orbitals as suggested by Andersen. The results of the calculations are that the LC phase gives way at lower dopings to an antiferromagnetism phase, and at larger dopings to superconductivity and Fermi liquid phases. PMID:24702405

Weber, Cédric; Giamarchi, T; Varma, C M

2014-03-21

16

Complete phase diagram for three-band Hubbard model with orbital degeneracy lifted by crystal field splitting  

NASA Astrophysics Data System (ADS)

Motivated by the unexplored complexity of the phase diagrams for multiorbital Hubbard models, a three-band Hubbard model at integer fillings (N=4) with orbital degeneracy lifted partially by crystal field splitting is analyzed systematically in this work. By using the single-site dynamical mean-field theory and rotationally invariant Gutzwiller approximation, we have computed the full phase diagram with Coulomb interaction strength U and crystal field splitting ?. We find a large region in the phase diagram where an orbital-selective Mott phase will be stabilized by the positive crystal field lifting the orbital degeneracy. Further analysis indicates that Hund's rule coupling is essential for the orbital-selective Mott phase, and the transition toward this phase is accompanied by a high-spin to low-spin transition. Such a model may be relevant for the recently discovered Ru-based materials.

Huang, Li; Du, Liang; Dai, Xi

2012-07-01

17

Fragment molecular orbital method: application to polypeptides  

NASA Astrophysics Data System (ADS)

Recently we have proposed the fragment molecular orbital method for calculating large molecules such as proteins. The method, with some modifications for a practical convenience, was applied to the model peptides of (Gly) n and (Ala) n ( n=5-20), [Met 5]enkephalin (YGGFM), and the synthetic designed peptide ALPHA-1 (acetyl-ELLKKLLEELKG). The calculated total energies compare well with those from the conventional ab initio MO method; the errors were within ˜2 kcal/mol. It indicates that the fragment MO method is sufficiently accurate and useful to study electronic properties of large molecules.

Nakano, Tatsuya; Kaminuma, Tsuguchika; Sato, Toshiyuki; Akiyama, Yutaka; Uebayasi, Masami; Kitaura, Kazuo

2000-03-01

18

Rotation and Anisotropic Molecular Orbital Effect in a Single H2TPP Molecule Transistor  

NASA Astrophysics Data System (ADS)

Electron transport through a single molecule is determined not only by the intrinsic properties of the molecule but also by the configuration of the molecule with respect to the lead electrodes. Here, we show how electron transport through a single H2TPP molecule is modulated by changes in the configuration. The Coulomb stability diagram of a single H2TPP molecule transistor exhibited a few different patterns in different measurement scans. Furthermore, the sample exhibited negative differential resistance, the magnitude of which changed with the pattern in the Coulomb stability diagram. Such behavior can be explained by the rotation of the molecule with anisotropic molecular orbitals in the gap electrodes induced by electrical stress. Moreover, we find that the energy separations between molecular orbitals are also affected by the rotation, confirming that the metal-molecule interface configuration renormalizes the electronic levels in the molecule.

Sakata, Shuichi; Yoshida, Kenji; Kitagawa, Yuichi; Ishii, Kazuyuki; Hirakawa, Kazuhiko

2013-12-01

19

Molecular orbital model for Be isotopes  

NASA Astrophysics Data System (ADS)

The chain of Be isotopes is an interesting object because of the unique combination of shell, cluster, pairing, deformation and halo effects. Nuclear structure of Be isotopes is studied in the framework of the fully microscopic model where the trial wave function of the ^8Be skeleton has a two-center spatial configuration with the parameters determined by variation of energy (an expectation value of the total hamiltonian of interacting nucleons) after projecting out a proper value of angular momentum. Additional neutrons in heavier Be isotopes are placed on the molecular orbitals with energy minimization for different geometrical configurations. The energy spectra, quadrupole moments and mean square radii are calculated. The extension of the approach for the case of hole configurations in ^7Li is suggested.

Sakharuk, Alexander; Zelevinsky, Vladimir

2000-04-01

20

Molecular-orbital tomography beyond the plane-wave approximation  

NASA Astrophysics Data System (ADS)

The use of plane-wave approximation in molecular-orbital tomography via high-order-harmonic generation has been questioned since it was proposed, owing to the fact that it ignores the essential property of the continuum-wave function. To address this problem, we develop a theory to retrieve the valence molecular orbital directly, utilizing a molecular continuum-wave function which takes into account the influence of the parent ion field on the continuum electrons. By transforming this wave function into momentum space, we show that the mapping from the relevant molecular orbital to the high-order-harmonic spectra is still invertible. As an example, the highest orbital of N2 is successfully reconstructed and it shows good agreement with the ab initio orbital. Our work clarifies the long-standing controversy and strengthens the theoretical basis of molecular-orbital tomography.

Li, Yang; Zhu, Xiaosong; Lan, Pengfei; Zhang, Qingbin; Qin, Meiyan; Lu, Peixiang

2014-04-01

21

Application of the Characteristic Bisection Method for locating and computing periodic orbits in molecular systems  

NASA Astrophysics Data System (ADS)

The Characteristic Bisection Method for finding the roots of non-linear algebraic and/or transcendental equations is applied to LiNC/LiCN molecular system to locate periodic orbits and to construct the continuation/bifurcation diagram of the bend mode family. The algorithm is based on the Characteristic Polyhedra which define a domain in phase space where the topological degree is not zero. The results are compared with previous calculations obtained by the Newton Multiple Shooting algorithm. The Characteristic Bisection Method not only reproduces the old results, but also, locates new symmetric and asymmetric families of periodic orbits of high multiplicity.

Vrahatis, M. N.; Perdiou, A. E.; Kalantonis, V. S.; Perdios, E. A.; Papadakis, K.; Prosmiti, R.; Farantos, S. C.

2001-07-01

22

Fermi-liquid computation of the phase diagram of high-Tc cuprate superconductors with an orbital antiferromagnetic pseudogap.  

PubMed

A 4-parameter Fermi-liquid calculation of the high-Tc cuprate phase diagram is reported. Simultaneously accounted for are the special doping densities of 5% and 16%, the d-wave functional form of the (orbital antiferromagnetic) pseudogap, the measured Tc, superconducting gap, pseudogap and superfluid density as a function of doping, the particle-hole doping asymmetry and the half-filling spin wave velocity. PMID:24483922

Laughlin, R B

2014-01-10

23

Fermi-Liquid Computation of the Phase Diagram of High-Tc Cuprate Superconductors with an Orbital Antiferromagnetic Pseudogap  

NASA Astrophysics Data System (ADS)

A 4-parameter Fermi-liquid calculation of the high-Tc cuprate phase diagram is reported. Simultaneously accounted for are the special doping densities of 5% and 16%, the d-wave functional form of the (orbital antiferromagnetic) pseudogap, the measured Tc, superconducting gap, pseudogap and superfluid density as a function of doping, the particle-hole doping asymmetry and the half-filling spin wave velocity.

Laughlin, R. B.

2014-01-01

24

Molecular gap and energy level diagram for pentacene adsorbed on filled d-band metal surfaces  

NASA Astrophysics Data System (ADS)

The authors present a combined photoemission and scanning-tunneling spectroscopy study of the filled electronic states, the molecular energy gap, and the energy level diagram of highly ordered arrays of pentacene deposited on the Cu(119) vicinal surface. The states localized at the interface are clearly singled out, comparing the results at different pentacene thicknesses and with gas-phase photoemission data. The molecular gap of 2.35 eV, the hole injection barrier of 1.05 eV, and the electron injection barrier of 1.30 eV determine the energy level diagram of the states localized at the pentacene molecules.

Baldacchini, Chiara; Mariani, Carlo; Betti, Maria Grazia; Gavioli, L.; Fanetti, M.; Sancrotti, M.

2006-10-01

25

Manipulating Localized Molecular Orbitals by Single-Atom Contacts  

NASA Astrophysics Data System (ADS)

We have fabricated atom-molecule contacts by attachment of single Cu atoms to terpyridine side groups of bis-terpyridine tetra-phenyl ethylene molecules on a Cu(111) surface. By means of scanning tunneling microscopy, spectroscopy, and density functional calculations, we have found that, due to the localization characteristics of molecular orbitals, the Cu-atom contact modifies the state localized at the terpyridine side group which is in contact with the Cu atom but does not affect the states localized at other parts of the molecule. These results illustrate the contact effects at individual orbitals and offer possibilities to manipulate orbital alignments within molecules.

Wang, Weihua; Shi, Xingqiang; Lin, Chensheng; Zhang, Rui Qin; Minot, Christian; van Hove, Michel A.; Hong, Yuning; Tang, Ben Zhong; Lin, Nian

2010-09-01

26

Molecular orbitals and {alpha}+ {sup 18}O molecular bands of {sup 22}Ne  

SciTech Connect

Focusing on {alpha} clustering, the structure of {sup 22}Ne was studied. We predict the presence of the molecular orbital bands that have an {alpha}+ {sup 16}O cluster core surrounded by two neutrons occupying the molecular orbitals, together with {alpha}+ {sup 18}O molecular bands. The formation of the {alpha}+ {sup 16}O cluster core and its close relation to the configuration of two valence neutrons are discussed.

Kimura, Masaaki [Yukawa Institute for Theoretical Physics, Kyoto University, Kyoto 606-8502 (Japan)

2007-03-15

27

A combined reaction class approach with integrated molecular orbital+molecular orbital (IMOMO) methodology: A practical tool for kinetic modeling  

SciTech Connect

We present a new practical computational methodology for predicting thermal rate constants of reactions involving large molecules or a large number of elementary reactions in the same class. This methodology combines the integrated molecular orbital+molecular orbital (IMOMO) approach with our recently proposed reaction class models for tunneling. With the new methodology, we show that it is possible to significantly reduce the computational cost by several orders of magnitude while compromising the accuracy in the predicted rate constants by less than 40% over a wide range of temperatures. Another important result is that the computational cost increases only slightly as the system size increases. (c) 2000 American Institute of Physics.

Truong, Thanh N. [Henry Eyring Center for Theoretical Chemistry, Department of Chemistry, University of Utah, 315 S 1400 E, Room Dock, Salt Lake City, Utah 84112 (United States)] [Henry Eyring Center for Theoretical Chemistry, Department of Chemistry, University of Utah, 315 S 1400 E, Room Dock, Salt Lake City, Utah 84112 (United States); Maity, Dilip K. [Henry Eyring Center for Theoretical Chemistry, Department of Chemistry, University of Utah, 315 S 1400 E, Room Dock, Salt Lake City, Utah 84112 (United States)] [Henry Eyring Center for Theoretical Chemistry, Department of Chemistry, University of Utah, 315 S 1400 E, Room Dock, Salt Lake City, Utah 84112 (United States); Truong, Thanh-Thai T. [Henry Eyring Center for Theoretical Chemistry, Department of Chemistry, University of Utah, 315 S 1400 E, Room Dock, Salt Lake City, Utah 84112 (United States)] [Henry Eyring Center for Theoretical Chemistry, Department of Chemistry, University of Utah, 315 S 1400 E, Room Dock, Salt Lake City, Utah 84112 (United States)

2000-01-01

28

Nonorthogonal molecular orbital method: Single-determinant theory.  

PubMed

Using the variational principle, we have derived a variant of the Adams-Gilbert equation for nonorthogonal orbitals of a single-determinant wave function, which we name the modified Adams-Gilbert equation. If we divide the molecular system into several subsystems, such as bonds, lone pairs, and residues, we can solve the equations for the subsystems one by one. Thus, this procedure has linear scaling. We have presented a practical procedure for solving the equations that is also applicable to macromolecular calculations. The numerical examples show that the procedure yields, with reasonable effort, results comparable with those of the Hartree-Fock-Roothaan method for orthogonal orbitals. To resolve the convergence difficulty in the self-consistent-field iterations, we have found that virtual molecular-orbital shifts are very effective. PMID:24880270

Watanabe, Yoshihiro; Matsuoka, Osamu

2014-05-28

29

Intracellular molecular distributions in spacecraft experiments in orbit around Earth  

NASA Astrophysics Data System (ADS)

It is possible that the nucleolous inside the cell plays the role of a "gravity receptor". Furthermore, cells up to 10 ?m in diameter can demonstrate some effect due to the redistribution of mitochondria or nucleolous. Effects of gravity should be present in various cell systems where larger objects such as the ribosomes move from cell to cell. In this paper we study the effects of gravity on cells. In particular, we examine the resulting intracellular molecular distribution due to Brownian motion and the ordered distribution of molecules under the action of gravity, where n0 is the number per unit volume at certain level, and n is the number per unit volume above that level. This is an experiment that takes place at a certain orbital altitude in a spacecraft in orbit around Earth, where the acceleration due to the central field is corrected for the oblateness and also the rotation of the Earth. We found that equatorial circular and elliptical orbits have the highest n/n0 ratios. This experiment takes place in circular and elliptical orbits, with eccentricities e = 0, 0.1 and involves a bacterial cell at an orbital altitude of 300 km. We found that n/n0 = 1.00299 and 1.0037 respectively, which is still a 0.6-0.7 % higher than n/n0 = 0.0996685 calculated on the surface of the Earth. Examining mitochondria in similar orbital experiments we found that equatorial orbits result to higher n/n0 ratios. In particular, we found that n/n0 = 8.38119, where an elliptical orbit of eccentricity e = 0.1 results to n/n0 = 13.8525. Both are high above 100%, signifying the importance of Brownian motion over gravity. Our results are of interest to biomedical applications. Molecular concentrations are important for various processes such as the embryogenesis, positional homeostasis and its relation to cell energy expenditure, cell torque, cell deformation, and more. These results indicate that statistical molecular distributions play an important role for the recognition of a particular environment by the cell, in biological space experiment to come.

Haranas, Ioannis; Gkigkitzis, Ioannis; Zouganelis, George D.

2012-04-01

30

Molecular excitation energies computed with Kohn-Sham orbitals and exact exchange potentials  

Microsoft Academic Search

Exact local exchange potentials are computed for the diatomic molecules N2, O2, and CO, based on expansions in terms of molecular orbitals. Kohn-Sham orbitals and orbital energies are obtained for the exact exchange potentials, with correlation effects neglected. The ionization potential is in all cases found to be accurately predicted by the orbital energy of the highest occupied orbital. Limited

L. Veseth

2001-01-01

31

Bonding in Transition Metal Silyl Dimers. Molecular Orbital Theory.  

National Technical Information Service (NTIS)

Molecular orbital studies of Mn2(CO)8 (Si(C6H5)2)2 and Pt2(H3P)4(SiC6H5C1)2 have been made by interacting disilene fragments with transition metal dimers. In the former complex, it is found that the Mn-Mn distance is close to the sum of the atomic radii b...

A. B. Anderson C. A. Tessier-Youngs E. A. Zarate P. Shiller W. J. Youngs

1989-01-01

32

Molecular orbital theory of ballistic electron transport through molecules  

NASA Astrophysics Data System (ADS)

Electron transport through molecules occurs, for instance, in STM imaging and in conductance measurements on molecular electronic devices (MEDs). To model these phenomena, we use a non-Hermitian model Hamiltonian [1] for the description of open systems that exchange current density with their environment. We derive qualitative, molecular-orbital-based rules relating molecular structure and conductance. We show how side groups attached to molecular conductors [2] can completely suppress the conductance. We discuss interference effects in aromatic molecules [3] that can also inhibit electron transport. Rules are developed [1] for the prediction of Fano resonances. All these phenomena are explained with a molecular orbital theory [1,4] for molecules attached to macroscopic reservoirs. [1] F. Goyer, M. Ernzerhof, and M. Zhuang, JCP 126, 144104 (2007); M. Ernzerhof, JCP 127, 204709 (2007). [2] M. Ernzerhof, M. Zhuang, and P. Rocheleau, JCP 123, 134704 (2005); G. C. Solomon, D Q. Andrews, R P. Van Duyne, and M A. Ratner, JACS 130, 7788 (2008). [3] M. Ernzerhof, H. Bahmann, F. Goyer, M. Zhuang, and P. Rocheleau, JCTC 2, 1291 (2006); G. C. Solomon, D. Q. Andrews, R. P. Van Duyne, and M. A. Ratner, JCP 129, 054701 (2008). [4] B.T. Pickup, P.W. Fowler, CPL 459, 198 (2008); P. Rocheleau and M. Ernzerhof, JCP, submitted.

Ernzerhof, Matthias; Rocheleau, Philippe; Goyer, Francois

2009-03-01

33

Configuration interaction singles method with multilayer fragment molecular orbital scheme  

NASA Astrophysics Data System (ADS)

We have developed a parallelized integral-direct solver for configuration interaction singles (CIS) in the A BINIT-MP program, by accepting the recently proposed multilayer fragment molecular orbital (MLFMO) method. In the MLFMO-CIS scheme, the region of interest in photoactive issues can be treated with the environmental potential at the Hartree-Fock (HF) level. The parallel efficiency is observed to be reasonable for the formaldehyde hydration system. A realistic applicability of the method is demonstrated for the photoactive yellow protein (PYP) including 125 amino acid residues.

Mochizuki, Yuji; Koikegami, Shigeru; Amari, Shinji; Segawa, Katsunori; Kitaura, Kazuo; Nakano, Tatsuya

2005-05-01

34

alpha-clustering and molecular-orbital states in sd-shell nuclei  

SciTech Connect

The alpha-clustering and molecular-orbitals of {sup 22}Ne and F isotopes are investigated based on antisymmetrized molecular dynamics (AMD). The observed candidates for the alpha cluster state of {sup 22}Ne are understood as the molecular-orbital states and alpha+{sup 18}O di-nuclei states. The presence of the molecular-orbital states in the O and F isotopes and the drastic reduction of their excitation energy near the neutron-drip line are predicted.

Kimura, M. [Creative Research Institution Sousei Research Department, Hokkaido University, Sapporo 011-0021 (Japan); Furutachi, N. [Meme Media Laboratory, Hokkaido University, Sapporo 060-8628 (Japan)

2010-05-12

35

Molecular orbital calculations on transition metal complexes part VII  

Microsoft Academic Search

INDO SCF Molecular Orbital Calculations have been made for manganocene (MnCp2), its molecular cation (MnCp\\u000a 2\\u000a +\\u000a ) and the ferricenium ion FeCp\\u000a 2\\u000a +\\u000a . The computations yield a high spin 6\\u000a A\\u000a 1g\\u000a (e\\u000a \\u000a 2g\\u000a \\u000a 2\\u000a \\u000a a\\u000a \\u000a 1g\\u000a \\u000a 1\\u000a \\u000a e\\u000a \\u000a 1g\\u000a \\u000a 2\\u000a ) ground state for MnCp2, contrary to that which was assumed to interpret the photoelectron spectrum.

Denis W. Clack

1974-01-01

36

Molecular-frame photoelectron angular distributions of strong-field tunneling from inner orbitals  

NASA Astrophysics Data System (ADS)

Using photoelectron angular streaking by strong circularly polarized laser pulses, we measure angular-dependent tunneling rates from the inner orbitals of O2 in the molecular frame, which correlate with the strong-field molecular dissociative ionization process. We show that the electronic density of molecular inner orbitals can be visualized by angular tunneling rates in the molecular frame. We demonstrate the orbital-by-orbital characterization of tunneling ionization from randomly oriented molecules. Compared with the single-active-electron approximation theories, i.e., the molecular strong-field approximation and the molecular Ammosov-Delone-Krainov model, the experiment shows that the tunneling from the excited states and the state coupling might play an important role in strong-field molecular tunneling ionization. Our results suggest major advances in quantum theory needed for molecular inner orbital tunneling and open intriguing perspectives to probe quantum dynamics related with molecular core electrons.

Liu, Hong; Zhao, Song-Feng; Li, Min; Deng, Yongkai; Wu, Chengyin; Zhou, Xiao-Xin; Gong, Qihuang; Liu, Yunquan

2013-12-01

37

Assessment of delocalized and localized molecular orbitals through electron momentum spectroscopy  

NASA Astrophysics Data System (ADS)

Recently, there was a hot controversy about the concept of localized orbitals, which was triggered by Grushow's work titled “Is it time to retire the hybrid atomic orbital?” [J. Chem. Educ. 88, 860 (2011)]. To clarify the issue, we assess the delocalized and localized molecular orbitals from an experimental view using electron momentum spectroscopy. The delocalized and localized molecular orbitals based on various theoretical models for CH4, NH3, and H2O are compared with the experimental momentum distributions. Our results show that the delocalized molecular orbitals rather than the localized ones can give a direct interpretation of the experimental (e, 2e) results.

Liu, Yuan; Cheung, Ling-Fung; Ning, Chuan-Gang

2014-06-01

38

On the limits of highest-occupied molecular orbital driven reactions: the frontier effective-for-reaction molecular orbital concept.  

PubMed

We carried out Hartree-Fock (HF) and density functional theory calculations for 61 compounds, the conjugated bases of carboxylic acids, phenols, and alcohols, and analyzed their acid-base behavior using molecular orbital (MO) energies and their dependence on solvent effects. Despite the well-known correlation between highest-occupied MO (HOMO) energies and pKa, we observed that HOMO energies are inadequate to describe the acid-base behavior of these compounds. Therefore, we established a criterion to identify the best frontier MO for describing pKa values and also to understand why the HOMO approach fails. The MO that fits our criterion provided very good correlations with pKa values, much better than those obtained by HOMO energies. Since they are the frontier molecular orbitals that drive the acid-base reactions in each compound, they were called frontier effective-for-reaction MOs, or FERMOs. By use of the FERMO concept, the reactions that are HOMO driven, and those that are not, can be better explained, independently from the calculation method used, as both HF and Kohn-Sham methodologies lead to the same FERMO. PMID:16420004

da Silva, Rodrigo R; Ramalho, Teodorico C; Santos, Joana M; Figueroa-Villar, J Daniel

2006-01-26

39

Ab initio Path Integral Molecular Dynamics Based on Fragment Molecular Orbital Method  

NASA Astrophysics Data System (ADS)

We have developed an ab initio path integral molecular dynamics method based on the fragment molecular orbital method. This “FMO-PIMD” method can treat both nuclei and electrons quantum mechanically, and is useful to simulate large hydrogen-bonded systems with high accuracy. After a benchmark calculation for water monomer, water trimer and glycine pentamer have been studied using the FMO-PIMD method to investigate nuclear quantum effects on structure and molecular interactions. The applicability of the present approach is demonstrated through a number of test calculations.

Fujita, Takatoshi; Watanabe, Hirofumi; Tanaka, Shigenori

2009-10-01

40

A non-orthogonal Kohn-Sham method using partially fixed molecular orbitals  

Microsoft Academic Search

A density functional theory method using partially fixed molecular orbitals (PFMOs) is presented. The PFMOs, which have some fixed molecular orbital coefficients and are non-orthogonal, are a generalization of the extreme localized orbitals (ELMOs) of Couty, Bayse, and Hall (1997) Theor Chem Acc 97:96. A non-orthogonal Kohn-Sham method with these PFMOs is derived, and is applied to molecular calculations on

Kazushi Sorakubo; Takeshi Yanai; Kenichi Nakayama; Muneaki Kamiya; Haruyuki Nakano; Kimihiko Hirao

2003-01-01

41

Monoclonal origin of localised orbital amyloidosis detected by molecular analysis.  

PubMed Central

AIMS: Primary localised orbital amyloidosis is a rare disease. The purpose of this study was to describe two cases of primary orbital amyloidosis and emphasise the value of molecular analysis of immunoglobulin gene rearrangement in identifying a monoclonal population of cells responsible for the amyloid production. METHODS: Charts and biopsy specimens of each case were reviewed. Conventional light microscopy, immunohistochemistry, and polymerase chain reaction (PCR) analysis for immunoglobulin gene rearrangement were performed in both cases. RESULTS: An unusual presentation of localised primary amyloidosis with bilateral and extensive enlargement of multiple extraocular muscles was seen in case 1. The presence of amyloid deposits was confirmed by biopsy in both cases. Evidence of a monoclonal population of plasma cells was shown by immunohistochemical analysis in case 2 only. The monoclonal origin of the cells responsible for the amyloid deposition was determined by PCR analysis demonstrating immunoglobulin heavy chain gene rearrangement in both cases. CONCLUSIONS: A monoclonal population of plasma cells responsible for the amyloid deposition was present in these two cases. PCR analysis is extremely helpful in determining monoclonality, a finding that may have important therapeutic and prognostic implications. Images

Pasternak, S; White, V A; Gascoyne, R D; Perry, S R; Johnson, R L; Rootman, J

1996-01-01

42

Halogen Bonding versus Hydrogen Bonding: A Molecular Orbital Perspective.  

PubMed

We have carried out extensive computational analyses of the structure and bonding mechanism in trihalides DX???A(-) and the analogous hydrogen-bonded complexes DH???A(-) (D, X, A=F, Cl, Br, I) using relativistic density functional theory (DFT) at zeroth-order regular approximation ZORA-BP86/TZ2P. One purpose was to obtain a set of consistent data from which reliable trends in structure and stability can be inferred over a large range of systems. The main objective was to achieve a detailed understanding of the nature of halogen bonds, how they resemble, and also how they differ from, the better understood hydrogen bonds. Thus, we present an accurate physical model of the halogen bond based on quantitative Kohn-Sham molecular orbital (MO) theory, energy decomposition analyses (EDA) and Voronoi deformation density (VDD) analyses of the charge distribution. It appears that the halogen bond in DX???A(-) arises not only from classical electrostatic attraction but also receives substantial stabilization from HOMO-LUMO interactions between the lone pair of A(-) and the ?* orbital of D-X. PMID:24551497

Wolters, Lando P; Bickelhaupt, F Matthias

2012-04-01

43

Halogen Bonding versus Hydrogen Bonding: A Molecular Orbital Perspective  

PubMed Central

We have carried out extensive computational analyses of the structure and bonding mechanism in trihalides DX???A? and the analogous hydrogen-bonded complexes DH???A? (D, X, A=F, Cl, Br, I) using relativistic density functional theory (DFT) at zeroth-order regular approximation ZORA-BP86/TZ2P. One purpose was to obtain a set of consistent data from which reliable trends in structure and stability can be inferred over a large range of systems. The main objective was to achieve a detailed understanding of the nature of halogen bonds, how they resemble, and also how they differ from, the better understood hydrogen bonds. Thus, we present an accurate physical model of the halogen bond based on quantitative Kohn–Sham molecular orbital (MO) theory, energy decomposition analyses (EDA) and Voronoi deformation density (VDD) analyses of the charge distribution. It appears that the halogen bond in DX???A? arises not only from classical electrostatic attraction but also receives substantial stabilization from HOMO–LUMO interactions between the lone pair of A? and the ?* orbital of D–X.

Wolters, Lando P; Bickelhaupt, F Matthias

2012-01-01

44

Sulfur at nickel-alumina interfaces - Molecular orbital theory  

NASA Technical Reports Server (NTRS)

Previous studies on Al-Ni alloys containing sulfur as an impurity suggest that, when S is in the interface between a metal and an oxide scale, it weakens the chemical bonding between them. This paper investigates factors responsible for this effect, using a molecular orbital theory to predict sulfur structures and electronic properties on the Ni-Al2O3 interface. It is shown that, in absence of S, the basal plane of Al2O3 will bind strongly through the Al(3+) cation surface to Ni (111). When segregated S impurity is present on the Ni surface, there are too few interfacial AlS bonds to effect good adhesion, leading to an inhibition of the oxide scale adhesion in NiCrAl alloys.

Hong, S. Y.; Anderson, Alfred B.; Smialek, James L.

1990-01-01

45

Charge transfer processes: the role of optimized molecular orbitals.  

PubMed

The influence of the molecular orbitals on charge transfer (CT) reactions is analyzed through wave function-based calculations. Characteristic CT processes in the organic radical 2,5-di-tert-butyl-6-oxophenalenoxyl linked with tetrathiafulvalene and the inorganic crystalline material LaMnO3 show that changes in the inner shells must be explicitly taken into account. Such electronic reorganization can lead to a reduction of the CT vertical transition energy up to 66%. A state-specific approach accessible through an adapted CASSCF (complete active space self-consistent field) methodology is capable of reaching good agreement with the experimental spectroscopy of CT processes. A partitioning of the relaxation energy in terms of valence- and inner-shells is offered and sheds light on their relative importance. This work paves the way to the intimate description of redox reactions using quantum chemistry methods. PMID:24781811

Meyer, Benjamin; Domingo, Alex; Krah, Tim; Robert, Vincent

2014-08-01

46

Comparison of DFT methods for molecular orbital eigenvalue calculations.  

PubMed

We report how closely the Kohn-Sham highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) eigenvalues of 11 density functional theory (DFT) functionals, respectively, correspond to the negative ionization potentials (-IPs) and electron affinities (EAs) of a test set of molecules. We also report how accurately the HOMO-LUMO gaps of these methods predict the lowest excitation energies using both time-independent and time-dependent DFT (TD-DFT). The 11 DFT functionals include the local spin density approximation (LSDA), five generalized gradient approximation (GGA) functionals, three hybrid GGA functionals, one hybrid functional, and one hybrid meta GGA functional. We find that the HOMO eigenvalues predicted by KMLYP, BH&HLYP, B3LYP, PW91, PBE, and BLYP predict the -IPs with average absolute errors of 0.73, 1.48, 3.10, 4.27, 4.33, and 4.41 eV, respectively. The LUMOs of all functionals fail to accurately predict the EAs. Although the GGA functionals inaccurately predict both the HOMO and LUMO eigenvalues, they predict the HOMO-LUMO gap relatively accurately (approximately 0.73 eV). On the other hand, the LUMO eigenvalues of the hybrid functionals fail to predict the EA to the extent that they include HF exchange, although increasing HF exchange improves the correspondence between the HOMO eigenvalue and -IP so that the HOMO-LUMO gaps are inaccurately predicted by hybrid DFT functionals. We find that TD-DFT with all functionals accurately predicts the HOMO-LUMO gaps. A linear correlation between the calculated HOMO eigenvalue and the experimental -IP and calculated HOMO-LUMO gap and experimental lowest excitation energy enables us to derive a simple correction formula. PMID:17279730

Zhang, Gang; Musgrave, Charles B

2007-03-01

47

Ab initio molecular simulations with numeric atom-centered orbitals  

NASA Astrophysics Data System (ADS)

We describe a complete set of algorithms for ab initio molecular simulations based on numerically tabulated atom-centered orbitals (NAOs) to capture a wide range of molecular and materials properties from quantum-mechanical first principles. The full algorithmic framework described here is embodied in the Fritz Haber Institute " ab initio molecular simulations" ( FHI-aims) computer program package. Its comprehensive description should be relevant to any other first-principles implementation based on NAOs. The focus here is on density-functional theory (DFT) in the local and semilocal (generalized gradient) approximations, but an extension to hybrid functionals, Hartree-Fock theory, and MP2/ GW electron self-energies for total energies and excited states is possible within the same underlying algorithms. An all-electron/full-potential treatment that is both computationally efficient and accurate is achieved for periodic and cluster geometries on equal footing, including relaxation and ab initio molecular dynamics. We demonstrate the construction of transferable, hierarchical basis sets, allowing the calculation to range from qualitative tight-binding like accuracy to meV-level total energy convergence with the basis set. Since all basis functions are strictly localized, the otherwise computationally dominant grid-based operations scale as O( N) with system size N. Together with a scalar-relativistic treatment, the basis sets provide access to all elements from light to heavy. Both low-communication parallelization of all real-space grid based algorithms and a ScaLapack-based, customized handling of the linear algebra for all matrix operations are possible, guaranteeing efficient scaling (CPU time and memory) up to massively parallel computer systems with thousands of CPUs.

Blum, Volker; Gehrke, Ralf; Hanke, Felix; Havu, Paula; Havu, Ville; Ren, Xinguo; Reuter, Karsten; Scheffler, Matthias

2009-11-01

48

Band Formation in a Molecular Quantum Well via 2D Superatom Orbital Interactions  

SciTech Connect

By scanning tunneling microscopy and spectroscopy, we study nearly free electron band formation of the ?*lowest unoccupied molecular orbital of C?F? on a Cu(111) surface. In fractal islands, the lowest unoccupied molecular orbital energy systematically stabilizes with the number of interacting near-neighbor C?F? molecules. Density functional theory calculations reveal the origin of effective intermo- lecular orbital overlap in the previously unrecognized superatom character of the ?*orbital of ?F? molecules. The discovery of superatom orbitals in planar molecules offers a new universal principle for effective band formation, which can be exploited in designing organic semiconductors with nearly free electron properties

Dougherty, D. B.; Feng, Min; Petek, Hrvoje; Yates, John T.; Zhao, Jin

2012-12-28

49

Band Formation in a Molecular Quantum Well via 2D Superatom Orbital Interactions  

NASA Astrophysics Data System (ADS)

By scanning tunneling microscopy and spectroscopy, we study nearly free electron band formation of the ?* lowest unoccupied molecular orbital of C6F6 on a Cu(111) surface. In fractal islands, the lowest unoccupied molecular orbital energy systematically stabilizes with the number of interacting near-neighbor C6F6 molecules. Density functional theory calculations reveal the origin of effective intermolecular orbital overlap in the previously unrecognized superatom character of the ?* orbital of C6F6 molecules. The discovery of superatom orbitals in planar molecules offers a new universal principle for effective band formation, which can be exploited in designing organic semiconductors with nearly free electron properties.

Dougherty, Daniel B.; Feng, Min; Petek, Hrvoje; Yates, John T., Jr.; Zhao, Jin

2012-12-01

50

Elimination of translational and rotational motions in nuclear orbital plus molecular orbital theory: Application of Møller-Plesset perturbation theory  

Microsoft Academic Search

The translation- and rotation-free nuclear orbital plus molecular orbital (TRF-NOMO) theory was developed to determine the nonadiabatic nuclear and electronic wave functions. This study presents a formulation of TRF-NOMO second-order Møller-Plesset (MP2) perturbation and Epstein-Nesbet (EN) theory with the use of the TRF Hamiltonian. Numerical assessment of the TRF-NOMO\\/MP2 and EN is performed for several molecules. We confirm the importance

Minoru Hoshino; Hiromi Nakai

2006-01-01

51

Asymmetric electron transport and highest occupied molecular orbital assisted tunneling through Zn-porphyrin molecular junctions  

NASA Astrophysics Data System (ADS)

We report electron transport measurements from gold-zinc-porphyrin-gold molecular junctions formed in an electromigrated nanogap. Asymmetric current-voltage (I-V) behaviors about the zero bias voltage were observed at room temperature and 4.2 K. These observations are in contrast to measurements from a nanogap without any molecules, which are dominated by tunneling and display symmetric I-V characteristics. In addition, increasing the gate voltage suppressed the current through the junction at room temperature, indicating electron tunneling proceeded through the highest occupied molecular orbital. Density of states calculations were performed to explain these findings and understand the microscopic origins of the observations.

Saha, Swatilekha; Owens, Jonathan R.; Meunier, Vincent; Lewis, K. M.

2013-10-01

52

Analyzing and Interpreting NMR Spin-Spin Coupling Constants Using Molecular Orbital Calculations  

ERIC Educational Resources Information Center

Molecular orbital plots are used to analyze and interpret NMR spin-spin coupling constants, also known as J coupling constants. Students have accepted the concept of contributions to molecular properties from individual orbitals without the requirement to provide explicit equations.

Autschbach, Jochen; Le Guennic, Boris

2007-01-01

53

Construction of Ligand Group Orbitals for Polyatomics and Transition-Metal Complexes Using an Intuitive Symmetry-Based Approach  

ERIC Educational Resources Information Center

A molecular orbital (MO) diagram, especially its frontier orbitals, explains the bonding and reactivity for a chemical compound. It is therefore important for students to learn how to construct one. The traditional methods used to derive these diagrams rely on linear algebra techniques to combine ligand orbitals into symmetry-adapted linear…

Johnson, Adam R.

2013-01-01

54

Effect of molecular crowding on the temperature-pressure stability diagram of ribonuclease A.  

PubMed

FT-IR spectroscopic and thermodynamic measurements were designed to explore the effect of a macromolecular crowder, dextran, on the temperature and pressure-dependent phase diagram of the protein Ribonuclease A (RNase A), and we compare the experimental data with approximate theoretical predictions based on configuration entropy. Exploring the crowding effect on the pressure-induced unfolding of proteins provides insight in protein stability and folding under cell-like dense conditions, since pressure is a fundamental thermodynamic variable linked to molecular volume. Moreover, these studies are of relevance for understanding protein stability in deep-sea organisms, which have to cope with pressures in the kbar range. We found that not only temperature-induced equilibrium unfolding of RNase A, but also unfolding induced by pressure is markedly prohibited in the crowded dextran solutions, suggesting that crowded environments such as those found intracellularly, will also oppress high-pressure protein unfolding. The FT-IR spectroscopic measurements revealed a marked increase in unfolding pressure of 2 kbar in the presence of 30 wt % dextran. Whereas the structural changes upon thermal unfolding of the protein are not significantly influenced in the presence of the crowding agent, through stabilization by dextran the pressure-unfolded state of the protein retains more ordered secondary structure elements, which seems to be a manifestation of the entropic destabilization of the unfolded state by crowding. PMID:23281099

Zhai, Yong; Winter, Roland

2013-02-01

55

Polarized Molecular Orbital Model Chemistry 3. The PMO Method Extended to Organic Chemistry  

PubMed Central

The polarized molecular orbital (PMO) method, a neglect-of-diatomic-differential-overlap (NDDO) semiempirical molecular orbital method previously parameterized for systems composed of O and H, is here extended to carbon. We modified the formalism and optimized all the parameters in the PMO Hamiltonian by using a genetic algorithm and a database containing both electrostatic and energetic properties; the new parameter set is called PMO2. The quality of the resulting predictions is compared to results obtained by previous NDDO semiempirical molecular orbital methods, both including and excluding dispersion terms. We also compare the PMO2 properties to SCC-DFTB calculations. Within the class of semiempirical molecular orbital methods, the PMO2 method is found to be especially accurate for polarizabilities, atomization energies, proton transfer energies, noncovalent complexation energies, and chemical reaction barrier heights and to have good across-the-board accuracy for a range of other properties, including dipole moments, partial atomic charges, and molecular geometries.

Isegawa, Miho; Fiedler, Luke; Leverentz, Hannah R.; Wang, Yingjie; Nachimuthu, Santhanamoorthi; Gao, Jiali; Truhlar, Donald G.

2013-01-01

56

Moving Beyond the Single Center--Ways to Reinforce Molecular Orbital Theory in an Inorganic Course  

ERIC Educational Resources Information Center

It is suggested that molecular theory should be taught earlier in the inorganic chemistry curriculum even in the introductory chemistry course in order to integrate molecular orbital arguments more effectively throughout the curriculum. The method of teaching relies on having access to molecular modeling software as having access to such software…

Cass, Marion E.; Hollingsworth, William E.

2004-01-01

57

Transport properties of lithium hydride from quantum molecular dynamics and orbital-free molecular dynamics  

SciTech Connect

We have performed a systematic study of lithium hydride in the warm-dense-matter regime for a density range from one to four times ambient solid and for temperatures from 2 to 6 eV using both finite-temperature density-functional theory quantum molecular dynamics (QMD) and orbital-free molecular dynamics (OFMD) with a focus on dynamical properties such as diffusion and viscosity. The validity of various mixing rules, especially those utilizing pressure, were checked for composite properties determined from QMD/OFMD simulations of the pure species against calculations on the fully interacting mixture. These rules produce pressures within about 10% of the full-mixture values but mutual-diffusion coefficients as different as 50%. We found very good agreement overall between the QMD, employing a three-electron pseudopotential, and the OFMD in the local-density approximation, especially at the higher temperatures and densities.

Horner, D. A.; Kress, J. D.; Collins, L. A. [Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Lambert, F. [CEA, DAM, DIF, F-91297 Arpajon (France)

2009-07-01

58

A unified scheme for ab initio molecular orbital theory and path integral molecular dynamics  

NASA Astrophysics Data System (ADS)

We present a general approach for accurate calculation of chemical substances which treats both nuclei and electrons quantum mechanically, adopting ab initio molecular orbital theory for the electronic structure and path integral molecular dynamics for the nuclei. The present approach enables the evaluation of physical quantities dependent on the nuclear configuration as well as the electronic structure, within the framework of Born-Oppenheimer adiabatic approximation. As an application, we give the path integral formulation of electric response properties-dipole moment and polarizability, which characterize the changes both in electronic structure and nuclear configuration at a given temperature when uniform electrostatic field is present. We also demonstrate the calculation of a water molecule using the present approach and the result of temperature and isotope effects is discussed.

Shiga, Motoyuki; Tachikawa, Masanori; Miura, Shinichi

2001-11-01

59

Magnetic phase diagram of a five-orbital Hubbard model in the real-space Hartree-Fock approximation varying the electronic density  

NASA Astrophysics Data System (ADS)

Using the real-space Hartree-Fock approximation, the magnetic phase diagram of a five-orbital Hubbard model for the iron-based superconductors is studied varying the electronic density n in the range from five to seven electrons per transition metal atom. The Hubbard interaction U is also varied, at a fixed Hund coupling J /U=0.25. Several qualitative trends and a variety of competing magnetic states are observed. At n =5, a robust G-type antiferromagnetic insulator is found, in agreement with experimental results for BaMn2As2. As n increases away from 5, magnetic states with an increasing number of nearest-neighbors ferromagnetic links become energetically stable. This includes the well-known C-type antiferromagnetic state at n =6, the E-phase known to exist in FeTe, and also a variety of novel states not found yet experimentally, some of them involving blocks of ferromagnetically oriented spins. Regions of phase separation, as in Mn oxides, have also been detected. Comparison to previous theoretical investigations indicate that these qualitative trends may be generic characteristics of phase diagrams of multi-orbital Hubbard models.

Luo, Qinlong; Dagotto, Elbio

2014-01-01

60

Effective spin-orbital Hamiltonian for the double perovskite Sr2FeWO6: Derivation of the phase diagram  

Microsoft Academic Search

We formulate a superexchange theory of insulating double-perovskite compounds such as Sr2FeWO6. An effective spin-orbital Hamiltonian is derived in the strong-coupling limit of Hubbard model for d electrons on Fe and W ions. The relevant degrees of freedom are the spins S=2 and the threefold orbital degeneracy of Fe2+ ions. W sites are integrated out by means of a fourth-order

S. di Matteo; G. Jackeli; N. B. Perkins

2003-01-01

61

Theory of the azimuthal distribution of molecular orbital x-ray emission  

NASA Astrophysics Data System (ADS)

Full dynamical calculations, including electron slip, of molecular-orbital X-ray emission in heavy-ion-atom collisions give very small azimuthal anisotropies, in qualitative agreement with experiments.

Anholt, R.

1981-07-01

62

Orbital momentum profiles and binding energy spectra for the complete valence shell of molecular fluorine.  

National Technical Information Service (NTIS)

The first electronic structural study of the complete valence shell binding energy spectrum of molecular fluorine, encompassing both the outer and inner valence regions, is reported. These binding energy spectra as well as the individual orbital momentum ...

Y. Zheng C. E. Brion M. J. Brunger K. Zhao A. M. Grisogono

1996-01-01

63

Ab initio molecular orbital calculation considering the quantum mechanical effect of nuclei by path integral molecular dynamics  

NASA Astrophysics Data System (ADS)

We present an accurate calculational scheme for many-body systems composed of electrons and nuclei, by path integral molecular dynamics technique combined with the ab initio molecular orbital theory. Based upon the scheme, the simulation of a water molecule at room temperature is demonstrated, applying all-electron calculation at the Hartree-Fock level of theory.

Shiga, Motoyuki; Tachikawa, Masanori; Miura, Shinichi

2000-12-01

64

Effective spin-orbital Hamiltonian for the double perovskite Sr2FeWO6: Derivation of the phase diagram  

Microsoft Academic Search

We formulate a superexchange theory of insulating double-perovskite compounds\\u000asuch as Sr$_2$FeWO$_6$. An effective spin-orbital Hamiltonian is derived in the\\u000astrong coupling limit of Hubbard model for d-electrons on Fe and W ions. The\\u000arelevant degrees of freedom are the spins S=2 and the three-fold orbital\\u000adegeneracy of Fe$^{2+}$-ions. W-sites are integrated out by means of a\\u000afourth-order perturbative expansion.

S. Di Matteo; G. Jackeli; N. B. Perkins

2003-01-01

65

Linear-scaling quantum calculations using non-orthogonal localized molecular orbitals  

PubMed Central

An absolute energy minimum variational principle is used for carrying out linear scaling calculations with non-orthogonal localized orbitals. Compared with results based on orthogonal localized molecular orbitals, the method is shown to give significantly more accurate results when the localized molecular orbitals are allowed to be non-orthogonal. This is made possible by introducing a second minimization for approximating the inverse overlap matrix. We also show how an exact line search may be used efficiently with the conjugate gradient method for minimizing the energy functional.

Burger, Steven K.; Yang, Weitao

2013-01-01

66

Density functional theory, molecular dynamics, and differential scanning calorimetry study of the RbF-CsF phase diagram.  

PubMed

A multiscale modeling approach is developed to compute the phase diagram of the RbF-CsF binary system. The mixing enthalpies of the (Rb,Cs)F solid and liquid solutions are evaluated using density functional theory and classical molecular dynamics calculations, respectively. For the solid solution, 18 different configurations are studied with density functional theory and the surrounded atom model is applied in order to compute the configurational partition function. We also measure the solidus and liquidus equilibria using differential scanning calorimetry. Finally the RbF-CsF phase diagram is constructed using the calculated excess free enthalpies of the solid and liquid solutions and a very good agreement with our experimental data is found. PMID:19355773

Benes, O; Zeller, Ph; Salanne, M; Konings, R J M

2009-04-01

67

Molecular systems biology: data-flow diagram modeling of process in protein  

Microsoft Academic Search

In this paper, we introduce a new method of modeling tool for a biological process - central dogma. The data-flow diagram is used as a representation of the whole data input and output, which enables us to simulate, analyze, and manipulate (in the future) at our disposal. From DNA to protein via RNA is the one of most well-known biological

J. W. Yeol; I. Barjis; Y. S. Ryu

2005-01-01

68

Crystallization of molecular systems from solution: phase diagrams, supersaturation and other basic concepts.  

PubMed

The aim of the tutorial review is to show that any crystallization from solution is guided by stable or metastable equilibria and thus can be rationalized by using phase diagrams. Crystallization conducted by cooling, by evaporation and by anti-solvent addition is mainly considered. The driving force of crystallization is quantified and the occurrence of transient metastable states is logically explained by looking at the pathways of crystallization and the progressive segregation which might occur in a heterogeneous system. PMID:24457270

Coquerel, Gérard

2014-04-01

69

Molecular dynamics of spin crossover: The (P, T) phase diagram of [Fe(PM-BIA)2(NCS)2  

NASA Astrophysics Data System (ADS)

The spin crossover properties and the domains of existence of the different phases for the [Fe(PM-BIA)2(NCS)2] complex are obtained from combining DFT and classical molecular dynamics (MD). The potential energy surfaces expressed in the Morse form for Fe-N interactions are deduced from molecular DFT calculations and they allow producing Infra Red and Raman frequencies. These Fe-N potentials inserted in a classical force field lead from MD calculations to the relative energies of the high spin and low spin configurations of the orthorhombic structure. The MD investigations have also allowed assessing the experimental (P, T) phase diagram by showing the monoclinic polymorph in its two spin-states, and generating two triple points.

Marbeuf, A.; Matar, S. F.; Négrier, P.; Kabalan, L.; Létard, J. F.; Guionneau, P.

2013-07-01

70

Electronic mapping of molecular orbitals at the molecule-metal interface.  

PubMed

The molecule-metal interface formed by pyridine-2,5-dicarboxylic acid chemically bonded to the Cu(110) surface is investigated by scanning tunneling microscopy and first-principles calculations. Our current-voltage spectroscopy studies reveal an electronic mapping of molecular orbitals as a function of tip position. By combining experimental and theoretical investigations, individual molecular orbitals are characterized by their energy and spatial distribution. The importance of adsorption geometries and conformational changes on the electron transport properties is highlighted. PMID:20867996

Lennartz, M C; Caciuc, V; Atodiresei, N; Karthäuser, S; Blügel, S

2010-08-01

71

Molecular dynamics study of network statistics in lithium disilicate: Qn distribution and the pressure-volume diagram  

NASA Astrophysics Data System (ADS)

Molecular dynamics simulations have been performed to study the structures along the pressure-volume diagram of network-glasses and melts exemplified by the lithium disilicate system. Experimentally, densification of the disilicate glass by elevated pressure is known and this feature is reasonably reproduced by the simulations. During the process of densification or decompression of the system, the statistics of Qn (i.e., SiO4 tetrahedron unit with n bridging oxygen linked to the silicon atom where n = 0, 1, 2, 3, or 4) change, and the percentage of the Q3 structures show the maximum value near atmospheric pressure at around Tg. Changes of Qn distribution are driven by the changes of volume (or pressure) and are explained by the different volumes of structural units. Furthermore, some pairs of network structures with equi-volume, but having different distributions of Qn (or different heterogeneity), are found. Therefore, for molecular dynamics simulations of the Qn distributions, it is important to take into account the complex phase behavior including poly-structures with different heterogeneities as well as the position of the system in the P-V-T diagram.

Habasaki, J.; Ngai, K. L.

2013-08-01

72

Dispersion energy evaluated by using locally projected occupied and excited molecular orbitals for molecular interaction  

NASA Astrophysics Data System (ADS)

The dispersion terms are evaluated with the perturbation theory based on the locally projected molecular orbitals. A series of model systems, including some of the S22 set, is examined, and the calculated binding energies are compared with the published results. The basis set dependence is also examined. The dispersion energy correction is evaluated by taking into account the double excitations only of the dispersion type electron configurations and is added to the 3rd order single excitation perturbation energy, which is a good approximation to the counterpoise (CP) corrected Hartree-Fock (HF) binding energy. The procedure is the approximate ``CP corrected HF + D'' method. It ensures that the evaluated binding energy is approximately free of the basis set superposition error without the CP procedure. If the augmented basis functions are used, the evaluated binding energies for the predominantly dispersion-bound systems, such as rare gas dimers and halogen bonded clusters, agree with those of the reference calculations within 1 kcal mol-1 (4 kJ mol-1). The limitation of the present method is also discussed.

Iwata, Suehiro

2011-09-01

73

Molecular orbital ordering in titania and the associated semiconducting behavior  

SciTech Connect

RF-sputtered TiO{sub x} layers were thermally treated and the associated thin-film transistor properties were studied. X-ray diffraction and x-ray absorption spectroscopy analyses indicate that as-grown amorphous TiO{sub x} films crystallize to anatase at temperatures above 450 deg. C in air. Thin-film transistors incorporating anatase active layers exhibit n-type behavior, with field effect mobility values near 0.11 cm{sup 2}/Vs when annealed at 550 deg. C. Such a phenomenon is suggested to originate from the ordering of Ti 3d orbitals upon crystallization, and the mobility enhancement at higher annealing temperatures may be attributed to the reduced grain boundary scattering of carriers by virtue of enlarged average grain size.

Park, Joseph; Ok, Kyung-Chul; Park, Jin-Seong [Department of Materials Science and Engineering, Dankook University, Mt. 29, Anseo-Dong, Cheonan 330-714 (Korea, Republic of); Du Ahn, Byung; Hun Lee, Je; Park, Jae-Woo [Samsung Electronics, Giheung-Gu, Yongin-Si, Gyeonggi-Do 446-711 (Korea, Republic of); Chung, Kwun-Bum [Department of Physics, Dankook University, Mt. 29, Anseo-Dong, Cheonan 330-714 (Korea, Republic of)

2011-10-03

74

Phosphate Bonding Configuration on Ferrihydrite Based on Molecular Orbital Calculations and XANES Fingerprinting  

SciTech Connect

Sorption of phosphate by Fe(III)- and Al(III)-(hydr)oxide minerals regulates the mobility of this potential water pollutant in the environment. The objective of this research was to determine the molecular configuration of phosphate bound on ferrihydrite at pH 6 by interpreting P K-edge XANES spectra in terms of bonding mode. XANES and UV-visible absorption spectra for aqueous Fe(III)-PO4 solutions (Fe/P molar ratio = 0-2.0) provided experimental trends for energies of P(3p)-O(2p) and Fe(3d)-O(2p) antibonding molecular orbitals. Molecular orbitals for Fe(III)-PO4 or Al(III)-PO4 complexes in idealized monodentate or bidentate bonding mode were generated by conceptual bonding arguments, and Extended-Hueckel molecular orbital computations were used to understand and assign XANES spectral features to bound electronic states. The strong white line at the absorption edge in P K-edge XANES spectra for Fe-PO4 or Al-PO4 systems is attributable to an electronic transition from a P 1s atomic orbital into P(3p)-O(2p) or P(3p)-O(2p)-Al(3p) antibonding molecular orbitals, respectively. For Fe-PO4 systems, a XANES peak at 2-5 eV below the edge was assigned to a P 1s electron transition into Fe(4p)-O(2p) antibonding molecular orbitals. Similarly, a shoulder on the low-energy side of the white line for variscite corresponds to a transition into Al(3p)-O(2p) orbitals. In monodentate-bonded phosphate, Fe-O bonding is optimized and P-O bonding is weakened, and the converse is true of bidentate-bonded phosphate. These differences explained an inverse correlation between energies of P(3p)-O(2p) and Fe(3d)-O(2p) antibonding molecular orbitals consistent with a monodentate-to-bidentate transition in aqueous Fe(III)-PO4 solutions. The intensity of the XANES pre-edge feature in Fe(III)-bonded systems increased with increasing number of Fe(III)-O-P bonds. Based on the similarity of intensity and splitting of the pre-edge feature for phosphate sorbed on ferrihydrite at 750 mmol/kg at pH 6 and aqueous Fe-PO4 solutions containing predominantly bidentate complexes, XANES results indicated that phosphate adsorbed on ferrihydrite was predominantly a bidentate-binuclear surface complex.

Khare,N.; Martin, J.; Hesterberg, D.

2007-01-01

75

Molecular dynamics determination of the time–temperature–transformation diagram for crystallization of an undercooled liquid Ni 50Al 50 alloy  

Microsoft Academic Search

Molecular dynamics simulations with an embedded-atom method potential are used for the first time to determine the time–temperature–transformation diagram for crystallization of stoichiometric intermetallic NiAl. This diagram shows a typical nose-like shape. It is found that the shortest time, about 1ns, needed for the beginning of the crystallization process of the undercooled liquid Ni50Al50 alloy is at a temperature about

Elena V. Levchenko; Alexander V. Evteev; Irina V. Belova; Graeme E. Murch

2011-01-01

76

Pyrite oxidation and reduction - Molecular orbital theory considerations. [for geochemical redox processes  

NASA Technical Reports Server (NTRS)

In this paper, molecular orbital theory is used to explain a heterogeneous reaction mechanism for both pyrite oxidation and reduction. The mechanism demonstrates that the oxidation of FeS2 by Fe(3+) may occur as a result of three important criteria: (1) the presence of a suitable oxidant having a vacant orbital (in case of liquid phase) or site (solid phase) to bind to the FeS2 via sulfur; (2) the initial formation of a persulfido (disulfide) bridge between FeS2 and the oxidant, and (3) an electron transfer from a pi(asterisk) orbital in S2(2-) to a pi or pi(asterisk) orbital of the oxidant.

Luther, George W., III

1987-01-01

77

High resolution NEXAFS of perylene and PTCDI: a surface science approach to molecular orbital analysis.  

PubMed

We made use of synchrotron radiation to perform near edge X-ray absorption fine structure spectroscopy, NEXAFS, at the carbon K-edge of perylene and perylene-tetracarboxylic-diimide, PTCDI. Reference spectra measured for isolated molecules in the gas phase are compared with polarization dependent NEXAFS spectra measured on highly oriented thin films in order to study the symmetry of the molecular orbitals. The molecular overlayers are grown onto the rutile TiO2(110) surface for which the large anisotropic corrugation effectively drives the molecular orientation, while its dielectric nature prevents the rehybridization of the molecular orbitals. We employed density functional theory, DFT, calculations to disentangle the contribution of specific carbon atoms to the molecular density of states. Numerical simulations correctly predict the observed NEXAFS azimuthal dichroism of the ?* resonances above the ionization threshold, from which we determine the full geometric orientation of the overlayer molecules. A discrepancy observed for the spectral contribution of the imide carbon atom to the calculated unoccupied molecular orbitals has been explained in terms of initial state effects, as determined by Hartree-Fock corrections and in full agreement with the corresponding shift of the C 1s core level measured by X-ray photoelectron spectroscopy, XPS. PMID:24924641

Fratesi, Guido; Lanzilotto, Valeria; Stranges, Stefano; Alagia, Michele; Brivio, Gian Paolo; Floreano, Luca

2014-06-25

78

Observation of peaked 2p ? molecular-orbital X-ray spectra  

NASA Astrophysics Data System (ADS)

Measured continuum X-ray spectra in 5 to 56 MeV Br + V collisions are compared with theoretical calculations of 2p ? molecular-orbital X-rays. Peaks are seen at low projectile energies, whose intensities are in good agreement with theory.

Stöckli, M. P.; Anholt, R.

1984-11-01

79

An extension of ab initio molecular orbital theory to nuclear motion  

Microsoft Academic Search

We propose an extension of the quantum chemical molecular orbital (MO) method to describe the nuclear motion. Both electronic and nuclear wavefunctions are simultaneously solved with the full variational MO method, by which exponents and centers of gaussian-type function (GTF) basis sets are optimized as well as the linear combination of GTF coefficients. Applications of the method to [F?;e+], FH

Masanori Tachikawa; Kazuhide Mori; Hiromi Nakai; Kaoru Iguchi

1998-01-01

80

Comparison of Two Statistical Approaches to Calculate Atomic and Molecular Orbitals.  

National Technical Information Service (NTIS)

The Xalpha method for the calculation of atomic and molecular orbitals is compared to a method employing ensemble averages. The formal theory as well as calculated results are discussed and the choice of alpha parameter values for the local exchange appro...

P. Jorgensen Y. Ohrn

1973-01-01

81

Spin and molecular electronics in atomically generated orbital landscapes  

NASA Astrophysics Data System (ADS)

Ab initio computational methods for electronic transport in nanoscaled systems are an invaluable tool for the design of quantum devices. We have developed a flexible and efficient algorithm for evaluating I-V characteristics of atomic junctions, which integrates the nonequilibrium Green’s function method with density functional theory. This is currently implemented in the package SMEAGOL. The heart of SMEAGOL is our scheme for constructing the surface Green’s functions describing the current-voltage probes. It consists of a direct summation of both open and closed scattering channels together with a regularization procedure of the Hamiltonian and provides great improvements over standard recursive methods. In particular it allows us to tackle material systems with complicated electronic structures, such as magnetic transition metals. Here we present a detailed description of SMEAGOL together with an extensive range of applications relevant for the two burgeoning fields of spin and molecular electronics.

Rocha, A. R.; García-Suárez, V. M.; Bailey, S.; Lambert, C.; Ferrer, J.; Sanvito, S.

2006-02-01

82

Stereo Diagrams  

NSDL National Science Digital Library

This exercise is an introduction to stereo diagrams. Students draw stereo diagrams for various models, determine the point group and crystal system of certain crystal shapes, and determine which block models match given stereo diagrams.

Perkins, Dexter

83

Extending electron orbital precession to the molecular case: Use of orbital alignment for observation of wavepacket dynamics  

NASA Astrophysics Data System (ADS)

The complexity of ultrafast molecular photoionization presents an obstacle to the modeling of pump-probe experiments. Here, a simple optimized model of atomic rubidium is combined with a molecular dynamics model to predict quantitatively the results of a pump-probe experiment in which long-range rubidium dimers are first excited, then ionized after a variable delay. The method is illustrated by the outline of two proposed feasible experiments and the calculation of their outcomes. Both of these proposals use Feshbach Rb872 molecules. We show that long-range molecular pump-probe experiments should observe spin-orbit precession given a suitable pump pulse, and that the associated high-frequency beat signal in the ionization probability decays after a few tens of picoseconds. If the molecule was to be excited to only a single fine-structure state, then a low-frequency oscillation in the internuclear separation would be detectable through the time-dependent ionization cross section, giving a mechanism that would enable observation of coherent vibrational motion in this molecule.

Martay, Hugo E. L.; England, Duncan G.; McCabe, David J.; Walmsley, Ian A.

2011-04-01

84

Measurement of Thermopower and Current-Voltage Characteristics of Molecular Junctions to Identify Orbital Alignment  

SciTech Connect

We report an experimental technique that concurrently measures the Seebeck coefficient and the current-voltage (I-V) characteristics of a molecular junction to determine the identity and the effective energetic separation of the molecular orbital closest to the electrodes’ Fermi level. Junctions created by contacting a gold-coated atomic force microscope tip with a monolayer of molecules assembled on a gold substrate were found to have a Seebeck coefficient of (+16.9±1.4) ?V/K. This positive value unambiguously shows that the highest occupied molecular orbital (HOMO) dominates charge transport. Further, by analyzing the (I-V) characteristics, the HOMO level is estimated to be ? 0.69?eV with respect to the Fermi level.

Tan, Aaron; Sadat, Seid; Reddy, Pramod

2010-01-01

85

MOLE: a Voronoi diagram-based explorer of molecular channels, pores, and tunnels.  

PubMed

We have developed an algorithm, "MOLE," for the rapid, fully automated location and characterization of molecular channels, tunnels, and pores. This algorithm has been made freely available on the Internet (http://mole.chemi.muni.cz/) and overcomes many of the shortcomings and limitations of the recently developed CAVER software. The core of our MOLE algorithm is a Dijkstra's path search algorithm, which is applied to a Voronoi mesh. Tests on a wide variety of biomolecular systems including gramicidine, acetylcholinesterase, cytochromes P450, potassium channels, DNA quadruplexes, ribozymes, and the large ribosomal subunit have demonstrated that the MOLE algorithm performs well. MOLE is thus a powerful tool for exploring large molecular channels, complex networks of channels, and molecular dynamics trajectories in which analysis of a large number of snapshots is required. PMID:17997961

Petrek, Martin; Kosinová, Pavlína; Koca, Jaroslav; Otyepka, Michal

2007-11-01

86

Eutectics and Phase Diagrams of Molten Salts from Molecular Dynamics simulations  

NASA Astrophysics Data System (ADS)

The use of alkali nitrate salt mixtures as heat transfer fluids in solar thermal power plants is limited by their relatively high melting point. Certain compositions of quaternary and higher dimensional mixtures of alkali and alkaline earth nitrates and nitrites have low melting points. However, the high dimensionality of the search space makes it difficult to find lowest melting compositions. Molecular simulations offer an efficient way to screen for promising mixtures. A molecular dynamics scheme general enough to identify eutectics of any HTF candidate mixture will be presented. The eutectic mixture and temperature are located as the tangent point between free energies of mixing for the liquid and a linear plane connecting the pure solid-liquid free energy differences. The free energy of mixing of the liquid phase is obtained using thermodynamic integration over "alchemical" transmutations sampled with molecular dynamics, in which particle identities are swapped gradually. Numerical results for binary and ternary mixtures of alkali nitrates agree well with experimental measurements.

Jayaraman, Saivenkataraman; von Lilienfeld, Anatole; Thompson, Aidan

2011-03-01

87

Molecular orbital propagation to accelerate self-consistent-field convergence in an ab initio molecular dynamics simulation.  

PubMed

Based on the idea of molecular orbital (MO) propagation, we propose a novel effective method for predicting initial guesses for the self-consistent-field calculations in direct ab initio molecular dynamics (AIMD) simulations. This method, called LIMO, adopts the Lagrange interpolation (LI) polynomial technique and predicts initial MO coefficients at the next AIMD step by using several previous results. Taking into account the crossing and/or mixing of MOs leads to orbital invariant formulas for the LIMO method. We also propose a simple method for determining the optimal degree of the LI polynomial, which corresponds to the number of previous steps. Numerical tests confirm that this proposed method is both effective and feasible. PMID:18331081

Atsumi, Teruo; Nakai, Hiromi

2008-03-01

88

Accurate description of phase diagram of clathrate hydrates at the molecular level  

NASA Astrophysics Data System (ADS)

In order to accurately estimate the thermodynamic properties of hydrogen clathrate hydrates, we developed a method based on the solid solution theory of van der Waals and Platteeuw. This model allows one to take into account the influence of guest molecules on the host lattice and guest-guest interactions-especially when more than one guest molecule occupies a cage. The free energies, equations of state, and chemical potentials of hydrogen and mixed propane-hydrogen clathrate hydrates of cubic structure II with different cage fillings have been estimated using this approach. Moreover, the proposed theory has been used for construction p-T phase diagrams of hydrogen hydrate and mixed hydrogen-propane hydrates in a wide range of pressures and temperatures. For the systems with well defined interactions the calculated curves of ``guest gas-hydrate-ice Ih'' equilibrium agree with the available experimental data. We also believe that the present model allows one not only to calculate the hydrogen storage ability of known hydrogen hydrate but also predict this value for structures that have not yet been realized by experiment.

Belosudov, Rodion V.; Subbotin, Oleg S.; Mizuseki, Hiroshi; Kawazoe, Yoshiyuki; Belosludov, Vladimir R.

2009-12-01

89

Effect of vacuum processing on outgassing within an orbiting molecular shield  

NASA Technical Reports Server (NTRS)

The limiting hydrogen number density in an orbiting molecular shield is highly dependent on the outgassing rates from the materials of construction for the shield, experimental apparatus, and other hardware contained within the shield. Ordinary degassing temperatures used for ultrahigh vacuum studies (less than 450 C) are not sufficient to process metals so that the contribution to the number density within the shield due to outgassing is less than the theoretically attainable level (approximately 200 per cu. cm). Pure aluminum and type 347 stainless steel were studied as candidate shield materials. Measurements of their hydrogen concentration and diffusion coefficients were made, and the effects of high temperature vacuum processing (greater than 600 C) on their resulting outgassing rates was determined. The densities in a molecular shield due to the outgassing from either metal were substantially less ( 0.003) than the density due to the ambient atomic hydrogen flux at an orbital altitude of 500 km.

Outlaw, R. A.

1982-01-01

90

Direct calculation of equilibrium constants for isotopic exchange reactions by ab initio molecular orbital theory  

SciTech Connect

The ability of simple levels of ab initio molecular orbital theory to describe with reasonable accuracy the energetics of isotopic exchange processes is demonstrated. Three levels of ab initio molecular orbital theory have been surveyed. The first two levels are single-determinant Hartree-Foch methods utilizing the 3-21G split-valence and 6-31G* polarization basis sets. The third level, which is computationally the most complex, uses the 6-31G* basis set but allows for partial account of electron correlation by way of Moller-Plesset perturbation theory terminated at second order. Theoretical and spectroscopic equilibrium constants for reactions XH + XD reversible XD + H/sub 2/ where XD is a hydride of the first row of the periodic table are tabulated. (BLM)

Hout, R.F. Jr.; Wolfsberg, M.; Hehre, W.J.

1980-04-23

91

Spin-orbital entangled molecular jeff states in lacunar spinel compounds.  

PubMed

The entanglement of the spin and orbital degrees of freedom through the spin-orbit coupling has been actively studied in condensed matter physics. In several iridium oxide systems, the spin-orbital entangled state, identified by the effective angular momentum jeff, can host novel quantum phases. Here we show that a series of lacunar spinel compounds, GaM4X8 (M=Nb, Mo, Ta and W and X=S, Se and Te), gives rise to a molecular jeff state as a new spin-orbital composite on which the low-energy effective Hamiltonian is based. A wide range of electron correlations is accessible by tuning the bandwidth under external and/or chemical pressure, enabling us to investigate the cooperation between spin-orbit coupling and electron correlations. As illustrative examples, a two-dimensional topological insulating phase and an anisotropic spin Hamiltonian are investigated in the weak and strong coupling regimes, respectively. Our finding can provide an ideal platform for exploring jeff physics and the resulting emergent phenomena. PMID:24889209

Kim, Heung-Sik; Im, Jino; Han, Myung Joon; Jin, Hosub

2014-01-01

92

Density Functional Molecular Orbital Calculations on Longer DNA–DNA and PNA–DNA Double Strands  

Microsoft Academic Search

Summary. Stable structures and electronic properties of hybridized DNA–DNA and PNA–DNA double strands with common base sequences were theoretically investigated by molecular orbital calculations based on the density functional theory. The computed hybridization energy in PNA–DNA is greater than that in the DNA– DNA double strand. The origin of the larger stability of PNA–DNA double strand is ascribed to the

Takayuki Natsume; Yasuyuki Ishikawa; Kenichi Dedachi; Noriyuki Kurita

93

Use of an auxiliary basis set to describe the polarization in the fragment molecular orbital method  

NASA Astrophysics Data System (ADS)

We developed a dual basis approach within the fragment molecular orbital formalism enabling efficient and accurate use of large basis sets. The method was tested on water clusters and polypeptides and applied to perform geometry optimization of chignolin (PDB: 1UAO) in solution at the level of DFT/6-31++G??, obtaining a structure in agreement with experiment (RMSD of 0.4526 Å). The polarization in polypeptides is discussed with a comparison of the ?-helix and ?-strand.

Fedorov, Dmitri G.; Kitaura, Kazuo

2014-03-01

94

Molecular orbital study on antiferromagnetic coupling mechanism in a silver (I) complex  

Microsoft Academic Search

The mechanism of antiferromagnetic coupling in an Ag (I) complex of nitronyl nitroxide is investigated by means of the broken-symmetry approach within the density functional method (DFT-BS). The magneto-structural corre- lation and the single-occupied molecular orbital (SOMO) analysis reveal the existence of the antiferromagnetic cou- pling pathway along nitronyl nitroxide units via Ag (I) ion, and that the Ag (I)

Guiqin ZHANG; HUANG Jiangen; HUANG Yuanhe; FANG Decai; ZHANG Deqing

2005-01-01

95

Spin-orbit interactionsand magnetic field in antiferromagnetic triangular molecular magnets  

Microsoft Academic Search

Frustrated triangular molecular magnets such as Cu3 are characterized by a doubly generate S=1\\/2 ground-state (GS) with opposite chirality. Recently it has been proposed theoretically [1] and verified by ab-initio calculations [2] that an external electric field can efficiently couple these two chiral spin states, even in the absence of spin-orbit interaction (SOI). SOIs are nevertheless important, since they introduce

J. F. Nossa; M. F. Islam; C. M. Canali; M. R. Pederson

2011-01-01

96

Calculations of molecular-orbital — separated-atom x-ray coincidences  

NASA Astrophysics Data System (ADS)

The calculated cross section for the production of 1 s? molecular orbital (MO) x-rays in coincidence with projectile and target K x-rays is a factor of 0.2 to 0.3 smaller than the non-coincident cross section. The K-coincident MO x-rays are emitted with a much larger anisotropy than the non-coincident MO x-rays.

Anholt, R.

1983-09-01

97

Nonempirical molecular orbital study of the siting and pairing of aluminum in ferrierite  

SciTech Connect

Ab initio molecular orbital calculations were performed on model clusters with a geometry derived from the known structure of ferrierite. The data show that siting and pairing of aluminum probably take place preferentially in the six-membered rings. As observed earlier for mordenite and zeolite ZSM-5, charge distribution analyses indicate the highly covalent nature of the zeolitic framework and its behavior as a weak but soft (anionic) base. 26 references, 10 figures, 8 tables.

Fripiat, J.G.; Galet, P.; Delhalle, J.; Andre, J.M.; Nagy, J.B.; Derouane, E.G.

1985-05-09

98

Electron correlation effects on the shape of the Kohn–Sham molecular orbital  

Microsoft Academic Search

.   Even systems in which strong electron correlation effects are present, such as the large near-degeneracy correlation in a\\u000a dissociating electron pair bond exemplified by stretched H2, are represented in the Kohn–Sham (KS) model of non-interacting electrons by a determinantal wavefunction built from the\\u000a KS molecular orbitals. As a contribution to the discussion on the status and meaning of the

Oleg V. Gritsenko; Evert Jan Baerends

1997-01-01

99

Ab initio molecular orbital calculations on the associated complexes of lithium cyanide with ammonia  

Microsoft Academic Search

Ab initio molecular orbital (MO) calculations with the 3-21G and 6-31G basis sets are carried out on a series of complexes of NHâ with Li{sup +}, C{triple_bond}N⁻, LiCN, and its isomer LiNC. The BSSE-corrected interaction energies, geometrical parameters, internal force constants, and harmonic vibrational frequencies are evaluated for 15 species. Complexes with trifurcated (C{sub 3v}) structures are calculated to be

P. Mohandas; M. C. Shivaglal; J. Chandrasekhar; Surjit Singh

1995-01-01

100

Molecular orbital view of the electronic coupling between two metal nanoparticles  

SciTech Connect

The electronic coupling between metal nanoparticles is responsible for intriguing new phenomena observed when the particles are near touching contact, which is exemplified by recent investigations of nanoparticle dimers. However, little is known about the role of the molecular orbitals of the nanoparticle dimers. The expectation is that the physics and chemistry of the system must be reflected in the orbitals that control the bonding at touching contact. This expectation is borne out in the present investigation in which we present a comprehensive theoretical study based on density-functional theory of the electronic coupling between two silver nanoparticles. We explain our findings by studying the molecular orbitals of the dimers as a function of the separation and relative orientation between the nanoparticles. We show that as the nanoparticles approach each other a bond-forming step takes place, and that the strength of the hybridization is a key element to determine various properties of the system. We find that the relative orientation between the nanoparticles plays an important role in determining the strength of the coupling which can be visualized by the spatial distribution of the highest occupied molecular orbitals. Moreover, the strength of the coupling will in turn determine the ease of their transition to the nonlinear dielectric-response regime. This effect allows for the tunability of the electronic coupling and magnetic moment of the dimer. Our findings are essential for understanding and tailoring desired physical and chemical properties of closely aggregated nanoparticles relevant for applications such as surface-enhanced Raman scattering and quantum transport in molecular devices.

Troparevsky, Claudia [University of Tennessee, Knoxville (UTK); Zhao, Ke [University of Tennessee, Knoxville (UTK); Xiao, Di [ORNL; Eguiluz, Adolfo G [ORNL; Zhang, Zhenyu [ORNL

2010-01-01

101

Spectral studies and molecular orbital PPP-calculations of some azo-dyes  

NASA Astrophysics Data System (ADS)

The UV, IR and 1H-NMR spectra of some 4-( R-phenyl azo) 1-hydroxy 2-naphthoic acid derivatives are studied. The effects of substituent groups and the solvent polarity on electronic spectral, IR bands and 1H-NMR proton chemical shifts are considered, the molecular orbital calculations obtained are rationalized quantitatively with that obtained practically using the PPP-model with configuration interaction (CI).

Shalabi, A. S.; Dessouki, H. A.; Issa, Y. M.; Ahmed, I. S.

2002-10-01

102

Ab initio derivation of multi-orbital extended Hubbard model for molecular crystals.  

PubMed

From configuration interaction (CI) ab initio calculations, we derive an effective two-orbital extended Hubbard model based on the gerade (g) and ungerade (u) molecular orbitals (MOs) of the charge-transfer molecular conductor (TTM-TTP)I(3) and the single-component molecular conductor [Au(tmdt)(2)]. First, by focusing on the isolated molecule, we determine the parameters for the model Hamiltonian so as to reproduce the CI Hamiltonian matrix. Next, we extend the analysis to two neighboring molecule pairs in the crystal and we perform similar calculations to evaluate the inter-molecular interactions. From the resulting tight-binding parameters, we analyze the band structure to confirm that two bands overlap and mix in together, supporting the multi-band feature. Furthermore, using a fragment decomposition, we derive the effective model based on the fragment MOs and show that the staking TTM-TTP molecules can be described by the zig-zag two-leg ladder with the inter-molecular transfer integral being larger than the intra-fragment transfer integral within the molecule. The inter-site interactions between the fragments follow a Coulomb law, supporting the fragment decomposition strategy. PMID:22299903

Tsuchiizu, Masahisa; Omori, Yukiko; Suzumura, Yoshikazu; Bonnet, Marie-Laure; Robert, Vincent

2012-01-28

103

Terazulene: a high-performance n-type organic field-effect transistor based on molecular orbital distribution control.  

PubMed

We present herein a linear expanded ?-conjugation system comprising azulene units: 2,6':2',6?-terazulene. This simple hydrocarbon exhibits excellent n-type transistor performance with an electron mobility of up to 0.29 cm(2) V(-1) s(-1). The lowest unoccupied molecular orbital (LUMO) is well distributed over the entire molecule, whereas the highest occupied molecular orbital (HOMO) is localized at one end. These findings indicate a disadvantage of hole carrier transport and an advantage of n-type-specific transport behavior. This system presents an unconventional concept: polarity control of OFET by molecular orbital distribution control. PMID:24328146

Yamaguchi, Yuji; Ogawa, Keisuke; Nakayama, Ken-Ichi; Ohba, Yoshihiro; Katagiri, Hiroshi

2013-12-26

104

``On the fly'' localization of electronic orbitals in Car-Parrinello molecular dynamics: Toward a linear scaling ab initio molecular dynamics algorithm  

Microsoft Academic Search

begincenter Large ``On the fly'' localization of electronic orbitals in Car-Parrinello molecular dynamics: Toward a linear scaling ab initio molecular dynamics algorithm center begincenter Mark E. Tuckerman Department of Chemistry and Courant Institute of Mathematical Sciences New York University, New York, NY 10003 center Ab initio molecular dynamics (AIMD), the technique that generates finite temperature dynamics using forces obtained from

Mark Tuckerman

2004-01-01

105

Analytical evaluation of molecular electronic integrals using Poisson's equation: Exponential-type orbitals and atom pairs  

NASA Astrophysics Data System (ADS)

The integral bottleneck in evaluating molecular energies arises from the two-electron contributions. These are difficult and time-consuming to evaluate, especially over exponential type orbitals, used here to ensure the correct behavior of atomic orbitals. The two-center two-electron integrals are essential to describe atom pairs in molecules and distinguish those that are bound. In this work on analytical integration, it is shown that the two-center Coulomb integrals involved can be expressed as one-electron kinetic energy-like integrals. This is accomplished using the fact that the Coulomb operator is a Green's function of the Laplacian. The ensuing integrals may be further simplified by defining spectral forms for the one-electron potential satisfying Poisson's equation therein. A sum of overlap integrals with the atomic orbital energy eigenvalue as a factor is then obtained to give the Coulomb energy. This is most easily evaluated by direct integration. The orbitals involved in three and four center integrals are translated to two centers. This is discussed very briefly. The evaluation of exchange energy is a straightforward extension of this work. The summation coefficients in spectral forms are evaluated analytically from Gaunt coefficients. The Poisson method may be used to calculate Coulomb energy integrals efficiently. For a single processor, gains of CPU time for a given chemical accuracy exceed a factor of 4. This method lends itself to efficient evaluation on a parallel computer.

Absi, Noureddine; Hoggan, Philip

106

Molecular-orbital-free algorithm for excited states in time-dependent perturbation theory  

NASA Astrophysics Data System (ADS)

A nonlinear conjugate gradient optimization scheme is used to obtain excitation energies within the random phase approximation (RPA). The solutions to the RPA eigenvalue equation are located through a variational characterization using a modified Thouless functional, which is based upon an asymmetric Rayleigh quotient, in an orthogonalized atomic orbital representation. In this way, the computational bottleneck of calculating molecular orbitals is avoided. The variational space is reduced to the physically-relevant transitions by projections. The feasibility of an RPA implementation scaling linearly with system size N is investigated by monitoring convergence behavior with respect to the quality of initial guess and sensitivity to noise under thresholding, both for well- and ill-conditioned problems. The molecular-orbital-free algorithm is found to be robust and computationally efficient, providing a first step toward large-scale, reduced complexity calculations of time-dependent optical properties and linear response. The algorithm is extensible to other forms of time-dependent perturbation theory including, but not limited to, time-dependent density functional theory.

Lucero, Melissa J.; Niklasson, Anders M. N.; Tretiak, Sergei; Challacombe, Matt

2008-08-01

107

Molecular-orbital-free algorithm for excited states in time-dependent perturbation theory.  

PubMed

A nonlinear conjugate gradient optimization scheme is used to obtain excitation energies within the random phase approximation (RPA). The solutions to the RPA eigenvalue equation are located through a variational characterization using a modified Thouless functional, which is based upon an asymmetric Rayleigh quotient, in an orthogonalized atomic orbital representation. In this way, the computational bottleneck of calculating molecular orbitals is avoided. The variational space is reduced to the physically-relevant transitions by projections. The feasibility of an RPA implementation scaling linearly with system size N is investigated by monitoring convergence behavior with respect to the quality of initial guess and sensitivity to noise under thresholding, both for well- and ill-conditioned problems. The molecular-orbital-free algorithm is found to be robust and computationally efficient, providing a first step toward large-scale, reduced complexity calculations of time-dependent optical properties and linear response. The algorithm is extensible to other forms of time-dependent perturbation theory including, but not limited to, time-dependent density functional theory. PMID:18715058

Lucero, Melissa J; Niklasson, Anders M N; Tretiak, Sergei; Challacombe, Matt

2008-08-14

108

Determination of outer molecular orbitals by collisional ionization experiments and comparison with Hartree-Fock, Kohn-Sham, and Dyson orbitals  

Microsoft Academic Search

Although the outer shapes of molecular orbitals (MO's) are of great importance in many phenomena, they have been difficult to be probed by experiments. Here we show that metastable helium (He{sup *}) atoms can sensitively probe the outer properties of molecules and that an electron spectroscopic technique using velocity-selected He{sup *} atoms in combination with classical trajectory simulations leads to

Masakazu Yamazaki; Takuya Horio; Naoki Kishimoto; Koichi Ohno

2007-01-01

109

Determination of outer molecular orbitals by collisional ionization experiments and comparison with Hartree-Fock, Kohn-Sham, and Dyson orbitals  

Microsoft Academic Search

Although the outer shapes of molecular orbitals (MO's) are of great importance in many phenomena, they have been difficult to be probed by experiments. Here we show that metastable helium (He*) atoms can sensitively probe the outer properties of molecules and that an electron spectroscopic technique using velocity-selected He* atoms in combination with classical trajectory simulations leads to a consistent

Masakazu Yamazaki; Takuya Horio; Naoki Kishimoto; Koichi Ohno

2007-01-01

110

Alternative Sturmian bases and momentum space orbitals: an application to the hydrogen molecular ion  

NASA Astrophysics Data System (ADS)

The relationship between alternative separable solutions of the Coulomb problem both in configuration and in momentum space is exploited in order to obtain Sturmian orbitals of use as expansion basis sets in atomic and molecular problems. The usual spherical basis is obtained by separation in polar coordinates. The mathematical properties are explored for a type of basis set for quantum mechanical problems with axial symmetry, examples being diatomic molecules, or atoms under the influence of a uniform electric field. Because of its appropriateness for treatment of the Stark effect in atomic physics, this alternative basis set is called Stark basis. The Stark basis corresponds to separation in parabolic coordinates in configuration space and in cylindrical coordinates in momentum space. Fock's projection onto the surface of a sphere in the four dimensional hyperspace allows us to establish the connections of the momentum space wave functions with hyperspherical harmonics. As an application, the Shobuya and Wulfman analysis of momentum space molecular orbitals is reformulated and monoelectronic multicenter integrals are calculated by angular momentum algebra. Properties of the Stark basis, which exhibits less coupling at long range, are illustrated with reference to the case of the hydrogen molecular ion in the fixed nuclei approximation.

Aquilanti, Vincenzo; Cavalli, Simonetta; Coletti, Cecilia; Grossi, Gaia

1996-09-01

111

DETECTION OF A MOLECULAR DISK ORBITING THE NEARBY, 'OLD', CLASSICAL T TAURI STAR MP MUSCAE  

SciTech Connect

We have used the Atacama Pathfinder Experiment 12 m telescope to detect circumstellar CO emission from MP Muscae (MP Mus; K1 IVe), a nearby (D {approx} 100 pc), actively accreting, {approx}7 Myr old pre-main-sequence (pre-MS) star. The CO emission line profile measured for MP Mus is indicative of an orbiting disk with radius {approx}120 AU, assuming that the central star mass is 1.2 M {sub sun} and the disk inclination is i {approx} 30{sup 0}. The inferred disk molecular gas mass is {approx}3 M {sub +}. MP Mus thereby joins TW Hya and V4046 Sgr as the only late-type (low-mass), pre-MS star systems within {approx}100 pc of Earth that are known to retain orbiting, molecular disks. We also report the nondetection (with the Institut de Radio Astronomie Millimetrique 30 m telescope) of CO emission from another 10 nearby (D {approx_lt} 100 pc), dusty, young (age {approx}10-100 Myr) field stars of spectral type A-G. We discuss the implications of these results for the timescales for stellar and Jovian planet accretion from, and dissipation of, molecular disks around young stars.

Kastner, Joel H.; Sacco, G. G. [Center for Imaging Science, Rochester Institute of Technology, 54 Lomb Memorial Drive, Rochester, NY 14623 (United States); Hily-Blant, Pierry; Forveille, Thierry [Laboratoire d'Astrophysique de Grenoble, Universite Joseph Fourier-CNRS, BP 53, 38041 Grenoble Cedex (France); Zuckerman, B., E-mail: jhk@cis.rit.ed [Department of Physics and Astronomy, University of California, Los Angeles 90095, CA (United States)

2010-11-10

112

Fragment molecular orbital calculation using the RI-MP2 method  

NASA Astrophysics Data System (ADS)

The resolution of the identity second-order Møller-Plesset perturbation theory (RI-MP2) was introduced into the fragment molecular orbital (FMO) method, where the program of the RI-MP2 method was newly developed. After some test calculations with a small peptide, the performance of the RI-MP2 method with the FMO scheme was demonstrated for two biomolecular systems: the human immunodeficiency virus type 1 protease with the lopinavir molecule, and the prion protein with the GN8 molecule. These calculations showed the great advantage of FMO calculations using the RI-MP2 method over ordinary FMO calculations.

Ishikawa, Takeshi; Kuwata, Kazuo

2009-05-01

113

The importance of three-body terms in the fragment molecular orbital method  

Microsoft Academic Search

A previously proposed two-body fragment molecular orbital method based on the restricted Hartree-Fock (RHF) method was extended to include explicit three-body terms. The accuracy of the method was tested on a set of representative molecules: (H2O)n, n=16, 32, and 64, as well as alpha and beta n-mers of alanine, n=10, 20, and 40, using STO-3G, 3-21G, 6-31G, and 6-31++G** basis

Dmitri G. Fedorov; Kazuo Kitaura

2004-01-01

114

The role of the exchange in the embedding electrostatic potential for the fragment molecular orbital method.  

PubMed

We have examined the role of the exchange in describing the electrostatic potential in the fragment molecular orbital method and showed that it should be included in the total Fock matrix to obtain an accurate one-electron spectrum; however, adding it to the Fock matrices of individual fragments and pairs leads to very large errors. For the error analysis we have used the virial theorem; numerical tests have been performed for solvated phenol at the Hartree-Fock level with the 6-31G( *) and 6-311G( * *) basis sets. PMID:19894991

Fedorov, Dmitri G; Kitaura, Kazuo

2009-11-01

115

Efficient vibrational analysis for unrestricted Hartree-Fock based on the fragment molecular orbital method  

NASA Astrophysics Data System (ADS)

We developed the analytic second derivative of the energy for unrestricted Hartree-Fock based on the fragment molecular orbital (FMO) method. We formulated the second order derivative for the separated dimer approximation in both restricted and unrestricted methods, which accelerated the calculations by the factor of 9 for a radical system containing 704 atoms. The accuracy was evaluated for organic radicals in explicit solvent, in comparison to full ab initio results. The method was applied to study the change of IR absorption spectra in the tyrosine oxidation reaction for a polypeptide representing the active part of the photosynthetic reaction center.

Nakata, Hiroya; Fedorov, Dmitri G.; Yokojima, Satoshi; Kitaura, Kazuo; Nakamura, Shinichiro

2014-05-01

116

Envelope molecular-orbital theory of extended systems. I. Electronic states of organic quasilinear nanoheterostructures  

NASA Astrophysics Data System (ADS)

A conceptually appealing and computationally economical course-grained molecular-orbital (MO) theory for extended quasilinear molecular heterostructures is presented. The formalism, which is based on a straightforward adaptation, by including explicitly the vacuum, of the envelope-function approximation widely employed in solid-state physics leads to a mapping of the three-dimensional single-particle eigenvalue equations into simple one-dimensional hole and electron Schrödinger-like equations with piecewise-constant effective potentials and masses. The eigenfunctions of these equations are envelope MO's in which the short-wavelength oscillations present in the full MO's, associated with the atomistic details of the molecular potential, are smoothed out automatically. The approach is illustrated by calculating the envelope MO's of high-lying occupied and low-lying virtual ? states in prototypical nanometric heterostructures constituted by oligomers of polyacetylene and polydiacetylene. Comparison with atomistic electronic-structure calculations reveals that the envelope-MO energies agree very well with the energies of the ? MO's and that the envelope MO's describe precisely the long-wavelength variations of the ? MO's. This envelope MO theory, which is generalizable to extended systems of any dimensionality, is seen to provide a useful tool for the qualitative interpretation and quantitative prediction of the single-particle quantum states in mesoscopic molecular structures and the design of nanometric molecular devices with tailored energy levels and wavefunctions.

Arce, J. C.; Perdomo-Ortiz, A.; Zambrano, M. L.; Mujica-Martínez, C.

2011-03-01

117

Hybrid treatment combining the translation- and rotation-free nuclear orbital plus molecular orbital theory with generator coordinate method: TRF-NOMO/GCM  

NASA Astrophysics Data System (ADS)

The translation- and rotation-free nuclear orbital plus molecular orbital (TRF-NOMO) theory was developed in order to accurately determine the nonadiabatic nuclear and electronic wave functions without Born-Oppenheimer approximation. This study presents a hybrid method combining the TRF-NOMO theory with the generator coordinate method (GCM). The TRF-NOMO/GCM treatment is capable of giving the vibrational excited states with high accuracy, as well as improving the ground-state description by inclusion of the many-body effect. Numerical applications of the TRF-NOMO/GCM calculations to an HF molecule confirm its reliability and usefulness.

Sodeyama, Keitaro; Nishizawa, Hiroaki; Hoshino, Minoru; Kobayashi, Masato; Nakai, Hiromi

2007-01-01

118

Comment on ``Elimination of translational and rotational motions in nuclear orbital plus molecular orbital theory'' [J. Chem. Phys. 122, 164101 (2005)  

NASA Astrophysics Data System (ADS)

In moving-nuclei calculations on some simple diatomics and on water, Nakai et al. [J. Chem. Phys.122, 164101 (2005)] extend their earlier translation-free nuclear orbital plus molecular orbital (TF-NOMO) theory, in which the translational part of the Hamiltonian is subtracted from the full Hamiltonian, to a translation- and rotation-free approach, in which a rotational term is subtracted from the TF-NOMO Hamiltonian. It is suggested that the chosen rotational term is not unique and is not valid over all regions of space.

Sutcliffe, Brian

2005-12-01

119

Electron-correlated fragment-molecular-orbital calculations for biomolecular and nano systems.  

PubMed

Recent developments in the fragment molecular orbital (FMO) method for theoretical formulation, implementation, and application to nano and biomolecular systems are reviewed. The FMO method has enabled ab initio quantum-mechanical calculations for large molecular systems such as protein-ligand complexes at a reasonable computational cost in a parallelized way. There have been a wealth of application outcomes from the FMO method in the fields of biochemistry, medicinal chemistry and nanotechnology, in which the electron correlation effects play vital roles. With the aid of the advances in high-performance computing, the FMO method promises larger, faster, and more accurate simulations of biomolecular and related systems, including the descriptions of dynamical behaviors in solvent environments. The current status and future prospects of the FMO scheme are addressed in these contexts. PMID:24740821

Tanaka, Shigenori; Mochizuki, Yuji; Komeiji, Yuto; Okiyama, Yoshio; Fukuzawa, Kaori

2014-06-14

120

Spin-orbit force, recoil corrections, and possible BB¯* and DD¯* molecular states  

NASA Astrophysics Data System (ADS)

In the framework of the one-boson exchange model, we have calculated the effective potentials between two heavy mesons BB¯* and DD¯* from the t- and u-channel ?-, ?-, ?-, ?-, and ?-meson exchanges with four kinds of quantum number: I=0, JPC=1++; I =0, JPC=1+-; I =1, JPC=1++; I =1, JPC=1+-. We keep the recoil corrections to the BB¯* and DD¯* systems up to O(1/M2). The spin-orbit force appears at O(1/M), which turns out to be important for the very loosely bound molecular states. Our numerical results show that the momentum-related corrections are unfavorable to the formation of the molecular states in the I =0, JPC=1++ and I =1, JPC=1+- channels in the DD¯* system.

Zhao, Lu; Ma, Li; Zhu, Shi-Lin

2014-05-01

121

Venn Diagrams  

NSDL National Science Digital Library

In this activity, students are given a Venn diagram with certain rules and an element. They must then determine where in the Venn diagram the element belongs. This activity allows students to practice placing elements in Venn diagrams as well as reviewing mathematical terms associated with the different rules. This activity includes supplemental materials, including background information about the topics covered, a description of how to use the application, and exploration questions for use with the java applet.

2010-01-01

122

Lucidchart: Diagramming  

NSDL National Science Digital Library

For all those who have wrestled with creating charts and diagrams in word processors, the Google Chrome application Lucidchart may be a long-awaited answer. Users can start using the intuitive drag-and-drop interface right away, although a free signup is required to save diagrams. By sharing a link with coworkers, project collaborators can work on the same diagram at the same time. This application is compatible with all computers running Google Chrome.

2012-08-24

123

Carroll Diagrams  

NSDL National Science Digital Library

In this number sorting activity students must use a Carroll Diagram to determine which two categories each number fits into. This activity can be completed in pairs or groups on printable versions or it can be completed as a whole class using the interactive white board (IWB). Included with this resource are printable versions of the Carroll Diagrams, guiding questions, extension and support suggestions, and a link to more challenging "More Carroll Diagrams".

Team, Nrich

2012-01-01

124

Analyzing the electric response of molecular conductors using "electron deformation" orbitals and occupied-virtual electron transfer.  

PubMed

The concept of "electron deformation orbitals" (EDOs) is used to investigate the electric response of conducting metals and oligophenyl chains. These orbitals and their eigenvalues are obtained by diagonalization of the deformation density matrix (difference between the density matrices of the perturbed and unperturbed systems) and can be constructed as linear combinations of the unperturbed molecular orbitals within "frozen geometry" conditions. This form of the EDOs allows calculating the part of the electron deformation density associated to an effective electron transfer from occupied to virtual orbitals (valence to conduction band electron transfer in the band model of conductivity). It is found that the "electron deformation" orbitals pair off, displaying the same eigenvalue but opposite sign. Each pair represents an amount of accumulation/depletion of electron charge at different molecular regions. In the oligophenyl systems investigated only one pair contributes effectively to the charge flow between molecular ends, resulting from the promotion of electrons from occupied orbitals to close in energy virtual orbitals of appropriate symmetry and overlapping. Analysis of this pair along explains the differences in conductance of olygophenyl chains based on phenyl units. © 2014 Wiley Periodicals, Inc. PMID:24676839

Mandado, Marcos; Ramos-Berdullas, Nicolás

2014-06-30

125

Channeling of a subangstrom electron beam in a crystal mapped to two-dimensional molecular orbitals  

NASA Astrophysics Data System (ADS)

The propagation of high-energy electrons in crystals is in general a complicated multiple-scattering problem. However, along high-symmetry zone axes the problem can be mapped to the time evolution of a two-dimensional (2D) molecular system. Each projected atomic column can be approximated by the potential of a 2D screened hydrogenic atom. When two columns are in close proximity, their bound states overlap and form analogs to molecular orbitals. For subangstrom electron beams, excitation of antisymmetric orbitals can result in the failure of the simple incoherent imaging approximation. As a result, the standard resolution test and the one-to-one correspondence of atomic positions of a crystal imaged along a zone axis with closely spaced projected columns (“dumbbells”) can fail dramatically at finite and realistic sample thicknesses. This is demonstrated experimentally in high-angle annular dark-field scanning transmission electron microscope (HAADF STEM) images of [211]-oriented Si showing an apparent intercolumn spacing of 1.28(±0.09) Å, over 64% larger than the actual 0.78 Å spacing. Furthermore, the apparent spacing can be tuned with sample thickness and probe size to produce a larger, smaller, or even the actual spacing under conditions when the peaks of two adjacent Si columns should not even have been resolved given the electron probe size.

Hovden, Robert; Xin, Huolin L.; Muller, David A.

2012-11-01

126

Methane activation by metals and semiconductors. Molecular orbital theory. Annual report, September 1987-August 1988  

SciTech Connect

An atom-superposition and electron delocalization molecular orbital study was made of CHn and CO reactions over coordinatively unsaturated Mo(IV) edge cations in MoS2. Coupling to C2H6 and C2H5(a) proceed with high barriers. CH2(a) coupling to strongly adsorbed ethylene proceeds with a lower barrier, and hydrogenation to ethane is possible. CO binds relatively weakly to 5-fold coordinated Mo and strongly to 4-fold coordinated sites. Over two such sites, CO easily tilts to a di-Sigma bridging orientation and dissociates with a low barrier. In the Fischer-Tropsch process hydrogenation to CH3(ads) and H2O(g) is expected. CO inserts into the Mo-CH3 bond with a low barrier, and subsequent hydrogenations to form C2H6+H2O or CH3CH2OH are favorable. It is proposed that the selectivity toward alcohol formation over alkali-doped MoS2 (the DOW process) may stem from the ability of the alkali cations to stabilize alkoxy intermediates. A second molecular orbital study shows AlN behaves similarly to MgO toward CH4. Stoichiometric AlN is inactive. CH4 is activated by surface N(2-) hole sites, forming surface HN(2-) and methyl radicals.

Anderson, A.B.

1988-09-01

127

Molecular structure of ethynylbenzene from electron diffraction and ab initio molecular orbital calculations  

Microsoft Academic Search

The molecular structure and benzene ring distortions of ethynylbenzene have been investigated by gas-phase electron diffraction and ab initio MO calculations at the HF\\/6-31G* and 6-3G** levels. Least-squares refinement of a model withC2v, symmetry, with constraints from the MO calculations, yielded the following important bond distances and angles:rg(Ci-Co)=1.407±0.003 Å,rg(Co-Cm)=1.397±0.003 Å,rg(Cm-Cp)=1.400±0.003 Å,rg(Cri-CCH)=1.436 ±0.004 Å,rg(C=C)=1.205±0.005 Å, ?Co-Ci-Co=119.8±0.4°. The deformation of the benzene

György Schultz; Tamás Nagy; Gustavo Portalone; Fabio Ramondo; István Hargittai; Aldo Domenicano

1993-01-01

128

Generation of molecular symmetry orbitals for the point and double groups  

NASA Astrophysics Data System (ADS)

Symmetry-adapted molecular basis functions are widely applied for the electronic structure computations of molecules and clusters. These functions are obtained by exploiting the symmetry of the system and often help to simplify the computations considerably. In order to facilitate their use in algebraic and numerical computations, here we provide a set of MAPLE procedures which generates these functions by means of projection operators, both within the nonrelativistic and relativistic theory. All commonly applied point and double groups are supported by the program including, in addition, the access to their group-theoretical data such as the symmetry operators, characters, or irreducible representations. Program summaryTitle of program:BETHE Catalogue identifier:ADVU Program summary URL:http://cpc.cs.qub.ac.uk/summaries/ADVU Program obtainable from: CPC Program Library, Queen's University of Belfast, N. Ireland Licensing provisions:none Computer for which the program is designed: All computers with a license of the computer algebra package MAPLE (Maple is a registered trademark of Waterloo Maple Inc.) Installations:University of Kassel (Germany) Operating systems or monitors under which the program has been tested:Linux 8.1+ and Windows2000 Programming language used:MAPLE 7 and 8 Memory required to execute with typical data:10-30 MB No. of lines in distributed program, including test data, etc.:14 190 No. of bytes in distributed program, including test data, etc.:370 795 Distribution format:tar.gz Nature of the physical problem:Molecular and solid-state quantum computations can be simplified considerably if the symmetry of the systems with respect to the rotation and inversion of the coordinates is taken into account. To exploit such symmetries, however, symmetry-adapted basis functions need to be constructed instead of using—as usual—the atomic orbitals as the (one-particle) basis. These so-called symmetry orbitals are invariant with respect to the symmetry operations of the group and are different for the point and double groups, i.e. for nonrelativistic and relativistic computations. Method of solution:Projection operator techniques are applied to generate the symmetry-adapted orbital functions as a linear combinations of atomic orbitals. Restrictions onto the complexity of the problem:The generation of the symmetry orbitals is supported for the cyclic and related groups C, C, C, C, C, the dihedral groups D, D, D, the improper cyclic groups S2n(n?10), the cubic groups O, T, O, T, T as well as the icosahedral groups I and I. In all these cases, the symmetry orbitals can be obtained for either the point or double groups by using a nonrelativistic or, respectively, relativistic framework for the computations. Unusual features of the program:All commands of the BETHE program are available for interactive work. Apart from the symmetry orbitals generation, the program also provides a simple access to the group theoretical data for the presently implemented groups from above. The notation of the symmetry operations and the irreducible representations follows the compilation by Altmann and Herzig [Point-Group Theory Tables, Clarendon Press, Oxford, 1994]. For a quick reference to the program, a description of all user-relevant commands is given in the (user) manual Bethe-commands.ps and is distributed together with the code. Typical running time:Although the program replies 'promptly' on most requests, the running time depends strongly on the particular task.

Rykhlinskaya, K.; Fritzsche, S.

2005-09-01

129

Venn Diagrams  

NSDL National Science Digital Library

This interactive problem provides an opportunity for children to become familiar with Venn diagrams, while reinforcing knowledge of number properties. Students must place the numbers from 1 to 40 into a Venn diagram of two sets with an intersection. The Teachers' Notes page offers rationale, suggestions for implementation, discussion questions, ideas for extension and support.

2007-09-01

130

Molecular geometry, conformational, vibrational spectroscopic, molecular orbital and Mulliken charge analysis of 2-acetoxybenzoic acid  

NASA Astrophysics Data System (ADS)

The Fourier transform infrared (FT-IR) and FT-Raman spectra of 2-acetoxybenzoic acid (2ABA), a painkiller agent were recorded in the region 4000-450 cm-1 and 5000-50 cm-1 respectively. Hartree Fock (HF) and Density functional theory (DFT) methods have been used to determine its optimized geometrical parameter, atomic charges, and vibrational wavenumbers and intensity of the vibrational bands of the title molecule. The computed vibrational wave numbers were compared with the FT-IR and FT-Raman experimental data. The computational calculations were done at HF and DFT/B3LYP level with 6-311++G(d,p) basis set. The complete vibrational assignments were performed on the basis of the potential energy distribution (PED) analysis. The Mulliken charges, UV-Visible spectral analysis and HOMO-LUMO energy gap have been calculated and reported. The B3LYP method of calculated parameters is a good complement with the experimental findings. The thermodynamic properties like entropy, heat capacity and zero vibrational energy have been calculated and discussed. The electrostatic potential (ESP) contour surface and molecular electrostatic potential (MESP) of the molecule were constructed.

Govindasamy, P.; Gunasekaran, S.; Srinivasan, S.

2014-09-01

131

Molecular geometry, conformational, vibrational spectroscopic, molecular orbital and Mulliken charge analysis of 2-acetoxybenzoic acid.  

PubMed

The Fourier transform infrared (FT-IR) and FT-Raman spectra of 2-acetoxybenzoic acid (2ABA), a painkiller agent were recorded in the region 4000-450 cm(-1) and 5000-50 cm(-1) respectively. Hartree Fock (HF) and Density functional theory (DFT) methods have been used to determine its optimized geometrical parameter, atomic charges, and vibrational wavenumbers and intensity of the vibrational bands of the title molecule. The computed vibrational wave numbers were compared with the FT-IR and FT-Raman experimental data. The computational calculations were done at HF and DFT/B3LYP level with 6-311++G(d,p) basis set. The complete vibrational assignments were performed on the basis of the potential energy distribution (PED) analysis. The Mulliken charges, UV-Visible spectral analysis and HOMO-LUMO energy gap have been calculated and reported. The B3LYP method of calculated parameters is a good complement with the experimental findings. The thermodynamic properties like entropy, heat capacity and zero vibrational energy have been calculated and discussed. The electrostatic potential (ESP) contour surface and molecular electrostatic potential (MESP) of the molecule were constructed. PMID:24793483

Govindasamy, P; Gunasekaran, S; Srinivasan, S

2014-09-15

132

Role of Spin-Orbit Coupling on the Spin Triplet Pairing in NaxCoO2\\cdotyH2O II: Multiple Phase Diagram under the Magnetic Field  

NASA Astrophysics Data System (ADS)

The possibility of multiple phase diagram in the novel superconductor NaxCoO2\\cdotyH2O is analyzed on the basis of the multi-orbital Hubbard model including the atomic spin-orbit coupling. We have shown that the spin triplet pairing state is stable in this model. The p-wave ( f-wave) state is stabilized when the Hund’s rule coupling is large (small). In the precedent paper, we have determined the direction of d-vector at T=Tc and H=0 within the linearized Dyson-Gorkov equation. In this paper, the pairing state below Tc and under the magnetic field is determined within the weak coupling approximation including the paramagnetic effect. We find that the p+ f coexistent state is stabilized at low temperatures in a part of parameter range. We point out that the phase diagram in the H-T plane is quite different between the p-wave, f-wave and p+ f-wave superconductivities. The characteristics of each phase are clarified by showing the magnetic susceptibility and specific heat. We discuss the comparison with experimental results and suggest some future experiments to detect the multiple phase transition.

Yanase, Youichi; Mochizuki, Masahito; Ogata, Masao

2005-12-01

133

Conservative generalized bifurcation diagrams  

NASA Astrophysics Data System (ADS)

Bifurcation cascades in conservative systems are shown to exhibit a generalized diagram, which contains all relevant informations regarding the location of periodic orbits (resonances), their width (island size), irrational tori and the infinite higher-order resonances, showing the intricate way they are born. Contraction rates for islands sizes, along period-doubling bifurcations, are estimated to be ?I?3.9. Results are demonstrated for the standard map and for the continuous Hénon-Heiles potential. The methods used here are very suitable to find periodic orbits in conservative systems, and to characterize the regular, mixed or chaotic dynamics as the nonlinear parameter is varied.

Manchein, Cesar; Beims, Marcus W.

2013-04-01

134

Efficient GW methods implemented in molecular orbital space: Ionization energy and electron affinity of conjugated molecules  

NASA Astrophysics Data System (ADS)

An efficient all-electron non-selfconsistent GW (G^0W^0) method is proposed, which is based on the full random-phase approximation and implemented in the molecular-orbital space with algorithms for reducing the error coming from the incompleteness of the basis set. The convergence of its result with regard to the size of the basis set is examined. Based on this, we further implement a quasiparticle self-consistent GW (QSGW) approach with Gaussian basis functions. The high computational efficiency allows us to deal with larger molecules from the first principles, and we applied our methods to calculate the ionization energy (IE) and electron affinity (EA) of ten conjugated molecules with up to 32 atoms. The G^0W^0 result improves the Hartree-Fock result significantly, especially for EA, and, furthermore, the QSGW improves the G^0W^0 and gives results of both IE and EA in very good agreement with the available experimental data and also with the results from the ?SCF calculation using the B3LYP functional. This indicates that our all-electron ab initio GW calculation can describe very well molecular electronic structures, making the QSGW approach a good candidate for investigating electronic and transport properties of molecular systems.

Ke, San-Huang

2012-02-01

135

IMAGING THE MOLECULAR DISK ORBITING THE TWIN YOUNG SUNS OF V4046 Sgr  

SciTech Connect

We have imaged the disk surrounding the nearby (D {approx} 73 pc), {approx}12 Myr, classical T Tauri binary system V4046 Sgr with the Submillimeter Array (SMA) at an angular resolution of {approx}2''. We detect a rotating disk in {sup 12}CO(2-1) and {sup 13}CO(2-1) emission and resolve the continuum emission at 1.3 mm. We infer disk gas and dust masses of {approx}110 and {approx}40 Earth masses, respectively. Fits to a power-law disk model indicate that the molecular disk extends to {approx}370 AU and is viewed at an inclination of between {approx}33{sup 0} and {approx}39{sup 0} for dynamical stellar masses ranging from 1.8 M {sub sun} down to 1.5 M {sub sun} (the range of the total mass previously determined for the central, 2.4 day spectroscopic binary). This range of disk inclination is consistent with that assumed in deducing the central binary mass (i.e., 35{sup 0}), suggesting that the V4046 Sgr binary system and its circumbinary, molecular disk are coplanar. In light of the system's age and binarity, the presence of an extensive molecular disk orbiting V4046 Sgr provides constraints on the timescales of processes related to Jovian planet formation and demonstrates that circumbinary Jovian planets potentially could form around close binary systems.

Rodriguez, David R. [Department of Physics and Astronomy, University of California, Los Angeles, CA 90095 (United States); Kastner, Joel H. [Center for Imaging Science, Rochester Institute of Technology, 54 Lomb Memorial Drive, Rochester, NY 14623 (United States); Wilner, David; Qi, Chunhua, E-mail: drodrigu@astro.ucla.ed, E-mail: jhk@cis.rit.ed, E-mail: dwilner@cfa.harvard.ed, E-mail: cqi@cfa.harvard.ed [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Mail Stop 42, Cambridge, MA 02138 (United States)

2010-09-10

136

Kohn-Sham orbitals and potentials from quantum Monte Carlo molecular densities.  

PubMed

In this work we show the possibility to extract Kohn-Sham orbitals, orbital energies, and exchange correlation potentials from accurate Quantum Monte Carlo (QMC) densities for atoms (He, Be, Ne) and molecules (H2, Be2, H2O, and C2H4). The Variational Monte Carlo (VMC) densities based on accurate Jastrow Antisymmetrised Geminal Power wave functions are calculated through different estimators. Using these reference densities, we extract the Kohn-Sham quantities with the method developed by Zhao, Morrison, and Parr (ZMP) [Phys. Rev. A 50, 2138 (1994)]. We compare these extracted quantities with those obtained form CISD densities and with other data reported in the literature, finding a good agreement between VMC and other high-level quantum chemistry methods. Our results demonstrate the applicability of the ZMP procedure to QMC molecular densities, that can be used for the testing and development of improved functionals and for the implementation of embedding schemes based on QMC and Density Functional Theory. PMID:24511917

Varsano, Daniele; Barborini, Matteo; Guidoni, Leonardo

2014-02-01

137

Kohn-Sham orbitals and potentials from quantum Monte Carlo molecular densities  

NASA Astrophysics Data System (ADS)

In this work we show the possibility to extract Kohn-Sham orbitals, orbital energies, and exchange correlation potentials from accurate Quantum Monte Carlo (QMC) densities for atoms (He, Be, Ne) and molecules (H2, Be2, H2O, and C2H4). The Variational Monte Carlo (VMC) densities based on accurate Jastrow Antisymmetrised Geminal Power wave functions are calculated through different estimators. Using these reference densities, we extract the Kohn-Sham quantities with the method developed by Zhao, Morrison, and Parr (ZMP) [Phys. Rev. A 50, 2138 (1994)]. We compare these extracted quantities with those obtained form CISD densities and with other data reported in the literature, finding a good agreement between VMC and other high-level quantum chemistry methods. Our results demonstrate the applicability of the ZMP procedure to QMC molecular densities, that can be used for the testing and development of improved functionals and for the implementation of embedding schemes based on QMC and Density Functional Theory.

Varsano, Daniele; Barborini, Matteo; Guidoni, Leonardo

2014-02-01

138

Investigations into the molecular-level adhesion characteristics of hydroxyapatite-coated and anodized titanium surfaces using the molecular orbital approach.  

PubMed

It has been established that the adhesion of cells on to the surfaces of orthopaedic implants depends on the ability of the surfaces to accommodate protein molecules. Hydroxyapatite coating and anodizing are the most common methods to make TiAl6V4 implants (Ti) more biocompatible. In this paper Spartan 02, a molecular dynamics software, is used to analyze and predict the bonding characteristics of Extra cellular matrix protein sequence arginine-glycine-aspartic acid (RGD) on a Hyrdoxyapatite (HA) coated Ti and an anodized Ti surface based on the property of its constituent atoms, their polarity (net electrostatic charge, Qr), the energies of the molecular orbital E_HOMO (energy of the highest occupied molecular orbital), and E_LUMO (energy of the lowest unoccupied molecular orbital). The results show favourable criterion for formation of bonding between the HOMO orbital of the HA coated and anodized surfaces and LUMO orbital of the glycine strand from the RGD unit. The mechanism of bonding of individual atoms to form primary calcium oxide compounds is likely only in the case of HA coated surfaces . The surface texture of the anodized Ti with inherent porosities appear more responsible for the adsorption of proteins on to them by mechanical interlocking than the formation of any intermediate calcium oxide compounds. PMID:21485326

Saju, K K; Jayadas, N H; Vidyanand, S; James, J

2011-03-01

139

Ab initio molecular orbital calculations of the vibrational frequencies of XY4/sup -n/ anions  

NASA Astrophysics Data System (ADS)

The vibrational frequencies of a seris of XY4/sup -n/ anions (BeF4(-2), BF4(-), AlF4(-), MgCl4(-2), and AlCl4(-)) have been calculated by ab initio molecular orbital theory using the 3-21G and 6-31G* basis sets. The predicted harmonic frequencies are for the most part in good agreement with the observed frequencies of these anions in molten alkali halide mixtures. At the 3-21G basis set level the average difference between the observed and predicted frequencies is 12% while at the 6-31G* basis set level the average difference is 6%. Calculations of this type may be helpful in predicting the vibrational frequencies of other anions in molten salts.

Curtiss, L. A.; Nichols, R.

140

Oxygen evolution on a SrFeO3 anode - Mechanistic considerations from molecular orbital theory  

NASA Technical Reports Server (NTRS)

Various pathways proposed in the literature for the evolution of O2 in electrochemical oxidations are explored using the atom superposition and electron delocalization molecular orbital (ASED-MO) theory and the cluster models of the SrFeO3 surface as a prototype material. Calculations indicate that oxygen atoms can be easily formed on the (100) surface as well as on the edge cation sites of a SrFeO3 anode by the discharge of OH(-), followed by its deprotonation and electron transfer to the electrode. The O atoms can form O2 on the edge and corner sites, where the Fe(4+) is coordinated to four and three bulk oxygen anions, respectively. The calculations strongly disfavor mechanisms involving coupling of oxygen atoms adsorbed on different cations as well as a mechanism featuring an ozone intermediate.

Mehandru, S. P.; Anderson, Alfred B.

1989-01-01

141

Spectroscopic studies and molecular orbital analysis on platinanaphthalenes and ring-fused B-N platinanaphthalenes  

NASA Astrophysics Data System (ADS)

The electronic structure and properties of the platinanaphthalenes, and ring-fused B-N platinanaphthalenes isomers have been explored using the hybrid density functional mpw1pw91 theory. The energetic aspect shows that stability of Ptb and Pta isomers are isoenergetic in platinanaphthalenes. On the other hand, BNa1 isomer is the most stable isomer of ring-fused B-N platinanaphthalenes. This is compatible with principles of minimum energy and minimum polarizability in ring-fused B-N platinanaphthalenes. Molecular orbital analysis shows increasing of hardness in ring-fused B-N platinanaphthalenes isomers. Also, electronic spectra analysis indicates that, in all the molecules HOMO-1 ? LUMO transition makes the major contribution in most intense electronic transition.

Ghiasi, Reza; Ara, Taherh Jahan; Hakimyoun, Amir Hossein

2014-04-01

142

?-Frontier molecular orbitals in S = 2 ferryl species and elucidation of their contributions to reactivity  

PubMed Central

S = 2 FeIV?O species are key intermediates in the catalysis of most nonheme iron enzymes. This article presents detailed spectroscopic and high-level computational studies on a structurally-defined S = 2 FeIV?O species that define its frontier molecular orbitals, which allow its high reactivity. Importantly, there are both ?- and ?-channels for reaction, and both are highly reactive because they develop dominant oxyl character at the transition state. These ?- and ?-channels have different orientation dependences defining how the same substrate can undergo different reactions (H-atom abstraction vs. electrophilic aromatic attack) with FeIV?O sites in different enzymes, and how different substrates can undergo different reactions (hydroxylation vs. halogenation) with an FeIV?O species in the same enzyme.

Srnec, Martin; Wong, Shaun D.; England, Jason; Que, Lawrence; Solomon, Edward I.

2012-01-01

143

Molecular orbital studies in oxidation: Sulfate formation and metal-metal oxide adhesion  

NASA Technical Reports Server (NTRS)

The chemical mechanisms for sulfate formation from sodium chloride and sulfur trioxide, which is a product of jet fuel combustion was determined. Molten sodium sulfate leads to hot corrosion of the protective oxide layers on turbine blades. How yttrium dopants in nidkel-aluminum alloys used in turbine blades reduce the spalling rate of protective alumina films and enhance their adhesion was also determined. Two other fulfate mechanisms were deduced and structure of carbon monoxide on a clean chronium and clean platinum-titanium alloys surfaces was determined. All studies were by use of the atom superposition and electron delocalization molecular orbital (ASED-MO) theory. Seven studies were completed. Their titles and abstracts are given.

Anderson, A. B.

1985-01-01

144

Mapping Enzymatic Catalysis Using the Effective Fragment Molecular Orbital Method: Towards all ab initio Biochemistry  

PubMed Central

We extend the Effective Fragment Molecular Orbital (EFMO) method to the frozen domain approach where only the geometry of an active part is optimized, while the many-body polarization effects are considered for the whole system. The new approach efficiently mapped out the entire reaction path of chorismate mutase in less than four days using 80 cores on 20 nodes, where the whole system containing 2398 atoms is treated in the ab initio fashion without using any force fields. The reaction path is constructed automatically with the only assumption of defining the reaction coordinate a priori. We determine the reaction barrier of chorismate mutase to be kcal mol?1 for MP2/cc-pVDZ and for MP2/cc-pVTZ in an ONIOM approach using EFMO-RHF/6-31G(d) for the high and low layers, respectively.

Steinmann, Casper; Fedorov, Dmitri G.; Jensen, Jan H.

2013-01-01

145

New methods for accelerating the convergence of molecular electronic integrals over exponential type orbitals  

NASA Astrophysics Data System (ADS)

This review on molecular integrals for large electronic systems (MILES) places the problem of analytical integration over exponential-type orbitals (ETOs) in a historical context. After reference to the pioneering work, particularly by Barnett, Shavitt and Yoshimine, it focuses on recent progress towards rapid and accurate analytic solutions of MILES over ETOs. Software such as the hydrogenlike wavefunction package Alchemy by Yoshimine and collaborators is described. The review focuses on convergence acceleration of these highly oscillatory integrals and in particular it highlights suitable nonlinear transformations. Work by Levin and Sidi is described and applied to MILES. A step by step description of progress in the use of nonlinear transformation methods to obtain efficient codes is provided. The recent approach developed by Safouhi is also presented. The current state of the art in this field is summarized to show that ab initio analytical work over ETOs is now a viable option.

Safouhi, Hassan; Hoggan, Philip

2003-01-01

146

Derivative discontinuity, bandgap and lowest unoccupied molecular orbital in density functional theory  

NASA Astrophysics Data System (ADS)

The conventional analysis of Perdew and Levy, and Sham and Schlüter shows that the functional derivative discontinuity of the exchange-correlation density functional plays a critical role in the correct prediction of bandgaps, or the chemical hardness. In a recent work by the present authors, explicit expressions for bandgap prediction with all common types of exchange-correlation functionals have been derived without invoking the concept of exchange-correlation energy functional derivative discontinuity at all. We here analyze the two approaches and establish their connection and difference. The present analysis further leads to several important results: (1) The lowest unoccupied molecular orbital (LUMO) in DFT has as much meaning in describing electron addition as the highest occupied molecular orbital (HOMO) in describing electron removal. (2) Every term in the total energy functional contributes to the energy gap because of the discontinuity of the derivative of the density (or density matrix) with respect to the number of electrons, ((??s(r',r))/?N)vs, at integers. (3) Consistent with the Perdew-Levy-Sham-Schlüter conclusion that the exact Kohn-Sham energy gap differs from the fundamental bandgap by a finite correction due to the functional derivative discontinuity of the exchange-correlation energy, we show that the exchange-correlation functional cannot be an explicit and differentiable functional of the electron density, either local or nonlocal. The last result is further strengthened when we consider Mott insulators. There, the exact exchange-correlation functional needs to have an explicitly discontinuous (nondifferentiable) dependence on the density or the density matrix. (4) We obtain exact conditions on the derivatives of total energy with respect to the spin-up and spin-down number of electrons.

Yang, Weitao; Cohen, Aron J.; Mori-Sánchez, Paula

2012-05-01

147

Hovmoller Diagrams  

NSDL National Science Digital Library

Hovmoller diagrams are great for displaying large amounts of data in a meaningful and understandable form. The image on the left graphical shows the El Nino signal in the equatorial Pacific (100 W to 140 E ...

148

Generalized hybrid-orbital method for combining density functional theory with molecular mechanicals.  

PubMed

The generalized hybrid orbital (GHO) method has previously been formulated for combining molecular mechanics with various levels of quantum mechanics, in particular semiempirical neglect of diatomic differential overlap theory, ab initio Hartree-Fock theory, and self-consistent charge density functional tight-binding theory. To include electron-correlation effects accurately and efficiently in GHO calculations, we extend the GHO method to density functional theory in the generalized-gradient approximation and hybrid density functional theory (denoted by GHO-DFT and GHO-HDFT, respectively) using Gaussian-type orbitals as basis functions. In the proposed GHO-(H)DFT formalism, charge densities in auxiliary hybrid orbitals are included to calculate the total electron density. The orthonormality constraints involving the auxiliary Kohn-Sham orbitals are satisfied by carrying out the hybridization in terms of a set of Löwdin symmetrically orthogonalized atomic basis functions. Analytical gradients are formulated for GHO-(H)DFT by incorporating additional forces associated with GHO basis transformations. Scaling parameters are introduced for some of the one-electron integrals and are optimized to obtain the correct charges and geometry near the QM/MM boundary region. The GHO-(H)DFT method based on the generalized gradient approach (GGA) (BLYP and mPWPW91) and HDFT methods (B3 LYP, mPW1PW91, and MPW1 K) is tested-for geometries and atomic charges-against a set of small molecules. The following quantities are tested: 1) the C--C stretch potential in ethane, 2) the torsional barrier for internal rotation around the central C--C bond in n-butane, 3) proton affinities for a set of alcohols, amines, thiols, and acids, 4) the conformational energies of alanine dipeptide, and 5) the barrier height of the hydrogen-atom transfer between n-C4H10 and n-C4H9, where the reaction center is described at the MPW1 K/6-31G(d) level of theory. PMID:16086343

Pu, Jingzhi; Gao, Jiali; Truhlar, Donald G

2005-09-01

149

Fragment molecular orbital study on electron tunneling mechanisms in bacterial photosynthetic reaction center.  

PubMed

The tunneling mechanisms of electron transfers (ETs) in photosynthetic reaction center of Blastochloris viridis are studied by the ab initio fragment molecular orbital (FMO) method combined with the generalized Mulliken-Hush (GMH) and the bridge Green function (GF) calculations of the electronic coupling T(DA) and the tunneling current method for the ET pathway analysis at the fragment-based resolution. For the ET from batctriopheophytin (H(L)) to menaquinone (MQ), a major tunneling current through Trp M250 and a minor back flow via Ala M215, Ala M216, and His M217 are quantified. For the ET from MQ to ubiquinone, the major tunneling pathway via the nonheme Fe(2+) and His L190 is identified as well as minor pathway via His M217 and small back flows involving His L230, Glu M232, and His M264. At the given molecular structure from X-ray experiment, the spin state of the Fe(2+) ion, its replacement by Zn(2+), or its removal are found to affect the T(DA) value by factors within 2.2. The calculated T(DA) values, together with experimentally estimated values of the driving force and the reorganization energy, give the ET rates in reasonable agreement with experiments. PMID:23039745

Kitoh-Nishioka, Hirotaka; Ando, Koji

2012-11-01

150

Spectroscopic studies and molecular orbital calculations on the charge transfer reaction between DDQ and 2-aminopyridine.  

PubMed

Charge transfer complex formation between 2-aminopyridine (donor, 2AP) with 2,3-dichloro-5,6-dicyano-p-benzoquinone (acceptor, DDQ) has been studied spectrophotometrically in acetonitrile (CH3CN). The newly formed CT-complex has reddish brown color and is characterized by the appearance of new absorption bands in the 375-650 nm regions where acceptor and donor do not have any absorption. Maximum and constant absorbance of the complex was obtained after 10 min at 20 °C with 1 mL 5×10(-3) M DDQ in CH3CN. Based on photometric titration method, the stoichiometry of the formed CT-complex was found to be 1:1 [(2AP)(DDQ)]. Minimum-maximum absorbances method has been applied to estimate the formation constant of the complex where it recorded large value confirming its high stability. Molecular orbital calculations utilizing GAMESS computations were carried out in order to record changes in the electronic structure and molecular geometry of the formed CT-complex. In addition, the infrared vibrational frequencies of the complex were computed and compared with experimental results. PMID:23583852

Al-Ahmary, Khairia M; El-Kholy, Moustafa M; Al-Solmy, Iman A; Habeeb, Moustafa M

2013-06-01

151

Ternary diagram plots  

SciTech Connect

A ternary diagram uses an equilateral triangle to graphically depict the relationship among three data values which sum to a constant value. Geologists in many fields use ternary diagrams for a variety of purposes: identification and classification of sedimentary, igneous, and metamorphic rocks; classification of soils; chemical and molecular representation of minerals; representation of the fractional crystallization of igneous rock-forming minerals. Traditionally, constructing a ternary diagram involves calculating the normalized values from the raw data for the three components to be plotted, then plotting the point that represents these values on an equilateral triangle. This can be a tedious and time-consuming process, especially if many samples must be plotted, or many combinations of components represented. Ternary is a program that allows manipulation of large amounts of data to create accurate ternary diagrams. The program allows input of data for hundreds of samples, each containing up to 20 components, any three of which can be combined to form a ternary diagram. Each component can be given a label up to five characters long for ease in identification. Data are entered in raw form (i.e. parts per million, percentages, real or whole numbers), normalized internally to 100, and plotted on a ternary diagram that can be printed to the screen or dot matrix printer.

Scott, A.J.; Guth, P.L.

1987-11-01

152

Mapping molecular orbital symmetry on high-order harmonic generation spectrum using two-color laser fields.  

PubMed

We have measured high-order harmonic generation spectra of D2, N2, and CO2 by mixing orthogonally polarized 800 and 400 nm laser fields. The intensity of the high-harmonic spectrum is modulated as we change the relative phase of the two pulses. For randomly orientated molecules, the phase of the intensity modulation depends on the symmetry of the molecular orbitals from which the high harmonics are emitted. This allows us to identify the symmetry of any orbital that contributes to high-harmonic generation, even without aligning the molecule. Our approach can be a route to imaging dynamical changes in three-dimensional molecular orbitals on a time scale as short as a few hundred attoseconds. PMID:20867910

Niikura, Hiromichi; Dudovich, Nirit; Villeneuve, D M; Corkum, P B

2010-07-30

153

General contraction of Gaussian basis sets. Part 2: Atomic natural orbitals and the calculation of atomic and molecular properties  

SciTech Connect

A recently proposed scheme for using natural orbitals from atomic configuration interaction (CI) wave functions as a basis set for linear combination of atomic orbitals (LCAO) calculations is extended for the calculation of molecular properties. For one-electron properties like multipole moments, which are determined largely by the outermost regions of the molecular wave function, it is necessary to increase the flexibility of the basis in these regions. This is most easily done by uncontracting the outmost Gaussian primitives, and/or by adding diffuse primitives. A similar approach can be employed for the calculation of polarizabilities. Properties which are not dominated by the long-range part of the wave function, such as spectroscopic constants or electric field gradients at the nucleus, can generally be treated satisfactorily with the original atomic natural orbital (ANO) sets.

Almloef, J.; Taylor, P.R.

1989-01-01

154

Molecular Orbital Effects on the Ti LMV Auger Spectra of TiO and TiO2.  

National Technical Information Service (NTIS)

The fine features of the Auger valence band spectra of TiO and TiO2 have been related to transitions arising from oxygen 2s and titanium 3d, 4s molecular orbitals. The N(E) valence band spectra have been unfolded and the resulting components correlated wi...

J. S. Solomon W. L. Baun

1976-01-01

155

Basis set effects on frontier molecular orbital energies and energy gaps: a comparative study between plane waves and localized basis functions in molecular systems.  

PubMed

In order to study the Kohn-Sham frontier molecular orbital energies in the complete basis limit, a comparative study between localized functions and plane waves, obtained with the local density approximation exchange-correlation functional is made. The analyzed systems are ethylene and butadiene, since they are theoretical and experimentally well characterized. The localized basis sets used are those developed by Dunning. For the plane-waves method, the pseudopotential approximation is employed. The results obtained by the localized basis sets suggest that it is possible to get an estimation of the orbital energies in the limit of the complete basis set, when the basis set size is large. It is shown that the frontier molecular orbital energies and the energy gaps obtained with plane waves are similar to those obtained with a large localized basis set, when the size of the supercell and the plane-wave expansion have been appropriately calibrated. PMID:15268062

Matus, Myrna H; Garza, Jorge; Galván, Marcelo

2004-06-01

156

Basis set effects on frontier molecular orbital energies and energy gaps: A comparative study between plane waves and localized basis functions in molecular systems  

Microsoft Academic Search

In order to study the Kohn-Sham frontier molecular orbital energies in the complete basis limit, a comparative study between localized functions and plane waves, obtained with the local density approximation exchange-correlation functional is made. The analyzed systems are ethylene and butadiene, since they are theoretical and experimentally well characterized. The localized basis sets used are those developed by Dunning. For

Myrna H. Matus; Jorge Garza; Marcelo Galván

2004-01-01

157

Basis set effects on frontier molecular orbital energies and energy gaps: A comparative study between plane waves and localized basis functions in molecular systems  

Microsoft Academic Search

In order to study the Kohn–Sham frontier molecular orbital energies in the complete basis limit, a comparative study between localized functions and plane waves, obtained with the local density approximation exchange-correlation functional is made. The analyzed systems are ethylene and butadiene, since they are theoretical and experimentally well characterized. The localized basis sets used are those developed by Dunning. For

Myrna H. Matus; Jorge Garza; Marcelo Galva´n

2004-01-01

158

?????????????????????????????????????????????????????????????? ????? ????????????????????? ????????? 3 ???? ILLUSTRATING THE DIMENSIONS OF THE BONDING MOLECULAR ORBITALS OF ETHANE, ETHENE, AND ETHYNE BY USING THE 3D ANIMATION MOVIES  

Microsoft Academic Search

In teaching Organic chemistry 1, the instructor developed the three 3D animation movies to illustrate the virtual models of the bonding molecular orbitals of the carbon-carbon bonds in the molecules of ethane, ethene, and ethyne. The created movies illustrated the dimensions around the bonding molecular orbitals. These computer assisted instruction (CAI) media could excite the students in class well. Introduction:

Itsara Khantikaew

159

Valence photoelectron spectroscopy of N2 and CO: recoil-induced rotational excitation, relative intensities, and atomic orbital composition of molecular orbitals.  

PubMed

Recoil-induced rotational excitation accompanying photoionization has been measured for the X, A, and B states of N(2)(+) and CO(+) over a range of photon energies from 60 to 900 eV. The mean recoil excitation increases linearly with the kinetic energy of the photoelectron, with slopes ranging from 0.73×10(-5) to 1.40×10(-5). These slopes are generally (but not completely) in accord with a simple model that treats the electrons as if they were emitted from isolated atoms. This treatment takes into account the atom from which the electron is emitted, the molecular-frame angular distribution of the electron, and the dependence of the photoelectron cross section on photon energy, on atomic identity, and on the type of atomic orbital from which the electron is ejected. These measurements thus provide a tool for investigating the atomic orbital composition of the molecular orbitals. Additional insight into this composition is obtained from the relative intensities of the various photolines in the spectrum and their variation with photon energy. Although there are some discrepancies between the predictions of the model and the observations, many of these can be understood qualitatively from a comparison of atomic and molecular wavefunctions. A quantum-mechanical treatment of recoil-induced excitation predicts an oscillatory variation with photon energy of the excitation. However, the predicted oscillations are small compared with the uncertainties in the data, and, as a result, the currently available results cannot provide confirmation of the quantum-mechanical theory. PMID:21054037

Thomas, T D; Kukk, E; Ouchi, T; Yamada, A; Fukuzawa, H; Ueda, K; Püttner, R; Higuchi, I; Tamenori, Y; Asahina, T; Kuze, N; Kato, H; Hoshino, M; Tanaka, H; Lindblad, A; Sæthre, L J

2010-11-01

160

On the room-temperature phase diagram of high pressure hydrogen: An ab initio molecular dynamics perspective and a diffusion Monte Carlo study.  

PubMed

The finite-temperature phase diagram of hydrogen in the region of phase IV and its neighborhood was studied using the ab initio molecular dynamics (MD) and the ab initio path-integral molecular dynamics (PIMD). The electronic structures were analyzed using the density-functional theory (DFT), the random-phase approximation, and the diffusion Monte Carlo (DMC) methods. Taking the state-of-the-art DMC results as benchmark, comparisons of the energy differences between structures generated from the MD and PIMD simulations, with molecular and dissociated hydrogens, respectively, in the weak molecular layers of phase IV, indicate that standard functionals in DFT tend to underestimate the dissociation barrier of the weak molecular layers in this mixed phase. Because of this underestimation, inclusion of the quantum nuclear effects (QNEs) in PIMD using electronic structures generated with these functionals leads to artificially dissociated hydrogen layers in phase IV and an error compensation between the neglect of QNEs and the deficiencies of these functionals in standard ab initio MD simulations exists. This analysis partly rationalizes why earlier ab initio MD simulations complement so well the experimental observations. The temperature and pressure dependencies for the stability of phase IV were also studied in the end and compared with earlier results. PMID:25028021

Chen, Ji; Ren, Xinguo; Li, Xin-Zheng; Alfè, Dario; Wang, Enge

2014-07-14

161

Stable conformation of full-length amyloid-? (1-42) monomer in water: Replica exchange molecular dynamics and ab initio molecular orbital simulations  

NASA Astrophysics Data System (ADS)

Aggregation of amyloid ?-proteins (A?) plays a key role in the mechanism of molecular pathogenesis of Alzheimer's disease (AD). It is known that full-length A?(1-42) is more prone to aggregation than A?(1-40). We here search stable conformations of solvated A?(1-42) monomer by replica exchange molecular dynamics simulations based on classical force fields, and the most stable conformation is determined from the total energies evaluated by the ab initio fragment molecular orbital (FMO) calculations. In addition, based on the FMO results, the amino acid residues of A?(1-42) contributing to the stabilization of the monomer are highlighted.

Okamoto, Akisumi; Yano, Atsushi; Nomura, Kazuya; Higai, Shin'ichi; Kurita, Noriyuki

2013-07-01

162

Liquid/liquid metal extraction: Phase diagram topology resulting from molecular interactions between extractant, ion, oil and water  

NASA Astrophysics Data System (ADS)

We consider the class of surfactants called "extractants" since they specifically interact with some cations and are used in liquid-liquid separation processes. We review here features of water-poor reverse micelles in water/oil/ extractant systems as determined by combined structural studies including small angle scattering techniques on absolute scale. Origins of instabilities, liquid-liquid separation as well as emulsification failure are detected. Phase diagrams contain the same multi-phase domains as classical microemulsions, but special unusual features appear due to the high spontaneous curvature directed towards the polar cores of aggregates as well as rigidity of the film made by extracting molecules.

Bauer, C.; Bauduin, P.; Dufrêche, J. F.; Zemb, T.; Diat, O.

2012-11-01

163

Venn diagrams  

NSDL National Science Digital Library

These online resources offer varied opportunities to work with Venn diagrams, one of many tools used in logic and reasoning. Their use is especially helpful in learning foundational notions of definition and set theory. One of the five Process Standards promoted by NCTM, Reasoning and Proof requires middle school students to sharpen such skills as they learn to develop mathematical argument.

National Science Digital Library (NSDL) Middle School Portal Staff

2008-03-10

164

Educational Diagrams.  

ERIC Educational Resources Information Center

According to Peirce, diagrammatic constructions are represented by words in a sentence, an algebraic formula, or a graphic display. They are the basis of all valid reasoning and provide significant means for discovering unexpected truths. Sources and uses of diagrams in education are discussed in relation to Peirce's ideas. Nineteen references are…

Moxley, Roy

1983-01-01

165

``On the fly'' localization of electronic orbitals in Car-Parrinello molecular dynamics: Toward a linear scaling ab initio molecular dynamics algorithm  

NASA Astrophysics Data System (ADS)

begincenter Large ``On the fly'' localization of electronic orbitals in Car-Parrinello molecular dynamics: Toward a linear scaling ab initio molecular dynamics algorithm center begincenter Mark E. Tuckerman Department of Chemistry and Courant Institute of Mathematical Sciences New York University, New York, NY 10003 center Ab initio molecular dynamics (AIMD), the technique that generates finite temperature dynamics using forces obtained from electronic structure calculations, is becoming a standard tool for studying chemical bond breaking and forming processes. The majority of AIMD calculations employ gradient-corrected density functional theory with a plane-wave basis set for expanding the electronic orbitals. This implementation scales as l O(N^2M), where N is the number of electrons and M is the number of basis functions. However, physics and chemistry tell us that the properties of matter should be local, suggesting that this scaling is an artifact of the algorithm. In this talk, we will discuss the two ingredients necessary for a linear scaling approach: Spatially localized orbitals and spatially localized basis functions. We will briefly review the use of discrete variable representations as a simple, localized, orthonormal basis set. The talk will focus primarily on a new approach for generating localized orbitals for periodic systems, the so called Wannier functions, within the Car-Parrinello extended Lagrangian approach to AIMD. It will be shown that orbital localization can be achieved ``on the fly'' in Car-Parrinello simulations by modifying the Lagrangian so as to make it fully invariant under time-dependent gauge transformations and then introducing a gauge-fixing procedure that minimizes the spatial spread of the orbitals.

Tuckerman, Mark

2004-03-01

166

Finite-temperature orbital-free GGA molecular dynamics for warm dense hydrogen  

NASA Astrophysics Data System (ADS)

The computational description of warm dense matter (WDM) by means of a combination of the Kohn-Sham (KS) finite-temperature density functional theory (DFT) for the electrons and classical molecular dynamics (MD) for the ions becomes an intractable task at high T (typically a few hundred kK). Finite-temperature orbital free DFT (OF-DFT) is a less expensive alternative. Only two non-interacting free-energy functionals for OF-DFT had been published and used until recently: the finite-temperature Thomas-Fermi (ftTF) model (Feynman et al., 1949) and ftTF with second-order gradient corrections (ftSGA) (Perrot, 1979). Here we report first results of OF-DFT MD simulations for warm dense H with a pair of newly developed ftGGA free energy functionals [1] for the non-interacting kinetic energy and entropy. The equation of state from these new functionals shows much better agreement with the reference KS MD results than results from the ftTF and ftSGA models. Other issues, e.g. convergence of the OF self-consistent procedure, also will be discussed.[4pt] [1]. V.V. Karasiev, T. Sjostrom and S.B. Trickey, Phys. Rev. B 86, 115101 (2012).

Karasiev, Valentin; Sjostrom, T.; Trickey, S. B.

2013-03-01

167

Time-dependent density functional theory based upon the fragment molecular orbital method  

NASA Astrophysics Data System (ADS)

Time-dependent density functional theory (TDDFT) was combined with the two-body fragment molecular orbital method (FMO2). In this FMO2-TDDFT scheme, the system is divided into fragments, and the electron density for fragments is determined self-consistently. Consequently, only one main fragment of interest and several fragment pairs including it are calculated by TDDFT. To demonstrate the accuracy of FMO2-TDDFT, we computed several low-lying singlet and triplet excited states of solvated phenol and polyalanine using our method and the standard TDDFT for the full system. The BLYP functional with the long-range correction (LC-BLYP) was employed with the 6-31G* basis set (some tests were also performed with 6-311G*, as well as with B3LYP and time-dependent Hartree-Fock). Typically, FMO2-TDDFT reproduced the full TDDFT excitation energies within 0.1 eV, and for one excited state the error was about 0.2 eV. Beside the accurate reproduction of the TDDFT excitation energies, we also automatically get an excitation energy decomposition analysis, which provides the contributions of individual fragments. Finally, the efficiency of our approach was exemplified on the LC-BLYP/6-31G* calculation of the lowest singlet excitation of the photoactive yellow protein which consists of 1931 atoms, and the obtained value of 3.1 eV is in agreement with the experimental value of 2.8 eV.

Chiba, Mahito; Fedorov, Dmitri G.; Kitaura, Kazuo

2007-09-01

168

A molecular orbital study of the dihedral angle dependencies of vicinal carbon-carbon coupling constants  

NASA Astrophysics Data System (ADS)

Theoretical studies are presented for the conformational dependencies of vicinal 13C? 13C coupling constants within a variety of saturated and unsaturated molecular frameworks. Using the MO approach of Blizzard and Santry ( J. Chem. Phys., 55, 950 (1971); 58, 4714 (1973)) , it is shown that three distinct patterns of dihedral angle vs 3JCCcontact coupling are produced, depending upon the degree of double bonding present within the direct coupling path. By means of calculations that involve modifying the various exchange integrals, two of these coupling patterns are found to depend on ?-? exchange. A rationalization of the origin of these coupling patterns is presented. In all systems studied, the orbital and dipolar contributions to the vicinal coupling constant are calculated to be negligible compared to the Fermi contact mechanism except in conjugated systems; in these cases the magnitude of the dipolar term is highly dependent on the dihedral angle and is approximately one-third of the total 3JCC at dihedral angles of 0 and 180°. The effect of substituents on 3JCC is discussed.

Severson, Mary L.; Maciel, Gary E.

169

A rational reduction of CI expansions: combining localized molecular orbitals and selected charge excitations.  

PubMed

Based on localized molecular orbitals, the proposed method reduces large configuration interaction (CI) spaces while maintaining agreement with reference values. Our strategy concentrates the numerical effort on physically pertinent CI-contributions and is to be considered as a tool to tackle large systems including numerous open-shells. To show the efficiency of our method we consider two 4-electron parent systems. First, we illustrate our approach by describing the van der Waals interactions in the (H2)2 system. By systematically including local correlation, dispersion and charge transfer mechanisms, we show that 90 % of the reference full CI dissociation energy of the H2 dimer is reproduced using only 3 % of the full CI space. Second, the conformational cis/trans rotation barrier of the butadiene molecule is remarkably reproduced (97 % of the reference value) with less than 1 % of the reference space. This work paves the way to numerical strategies which afford the electronic structure determination of large open-shell systems avoiding the exponential limitation. At the same time, a physical analysis of the contents of the wave function is offered. PMID:24935105

Krah, Tim; Ben Amor, Nadia; Maynau, Daniel; Berger, J A; Robert, Vincent

2014-07-01

170

Molecular structure and conformational composition of methyl chloroacetate: An electron-diffraction and ab initio molecular orbital investigation  

NASA Astrophysics Data System (ADS)

The molecular structure and conformational composition of methyl chloroacetate, H 2ClC sbnd C( dbnd O) sbnd O sbnd CH 3, have been determined by gas-phase electron-diffraction (GED), using results from ab initio molecular orbital calculations (HF, MP2 and MP3/6-311+G(d,p)) to obtain constraints on some of the structural parameters. The molecules exist in the gas-phase at 25 °C as a mixture of two stable conformers: syn with C sbnd Cl eclipsing C dbnd O and gauche with C sbnd H approximately eclipsing C dbnd O. In both of these conformers O sbnd CH 3 is also eclipsing C dbnd O. The experimentally observed conformational composition at 25 °C was 36(8)% syn and 64(8)% gauche (parenthesised values are 2 ?), corresponding to a free energy difference between conformers of ?Gexp° = 1.4(9) kJ/mol. The corresponding theoretical values obtained for ? G° are 1.1 kJ/mol (HF), 2.3 kJ/mol (MP2), and 2.4 kJ/mol (MP3). The results for the principal distances ( rh1) and angles ( ?h1) for the major gauche conformer obtained from the combined GED/ ab initio study (2 ? uncertainties) are r(CO sbnd CCl) = 1.502(9) Å, r(C sbnd H) = 1.084(6) Å (average value), r(C sbnd Cl) = 1.782(4) Å, r(C dbnd O) = 1.213(4) Å, r(CO sbnd O) = 1.346(4) Å, r(CH 3sbnd O) = 1.468(10) Å, ?C sbnd C sbnd Cl = 110.0(6)°, ?C sbnd C dbnd O = 124.7(6)°, ?C sbnd C sbnd O = 108.3(10)°, ?C sbnd O sbnd C = 115.9(8)°, ?(Cl sbnd C sbnd C dbnd O) = 111(2)°, ?(C sbnd O sbnd C dbnd O) = 3(3)°.

Aarset, Kirsten; Boldermo, Kjell Gunnar; Hagen, Kolbjørn

2010-08-01

171

Reduced explicitly correlated Hartree-Fock approach within the nuclear-electronic orbital framework: applications to positronic molecular systems.  

PubMed

In the application of the nuclear-electronic orbital (NEO) method to positronic systems, all electrons and the positron are treated quantum mechanically on the same level. Explicit electron-positron correlation can be included using Gaussian-type geminal functions within the variational self-consistent-field procedure. In this paper, we apply the recently developed reduced explicitly correlated Hartree-Fock (RXCHF) approach to positronic molecular systems. In the application of RXCHF to positronic systems, only a single electronic orbital is explicitly correlated to the positronic orbital. We apply NEO-RXCHF to three systems: positron-lithium, lithium positride, and positron-lithium hydride. For all three of these systems, the RXCHF approach provides accurate two-photon annihilation rates, average contact densities, electronic and positronic single-particle densities, and electron-positron contact densities. Moreover, the RXCHF approach is significantly more accurate than the original XCHF approach, in which all electronic orbitals are explicitly correlated to the positronic orbital in the same manner, because the RXCHF wavefunction is optimized to produce a highly accurate description of the short-ranged electron-positron interaction that dictates the annihilation rates and other local properties. Furthermore, RXCHF methods that neglect or approximate the electronic exchange interactions between the geminal-coupled electronic orbital and the regular electronic orbitals lead to virtually identical annihilation rates and densities as the fully antisymmetric RXCHF method but offer substantial advantages in computational tractability. Thus, NEO-RXCHF is a promising, computationally practical approach for studying larger positron-containing systems. PMID:23883006

Sirjoosingh, Andrew; Pak, Michael V; Swalina, Chet; Hammes-Schiffer, Sharon

2013-07-21

172

Investigation of the binding of Cr3+ to polysiloxane structures with semi-empirical molecular orbital models  

Microsoft Academic Search

The geometry and electronic spectra of small clusters comprised of hydrated Cr3+ interacting or binding with siloxane structures have been calculated with a semi-empirical molecular orbital method. The atomic parameters for silicon, oxygen, and chromium were first optimized using crystallographic and gas phase geometries. The electronic spectrum of the chromium hexa-aqua species was computed and matched the experimental spectrum within

James M. Kunetz; Rajiv D. Bendale; Larry L. Hench

1994-01-01

173

The Nonlocalized Molecular Orbital Model to Analyze Infrared and Vibrational Circular Dichroism Spectra: a Database Approach.  

NASA Astrophysics Data System (ADS)

The nonlocalized molecular orbital model (NMO) of Nafie and Freedman is implemented at the ab initio level to calculate IR and VCD intensities based on contributions of fixed partial charges (FPC), charge flow along bonds (CF) and atomic polarizations (PP). It is theoretically demonstrated that NMO is equivalent to the ab initio RHF formalism for IR intensities. Using local symmetry coordinates suitable for creating intensity parameters that are transferable among structurally related molecular fragments, NMO is applied to various molecules to test its validity, and its utility for a database approach for predicting IR and VCD intensities of larger systems. The IR intensities of propane are investigated in terms of FPC, CF and PP, which provides new conceptual insight into electronic effects of vibrations. The VCD spectra of (S)-1,1,1,2-tetradeuteropropane, (S)-1-deuteroethanol and (R)-2-methyloxetane are calculated with NMO, reproducing high level ab initio vibronic coupling and experimental intensities. Procedures are developed to create and retrieve transferable parameters for IR and VCD intensity databases. The concept is examined by compiling an intensity database from parameters of 10 small organic molecules and subsequently predicting the IR and VCD spectra of (R)-1-deutero-ethyl methyl ether and (R)-3-deutero-1-butene. The resulting absorption intensities correspond to those determined directly with NMO. The VCD spectrum of only the former is reproduced well. Discrepancies in the spectrum of the latter are mainly due to CF but also PP terms neglected in the database approach. The NMO-VCD model is tested on a series of terpenes. The measured IR and Raman spectra of alpha -pinene, beta-pinene, nopinone and verbenone are assigned based on non-uniformly scaled ab initio 6-31G^{*0.3} force fields in the range 0-1500 cm^{-1} . A total of 210 observed transitions are reproduced with an average error of 3.7 cm^{-1 }. The NMO-VCD intensities are shown to compare well to experimental features for well determined normal modes. Discrepancies observed in the range 1100-1350 cm ^{-1} are attributed to inaccuracies in the normal mode descriptions rather than shortcomings of the model. In general, the NMO model was shown to be a valid and useful method for predicting VCD intensities and expedient for database applications.

Maurer, Felix

174

Molecular structures and conformational compositions of 2-chlorobutane and 2-bromobutane; an investigation using gas-phase electron-diffraction data and ab initio molecular orbital calculations  

Microsoft Academic Search

The structure and conformational composition of 2-chlorobutane and 2-bromobutane have been studied by gas-phase electron diffraction (GED) at 25°C, together with ab initio molecular orbital calculations (HF\\/6-311+G(d,p)). These molecules may exist as three distinguishable conformers (G+, A, and G?). The symbols refer to anti (A) with a torsion angle ?2(X8–C2–C3–C4) of about 180° and gauche (G+ and G?) with torsion

Kirsten Aarset; Kolbjørn Hagen; Reidar Stølevik

2001-01-01

175

Molecular structure of tetramethoxygermane, Ge(OCH 3) 4, determined by gas-phase electron diffraction and ab initio molecular orbital calculations  

Microsoft Academic Search

The structure of tetramethoxygermane, Ge(OCH3)4, has been determined by gas-phase electron diffraction (GED) and ab initio molecular orbital calculations. Two distinct conformational geometries are feasible for this molecule, one having S4 symmetry and the other D2d symmetry. The S4 conformer was calculated to be about 3kcalmol?1 lower in energy than the D2d conformer. Refinements, based upon a dynamic model with

K. Aarset; F. J. Brady; E. M. Page; D. A. Rice

2000-01-01

176

Molecular structure and conformation of peroxydisulfuryl difluoride, S 2O 6F 2, as determined by gas-phase electron diffraction and ab initio molecular orbital calculations  

Microsoft Academic Search

The structure and conformational composition of peroxydisulfuryl difluoride, S2O6F2, have been investigated by gas-phase electron diffraction. Some of the results from ab initio molecular orbital calculations (MP2\\/6-311+G?) were used as constraints in the analysis. There is both experimental and theoretical evidence that only conformers with a gauche X–O–O–X torsion angle are present in the gaseous sample. Of these, only two

Kolbjørn Hagen; Kenneth Hedberg; Gary Gard; Felix Aubke

2001-01-01

177

The molecular structure of 2-bromostyrene and ( E)?-bromostyrene obtained by gas-phase electron diffraction and ab initio molecular orbital calculations  

Microsoft Academic Search

The molecular structures of 2-bromostyrene (C6H4Br–CH?CH2) and (E)?-bromostyrene (C6H5–CH?CHBr) have been studied using gas-phase electron diffraction at 378 and 373K, respectively, together with ab initio molecular orbital calculations (HF\\/6-311G(d) and MP2\\/6-311G(d)). The experimental data for 2-bromostyrene are consistent with a non-planar model in which the vinyl group is rotated away from the bromine atom (?(C8?C7–C1–C2)?155°). The presence of a small

Quang Shen; Jennifer Kuhns; Kolbjørn Hagen; Alan D Richardson

2001-01-01

178

Using Molecular Models To Show Steric Clash in Peptides: An Illustration of Two Disallowed Regions in the Ramachandran Diagram  

ERIC Educational Resources Information Center

In this activity, students manipulate three-dimensional molecular models of the Ala-Ala-Ala tripeptide, where Ala is alanine. They rotate bonds to show that the pairs of dihedral angles phi = 0 degrees, psi = 180 degrees, and phi = 0 degrees, psi = 0 degrees lead to unfavorable interactions among the main chain atoms of the tripeptide. This…

Halkides, Christopher J.

2013-01-01

179

Stereoelectronic Effects on the Basicity and Nucleophilicity of Phosphites and Phosphates. Ab Initio Molecular Orbital Calculations and the Alpha-Effect.  

National Technical Information Service (NTIS)

Ab initio molecular orbital calculations on phosphites, protonated phosphites, and protonated phosphates reveal important stereoelectronic effects. In the phosphites, an antiperiplanar lone pair on oxygen to the phosphite lone pair raises the energy of th...

K. Taira D. G. Gorenstein

1984-01-01

180

Kinetic temperatures toward X1/X2 orbit interceptions regions and giant molecular loops in the Galactic center region  

NASA Astrophysics Data System (ADS)

Context. It is well known that the kinetic temperatures, Tkin, of the molecular clouds in the Galactic center region are higher than in typical disk clouds. However, the Tkin of the molecular complexes found at higher latitudes towards the giant molecular loops in the central region of the Galaxy is so far unknown. The gas of these high-latitude molecular clouds (hereafter referred to as "halo clouds") is located in a region where the gas in the disk may interact with the gas in the halo in the Galactic center region. Aims: To derive Tkin in the molecular clouds at high latitude and understand the physical process responsible for the heating of the molecular gas both in the central molecular zone (the concentration of molecular gas in the inner ~500 pc) and in the giant molecular loops. Methods: We measured the metastable inversion transitions of NH3 from (J,K) = (1,1) to (6,6) toward six positions selected throughout the Galactic central disk and halo. We used rotational diagrams and large velocity gradient (LVG) modeling to estimate the kinetic temperatures toward all the sources. We also observed other molecules like SiO, HNCO, CS, C34S, C18O, and 13CO, to derive the densities and to trace different physical processes (shocks, photodissociation, dense gas) expected to dominate the heating of the molecular gas. Results: We derive for the first time Tkin of the high-latitude clouds interacting with the disk in the Galactic center region. We find high rotational temperatures in all the observed positions. We derive two kinetic temperature components (~150 K and ~40 K) for the positions in the central molecular zone, and only the warm kinetic temperature component for the clouds toward the giant molecular loops. The fractional abundances derived from the different molecules suggest that shocks provide the main heating mechanism throughout the Galactic center, also at high latitudes. Appendices A and B are available in electronic form at http://www.aanda.org

Riquelme, D.; Amo-Baladrón, M. A.; Martín-Pintado, J.; Mauersberger, R.; Martín, S.; Bronfman, L.

2013-01-01

181

Venn Diagrams  

NSDL National Science Digital Library

Unions, intersections, and differences: This can all be quite confusing to students trying to enter the potentially tricky world of Venn Diagrams. Fortunately, Alfredo Jiminez of Pennsylvania State University, Hazleton has created this handy Flash-enabled teaching application designed to provide students with an engaging way to learn about this subject. The project is party of the Digital Classroom Resources at the MAA Mathematical Sciences Digital Library, and visitors will find this particular learning activity quite easy to use. The interactive tool contains seven sections, including those dealing with the principles of union and intersection, distributive properties, and De Morgan's laws. Within each section, visitors can try their hand with a series of short questions and then take advantage of some review materials and, of course, a few basic tests.

Jiminez, Alfredo

182

Venn Diagrams  

NSDL National Science Digital Library

Unions, intersections, and differences: This can all be quite confusing to students trying to enter the potentially tricky world of Venn Diagrams. Fortunately, Alfredo Jiminez of Pennsylvania State University, Hazleton has created this handy Flash-enabled teaching application designed to provide students with an engaging way to learn about this subject. The project is party of the Digital Classroom Resources at the MAA Mathematical Sciences Digital Library, and visitors will find this particular learning activity quite easy to use. The interactive tool contains seven sections, including those dealing with the principles of union and intersection, distributive properties, and De Morgan's laws. Within each section, visitors can try their hand with a series of short questions and then take advantage of some review materials and, of course, a few basic tests.

Jiminez, Alfredo

2007-09-13

183

Formation of giant molecular clouds in global spiral structures: The role of orbital dynamics and cloud-cloud collisions  

NASA Technical Reports Server (NTRS)

The different roles played by orbital dynamics and dissipative cloud-cloud collisions in the formation of giant molecular clouds (GMCs) in a global spiral structure are investigated. The interstellar medium (ISM) is simulated by a system of particles, representing clouds, which orbit in a spiral-perturbed, galactic gravitational field. The overall magnitude and width of the global cloud density distribution in spiral arms is very similar in the collisional and collisionless simulations. The results suggest that the assumed number density and size distribution of clouds and the details of individual cloud-cloud collisions have relatively little effect on these features. Dissipative cloud-cloud collisions play an important steadying role for the cloud system's global spiral structure. Dissipative cloud-cloud collisions also damp the relative velocity dispersion of clouds in massive associations and thereby aid in the effective assembling of GMC-like complexes.

Roberts, W. W., Jr.; Stewart, G. R.

1987-01-01

184

Unrestricted absolutely localized molecular orbitals for energy decomposition analysis: theory and applications to intermolecular interactions involving radicals.  

PubMed

Radical-closed shell and radical-radical intermolecular interactions are less well-understood than those between closed shell species. With the objective of gaining additional insight, this work reports a generalization of the absolutely localized molecular orbital (ALMO) energy decomposition analysis (EDA) to open shell fragments, described by self-consistent field methods, such as standard density functional theory. The ALMO-EDA variationally partitions an intermolecular interaction energy into three separate contributions; frozen orbital interactions, polarization, and charge transfer. The first examples involve comparison of the interactions of alkanes and alkyl radicals (methyl radical, methane, tertiary butyl radical, and isobutane) with sodium, potassium, hydronium, and ammonium cations. A second series of examples involve benzene cation interacting with a series of nucleophiles in both on-top and side-on geometries. The ALMO-EDA yields a variety of interesting insights into the relative roles of its component contributions as the interacting partners and their geometries are changed. PMID:23574220

Horn, Paul R; Sundstrom, Eric Jon; Baker, Thomas A; Head-Gordon, Martin

2013-04-01

185

TES buffer-induced phase separation of aqueous solutions of several water-miscible organic solvents at 298.15 K: phase diagrams and molecular dynamic simulations.  

PubMed

Water and the organic solvents tetrahydrofuran, 1,3-dioxolane, 1,4-dioxane, 1-propanol, 2-propanol, tert-butanol, acetonitrile, or acetone are completely miscible in all proportions at room temperature. Here, we present new buffering-out phase separation systems that the above mentioned organic aqueous solutions can be induced to form two liquid phases in the presence of a biological buffer 2-[[1,3-dihydroxy-2-(hydroxymethyl)propan-2-yl]amino]ethanesulfonic acid (TES). The lower liquid phase is rich in water and buffer, and the upper phase is organic rich. This observation has both practical and mechanistic interests. The phase diagrams of these systems were constructed by experimental measurements at ambient conditions. Molecular dynamic (MD) simulations were performed for TES + water + THF system to understand the interactions between TES, water, and organic solvent at molecular level. Several composition-sets for this system, beyond and inside the liquid-liquid phase-splitting region, have been simulated. Interestingly, the MD simulation for compositions inside the phase separation region showed that THF molecules are forced out from the water network to start forming a new liquid phase. The hydrogen-bonds, hydrogen-bonds lifetimes, hydrogen-bond energies, radial distribution functions, coordination numbers, the electrostatic interactions, and the van der Waals interactions between the different pairs have been calculated. Additionally, MD simulations for TES + water + tert-butanol?acetonitrile?acetone phase separation systems were simulated. The results from MD simulations provide an explanation for the buffering-out phenomena observed in [TES + water + organic solvent] systems by a mechanism controlled by the competitive interactions of the buffer and the organic solvent with water. The molecular mechanism reported here is helpful for designing new benign separation materials. PMID:23822250

Taha, Mohamed; Lee, Ming-Jer

2013-06-28

186

Effect of molecular-orbital rotations on ground-state energies in the parametric two-electron reduced density matrix method  

NASA Astrophysics Data System (ADS)

Different sets of molecular orbitals and the rotations connecting them are of great significance in molecular electronic structure. Most electron correlation methods depend on a reference wave function that separates the orbitals into occupied and unoccupied spaces. Energies and properties from these methods depend upon rotations between the spaces. Some electronic structure methods, such as modified coupled electron pair approximations and the recently developed parametric two-electron reduced density matrix (2-RDM) methods [D. A. Mazziotti, Phys. Rev. Lett. 101, 253002 (2008)], also depend upon rotations between occupied orbitals and rotations between unoccupied orbitals. In this paper, we explore the sensitivity of the ground-state energies from the parametric 2-RDM method to rotations within the occupied space and within the unoccupied space. We discuss the theoretical origin of the rotational dependence and provide computational examples at both equilibrium and non-equilibrium geometries. We also study the effect of these rotations on the size extensivity of the parametric 2-RDM method. Computations show that the orbital rotations have a small effect upon the parametric 2-RDM energies in comparison to the energy differences observed between methodologies such as coupled cluster and parametric 2-RDM. Furthermore, while the 2-RDM method is rigorously size extensive in a local molecular orbital basis set, calculations reveal negligible deviations in nonlocal molecular orbital basis sets such as those from canonical Hartree-Fock calculations.

Sand, Andrew M.; Mazziotti, David A.

2013-06-01

187

Effect of molecular-orbital rotations on ground-state energies in the parametric two-electron reduced density matrix method.  

PubMed

Different sets of molecular orbitals and the rotations connecting them are of great significance in molecular electronic structure. Most electron correlation methods depend on a reference wave function that separates the orbitals into occupied and unoccupied spaces. Energies and properties from these methods depend upon rotations between the spaces. Some electronic structure methods, such as modified coupled electron pair approximations and the recently developed parametric two-electron reduced density matrix (2-RDM) methods [D. A. Mazziotti, Phys. Rev. Lett. 101, 253002 (2008)], also depend upon rotations between occupied orbitals and rotations between unoccupied orbitals. In this paper, we explore the sensitivity of the ground-state energies from the parametric 2-RDM method to rotations within the occupied space and within the unoccupied space. We discuss the theoretical origin of the rotational dependence and provide computational examples at both equilibrium and non-equilibrium geometries. We also study the effect of these rotations on the size extensivity of the parametric 2-RDM method. Computations show that the orbital rotations have a small effect upon the parametric 2-RDM energies in comparison to the energy differences observed between methodologies such as coupled cluster and parametric 2-RDM. Furthermore, while the 2-RDM method is rigorously size extensive in a local molecular orbital basis set, calculations reveal negligible deviations in nonlocal molecular orbital basis sets such as those from canonical Hartree-Fock calculations. PMID:23822222

Sand, Andrew M; Mazziotti, David A

2013-06-28

188

Interaction of anticonvulsant drugs with metals: a semi-empirical molecular orbital study of phenytoin–zinc(II) complexation  

Microsoft Academic Search

The interaction of Zn(II) cation with the anticonvulsant phenytoin (PHT) was investigated using semi-empirical AM1 molecular orbital calculations. All possible modes of PHT–Zn(II) complexation were systematically studied by aligning Zn(II) along the three amide faces of PHT’s imidazoline-2,4-dione ring. The AM1 calculations indicated that Zn(II) bridges two PHT molecules; six Zn(PHT)22+ complexes were evaluated. In more stable structures, Zn(II) coordinates

Paul Milne; Minhhuy Hô; Donald F Weaver

1999-01-01

189

Excited state geometry optimizations by time-dependent density functional theory based on the fragment molecular orbital method  

NASA Astrophysics Data System (ADS)

The energy gradient method is introduced to the fragment molecular orbital based time-dependent density functional theory (FMO-TDDFT), which we have recently developed to calculate excitation energies of large systems by dividing them into fragments. By using the energy gradient of FMO-TDDFT, excited state geometry optimizations of a polypeptide and solvated formaldehyde are carried out using the LC-BOP functional and the 6-31G? basis set. The accuracy of the optimized structures and the excitation energies in comparison to conventional TDDFT is discussed.

Chiba, Mahito; Fedorov, Dmitri G.; Nagata, Takeshi; Kitaura, Kazuo

2009-05-01

190

Demystifying Introductory Chemistry. Part 2: Bonding and Molecular Geometry Without Orbitals--the Electron Domain Model.  

ERIC Educational Resources Information Center

Presents an alternative approach to bonding and geometry--the electron domain model--which avoids some of the problems with the conventional approach. Discusses difficulties with the orbital model at the introductory level, electron spin and the Pauli exclusion principle, electron pair domains, nonequivalent domains, multiple bonds, and origins…

Gillespie, Ronald J.; And Others

1996-01-01

191

Analytic energy gradient for second-order Møller-Plesset perturbation theory based on the fragment molecular orbital method.  

PubMed

The first derivative of the total energy with respect to nuclear coordinates (the energy gradient) in the fragment molecular orbital (FMO) method is applied to second order Møller-Plesset perturbation theory (MP2), resulting in the analytic derivative of the correlation energy in the external self-consistent electrostatic field. The completely analytic energy gradient equations are formulated at the FMO-MP2 level. Both for molecular clusters (H(2)O)(64) and a system with fragmentation across covalent bonds, a capped alanine decamer, the analytic FMO-MP2 energy gradients with the electrostatic dimer approximation are shown to be complete and accurate by comparing them with the corresponding numeric gradients. The developed gradient is parallelized with the parallel efficiency of about 97% on 32 Pentium4 nodes connected by Gigabit Ethernet. PMID:21806093

Nagata, Takeshi; Fedorov, Dmitri G; Ishimura, Kazuya; Kitaura, Kazuo

2011-07-28

192

A third-generation density-functional-theory-based method for calculating canonical molecular orbitals of large molecules.  

PubMed

We used grid-free modified Cholesky decomposition (CD) to develop a density-functional-theory (DFT)-based method for calculating the canonical molecular orbitals (CMOs) of large molecules. Our method can be used to calculate standard CMOs, analytically compute exchange-correlation terms, and maximise the capacity of next-generation supercomputers. Cholesky vectors were first analytically downscaled using low-rank pivoted CD and CD with adaptive metric (CDAM). The obtained Cholesky vectors were distributed and stored on each computer node in a parallel computer, and the Coulomb, Fock exchange, and pure exchange-correlation terms were calculated by multiplying the Cholesky vectors without evaluating molecular integrals in self-consistent field iterations. Our method enables DFT and massively distributed memory parallel computers to be used in order to very efficiently calculate the CMOs of large molecules. PMID:24622472

Hirano, Toshiyuki; Sato, Fumitoshi

2014-06-25

193

Orbital-free molecular dynamics simulations of a warm dense mixture: Examination of the excess-pressure matching rule  

SciTech Connect

A form of the linear mixing rule involving the equality of excess pressures is tested with various mole fractions and various types of orbital-free molecular dynamics simulations. For all the cases considered, this mixing rule yields, within statistical error, the pressure of a mixture of helium and iron obtained by a direct simulation. In an attempt to interpret the robustness of the mixing rule, we show that it can be derived from thermodynamic stability if the system is regarded as a mixture of independent effective average atoms. The success of the mixing rule applied with equations of state including various degrees of approximation leads us to suggest its use in the thermodynamic domain where quantum molecular dynamics can be implemented.

Danel, J-F.; Kazandjian, L.; Zerah, G. [Centre DAM Ile-de-France, CEA, Bruyeres-le-Chatel, 91297 Arpajon Cedex (France)

2009-06-15

194

Analysis of electron correlation effects and contributions of NMR J-couplings from occupied localized molecular orbitals.  

PubMed

NMR J-coupling calculations at the second-order of polarization propagator approach, SOPPA, are among the most reliable. They include a high percentage of the total electron correlation effects in saturated and unsaturated molecular systems. Furthermore, J-couplings are quite sensitive to the whole electronic molecular framework. We present in this article the first study of all three response mechanisms, Fermi contact, FC, spin-dipolar, SD and paramagnetic spin-orbital, PSO, for J-couplings with occupied localized molecular orbitals at the SOPPA level of approach. Even though SOPPA results are not invariant under unitary transformations, the difference between results obtained with canonical and localized molecular orbitals, LMOs, are small enough to permit its application with confidence. The following small-size saturated and unsaturated compounds were analyzed: CH(4), CH(3)F, C(2)H(6), NH(3), C(2)H(4), CH(2)NH, H(2)C?CHF, and FHC?CHF. The local character of the FC mechanism that appears in J-couplings of these molecular models is shown through the analysis of contributions from LMOs. The importance of including the electron correlation on the engaged bonding orbitals for one-bond couplings is emphasized. Almost all electron correlation effects are included in such orbitals. Interesting findings were the large contributions by s-type LMOs to the C-H and C-C J-couplings; they are responsible for the variation of (1)J(C-C) when going from ethane to ethene and to 1,2-difluoroethene. The previously proposed hyperconjugative transfer mechanism has been tested. Among other tests we found the difference anti-syn of one-bond (1)J(C-H) in imine as due to both the corresponding ?(C-H) and the lone-pair, LP, contribution. Geminal and vicinal J-couplings were also analyzed. Our findings are in accord with a previous work by Pople and Bothner-by, who considered results taken from calculations or empirical data. For all geminal couplings the pattern of J-couplings, like the change of sign, is originated in the main bondings that participate in the coupling pathways. The finding of asymmetric contributions of LP to vicinal H-H couplings in imine is highlighted. The analysis of J-couplings by contributions from LMOs to the noncontact mechanisms, SD and PSO, show that the ? electronic framework makes both terms grow in the specific case of the model compounds studied here. The PSO mechanism is more efficient when a ? bond is vicinal to a ? bond. We found in this way an efficient and powerful scheme to get a deeper insight on the electronic molecular framework on which J-couplings are transmitted. PMID:22217318

Zarycz, Natalia; Aucar, Gustavo A

2012-02-01

195

Self-consistent field convergence for proteins: a comparison of full and localized-molecular-orbital schemes.  

PubMed

Proteins in the gas phase present an extreme (and unrealistic) challenge for self-consistent-field iteration schemes because their ionized groups are very strong electron donors or acceptors, depending on their formal charge. This means that gas-phase proteins have a very small band gap but that their frontier orbitals are localized compared to "normal" conjugated semiconductors. The frontier orbitals are thus likely to be separated in space so that they are close to, but not quite, orthogonal during the SCF iterations. We report full SCF calculations using the massively parallel EMPIRE code and linear scaling localized-molecular-orbital (LMO) calculations using Mopac2009. The LMO procedure can lead to artificially over-polarized wavefunctions in gas-phase proteins. The full SCF iteration procedure can be very slow to converge because many cycles are needed to overcome the over-polarization by inductive charge shifts. Example molecules have been constructed to demonstrate this behavior. The two approaches give identical results if solvent effects are included. PMID:24573500

Wick, Christian R; Hennemann, Matthias; Stewart, James J P; Clark, Timothy

2014-03-01

196

Beyond the spin model: exchange coupling in molecular magnets with unquenched orbital angular momenta.  

PubMed

In this critical review we review the problem of exchange interactions in polynuclear metal complexes involving orbitally degenerate metal ions. The key feature of these systems is that, in general, they carry an unquenched orbital angular momentum that manifests itself in all their magnetic properties. Thus, interest in degenerate systems involves fundamental problems related to basic models in magnetism. In particular, the conventional Heisenberg-Dirac-Van Vleck model becomes inapplicable even as an approximation. In the first part we attempt to answer two key questions, namely which theoretical tools are to be used in the case of degeneracy, and how these tools can be employed. We demonstrate that the exchange interaction between orbitally degenerate metal ions can be described by the so-called orbitally-dependent exchange Hamiltonian. This approach has shown to reveal an anomalously strong magnetic anisotropy that can be considered as the main physical manifestation of the unquenched orbital angular momentum in magnetic systems. Along with the exchange coupling, a set of other interactions (such as crystal field effects, spin-orbit and Zeeman coupling), which are specific for the degenerate systems, need to be considered. All these features will be discussed in detail using a pseudo-spin-1/2 Hamiltonian approach. In the second part, the described theoretical background will be used to account for the magnetic properties of several magnetic metal clusters and low-dimensional systems: (i) the dinuclear face-sharing unit [Ti(2)Cl(9)](3-), which exhibits a large magnetic anisotropy; (ii) the rare-earth compounds Cs(3)Yb(2)Cl(9) and Cs(3)Yb(2)Br(9), which, surprisingly, exhibit a full magnetic isotropy; (iii) a zig-zag Co(II) chain exhibiting unusual combination of single-chain magnet behavior and antiferromagnetic exchange coupling; (iv) a trigonal bipyramidal Ni(3)Os(2) complex; (v) various Co(II) clusters encapsulated by polyoxometalate ligands. In the two last examples a pseudospin-1/2 Hamiltonian approach is applied to account for the presence of exchange anisotropy (150 references). PMID:21431145

Palii, Andrei; Tsukerblat, Boris; Klokishner, Sophia; Dunbar, Kim R; Clemente-Juan, Juan M; Coronado, Eugenio

2011-06-01

197

Continuous corrections to the molecular Kohn-Sham gap and virtual orbitals  

Microsoft Academic Search

We use projector operators to correct the Kohn-Sham Hamiltonian of density functional theory (KS-DFT) so that the resulting mean-field scheme yields, in finite systems, virtual orbitals and energy gaps in better agreement with those predicted by quasiparticle theory. The proposed correction term is a scissors-like operator of the form $(\\\\hat{I}-\\\\hat{\\\\rho})\\\\delta \\\\hat{H}(\\\\hat{I}-\\\\hat{\\\\rho})$, where $\\\\hat{I}$ is the identity operator, $\\\\hat{\\\\rho}$ the density

Hector Mera

2008-01-01

198

Density matrix averaged atomic natural orbital (ANO) basis sets for correlated molecular wave functions  

Microsoft Academic Search

Generally contracted basis sets for the first row transition metal atoms Sc-Zn have been constructed using the atomic natural orbital (ANO) approach, with modifications for allowing symmetry breaking and state averaging. The ANOs are constructed by averaging over the three electronic configurationsdn,dn-1s, anddn-2s2 for the neutral atom as well as the ground state for the cation and the ground state

Rosendo Pou-Amérigo; Manuela Merchán; Ignacio Nebot-Gil; Per-Olof Widmark; Bjiirn O. Roos

1995-01-01

199

A group theoretical paradigm for describing the skeletal molecular orbitals of cluster compounds. Part 3  

NASA Astrophysics Data System (ADS)

The group theoretical consequences of the Tensor Surface Harmonic Theory have been developed for [ML2] n , [ML4] n and [ML5] n clusters where either the xz and yz or x 2- y 2 and xy components to L {/d ? } and L {/d ? } do not contribute equally to the bonding. The closed shell requirements for such clusters are defined and the orbital symmetry constraints pertaining to the interconversion of conformers of these clusters are described.

Mingos, D. M. P.; Zhenyang, Lin

1989-03-01

200

Facile photochemical synthesis of 5,10-disubstituted [5]helicenes by removing molecular orbital degeneracy.  

PubMed

Photocyclodehydrogenation is a key reaction to synthesize helicenes; however, because of overannulation, it is not applicable to the synthesis of [5]helicene. Introduction of a cyano group was found to remove the orbital degeneracy of the low-lying unoccupied MOs; consequently, the lowest excitation comprises a single transition involving the C2-antisymmetric MO. Therefore, the problematic overannulation can be effectively suppressed. Moreover, in combination with the Knoevenagel reaction, a one-pot synthesis of 5,10-dicyano[5]helicene with 67% yield was accomplished. PMID:24749957

Ito, Natsuki; Hirose, Takashi; Matsuda, Kenji

2014-05-01

201

Molecular structure of phenylsilane: a study by gas-phase electron diffraction and ab initio molecular orbital calculations  

Microsoft Academic Search

The molecular structure of phenylsilane has been determined accurately by gas-phase electron diffraction and ab initio MO calculations at the MP2(f.c.)\\/6-31G* level. The calculations indicate that the perpendicular conformation of the molecule, with a Si–H bond in a plane orthogonal to the plane of the benzene ring, is the potential energy minimum. The coplanar conformation, with a Si–H bond in

Gustavo Portalone; Fabio Ramondo; Aldo Domenicano; István Hargittai

1998-01-01

202

Bonding, Backbonding, and Spin-Polarized Molecular Orbitals:Basis for Magnetism and Semiconducting Transport in V[TCNE]x~;;2  

SciTech Connect

X-ray absorption spectroscopy (XAS) and magnetic circular dichroism (MCD) at the V L2,3 and C and N K edges reveal bonding/backbonding interactions in films of the 400 K magnetic semiconductor V[TCNE]x~;;2. In V spectra, dxy-like orbitals are modeled assuming V2+ in an octahedral ligand field, while dz2 and dx2-y2 orbitals involved in strong covalent bonding cannot be modeled by atomic calculations. C and N MCD, and differences in XAS from neutral TCNE molecules, reveal spin-polarized molecular orbitals in V[TCNE]x~;;2 associated with backbonding interactions that yield its novel properties.

Kortright, Jeffrey B; Kortright, Jeffrey B; Lincoln, Derek M; Edelstein, Ruth Shima; Epstein, Arthur J

2008-05-20

203

Molecular orbital calculation of proton shielding tensors for the interpretation of solid state NMR data  

NASA Astrophysics Data System (ADS)

We give a short review of the gauge-invariant calculation of shielding constants and susceptibilities from the ground state wvefunction. Since the method is well suited for localizad orbitals, PC ILO bond orbitals are used for the shielding calculation of glycine and its hydrogen bonded dimer (and for testing the theory also CH 4 and C 2H 6). From these values the 1H shielding tensors are constructed in an incrementary way. The calculated data are compared with experimental results and the N?H…O hydrogen bond is investigated in detail. The theory gives an anisotropy of a N?H…O hydrogen bonded proton of ?? = 28.3 ppm and a value of a NH proton without hydrogen bond of ?? = 18.8 ppm and for the CH proton ?? = 12.5 ppm results. When taking into account the rotation of the NH ?3 groups we find that the qualitative features of the experiment are correctly represented. For the anisotropy ?? = -6.55 ppm and for the asymmetry ? = 0.588 are obtained. The experimental values are -5.63 ppm and 0.805, respectively.

Sternberg, U.; Rosenberger, H.

1981-02-01

204

Abundances and Energetics for Water Group and Molecular Oxygen Ions in Saturn's Magnetosphere After 24 Cassini Orbits  

NASA Astrophysics Data System (ADS)

We present magnetospheric ion composition results from the Cassini Plasma Spectrometer (CAPS) for the first 24 orbits of Cassini about Saturn. Apoapses of these orbits have local times between 3 and 8 MLT. Data from the Ion Mass Spectrometer (IMS) are summed to achieve better statistics and to bring out features that are otherwise difficult to resolve from an individual orbital pass. We highlight some of our results here. As described previously, water group ions (O+, OH+, H2O+, H3O+; or collectively, W+) dominate over H+ in the inner plasmasphere (Young et al., 2005; Sittler et al., 2005). We find that on average, this dominance persists out to 20 Saturn Radii (RS), and although weakening rapidly, W+ ions are observed out to 25 RS. The density of hydronium, which is the dominant W+ species within 4 RS, peaks at 5 RS and rapidly drops with an radial length scale of 1 RS; hydronium is no longer detectable beyond 14 RS. The W+ plasma has both a core component and a higher-energy tail. The density ratio of the tail to the core increases (length scale of 1.3 RS) out to 10 RS and then flattens out to a constant factor of 0.1. The mean core energy increases by a factor of 20 between 4 and 20 RS, nearly following rigid co-rotation. However, the mean tail energy is flat between 4 and 15 RS, at 3 keV and then increases by a factor of 2 between 15 and 20 RS, indicating a separate dynamic history from the core. Finally, we detect molecular oxygen (O2+) out to 10 RS. At 4.5 RS, the O2+ density is 5% of the W+ density, and the O2+ density drops relative to W+ with a radial length scale of 2 RS.

Martens, Hilary R.; Reisenfeld, D. B.; Williams, J. D.; DiLorenzo, J.; Thomsen, M. F.; Smith, H. T.; Eviatar, A.; Johnson, R. E.; Young, D. T.; Sittler, E. C.; Baragiola, R. A.

2006-09-01

205

Molecular interactions of the quinone electron acceptors Q(A), Q(B), and Q(C) in photosystem II as studied by the fragment molecular orbital method.  

PubMed

Molecular interactions of the three plastoquinone electron acceptors, Q(A), Q(B), and Q(C), in photosystem II (PSII) were studied by fragment molecular orbital (FMO) calculations. Calculations at the FMO-MP2/6-31G level using PSII models deduced from the X-ray structure of the PSII complexes from Thermosynechococcus elongatus provided the binding energies of Q(A), Q(B), and Q(C) as -56.1, -37.9, and -30.1 kcal/mol, respectively. The interaction energies with surrounding fragments showed that the contributions of lipids and cofactors were 0, 24 and 45 % of the total interaction energies for Q(A), Q(B), and Q(C), respectively. These results are consistent with the fact that Q(A) is strongly bound to the PSII protein, whereas Q(B) functions as a substrate and is exchangeable with other quinones and herbicides, and the presence of Q(C) is highly dependent on PSII preparations. It was further shown that the isoprenoid tail is more responsible for the binding than the head group in all the three quinones, and that dispersion forces rather than electrostatic interactions mainly contribute to the stabilization. The relevance of the stability and molecular interactions of Q(A), Q(B), and Q(C) to their physiological functions is discussed. PMID:23208472

Hasegawa, Koji; Noguchi, Takumi

2014-05-01

206

Molecular-orbital X-rays and their anisotropies in heavy-ion collisions in solids and gases  

NASA Astrophysics Data System (ADS)

Molecular-orbital spectra and anisotropies were measured in Cl+NaCl, Cl+KCl, Cl +Ti, and Cl+Ar collisions at bombarding energies between 0.5 and 2.6MeV/a.m.u. The results suggest that at low bombarding energies MO x-rays in the KCl and NaCl targets are partly produced by a two-collision process. Qualitative differences between the anisotropies of gas- and solid-target induced MO x-ray spectra underline this result. Also, new information on the bombarding-energy dependency of anisotropies at higher projectile velocities has been obtained, confirming previous observations in low- Z systems.

Stoller, Ch; Anholt, R.; Meyerhof, W. E.

1981-06-01

207

Theoretical calculation of the low lying electronic states of the molecular ion RbH(+) with spin-orbit effects.  

PubMed

The potential energy has been calculated for the 42 lowest electronic states of symmetries Omega=12,32,52, for the molecular ion RbH(+). Using an ab initio method, the calculation is based on nonempirical pseudopotentials and parametrized [script-l]-dependent polarization potentials. Gaussian basis sets have been used for both atoms, and spin-orbit effects have been taken into account. The spectroscopic constants for 19 electronic states have been calculated by fitting the calculated energy values to a polynomial in terms of the internuclear distance r. The permanent dipole moment and the transition dipole moments have been calculated for the considered Omega states. Through the canonical functions approach the eigenvalue E(v), the abscissas of the corresponding turning points (r(min) and r(max)) and the rotational constants B(v) have been calculated. The comparison of the present results with those available in literature shows a very good agreement. PMID:19045861

Korek, M; Hammoud, S; Allouche, A R; Harb, T

2008-11-28

208

Investigation of the binding of Cr3+ to polysiloxane structures with semi-empirical molecular orbital models  

NASA Astrophysics Data System (ADS)

The geometry and electronic spectra of small clusters comprised of hydrated Cr3+ interacting or binding with siloxane structures have been calculated with a semi-empirical molecular orbital method. The atomic parameters for silicon, oxygen, and chromium were first optimized using crystallographic and gas phase geometries. The electronic spectrum of the chromium hexa-aqua species was computed and matched the experimental spectrum within a few 100 cm-1 of the UV and visible absorption maximums. The theoretical models reproduced the experimental peak shifting of the 4A2g yields 4T2g and 4A2g yields 4T1g transitions and elucidate the changes in the environment that the chromium ion might experience within the sol-gel porous network.

Kunetz, James M.; Bendale, Rajiv D.; Hench, Larry L.

1994-10-01

209

Vibrational spectra of 2 (3H) benzofuranone studied by Raman, IR spectroscopy and AM1 semiempirical molecular orbital calculations  

NASA Astrophysics Data System (ADS)

Raman spectra of 2 (3H) benzofuranone have been recorded in the region 400-3200 cm -1and the IR spectra have been recorded in the region 200-4000 cm -1. Vibrational frequencies for the fundamental modes of this bicyclic heteroatomic molecule have also been calculated using Austin method 1 (AM1) semiempirical molecular orbital method. Vibrational assignments have been made for the fundamental modes and the observed combination and overtone bands are also assigned. A splitting in the carbonyl group(C?O stretching) frequency observed at 1640-1660 cm -1 in both Raman and IR spectra, is explained as Fermi-resonance. Net atomic charges for each atom of this molecule along with its heat of formation were also calculated. It is evident from the calculations that the 2 (3H) benzofuranone is more stable than the 3 (2H) benzofuranone in contrast to earlier estimates.

Pandey, V. K.; Singh, V. B.; Rai, Amareshwer K.; Asthana, B. P.; Rai, S. B.; Rai, D. K.

2003-01-01

210

Vibrational spectra of 2 (3H) benzofuranone studied by Raman, IR spectroscopy and AM1 semiempirical molecular orbital calculations.  

PubMed

Raman spectra of 2 (3H) benzofuranone have been recorded in the region 400-3200 cm(-1) and the IR spectra have been recorded in the region 200-4000 cm(-1). Vibrational frequencies for the fundamental modes of this bicyclic heteroatomic molecule have also been calculated using Austin method 1 (AM1) semiempirical molecular orbital method. Vibrational assignments have been made for the fundamental modes and the observed combination and overtone bands are also assigned. A splitting in the carbonyl group (C=O stretching) frequency observed at 1640-1660 cm(-1) in both Raman and IR spectra, is explained as Fermi-resonance. Net atomic charges for each atom of this molecule along with its heat of formation were also calculated. It is evident from the calculations that the 2 (3H) benzofuranone is more stable than the 3 (2H) benzofuranone in contrast to earlier estimates. PMID:12685893

Pandey, V K; Singh, V B; Rai, Amareshwer K; Asthana, B P; Rai, S B; Rai, D K

2003-01-15

211

Ab initio quantum-chemical study on emission spectra of bioluminescent luciferases by fragment molecular orbital method  

NASA Astrophysics Data System (ADS)

Bioluminescence spectra of firefly Luciola cruciata were theoretically analyzed on the basis of the fragment molecular orbital (FMO) method. The CIS(D) and PR-CIS(Ds) methods were employed for the calculations of emission energies of wild-type and mutant luciferase-oxyluciferin systems, and various multi-layer FMO calculations were performed changing the sizes of the luciferase protein and of the chromophore to which the excited-state calculations were applied. We have thus reproduced the experimental emission energies of wild-type and mutant luciferase systems with good accuracy, which provides useful information concerning the roles of protein environment for the color tuning of the bioluminescence spectra of firefly.

Tagami, Ayumu; Ishibashi, Nobuhiro; Kato, Dai-ichiro; Taguchi, Naoki; Mochizuki, Yuji; Watanabe, Hirofumi; Ito, Mika; Tanaka, Shigenori

2009-04-01

212

Complete determination of molecular orbitals by measurement of phase symmetry and electron density.  

PubMed

Several experimental methods allow measuring the spatial probability density of electrons in atoms, molecules and solids, that is, the absolute square of the respective single-particle wave function. But it is an intrinsic problem of the measurement process that the information about the phase is generally lost during the experiment. The symmetry of this phase, however, is a crucial parameter for the knowledge of the full orbital information in real space. Here, we report on a key experiment that demonstrates that the phase symmetry can be derived from a strictly experimental approach from the circular dichroism in the angular distribution of photoelectrons. In combination with the electron density derived from the same experiment, the full quantum mechanical wave function can thus be determined experimentally. PMID:24910256

Wießner, M; Hauschild, D; Sauer, C; Feyer, V; Schöll, A; Reinert, F

2014-01-01

213

Controlling the Interference of Multiple Molecular Orbitals in High-Harmonic Generation  

SciTech Connect

We demonstrate a new method to investigate the origin of spectral structures in high-harmonic generation. We report detailed measurements of high-harmonic spectra in aligned nitrogen and carbon dioxide molecules. Varying the wavelength and intensity of the generating laser field, we show that the minimum in aligned N{sub 2} molecules is nearly unaffected, whereas the minimum in aligned CO{sub 2} molecules shifts over more than 15 eV. Our quantitative analysis shows that both the interference of multiple orbitals and their structural characteristics affect the position of the minimum. Our method provides a simple approach to the investigation of the high-harmonic generation process in more complex molecules.

Woerner, H. J.; Bertrand, J. B.; Hockett, P.; Corkum, P. B.; Villeneuve, D. M. [Joint Laboratory for Attosecond Science, National Research Council of Canada and University of Ottawa, 100 Sussex Drive, Ottawa, Ontario, K1A 0R6 (Canada)

2010-06-11

214

Efficient implementation of the three-dimensional reference interaction site model method in the fragment molecular orbital method  

NASA Astrophysics Data System (ADS)

The three-dimensional reference interaction site model (3D-RISM) method was efficiently implemented in the fragment molecular orbital (FMO) method. The method is referred to as the FMO/3D-RISM method, and allows us to treat electronic structure of the whole of a macromolecule, such as a protein, as well as the solvent distribution around a solute macromolecule. The formalism of the FMO/3D-RISM method, for the computationally available form and variational expressions, are proposed in detail. A major concern leading to the implementation of the method was decreasing the computational costs involved in calculating the electrostatic potential, because the electrostatic potential is calculated on numerous grid points in three-dimensional real space in the 3D-RISM method. In this article, we propose a procedure for decreasing the computational costs involved in calculating the electrostatic potential in the FMO method framework. The strategy involved in this procedure is to evaluate the electrostatic potential and the solvated Fock matrix in different manners, depending on the distance between the solute and the solvent. The electrostatic potential is evaluated directly in the vicinity of the solute molecule by integrating the molecular orbitals of monomer fragments of the solute molecule, whereas the electrostatic potential is described as the sum of multipole interactions when an analog of the fast multipole method is used. The efficiency of our method was demonstrated by applying it to a water trimer system and three biomolecular systems. The FMO/3D-RISM calculation can be performed within a reasonable computational time, retaining the accuracy of some physical properties.

Yoshida, Norio

2014-06-01

215

Efficient implementation of the three-dimensional reference interaction site model method in the fragment molecular orbital method.  

PubMed

The three-dimensional reference interaction site model (3D-RISM) method was efficiently implemented in the fragment molecular orbital (FMO) method. The method is referred to as the FMO/3D-RISM method, and allows us to treat electronic structure of the whole of a macromolecule, such as a protein, as well as the solvent distribution around a solute macromolecule. The formalism of the FMO/3D-RISM method, for the computationally available form and variational expressions, are proposed in detail. A major concern leading to the implementation of the method was decreasing the computational costs involved in calculating the electrostatic potential, because the electrostatic potential is calculated on numerous grid points in three-dimensional real space in the 3D-RISM method. In this article, we propose a procedure for decreasing the computational costs involved in calculating the electrostatic potential in the FMO method framework. The strategy involved in this procedure is to evaluate the electrostatic potential and the solvated Fock matrix in different manners, depending on the distance between the solute and the solvent. The electrostatic potential is evaluated directly in the vicinity of the solute molecule by integrating the molecular orbitals of monomer fragments of the solute molecule, whereas the electrostatic potential is described as the sum of multipole interactions when an analog of the fast multipole method is used. The efficiency of our method was demonstrated by applying it to a water trimer system and three biomolecular systems. The FMO/3D-RISM calculation can be performed within a reasonable computational time, retaining the accuracy of some physical properties. PMID:24908001

Yoshida, Norio

2014-06-01

216

Direct investigation of halogen bonds by solid-state multinuclear magnetic resonance spectroscopy and molecular orbital analysis.  

PubMed

Noncovalent interactions play a ubiquitous role in the structure, stability, and reactivity of a wide range of molecular and ionic cocrystals, pharmaceuticals, materials, and biomolecules. The halogen bond continues to be the focus of much attention, due in part to its strength and unique directionality. Here, we report a multifaceted experimental and computational study of halogen bonds in the solid state. A series of cocrystals of three different diiodobenzene molecules and various onium halide (Cl(-) or Br(-)) salts, designed to exhibit moderately strong halogen bonds (C-I···X(-)) in the absence of competing hydrogen bonds, has been prepared and characterized by single-crystal X-ray diffraction. Interestingly, a wide range of geometries about the halide anion are observed. (35/37)Cl and (79/81)Br solid-state NMR spectroscopy is applied to characterize the nuclear quadrupolar coupling constants (CQ) and asymmetry parameters (?Q) for the halogen-bonded anions at the center of bonding environments ranging from approximately linear to distorted square planar to octahedral. The relationship between the halogen bond environment and the quadrupolar parameters is elucidated through a natural localized molecular orbital (NLMO) analysis in the framework of density functional theory (DFT). These calculations reveal that the lone pair type orbitals on the halogen-bonded anion govern the magnitude and orientation of the quadrupolar tensor as the geometry about the anion is systematically altered. In -C-I···X(-)···I-C- environments, the value of ?Q is well-correlated to the I···X(-)···I angle. (13)C NMR and DFT calculations show a correlation between chemical shifts and halogen bond strength (through the C-I distance) in o-diiodotetrafluorobenzene cocrystals. Overall, this work provides a chemically intuitive understanding of the connection between the geometry and electronic structure of halogen bonds and various NMR parameters with the aid of NLMO analysis. PMID:24786448

Viger-Gravel, Jasmine; Leclerc, Sophie; Korobkov, Ilia; Bryce, David L

2014-05-14

217

Orbital order in vanadium spinels  

Microsoft Academic Search

Motivated by recent theoretical and experimental controversy, we present a theoretical study to clarify the orbital symmetry of the ground state of vanadium spinel oxides AV2O4 ( A=Zn , Mg, Cd). The study is based on an effective Hamiltonian with spin-orbital superexchange interaction and a local spin-orbit coupling term. We construct a classical phase diagram and prove the complex orbital

S. di Matteo; G. Jackeli; N. B. Perkins

2005-01-01

218

Stereochemical Diversity of {MNO}(10) Complexes: Molecular Orbital Analyses of Nickel and Copper Nitrosyls.  

PubMed

The great majority of {NiNO}(10) complexes are characterized by short Ni-N(O) distances of 1.60-1.65 Å and linear NO units. Against this backdrop, the {CuNO}(10) unit in the recently reported [Cu(CH3NO2)5(NO)](2+) cation (1) has a CuNO angle of about 120° and a very long 1.96 Å Cu-N(O) bond. According to DFT calculations, metal-NO bonding in 1 consists of a single Cu(dz(2))-NO(?*) ?-interaction and essentially no metal(d?)-NO(?*) ?-bonding, which explains both the bent CuNO geometry and the long, weak Cu-N(O) bond. This ?-interaction is strongly favored by a ligand trans to the NO; indeed such a trans ligand may be critical for the existence and stability of a {CuNO}(10) unit. By contrast, {NiNO}(10) complexes exhibit a strong avoidance of such trans ligands. Thus, a five-coordinate {NiNO}(10) complex appears to favor a trigonal-bipyramidal structure with the NO in an equatorial position, as in the case of [Ni(bipy)2(NO)](+) (6). An unusual set of Ni(d)-NO(?*) orbital interactions accounts for the strongly bent NiNO geometry for this complex. PMID:24796643

Conradie, Jeanet; Ghosh, Abhik

2014-05-19

219

Protein-specific force field derived from the fragment molecular orbital method can improve protein-ligand binding interactions.  

PubMed

Accurate computational estimate of the protein-ligand binding affinity is of central importance in rational drug design. To improve accuracy of the molecular mechanics (MM) force field (FF) for protein-ligand simulations, we use a protein-specific FF derived by the fragment molecular orbital (FMO) method and by the restrained electrostatic potential (RESP) method. Applying this FMO-RESP method to two proteins, dodecin, and lysozyme, we found that protein-specific partial charges tend to differ more significantly from the standard AMBER charges for isolated charged atoms. We did not see the dependence of partial charges on the secondary structure. Computing the binding affinities of dodecin with five ligands by MM PBSA protocol with the FMO-RESP charge set as well as with the standard AMBER charges, we found that the former gives better correlation with experimental affinities than the latter. While, for lysozyme with five ligands, both charge sets gave similar and relatively accurate estimates of binding affinities. PMID:23420697

Chang, Le; Ishikawa, Takeshi; Kuwata, Kazuo; Takada, Shoji

2013-05-30

220

A new hierarchical parallelization scheme: generalized distributed data interface (GDDI), and an application to the fragment molecular orbital method (FMO).  

PubMed

A two-level hierarchical scheme, generalized distributed data interface (GDDI), implemented into GAMESS is presented. Parallelization is accomplished first at the upper level by assigning computational tasks to groups. Then each group does parallelization at the lower level, by dividing its task into smaller work loads. The types of computations that can be used with this scheme are limited to those for which nearly independent tasks and subtasks can be assigned. Typical examples implemented, tested, and analyzed in this work are numeric derivatives and the fragment molecular orbital method (FMO) that is used to compute large molecules quantum mechanically by dividing them into fragments. Numeric derivatives can be used for algorithms based on them, such as geometry optimizations, saddle-point searches, frequency analyses, etc. This new hierarchical scheme is found to be a flexible tool easily utilizing network topology and delivering excellent performance even on slow networks. In one of the typical tests, on 16 nodes the scalability of GDDI is 1.7 times better than that of the standard parallelization scheme DDI and on 128 nodes GDDI is 93 times faster than DDI (on a multihub Fast Ethernet network). FMO delivered scalability of 80-90% on 128 nodes, depending on the molecular system (water clusters and a protein). A numerical gradient calculation for a water cluster achieved a scalability of 70% on 128 nodes. It is expected that GDDI will become a preferred tool on massively parallel computers for appropriate computational tasks. PMID:15011259

Fedorov, Dmitri G; Olson, Ryan M; Kitaura, Kazuo; Gordon, Mark S; Koseki, Shiro

2004-04-30

221

Ionization Potential, Electron Affinity, Electronegativity, Hardness, and Electron Excitation Energy: Molecular Properties from Density Functional Theory Orbital Energies  

SciTech Connect

Representative atomic and molecular systems, including various inorganic and organic molecules with covalent and ionic bonds, have been studied by using density functional theory. The calculations were done with the commonly used exchange-correlation functional B3LYP followed by a comprehensive analysis of the calculated highest-occupied and lowest-unoccupied Kohn-Sham orbital (HOMO and LUMO) energies. The basis set dependence of the DFT results shows that the economical 6-31+G* basis set is generally sufficient for calculating the HOMO and LUMO energies (if the calculated LUMO energies are negative) for use in correlating with molecular properties. The directly calculated ionization potential (IP), electron affinity (EA), electronegativity (c), hardness (h), and first electron excitation energy (t) are all in good agreement with the available experimental data. A generally applicable linear correlation relationship exists between the calculated HOMO energies and the experimental/calculated IP's. We have also found satisfactory linear correlation relationships between the calculated LUMO energies and experimental/calculated EA's (for the bound anionic states), between the calculated average HOMO/LUMO energies and c values, between the calculated HOMO-LUMO energy gaps and h values, and between the calculated HOMO-LUMO energy gaps and experimental/calculated first excitation energies. By using these linear correlation relationships, the calculated HOMO and LUMO energies can be employed to semi-quantitatively estimate ionization potential, electron affinity, electronegativity, hardness, and first excitation energy.

Zhan, Chang-Guo; Nichols, Jeffrey A.; Dixon, David A.

2003-05-22

222

Gas-phase structure and conformation of diethyl ketone studied by molecular orbital constrained electron diffraction  

Microsoft Academic Search

The molecular structure and conformation of diethyl ketone (3-pentanone), C(3)H3C(2)H2C(1)OC(4)H2C(5)H3, at 27°C were studied by gas electron diffraction (GED). Vibrational mean amplitudes and shrinkage corrections were calculated on the basis of the vibrational spectra measured in the vapor and liquid phases. Structural constraints were obtained from RHF\\/6-31G? ab initio calculations.Diffraction data were reproduced best by a mixture of two conformers,

Nobuhiko Kuze; Ema Kojima; Hideo Fujiwara; Hiroshi Takeuchi; Toru Egawa; Shigehiro Konaka

1996-01-01

223

Ab initio molecular orbital calculations on DNA radical ions. 3. Ionization potentials and ionization sites in components of the DNA sugar phosphate backbone  

SciTech Connect

Ab initio molecular orbital calculations of various fragments of the DNA backbone have been performed to aid our understanding of charge localization and transfer following DNA irradiation. Koopmans ionization potentials of H[sub 3]PO[sub 4], H[sub 2]PO[sub 4][sup [minus

Colson, A.O.; Sevilla, M.D. (Oakland Univ., Rochester, MI (United States)); Besler, B. (Wayne State Univ., Detroit, MI (United States))

1993-07-29

224

Exploring the Nature of the H[subscript 2] Bond. 1. Using Spreadsheet Calculations to Examine the Valence Bond and Molecular Orbital Methods  

ERIC Educational Resources Information Center

A three-part project for students in physical chemistry, computational chemistry, or independent study is described in which they explore applications of valence bond (VB) and molecular orbital-configuration interaction (MO-CI) treatments of H[subscript 2]. Using a scientific spreadsheet, students construct potential-energy (PE) curves for several…

Halpern, Arthur M.; Glendening, Eric D.

2013-01-01

225

Binding at molecule/gold transport interfaces. II. Orbitals and density of states  

NASA Astrophysics Data System (ADS)

The density of states diagrams, and the associated orbital populations and structure, are analyzed for the discrete models for dithiol bridged molecular junctions discussed in the previous paper. The orbitals closest to the Fermi surface are generally dominated by the high s and d densities of metal atoms. Some orbitals are mixed metal/sulfur/hydrocarbon, and a few (generally lower-lying occupied) are dominantly within the hydrocarbon itself. These orbital populations suggest that the frontier orbitals are, in themselves, not adequate for quantitative description of transport, essentially because the Green's functions of slightly lower-lying orbitals give large contributions to the mixing between electrodes that dominates the transport. Effects of different spin multiplicities and charges, as well as different choices of density functional, are also presented: the major conclusions seem robust, and are not strongly effected by these modifications.

Basch, Harold; Ratner, Mark A.

2003-12-01

226

Spectroscopic studies, potential energy surface and molecular orbital calculations of pramipexole.  

PubMed

A systematic vibrational spectroscopic assignment and analysis of pramipexole [(S)-N(6)-propyl-4,5,6,7-tetrahydro-1,3-benzothiazole-2,6-diamine] has been carried out using FT-IR and FT-Raman spectral data. The vibrational analysis was aided by an electronic structure calculation based on the hybrid density functional method B3LYP using a 6-311G(d, p) and cc-pVTZ basis sets. Molecular equilibrium geometries, electronic energies, IR and Raman intensities, harmonic vibrational frequencies have been computed. The assignments are based on the experimental IR and Raman spectra, and a complete assignment of the observed spectra has been proposed. The UV-visible spectrum of the compound was recorded and the electronic properties, such as HOMO and LUMO energies and the maximum absorption ?max were determined by time-dependent DFT (TD-DFT) method. The geometrical parameters, vibrational frequencies and absorption wavelengths were compared with the experimental data. The complete vibrational assignments are performed on the basis of the potential energy distributions (PEDs) of the vibrational modes in terms of natural internal coordinates. The simulated FT-IR, FT-Raman, and UV spectra of the title compound have been constructed. In addition, the potential energy surface, HOMO and LUMO energies, the molecular electrostatic potential and the first-order hyperpolarizability have been computed. The magnitude of the first-order hyperpolarizability is 5 times larger than that of urea and the title compound may be a potential applicant for the development of NLO materials. PMID:23831980

Muthu, S; Uma Maheswari, J; Srinivasan, S; Isac paulraj, E

2013-11-01

227

Beyond the molecular orbital conception of electronically excited states through the quantum theory of atoms in molecules.  

PubMed

We show that the use of the quantum theory of atoms in molecules (QTAIM) in electronically excited states allows expanding the knowledge that the molecular orbital (MO) framework provides about electronic rearrangements. Despite that historical prejudice seemed to preclude the use of QTAIM beyond the electronic ground state, this paper evidences that QTAIM is versatile enough to deal with excited states. As an example, the paradigmatic n ? ?* electronic transition of formaldehyde is analyzed. Using QTAIM, an energy partition of excited state energies into atomic and diatomic energies is carried out for the first time. This partition shows that upon electronic excitation the atoms of the CO bond experience a stabilization in their net energies, accompanied by a destabilization in their interaction, a fact which is in accordance with the idea of populating an antibonding ?* MO. The associated C-O bond elongation in the n?* state does not involve a change in the ? atomic populations - as one would expect from a ?* orbital - but in the ? ones. Moreover, it is also found that the n?* state is characterized by a weaker C-O interaction energy in comparison to that in the electronic ground state. In order to strengthen this interaction, the electron-electron repulsion between C and O is reduced via a symmetry-breaking of the electron density, causing the C pyramidalization. A topological analysis based on the Laplacian of the electron density and on the electron localization function (ELF) reveals that the n ? ?* transition can be visualized as a rotation of 90° of the oxygen lone pairs. PMID:24709865

Ferro-Costas, David; Pendás, Angel Martín; González, Leticia; Mosquera, Ricardo A

2014-04-23

228

Conformational effects, molecular orbitals, and reaction activities of bis(phthalocyaninato) lanthanum double-deckers: density functional theory calculations.  

PubMed

The conformational effects on the frontier molecular orbital energy and stability for reduced, neutral, and oxidized bis(phthalocyaninato) lanthanum double-deckers have been revealed on the basis of density functional theory calculations. Calculation results indicate that the frontier orbital coupling degree changes along with the molecular conformation of the double-decker compound, first decreasing along with the increase of rotation angle ? from 0 to 20° and then increasing along with the increase of rotation angle ? from 20 to 45°. In addition, the stability for the three forms of double-decker changes in the same order, but first increasing and then decreasing along with the change of the rotation angle ? in the range of 0 to 45° with a rotation energy barrier of (31.3 ± 3.1) kJ mol(-1) at 20°. This reveals that the rotation of the two phthalocyanine rings for the reduced, neutral, and oxidized bis(phthalocyaninato) lanthanum double-deckers are able to occur at room temperature. Nevertheless, the superior coordination reaction activity of the neutral bis(phthalocyaninato) lanthanum double-decker complex over their reduced form in forming sandwich-type tris(phthalocyaninato) lanthanum triple-decker compounds has also been clearly clarified on the basis of comparative calculations on the Fukui function of [La(Pc)(2)] and [La(Pc)(2)](-) using the DFT method. Fukui function analysis reveals the reaction center of the 18-electron-?-conjugated core in the bis(phthalocyaninato) lanthanum double-decker molecule against both electrophilic and radical attack. Nevertheless, the larger global chemical softness (S) for the neutral [La(Pc)(2)] than the reduced form [La(Pc)(2)](-) indicates the higher reaction activity of the former form over the latter one. This explains well the experimental findings that only the neutral instead of the reduced form of bis(tetrapyrrole) rare earth double-decker complexes, containing at least one phthalocyanine ligand, could be employed as starting materials towards the preparation of tris(tetrapyrrole) rare earth triple-decker complexes by a solution process. PMID:21709865

Qi, Dongdong; Zhang, Lijuan; Wan, Liang; Zhang, Yuexing; Bian, Yongzhong; Jiang, Jianzhuang

2011-08-01

229

Hertzsprung-Russell Diagram  

NSDL National Science Digital Library

This is a lecture that introduces the HR diagram. The HR diagram is a plot of luminosity in solar units on the Y axis and stellar temperature on the X axis. The HR diagram is a key tool in tracing the evolution of stars. The lecture discusses the location of different stars on the diagram. It also includes a discussion of thermonuclear fusion and the neutrino problem. A quiz follows the lecture.

Schombert, Jim

2008-12-15

230

A proposal for the proper use of pseudopotentials in molecular orbital cluster model studies of chemisorption  

NASA Technical Reports Server (NTRS)

The interaction of CO with Cu5, Ni5, and Al4 are treated as model systems for molecular adsorption on metal surfaces. The effect of the use of pseudopotentials for the metal atoms is studied by considering three types of clusters. In the first case, all of the metal electrons are explicitly included in the wave function; an all electron (AE) treatment. In the second case, the metal atom which directly interacts with the CO is described by AE but the remaining metal atoms include a pseudopotential for their core electrons. Finally, in the third case, all of the metal atoms in the cluster have a pseudopotential treatment for the core electrons. The AE cluster results are taken as reference values for the two pseudopotential treatments. The mixed cluster results are in excellent agreement with those of the all AE clusters; however, the results for the all pseudopotential cluster of Ni5CO or of Cu5CO are qualitatively different. The pseudopotential treatment for all of the metal atoms often leads to results that contain serious errors and it is not a reliable approach.

Bagus, P. S.; Bauschlicher, C. W., Jr.; Nelin, C. J.; Laskowski, B. C.; Seel, M.

1984-01-01

231

Molecular structures and conformational compositions of 2-chlorobutane and 2-bromobutane; an investigation using gas-phase electron-diffraction data and ab initio molecular orbital calculations  

NASA Astrophysics Data System (ADS)

The structure and conformational composition of 2-chlorobutane and 2-bromobutane have been studied by gas-phase electron diffraction (GED) at 25°C, together with ab initio molecular orbital calculations (HF/6-311+G(d,p)). These molecules may exist as three distinguishable conformers (G+, A, and G-). The symbols refer to anti (A) with a torsion angle ?2(X 8-C 2-C 3-C 4) of about 180° and gauche (G+ and G-) with torsion angles ?2(X 8-C 2-C 3-C 4) of about +60° and 300°(-60°), respectively. It was not possible; from our GED-data alone, to accurately determine the conformational composition because the distance distributions for two of the conformers (G+ and G-) are very similar. The conformational composition for 2-chlorobutane obtained from the ab initio calculations (G+ 62%, A 25% G- 13%) was found to fit the experimental data quite well. For 2-bromobutane the ab initio calculated conformational composition (G+ 58%, A 28% G- 14%) did not, however, fit the experimental data. Here a much better fit was obtained by using only 10% of the A conformer and using the relative energy for the two gauche conformers, as obtained in the ab initio molecular orbital calculations, to calculate the relative amounts of the two gauche forms (G+ 73%, A 10% G- 17%). The results for the principal distances ( rg) and angles ? ? for the G+ conformer of 2-chlorobutane, with estimated 2 ? uncertainties, obtained from the combined GED/ab initio study are: r( C1- C2)=1.524(3) Å, r( C2- C3)=1.528(3) Å, r( C3- C4)=1.539(3) Å, r( C- Cl)=1.812(3) Å, r( C- H) ave=1.098(4) Å, ?C 1C 2C 3=111.5(16)°, ?C 2C 3C 4=113.3(5)°, ?C 1C 2C1=110.4(9)°. The results for the G+ conformer of 2-bromobutane are: r( C1- C2)=1.526(4) Å, r( C2- C3)=1.530(4) Å, r( C3- C4)=1.540(4) Å, r( C- Br)=1.982(5) Å, r( C- H) ave=1.111(8) Å, ?C 1C 2C 3=112.5(16)°, ?C 2C 3C 4=114.6(15)°, ?C 1C 2Br=110.1(16)°. Only average values for r(C-C), r(C-H), ?CCC, and ?CCH could be determined in the least-squares refinements, the differences between these parameters in the same conformer, and between the different conformers, were kept constant at the values obtained in the ab initio molecular orbital calculations.

Aarset, Kirsten; Hagen, Kolbjørn; Stølevik, Reidar

2001-06-01

232

Generalized Block Diagrams  

Microsoft Academic Search

The conventions and rules for generalized block diagram representation are developed and the relationships between generalized block diagrams and network graphs discussed. The generalized block diagram as developed here should prove of value in the computer-aided study of complex systems.

A. G. J. MACFARLANE

1967-01-01

233

Molecular orbital calculations of /sup 13/C-/sup 13/C and /sup 1/H-/sup 1/H nuclear spin-spin coupling constants  

SciTech Connect

Theoretical studies are presented for the conformational dependencies of vicinal /sup 13/C-/sup 13/C coupling constants within a variety of saturated and unsaturated molecular frameworks. Using the molecular orbital approach of Blizzard and Santry, it is shown that three distinct patterns of dihedral angle versus /sup 3/H/sub CC/sup contract/ coupling are produced, depending upon the degree of double bonding present within the direct coupling path. By means of calculations that involve modifying the various exchange integrals, two of these coupling patterns are found to depend on sigma-..pi.. exchange. A rationalization of the origin of these coupling patterns is presented. In all systems studied, the orbital and dipolar contributions to the vicinal coupling constant are calculated to be negligible compared to the Fermi contact mechanism except in conjugated systems. The FP/INDO molecular orbital method is employed in the investigation of substitutent effects on /sup 1/H-/sup 1/H coupling constants in substituted ethanes, ethylenes, and benzenes. Substituent effects are simulated by varying the (1/2)(I + A) INDO parameters on two different types of pseudoatoms, one essentially a pseudo-hydrogen and the other involving 2s and 2p orbitals on two centers. A review of the theory of nuclear spin-spin coupling is presented.

Severson, M.L.

1984-01-01

234

Phase Equilibria Diagrams Database  

National Institute of Standards and Technology Data Gateway

SRD 31 NIST/ACerS Phase Equilibria Diagrams Database (PC database for purchase)   The Phase Equilibria Diagrams Database contains commentaries and more than 21,000 diagrams for non-organic systems, including those published in all 21 hard-copy volumes produced as part of the ACerS-NIST Phase Equilibria Diagrams Program (formerly titled Phase Diagrams for Ceramists): Volumes I through XIV (blue books); Annuals 91, 92, 93; High Tc Superconductors I & II; Zirconium & Zirconia Systems; and Electronic Ceramics I. Materials covered include oxides as well as non-oxide systems such as chalcogenides and pnictides, phosphates, salt systems, and mixed systems of these classes.

235

Cyclic oxyphosphoranes as model intermediates during splicing and cleavage of RNA: ab initio molecular orbital calculations on the conformational analysis.  

PubMed Central

Ab initio molecular orbital calculations have been carried out on hydrated adducts of methyl ethylene phosphate as a model intermediate during cleavage of RNA. Upon rotating the apical methoxyl group two kinds of stable conformers and two kinds of rotational transition states are located, the most stable conformation being gs-G where the dihedral angle between the apical methyl group and the basal ring oxygen is calculated to be 76 degrees. In this gs-G conformation one of the lone pairs on the apical oxygen is oriented antiperiplanar to the basal ring ester bond. The torsional energy required to rotate the methyl group about the phosphorus-apical oxygen bond leading to ts-C conformation, where the methyl group is eclipsed with the ring oxygen, is calculated to be 5.2 kcal/mol. Judging from the published substrate's coordinates in the RNase environment, the expected pentacoordinate-intermediate/transition state during the cleavage of RNA appears to be, in fact, the most stable gs-G conformation.

Taira, K; Uebayasi, M; Furukawa, K

1989-01-01

236

Calculation of positron binding energies of amino acids with the any-particle molecular-orbital approach  

NASA Astrophysics Data System (ADS)

We report positron binding energies (PBEs) for the 20 standard amino acids in the global minimum, hydrogen-bonded, and zwitterionic forms. The calculations are performed at the any-particle molecular-orbital (APMO) Hartree-Fock (HF), Koopmans' theorem (KT), second-order Möller-Plesset (MP2), and second-order propagator (P2) levels of theory. Our study reveals that the APMO KT and APMO P2 methods generally provide higher PBEs than the APMO HF and APMO MP2 methods, respectively, with only a fraction of the computational costs of the latter. We also discuss the impact of the choice of the positronic center on the PBEs and propose a simple and inexpensive procedure, based on the condensed Fukui functions of the parent molecules, to select the most suitable expansion center. The results reported so far indicate that APMO KT and APMO P2 methods are convenient options for a qualitative or semiquantitative analysis of positron binding in medium to large polyatomic systems.

Charry, J.; Romero, J.; Varella, M. T. do N.; Reyes, A.

2014-05-01

237

Characterization of methyl methacrylate oligomers using secondary ion mass spectrometry, APCI mass spectrometry and molecular orbital theory  

NASA Astrophysics Data System (ADS)

The ionization efficiency and fragmentation mechanism of methyl methacrylate (MMA) oligomers (3-mer˜8-mer) were investigated by using secondary ion mass spectrometry (SIMS) and APCI mass spectrometry (APCI-MS). Protonation and fragmentation mechanisms of MMA oligomers were clarified by using molecular orbital (MO) methods. MMA oligomers were synthesized in anionic polymerization, and the oligomers were fractionated into 3-mer˜8-mer using gel permeation chromatography (GPC). In SIMS of MMA oligomers (3-mer˜8-mer), [MH] +, [MH-CH 3OH] +, [MH-methyl formate] + and [MH-2CH 3OH-methyl formate] + appeared. The peak intensities of adduct ions [M+Li] +, [M+Na] + and [M+K] + increased with the increase of the polymerization degree. The optimized geometries and H +, Li +, Na + and K + affinities of MMA monomer (1-mer), dimer (2-mer), and trimer (3-mer) were calculated using the PM3 and ab initio MO methods. The calculated H +, Li +, Na + and K + affinities increased in order of 1-mer, 2-mer and 3-mer of MMA.

Takeuchi, T.; Iwai, K.; Momoji, K.; Miyamoto, I.; Saiki, K.; Hashimoto, K.

2003-01-01

238

Linear-scaling molecular orbital calculations for the pKa values of ionizable residues in proteins.  

PubMed

In this report, we present a computational methodology for the pKa prediction of proteins, based on linear-scaling molecular orbital calculations for their solution-conformations obtained from NMR measurements. The method is used to predict the pKa values of five carboxylic acids (Asp7, Glu10, Glu19, Asp27, and Glu43) in turkey ovomucoid third domain (OMTKY3), and six aspartates residues (Asp 22, Asp 44, Asp 54, Asp 75, Asp 83, and Asp 93) in barnase. For OMTKY3, all the predicted pKa values are within 1 pH units from the available experimental ones, except for the case of Glu 43. For barnase, the root-mean-square deviation from experiment is 1.46 pH units. As a result, the proposed pKa calculation method correctly reproduces the relative order of the pKa values among the carboxylic acids located in different sites of the proteins. The calculated pKa values are decomposed into the contributions of short- and long-range structural difference effects. The results indicate that in both proteins the pKa value of the given carboxylic acid is partially influenced by long-range interactions with distant charged residues, which significantly contribute to determining the relative order of the pKa values. The current methodology based on LSMO provides us useful information about the titration behavior in a protein. PMID:16550537

Ohno, Kazuki; Sakurai, Minoru

2006-05-01

239

Molecular orbital study on a mechanism of adhesion between carbides and optical glass with high refractive index  

NASA Astrophysics Data System (ADS)

A mechanism of adhesion between carbide molds and optical glass species with high refractive index in precision molding was elucidated on the basis of DV-X? molecular orbital calculations. An interfacial cluster model comprising Nb=P=Na=O glass and glassy carbon (GC) was applied in order to examine the changes in the chemical bonds between atoms at the interface and the effect of the substitution of niobium with other transition metals (denoted with; MdI) at the interface. The bond overlap population (BOP) between oxygen atoms at the surface of the glass and carbon atoms at the surface of the GC increases when the surface of the glass approaches the GC, while that between MeI=O correspondingly decreases. When introducing oxygen deficiency at the surface of the glass, the BOP of the MeI=carbon bonds against the MeI=oxygen increased in the order of Nb

Fujiwara, Yasuhiro; Yoshioka, Tomohiko; Tanaka, Junzo

240

Molecular structure, vibrational spectra (FTIR and FT Raman) and natural bond orbital analysis of 4-Aminomethylpiperidine: DFT study.  

PubMed

The FT-IR and FT-Raman spectra of 4-Aminomethylpiperidine have been recorded using Perkin Elmer Spectrophotometer and Nexus 670 spectrophotometer. The equilibrium geometrical parameters, various bonding features, the vibrational wavenumbers, the infrared intensities and the Raman scattering activities were calculated using Hartree-Fock and density functional method (B3LYP) with 6-311+G(d,p) basis set. Detailed interpretations of the vibrational spectra have been carried out with the aid of the normal coordinate analysis. The spectroscopic and natural bonds orbital (NBO) analysis confirms the occurrence of intra molecular hydrogen bonds, electron delocalization and steric effects. The changes in electron density in the global minimum and in the energy of hyperconjugative interactions of 4-Aminomethylpiperidine (4AMP) were calculated. The theoretical UV-Visible spectrum of the compound was computed in the region 200-400nm by time-dependent TD-DFT approach. The calculated HOMO and LUMO energies show that charge transfer occur within the molecule. The dipole moment (?) and polarizability (?), anisotropy polarizability (??) and hyperpolarizability (?) of the molecule have been reported. PMID:24853994

Mahalakshmi, G; Balachandran, V

2014-10-15

241

The molecular structures of tris(dimethylamino)-phosphane, -arsane and -stibane, E(NMe 2) 3, E ? P, As or Sb and Me ? CH 3, by gas electron diffraction and ab initio molecular orbital calculations  

Microsoft Academic Search

The molecular structures of E(NMe2)3, E ? P, As or Sb and Me ? CH3, have been determined by gas electron diffraction (GED) and ab initio molecular orbital calculations at the HF6–31G? level. The equilibrium structures have Cs symmetry with two NMe2 ligands oriented in such a manner that the direction of the electron lone pair on each N atom

P. E. Baskakova; Alexander V. Belyakov; Thomas Colacot; L. K. Krannich; Arne Haaland; Hans Vidar Volden; Ole Swang

1998-01-01

242

1,1,2-Triiododisilane (I 2HSi–SiH 2I): molecular structure, internal rotation and vibrational properties determined by gas-phase electron diffraction, infrared and Raman spectroscopy, and ab initio molecular orbital- and density functional calculations  

Microsoft Academic Search

The molecular structure, internal rotation and vibrational properties of 1,1,2-triiododisilane (TIDS), I2HSi–SiH2I, have been studied using gas phase electron diffraction (GED) data at an average temperature of 52°C, together with infrared and Raman spectroscopy, and ab initio molecular orbital- and density functional calculations. The title compound exists in the gas and liquid phases as a mixture of two minimum conformers,

T. H. Johansen; K. Hagen; K. Hassler; G. Tekautz; R. Stølevik

1999-01-01

243

1,2-Diiododisilane and 1,1,2,2-tetraiododisilane: a reinvestigation of the molecular structures and vibrational properties by gas-phase electron diffraction, temperature dependent Raman spectroscopy, and ab initio molecular orbital- and density functional calculations  

Microsoft Academic Search

The molecular structure, internal rotation and vibrational properties of 1,2-diiododisilane (DIDS), IH2Si–SiH2I, and 1,1,2,2-tetraiododisilane (TIDS), I2HSi–SiHI2, have been reinvestigated using gas phase electron diffraction (GED) data at temperatures of 55 (DIDS) and 155 (TIDS) °C, together with Raman spectroscopy, and ab initio molecular orbital (MO)- and density functional (DFT) calculations. The title compounds exist in the gas and liquid phases

Tore H. Johansen; Karl Hassler; Günter Tekautz; Kolbjørn Hagen

2001-01-01

244

1,1,2,2-tetrachlorodisilane (Cl 2HSi–SiHCl 2): molecular structure, conformation and torsional potential as determined by gas-phase electron diffraction, vibrational spectroscopic data and ab initio molecular orbital calculations  

Microsoft Academic Search

The molecular structure, conformational composition and torsional potential of 1,1,2,2-tetrachlorodisilane (TCDS), Cl2HSi–SiHCl2, were studied using gas phase electron diffraction (GED) data at 23°C, together with earlier recorded spectroscopic data and normal coordinate- and ab initio molecular orbital calculations. The title compound exists in the gas phase at room temperature as a mixture of two conformers, anti, with a torsion angle

Tore H. Johansen; Kolbjørn Hagen; Reidar Stølevik

1999-01-01

245

The Brauer loop scheme and orbital varieties  

NASA Astrophysics Data System (ADS)

A. Joseph invented multidegrees in Joseph (1984) to study orbital varieties, which are the components of an orbital scheme, itself constructed by intersecting a nilpotent orbit with a Borel subalgebra. Their multidegrees are known as Joseph polynomials, and these polynomials give a basis of a (Springer) representation of the Weyl group. In the case of the nilpotent orbit {M2=0}, the orbital varieties can be indexed by noncrossing chord diagrams in the disk.

Knutson, Allen; Zinn-Justin, Paul

2014-04-01

246

Interpretation of electron delocalization in benzene, cyclobutadiene, and borazine based on visualization of individual molecular orbital contributions to the induced magnetic field.  

PubMed

The magnetic response of the valence molecular orbitals (MOs) of benzene, cyclobutadiene, and borazine to an external magnetic field has been visualized by calculating the chemical shielding in two-dimensional grids of points on the molecular plane and on a plane perpendicular to it, using gauge-including atomic orbitals (GIAOs). The visualizations of canonical MO contributions to the induced magnetic field (CMO-IMF) provide a clear view of the spatial extension, the shape, and the magnitude of shielding and deshielding areas within the vicinity of the molecule, originating from the induced currents of each valence orbital. The results are used to investigate the delocalization of each valence MO and to evaluate its contribution to the aromatic character of systems under study. The differentiation of the total magnetic response among the three molecules originates exclusively from ?-HOMO orbitals because the magnetic response of the subsets of the remaining MOs is found to be almost identical. Borazine is classified as nonaromatic as the four electrons that occupy the ?-HOMO are found to be strongly localized on nitrogen centers. CMO-IMF can clarify the interpretation of various NICS indexes and can be applied for the investigation of various types of electron delocalization. PMID:24444188

Charistos, Nickolas D; Papadopoulos, Anastasios G; Sigalas, Michael P

2014-02-13

247

Multicomponent molecular orbital theory for electrons and nuclei including many-body effect with full configuration interaction treatment: isotope effects on hydrogen molecules  

Microsoft Academic Search

A multi-component molecular orbital (MC_MO) theory is developed for a combined quantum system of electrons and nuclei with the full configuration interaction (CI) scheme of Cartesian Gaussian-type functions. The technique of graphical unitary group approach (GUGA) is modified to obtain the CI matrix elements for many kinds of quantum particles efficiently. The optimum basis sets for quantum nuclei are proposed

Masanori Tachikawa

2002-01-01

248

A molecular orbital study of a model of the Mg2+ coordination complex of the self splicing reaction of ribosomal RNA  

NASA Technical Reports Server (NTRS)

Recent discoveries have established the fact that RNA is capable of acting as an enzyme. In this study two different types of molecular orbital calculations, INDO and ab initio, were used in an attempt to assess the structural/functional role of the Mg2+ hydrated complex in ribozyme reactions. Preliminary studies indicate that the reaction is multistep and that the Mg2+ complex exerts a stabilizing effect on the intermediate or midpoint of the reaction.

McCourt, M.; Shibata, M.; McIver, J. W.; Rein, R.

1988-01-01

249

Investigation of the spectroscopy and relaxation dynamics of benzaldehyde using molecular orbital calculations and laser ionization time-of-flight mass spectroscopy  

Microsoft Academic Search

Molecular orbital methods and laser ionization mass spectrometry measurements are used to investigate the spectroscopy and relaxation dynamics of benzaldehyde following excitation to its S2(\\/pi\\/pi\\/sp\\/*) state. Energies, equilibrium geometries and vibrational frequencies of ground and low-lying excited states of benzaldehyde neutral and cation determined by ab initio calculations provide a theoretical description of the electronic spectroscopy of benzaldehyde and of

Maria Cristina Rodrigues da Silva

1998-01-01

250

Chloromethyldichloromethylsilane and chloromethyldimethylchlorosilane: structure, conformational composition and torsional potential determined by gas-phase electron diffraction and ab initio molecular orbital calculations  

Microsoft Academic Search

The molecular structure and conformation of chloromethyldichloromethylsilane (TCS), ClH2C?SiCl2?CH3, and chloromethyldimethylchlorosilane (DCS), ClH2C?SiCl(CH3)2, have been studied using gas-phase electron diffraction at 24°C and ab initio molecular orbital calculations.These molecules exist in the gas phase as a mixture of two conformers, anti (A, torsion angle ?(ClCSiX) = 180°, X = CH3 (TCS) or Cl (DCS)) and gauche (G, torsion angle (?(ClCSiX)

Tore H. Johansen; Kjersti H. Wold; Kolbjørn Hagen; Reidar Stølevik

1996-01-01

251

Structures, molecular orbitals and UV-vis spectra investigations on Br2C6H4: a computational study.  

PubMed

The dibromobenzenes (1,2-, 1,3- and 1,4-Br2C6H4) have been studied by theoretical methods. The structures of these species are optimized and the structural characteristics are determined by density functional theory (DFT) and the second order Møller-Plesset perturbation theory (MP2) levels. The geometrical structures of Br2C6H4 show a little distortion of benzene ring due to the substitution of highly electronegativity of bromine atoms. The electronegativity of bromine atoms in 1,4-Br2C6H4 is predicted to be more negative than 1,2- and 1,3-Br2C6H4. In addition, dipole moment and frontier molecular orbitals (FMOs) of these Br2C6H4 are performed as well. The 1,4-Br2C6H4 is slightly more reactive than 1,2- and 1,3-Br2C6H4 because of its small HOMO-LUMO energy gap. The simulated UV-vis spectra are investigated by time-dependent density functional theory (TD-DFT) approach, which are in excellent agreement with the available experimental value. Our calculations show that a few of absorption features are between 140nm and 250nm, which is in ultraviolet C range, and the red shift of 1,3- and 1,4-Br2C6H4 are predicted. Moreover, the UV absorption features of these Br2C6H4 in water or methanol are predicted to be more intense than in gas phase due to solvent effect. PMID:23892349

Wang, Tsang-Hsiu; Hsu, Chen-Shuo; Huang, Wen-Lin; Lo, Yih-Hsing

2013-11-01

252

Improved constrained optimization method for reaction-path determination in the generalized hybrid orbital quantum mechanical/molecular mechanical calculations  

NASA Astrophysics Data System (ADS)

The nudged elastic band (NEB) and string methods are widely used to obtain the reaction path of chemical reactions and phase transitions. In these methods, however, it is difficult to define an accurate Lagrangian to generate the conservative forces. On the other hand, the constrained optimization with locally updated planes (CO-LUP) scheme defines target function properly and suitable for micro-iteration optimizations in quantum mechanical/molecular mechanical (QM/MM) systems, which uses the efficient second order QM optimization. However, the method does have problems of inaccurate estimation of reactions and inappropriate accumulation of images around the energy minimum. We introduce three modifications into the CO-LUP scheme to overcome these problems: (1) An improved tangent estimation of the reaction path, which is used in the NEB method, (2) redistribution of images using an energy-weighted interpolation before updating local tangents, and (3) reduction of the number of constraints, in particular translation/rotation constraints, for improved convergence. First, we test the method on the isomerization of alanine dipeptide without QM/MM calculation, showing that the method is comparable to the string method both in accuracy and efficiency. Next, we apply the method for defining the reaction paths of the rearrangement reaction catalyzed by chorismate mutase (CM) and of the phosphoryl transfer reaction catalyzed by cAMP-dependent protein kinase (PKA) using generalized hybrid orbital QM/MM calculations. The reaction energy barrier of CM is in high agreement with the experimental value. The path of PKA reveals that the enzyme reaction is associative and there is a late transfer of the substrate proton to Asp 166, which is in agreement with the recently published result using the NEB method.

Jung, Jaewoon; Re, Suyong; Sugita, Yuji; Ten-no, Seiichiro

2013-01-01

253

Structures, molecular orbitals and UV-vis spectra investigations on Br2C6H4: A computational study  

NASA Astrophysics Data System (ADS)

The dibromobenzenes (1,2-, 1,3- and 1,4-Br2C6H4) have been studied by theoretical methods. The structures of these species are optimized and the structural characteristics are determined by density functional theory (DFT) and the second order Møller-Plesset perturbation theory (MP2) levels. The geometrical structures of Br2C6H4 show a little distortion of benzene ring due to the substitution of highly electronegativity of bromine atoms. The electronegativity of bromine atoms in 1,4-Br2C6H4 is predicted to be more negative than 1,2- and 1,3-Br2C6H4. In addition, dipole moment and frontier molecular orbitals (FMOs) of these Br2C6H4 are performed as well. The 1,4-Br2C6H4 is slightly more reactive than 1,2- and 1,3-Br2C6H4 because of its small HOMO-LUMO energy gap. The simulated UV-vis spectra are investigated by time-dependent density functional theory (TD-DFT) approach, which are in excellent agreement with the available experimental value. Our calculations show that a few of absorption features are between 140 nm and 250 nm, which is in ultraviolet C range, and the red shift of 1,3- and 1,4-Br2C6H4 are predicted. Moreover, the UV absorption features of these Br2C6H4 in water or methanol are predicted to be more intense than in gas phase due to solvent effect.

Wang, Tsang-Hsiu; Hsu, Chen-Shuo; Huang, Wen-Lin; Lo, Yih-Hsing

2013-11-01

254

Conversion of phenol derivatives to hydroxylated products by phenol hydroxylase from Trichosporon cutaneum. A comparison of regioselectivity and rate of conversion with calculated molecular orbital substrate characteristics.  

PubMed

This study describes the regioselective hydroxylation and the rates of conversion of a series of fluorinated phenol derivatives by phenol hydroxylase from the yeast Trichosporon cutaneum. The natural logarithm of the kcat value for the conversion of the phenolic substrates correlates with the calculated energy of the reactive electrons in the highest occupied molecular orbital of the substrate (r = 0.85). This observation supports the hypothesis that at physiological pH (7.6) and 25 degrees C, in the absence of monovalent anions, the nucleophilic attack of the electrons in the highest occupied molecular orbital of the substrate on the C(4a)-hydroperoxyflavin enzyme intermediate is of major importance in determining the overall rate of catalysis. Results from 19F-NMR analysis of the incubation mixtures demonstrate for phenols with two identical ortho substituents, that the ortho position which becomes preferentially hydroxylated is the one with the highest density of the reactive electrons in the highest occupied molecular orbital. A halogen substituent at a meta position decreases the chances for hydroxylation at the adjacent ortho position further than expected on the basis of the calculated reactivity. This result indicates a contribution of a protein/substrate dipolar interaction, influencing the time-averaged orientation of the substrate with respect to the reactive C(4a)-hydroperoxyflavin intermediate. PMID:7851397

Peelen, S; Rietjens, I M; Boersma, M G; Vervoort, J

1995-01-15

255

Development of glue-type potentials for the Al-Pb system: Phase diagram calculation  

SciTech Connect

Empirical many-body potentials of the glue-type have been constructed for the Al-Pb system using the force matching method. The potentials are fitted to experimental data, physical quantities derived from ab initio linear muffin-tin orbitals calculations and a massive quantum mechanical database of atomic forces generated using ultrasoft pseudopotentials in conjunction with ab initio molecular statics simulations. Monte Carlo simulations using these potentials have been employed to compute an Al-Pb phase diagram which is in fair agreement with experimental data.

Landa, A.; Wynblatt, P.; Siegel, D.J.; Adams, J.B.; Mryasov, O.N.; Liu, X.Y.

2000-05-11

256

Simultaneous competition and coexistence between charge-density waves and reentrant superconductivity in the pressure-temperature phase diagram of the molecular conductor TTF [Ni(dmit)2]2 (TTF is tetrathiafulvalene and dmit is the 1,3-dithia-2-thione-4,5-dithiolato group)  

Microsoft Academic Search

The pressure-temperature phase diagram of the quasi-one-dimensional molecular superconductor TTF [Ni(dmit)2]2 has been carefully determined by ac resistivity measurements up to 14 kbar. Increasing pressures induce electronic phase transitions between a high-temperature metal and successive, metallic or semimetallic, semiconducting and reentrant superconducting ground states. This unusual phase diagram is compared with that of TTF [Pd(dmit)2]2. It is discussed in connection

L. Brossard; M. Ribault; L. Valade; P. Cassoux

1990-01-01

257

Revise Through Diagrams: Physics  

Microsoft Academic Search

This is a 72 page book organized in seven major sections covering the present GCSE physics syllabuses and the physics component of the present GCSE double-award science syllabuses. Each page consists of several boxed features covering the key aspects of a single topic within each section. Each feature box contains one or more diagrams and related text. The diagrams are

Jim Breithaupt

1997-01-01

258

Compact explosion diagrams  

Microsoft Academic Search

This paper presents a system to automatically generate compact explosion diagrams. Inspired by handmade illustrations, our approach reduces the complexity of an explosion diagram by rendering an exploded view only for a subset of the assemblies of an object. However, the exploded views are chosen so that they allow inference of the remaining unexploded assemblies of the entire 3D model.

Markus Tatzgern; Denis Kalkofen; Dieter Schmalstieg

2010-01-01

259

Diagrams in the Mind?  

Microsoft Academic Search

Clearly we can solve problems by thinking about them. Sometimes we have the impression that in doing so we use words, at other times diagrams or images. Often we use both. What is going on when we use mental diagrams or images? This question is addressed in relation to the more general multi-pronged question: what are representations, what are they

Aaron Sloman

260

Mollier Diagram for Nitrogen.  

National Technical Information Service (NTIS)

Thermodynamic data for nitrogen are presented in Mollier diagram form covering the temperature range of 30K to 15,000K and the density range of 0.0000001 to 1000 amagat. Data for the solid and liquid regions are included. The diagram contains all availabl...

C. H. Piper R. L. Humphrey

1967-01-01

261

Hertzsprung-Russell Diagram  

NSDL National Science Digital Library

This activity teaches students about the Hertzsprung-Russell diagram. The students will first describe differences between near and bright stars. Then they will discern a relationship between temperature and brightness. Finally they will correlate the evolution of stars to plotting the H-R diagram.

Slater, Tim P.

2004-07-16

262

Structures and stability of medium silicon clusters. II. Ab initio molecular orbital calculations of Si12-Si20  

NASA Astrophysics Data System (ADS)

Ab initio all-electron molecular-orbital calculations are carried out to study the structures and relative stability of low-energy silicon clusters (Sin,n=12-20). Selected geometric isomers include those predicted by Ho et al. [Nature (London) 392, 582 (1998)] based on an unbiased search with tight-binding/genetic algorithm, as well as those found by Rata et al. [Phys. Rev. Lett. 85, 546 (2000)] based on density-functional tight-binding/single-parent evolution algorithm. These geometric isomers are optimized at the Møller-Plesset (MP2) MP2/6-31G(d) level. The single-point energy at the coupled-cluster single and double substitutions (including triple excitations) [CCSD(T)] CCSD(T)/6-31G(d) level for several low-lying isomers are further computed. Harmonic vibrational frequency analysis at the MP2/6-31G(d) level of theory is also undertaken to assure that the optimized geometries are stable. For Si12-Si17 and Si19 the isomer with the lowest-energy at the CCSD(T)/6-31G(d) level is the same as that predicted by Ho et al., whereas for Si18 and Si20, the same as predicted by Rata et al. However, for Si14 and Si15, the vibrational frequency analysis indicates that the isomer with the lowest CCSD(T)/6-31G(d) single-point energy gives rise to imaginary frequencies. Small structural perturbation onto the Si14 and Si15 isomers can remove the imaginary frequencies and results in new isomers with slightly lower MP2/6-31G(d) energy; however the new isomers have a higher single-point energy at the CCSD(T)/6-31G(d) level. For most Sin (n=12-18,20) the low-lying isomers are prolate in shape, whereas for Si19 a spherical-like isomer is slightly lower in energy at the CCSD(T)/6-31G(d) level than low-lying prolate isomers.

Zhu, X. L.; Zeng, X. C.; Lei, Y. A.; Pan, B.

2004-05-01

263

Electron Momentum Distributions for 4a1 Orbitals of CFxCl4-x in Low Momentum Region: a Possible Evidence of Molecular Geometry Distortion  

NASA Astrophysics Data System (ADS)

Electron momentum distributions for 4a1 orbitals of serial freon molecules CF3Cl, CF2Cl2, and CFCl3 (CFxCl4-x, x = 1-3) have been reanalyzed due to the severe discrepancies between theory and experiment in low momentum region. The tentative calculations using equilibrium geometries of molecular ions have exhibited a great improvement in agreement with the experimental data, which suggests that the molecular geometry distortion may be responsible for the observed high intensities at p < 0.5 a.u. Further analyses show that the severe discrepancies at low momentum region mainly arise from the influence of molecular geometry distortion on C-Cl bonding electron density distributions.

Shan, Xu; Xu, Chun-kai; Yin, Xiao-feng; Zhou, Li-xia; Xu, Ke-zun; Chen, Xiang-jun

2009-12-01

264

Orbital order in vanadium spinels  

Microsoft Academic Search

Motivated by recent theoretical and experimental controversy, we present a\\u000atheoretical study to clarify the orbital symmetry of the ground state of\\u000avanadium spinel oxides AV$_2$O$_4$ (A=Zn, Mg, Cd). The study is based on an\\u000aeffective Hamiltonian with spin-orbital superexchange interaction and a local\\u000aspin-orbit coupling term. We construct a classical phase-diagram and prove the\\u000acomplex orbital nature of the

S. Di Matteo; G. Jackeli; N. B. Perkins

2005-01-01

265

Bibliographic Notes on Voronoi Diagrams.  

National Technical Information Service (NTIS)

The paper presents a comprehensive annotated bibliography on various theoretical and algorithmic aspects of Voronoi diagrams and related diagrams. Bibliographic notes on the relationship between Voronoi diagrams and solutions to the Euclidean traveling sa...

J. Bernal

1993-01-01

266

From experiment to theory: molecular orbital parameters to interpret the skin sensitization potential of 5-chloro-2-methylisothiazol-3-one and 2-methylisothiazol-3-one.  

PubMed

5-Chloro-2-methylisothiazol-3-one (MCI) and 2-methylisothiazol-3-one (MI) are the major constituents of the commercial biocide Kathon CG. These two compounds have both been shown to exhibit skin sensitization potential: MCI is classified as an extreme sensitizer while MI is classified as a moderate sensitizer. The purpose of the present investigation was to provide further insights into the chemistry underlying their skin sensitizing properties. First, a molecular modeling (in silico) study was carried out of the initial reaction pathways of MI and MCI with nucleophiles representative of those involved in the skin sensitization process, and we compared the findings with the reported chemical and allergenic properties of these compounds. These reaction pathways were assessed using molecular orbital calculations. A novel parameter, the activation energy (AE) index, is proposed and is calculated from a knowledge of the energy changes in the frontier molecular orbitals as the electrophile is converted to an anionic intermediate. The AE indices correspond to the reactivity of MCI and MI with nucleophiles and also their skin sensitization potential. Second, the previously unexplained formation of final reaction products from MCI and butylamine is discussed and a reaction mechanism is proposed. A key finding of this analysis is that the reaction produces "positive chlorine" in the form of N-chloro- and/or N,N-dichloro-butylamine, which could contribute to the skin sensitizing properties of MCI. PMID:15720139

Aptula, Aynur O; Roberts, David W; Cronin, Mark T D

2005-02-01

267

Satellite Venn Diagram  

NSDL National Science Digital Library

In this activity, students will use the background information they have read to organize a list of sources and objects, putting each item given in the appropriate part of the Venn diagram, depending on which instrument will study that item. Students will demonstrate their understanding of spectra, astronomical observations, and have read the background material on Chandra, Astro-E and the microcalorimeter, and the Constellation X-ray Observatory. They will write a five minute summary of the capabilities of the three observatories, based on their Venn diagram. Students' understanding of the background material will be evaluated based on the accuracy of their Venn diagrams and the interpretation of the information on the Venn diagrams from their closure paper.

2007-03-24

268

Diagram of Computer Keyboard  

NSDL National Science Digital Library

This is a line drawing of a Windows PC keyboard complete with labels for each key. This diagram is used on tests where students are asked to circle the keys that would be used to perform various functions.

Ward, Charles

2011-01-21

269

Symmetry and broken-symmetry in molecular orbital descriptions of unstable molecules. 3. The nature of chemical bonds of spin frustrated systems.  

PubMed

Symmetry and broken symmetry in the molecular orbital description of spin frustration systems have been investigated in relation to the resonating valence bond (RVB) theory of the spin liquid state and non-BCS superconductivity. Broken symmetry (BS) and resonating BS (RBS) molecular orbital (MO) methods have been employed to obtain resonating valence bond (RVB)-type explanations of spin frustrated systems. RBS MO solutions are expanded using the localized molecular orbitals (LMO) to elucidate a universal MO-VB description. The BS and RBS MO descriptions of triangular spin frustrated systems corresponding to transition structures for exchange-forbidden radical insertions were investigated in comparison with the RVB-type explanations of such systems. The BS and RBS calculations by the use of three different axial (SDW) solutions or three noncollinear GSO (helical SDW) solutions of a triangular hydrogen cluster were performed to obtain potential curves with and without resonance (quantum) effects. The resonating GSO (noncollinear) state responsible for short-range correlation was found to be the most stable for the system. The reliability of the approximate spin projection (AP) procedure to eliminate the high-spin component was also elucidated, comparing with the AP BS and RBS potential curves. The BS GSO (GHF) computations of several triangular systems, N(CH(2))(3), (CH(2))(3), and Mn(II)(3)O(4), were performed to obtain total energies and total spin angular momentums and effective exchange integrals (J) between local spins, which are crucial for construction of effective spin Hamiltonian models. The exact diagonalization of the Heisenberg models was also performed to depict the energy levels and magnetic susceptibility curves for triangular and kagome lattices to elucidate spin frustration effects and related quantum spin behaviors. Implications of the computational results have been discussed in relation to magnetic properties of several triangular and kagome systems synthesized recently and the superconductivity of triangular systems discovered recently. PMID:19908878

Kawakami, T; Takeda, R; Nishihara, S; Saito, T; Shoji, M; Yamada, S; Yamanaka, S; Kitagawa, Y; Okumura, M; Yamaguchi, K

2009-12-31

270

Phase Diagrams in Vivo  

NSDL National Science Digital Library

This activity uses three experiments for students to construct a phase diagram; the experiments have been videotaped and can be seen online. The purpose of this laboratory as designed is to gain familiarity with simple phase diagrams, their construction, and their applications to the understanding of geological and environmental problems. Subsidiary objectives include development of strategies for data processing including evaluation of assumptions and sources of errors, as well as honing of computer, spreadsheet, presentation (tabular and graphical), and report writing skills.

271

Venn Diagram Shape Sorter  

NSDL National Science Digital Library

This interactive Java applet helps students explore attributes of objects by sorting different sized, colored, shapes into Venn Diagrams. The user chooses the type of Venn Diagram including 2 intersecting circles, 2 non-intersecting circles, or a single circle. Two modes include "make the rule," where users create the rules of the circles and then sort, or "guess the rule," where users attempt to sort the shapes into the circles in order to guess the rule the computer has chosen.

2005-01-01

272

Temporal Verification Diagrams  

Microsoft Academic Search

. Most formal approaches to the verification of temporal propertiesof reactive programs infer temporal conclusions from verificationconditions that are state formulas, i.e., contain no temporal operators.These proofs can often be effectively presented by the use of verification diagrams. In this paper, we present a self-contained presentation ofverification diagrams for proving various temporal properties.Beginning with safety properties, we present WAIT-FOR and

Zohar Manna; Amir Pnueli

1994-01-01

273

Spin-orbit coupling, spin-lattice relaxation, and spin-memory studies of F -center-molecular-ion pairs in alkali halides  

Microsoft Academic Search

Summary  The spin-orbit parameter ?, spin-lattice relaxation timeT\\u000a 1, and spin-mixing parameter ? ofF\\u000a H(OH?) andF\\u000a H(CN?) centers in several alkali halides have been studied with magnetic circular dichroism at ?2 K. A close comparison of the\\u000a experimental results before and after optically induced association of theF center with the molecular ion has been made. In crystals of NaCl structure the

G. Baldacchini; S. Botti; U. M. Grassano; F. Luty

1993-01-01

274

Unrestricted density functional theory based on the fragment molecular orbital method for the ground and excited state calculations of large systems.  

PubMed

We extended the fragment molecular orbital (FMO) method interfaced with density functional theory (DFT) into spin unrestricted formalism (UDFT) and developed energy gradients for the ground state and single point excited state energies based on time-dependent DFT. The accuracy of FMO is evaluated in comparison to the full calculations without fragmentation. Electronic excitations in solvated organic radicals and in the blue copper protein, plastocyanin (PDB code: 1BXV), are reported. The contributions of solvent molecules to the electronic excitations are analyzed in terms of the fragment polarization and quantum effects such as interfragment charge transfer. PMID:24735282

Nakata, Hiroya; Fedorov, Dmitri G; Yokojima, Satoshi; Kitaura, Kazuo; Sakurai, Minoru; Nakamura, Shinichiro

2014-04-14

275

Unrestricted density functional theory based on the fragment molecular orbital method for the ground and excited state calculations of large systems  

NASA Astrophysics Data System (ADS)

We extended the fragment molecular orbital (FMO) method interfaced with density functional theory (DFT) into spin unrestricted formalism (UDFT) and developed energy gradients for the ground state and single point excited state energies based on time-dependent DFT. The accuracy of FMO is evaluated in comparison to the full calculations without fragmentation. Electronic excitations in solvated organic radicals and in the blue copper protein, plastocyanin (PDB code: 1BXV), are reported. The contributions of solvent molecules to the electronic excitations are analyzed in terms of the fragment polarization and quantum effects such as interfragment charge transfer.

Nakata, Hiroya; Fedorov, Dmitri G.; Yokojima, Satoshi; Kitaura, Kazuo; Sakurai, Minoru; Nakamura, Shinichiro

2014-04-01

276

Functions of key residues in the ligand-binding pocket of vitamin D receptor: Fragment molecular orbital interfragment interaction energy analysis  

NASA Astrophysics Data System (ADS)

Fragment molecular orbital-interfragment interaction energy calculations of the vitamin D receptor (VDR)/1?,25-dihydroxyvitamin D 3 complex were utilized to assign functions of key residues of the VDR. Only one residue forms a significant interaction with the corresponding hydroxy group of the ligand, although two residues are located around each hydroxy group. The degradation of binding affinity for derivatives upon removal of a hydroxy group is closely related to the trend in the strength of the hydrogen bonds. Type II hereditary rickets due to an Arg274 point mutation is caused by the lack of the strongest hydrogen bond.

Yamagishi, Kenji; Yamamoto, Keiko; Yamada, Sachiko; Tokiwa, Hiroaki

2006-03-01

277

Density matrix averaged atomic natural orbital (ANO) basis sets for correlated molecular wave functions III. First row transition metal atoms  

Microsoft Academic Search

Generally contracted basis sets for the first row transition metal atoms Sc–Zn have been constructed using the atomic natural orbital (ANO) approach, with modifications for allowing symmetry breaking and state averaging. The ANOs are constructed by averaging over the three electronic configurations d n, d n-1 s, and d n-2 s 2 for the neutral atom as well as the

Rosendo Pou-Amérigo; Manuela Merchán; Ignacio Nebot-Gil; Per-Olof Widmark; Björn O. Roos

1995-01-01

278

Orbital Exponent Optimization in Elementary VB Calculations of the Chemical Bond in the Ground State of Simple Molecular Systems  

ERIC Educational Resources Information Center

Orbital exponent optimization in the elementary ab-initio VB calculation of the ground states of H[subscript 2][superscript +], H[subscript 2], He[subscript 2][superscript +], He[subscript 2] gives a fair description of the exchange-overlap component of the interatomic interaction that is important in the bond region. Correct bond lengths and…

Magnasco, Valerio

2008-01-01

279

Mass Transport Properties of LiD-U Mixtures from Orbital Free Molecular Dynamics Simulations and a Pressure-Matching Mixing Rule  

SciTech Connect

Mass transport properties for LiD-U mixtures were calculated using a pressure matching mixture rule for the mixing of LiD and of U properties simulated with Orbital Free Molecular Dynamics (OFMD). The mixing rule was checked against benchmark OFMD simulations for the fully interacting three-component (Li, D, U) system. To obtain transport coefficients for LiD-U mixtures of different (LiD){sub x}U{sub (1-x)} compositions as functions of temperature and mixture density is a tedious task. Quantum molecular dynamics (MD) simulations can be employed, as in the case LiD or U. However, due to the presence of the heavy constituent U, such simulations proceed so slowly that only a limited number of numerical data points in the (x, {rho}, T) phase space can be obtained. To finesse this difficulty, transport coefficients for a mixture can be obtained using a pressure-matching mixing rule discussed. For both LiD and U, the corresponding transport coefficients were obtained earlier from quantum molecular dynamics simulations. In these simulations, the quantum behavior of the electrons was represented using an orbital free (OF) version of density functional theory, and ions were advanced in time using classical molecular dynamics. The total pressure of the system, P = nk{sub B}T/V + P{sub e}, is the sum of the ideal gas pressure of the ions plus the electron pressure. The mass self-diffusion coefficient for species {alpha}, D{sub {alpha}}, the mutual diffusion coefficient for species {alpha} and {beta}, D{alpha}{beta}, and the shear viscosity, {eta}, are computed from the appropriate autocorrelation function. The details of similar QMD calculations on LiH are described in Ref. [1] for 0.5 eV < T < 3 eV, and in Ref. [2] for 2 eV < T < 6 eV.

Burakovsky, Leonid [Los Alamos National Laboratory; Kress, Joel D. [Los Alamos National Laboratory; Collins, Lee A. [Los Alamos National Laboratory

2012-05-31

280

Orbital pseudotumor  

MedlinePLUS

Orbital pseudotumor is a swelling of the tissues behind the eye in an area called the orbit. The ... and tissue that surround it. Unlike cancerous tumors, orbital pseudotumor does not spread to other tissues or places ...

281

Upgrading Diagnostic Diagrams  

NASA Astrophysics Data System (ADS)

Diagnostic diagrams of forbidden lines have been a useful tool for observers in astrophysics for many decades now. They are used to obtain information on the basic physical properties of thin gaseous nebulae. Moreover they are also the initial tool to derive thermodynamic properties of the plasma from observations to get ionization correction factors and thus to obtain proper abundances of the nebulae. Some diagnostic diagrams are in wavelengths domains which were difficult to take either due to missing wavelength coverage or low resolution of older spectrographs. Thus they were hardly used in the past. An upgrade of this useful tool is necessary because most of the diagrams were calculated using only the species involved as a single atom gas, although several are affected by well-known fluorescence mechanisms as well. Additionally the atomic data have improved up to the present time. The new diagnostic diagrams are calculated by using large grids of parameter space in the photoionization code CLOUDY. For a given basic parameter the input radiation field is varied to find the solutions with cooling-heating-equilibrium. Empirical numerical functions are fitted to provide formulas usable in e.g. data reduction pipelines. The resulting diagrams differ significantly from those used up to now and will improve the thermodynamic calculations.

Proxauf, B.; Kimeswenger, S.; Öttl, S.

2014-04-01

282

Decomposition of Data Flow Diagrams  

Microsoft Academic Search

Data flow diagrams are an important design aid in system development. CASE tools allow data flow diagram construction and modification to be automated. Decomposition is the top-down development of a data flow diagram starting with the system inputs and the system outputs. Decomposition may also be automated, resulting in an interactive process for data flow diagram design. Adler (1988) described

Timothy Arndt; Angela Guercio

1992-01-01

283

Quantitative harmonization of the three molecular orbital, valence bond, and broken symmetry approaches to the exchange coupling constant: Corrections and discussion  

NASA Astrophysics Data System (ADS)

Three current methods, used to evaluate exchange coupling constants in molecular magnetism, i.e., the molecular orbital (MO) model [Hay et al., J. Am. Chem. Soc. 94, 4884 (1975)], the valence bond (VB) model [Kahn and Briat, J. Chem. Soc. Trans. II 72, 268 (1976)], and the broken symmetry (BS) model [Noodleman, J. Chem. Phys. 74, 5737 (1981)], have been revisited. In effect, the three published antiferromagnetic contributions seem mutually inconsistent, as far as their magnitudes are concerned. As it turns out, the VB term -2?S, where ? is the singly occupied MO gap in the triplet state and S the (natural) magnetic orbital overlap, is shown to be overestimated by a factor of 2 (the VB ferromagnetic term, supposedly small, is actually of the order of ?S>0). Moreover, Noodleman's explicit condition derived from the variational optimization of the BS state energy results in fact from the implicit neglect of the VB ionic contribution right from the start of his methodology. Alternative (both rigorous and approximate) expressions are proposed in both VB and BS cases. The MO approach, although not being the best physically appropriate for the study of weakly interacting monomers (i.e., defined by S2<<1), is left untouched at this level of the theory.

Mouesca, Jean-Marie

2000-12-01

284

Nickel(II) in chelate N2O2 environment. DFT approach and in-depth molecular orbital and configurational analysis.  

PubMed

The O-N-N-O-type tetradentate ligands H2S,S-eddp (H2S,S-eddp stands for S,S-ethylenediamine-N,N'-di-2-propionic acid) and H2edap (H2edap stands for ethylenediamine-N-acetic-N'-3-propionic acid) and the corresponding novel octahedral nickel(II) complexes have been prepared and characterized. N2O2 ligands coordinate to the nickel(II) ion via four donor atoms (two deprotonated carboxylate atoms and two amine nitrogens) affording octahedral geometry in the case of all investigated Ni(II) complexes. A six coordinate, octahedral geometry has been verified crystallographically for the s-cis-[Ni(S,S-eddp)(H2O)2] complex. Structural data correlating similarly chelated Ni(II) complexes have been used to carry out an extensive configuration analysis. Molecular mechanics and Density Functional Theory (DFT) have been used to model the most stable geometric isomer, yielding, at the same time, significant structural and spectroscopic (TDDFT) data. The results from density functional studies have been compared to X-ray data. Natural Bond Orbital (NBO) and Natural Energetic Decomposition Analysis (NEDA) have been done for the [Ni(edda-type)(H2O)(2-n)] and nH2O fragments. Molecular orbital analysis (MPA) is given as well. The infra-red and electronic absorption spectra of the complexes are discussed in comparison to the related complexes of known geometries. PMID:23884426

Trifunovi?, Sre?ko R; Mileti?, Vesna D; Jevti?, Verica V; Meetsma, Auke; Matovi?, Zoran D

2013-10-01

285

The projection diagram  

NASA Astrophysics Data System (ADS)

We describe a diagram, named the projection diagram (PD), that can be used for the interpretation of fringe projection operations in a similar way as the Holodiagram is used in holography and other branches in optics. It is obtained as a Moiré pattern between two spoke targets that mimic central projections, the same as those in a projection and observation system or two projection systems. N. Abramson [Academic, London (1981)] has already proposed its use in systems with two observation points (i.e., stereoscopic observation). By using this PD, several interesting features dealing with fringe projection are highlighted. Information on the sensitivity vector and the geometry of the contouring surfaces can be straightforwardly obtained in a graphical way. The effect of defocusing can also be included in the diagram.

Muramatsu, Mikaya; Torroba, Patricia; Cap, Nelly; Rabal, Hector

2003-08-01

286

Minkowski Diagram Model  

NSDL National Science Digital Library

The Minkowski Diagram model displays the spacetime diagrams for two inertial observers. One or two events may be displayed and moved with the mouse. Optionally, the corresponding light cones may be shown, as well as the simultaneity lines in both reference frames. The spacetime interval is automatically computed. The simulation may be used to discuss simultaneity and causality in special relativity. You can modify this simulation if you have Ejs installed by right-clicking within the plot and selecting "Open Ejs Model" from the pop-up menu item. The Minkowski Diagram model was created using the Easy Java Simulations (Ejs) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the ejs_ehu_special_relativity_minkowski.jar file will run the program if Java is installed. Please note that this resource requires at least version 1.5 of Java (JRE).

Aguirregabiria, Juan

2011-09-09

287

Diblock copolymer phase diagram  

NSDL National Science Digital Library

Adaptation of the Matsen and Bates BCP phase diagram predicted using Mean-field Theory. * Matsen MW, Bates FS, ''http://pubs3.acs.org/acs/journals/doilookup?in_doi=10.1021/ma951138i Unifying weak- and strong-segregation block copolymer theories. Diblock copolymer phase diagram as calculated using Mean-field Theory by Matsen and Bates, where fA is the Block fraction, Ï is the Flory-Huggins Chi Parameter, and N is the length of the block.

Iacovella, Christopher R.

2006-11-20

288

Correlated electronic structures and the phase diagram of hydrocarbon-based superconductors  

NASA Astrophysics Data System (ADS)

We have investigated correlated electronic structures and the phase diagram of electron-doped hydrocarbon molecular solids, based on the dynamical mean-field theory. We have found that the ground state of hydrocarbon-based superconductors such as electron-doped picene and coronene is a multi-band Fermi liquid, while that of non-superconducting electron-doped pentacene is a single-band Fermi liquid in the proximity of the metal-insulator transition. The size of the molecular orbital energy level splitting plays a key role in producing the superconductivity of electron-doped hydrocarbon solids. The multi-band nature of hydrocarbon solids would boost the superconductivity through the enhanced density of states at the Fermi level.

Kim, Minjae; Choi, Hong Chul; Shim, Ji Hoon; Min, B. I.

2013-11-01

289

On-Orbit Propulsion OMS/RCS  

NASA Technical Reports Server (NTRS)

This slide presentation reviews the Space Shuttle's On-Orbit Propulsion systems: the Orbital Maneuvering System (OMS) and the Reaction Control System (RCS). The functions of each of the systems is described, and the diagrams of the systems are presented. The OMS/RCS thruster is detailed and a trade study comparison of non-toxic propellants is presented.

Hurlbert, Eric A.

2001-01-01

290

Molecular-orbital study of late-fission times in deep-inelastic 238U+238U collisions  

NASA Astrophysics Data System (ADS)

The U-like K-vacancy production probability in 7.5-MeV/nucleon deep-inelastic 238U+238U collisions has been measured for no-fission, single-fission, and double-fission exit channels. The results are interpreted using quasimolecular orbital correlations for diatomic and triatomic configurations. This leads to the determination of lower limits for the time scale for late fission of U-like products (>=8 and >=4 as) and their probability (>=77% and >=52%), at mean initial-excitation energies of ~40 and ~105 MeV, respectively.

Molitoris, J. D.; Meyerhof, W. E.; Stoller, Ch.; Anholt, R.; Spooner, D. W.; Moretto, L. G.; Sobotka, L. G.; McDonald, R. J.; Wozniak, G. J.; McMahan, M. A.; Blumenfeld, L.; Colonna, N.; Nessi, M.; Morenzoni, E.

1993-02-01

291

Imaging momentum orbital densities of conformationally versatile molecules: a benchmark theoretical study of the molecular and electronic structures of dimethoxymethane.  

PubMed

The main purpose of the present work is to predict from benchmark many-body quantum mechanical calculations the results of experimental studies of the valence electronic structure of dimethoxymethane employing electron momentum spectroscopy, and to establish once and for all the guidelines that should systematically be followed in order to reliably interpret the results of such experiments on conformationally versatile molecules. In a first step, accurate calculations of the energy differences between stationary points on the potential energy surface of this molecule are performed using Hartree-Fock (HF) theory and post-HF treatments of improving quality (MP2, MP3, CCSD, CCSD(T), along with basis sets of increasing size. This study focuses on the four conformers of this molecule, namely the trans-trans (TT), trans-gauche (TG), gauche-gauche (G+G+), and gauche-gauche (G+G-) structures, belonging to the C2v, C1, C2, and Cs symmetry point groups, respectively. A focal point analysis supplemented by suited extrapolations to the limit of asymptotically complete basis sets is carried out to determine how the conformational energy differences at 0 K approach the full CI limit. In a second step, statistical thermodynamics accounting for hindered rotations is used to calculate Gibbs free energy corrections to the above energy differences, and to evaluate the abundance of each conformer in the gas phase. It is found that, at room temperature, the G+G+ species accounts for 96% of the conformational mixture characterizing dimethoxymethane. In a third step, the valence one-electron and shake-up ionization spectrum of dimethoxymethane is analyzed according to calculations on the G+G+ conformer alone by means of one-particle Green's function [1p-GF] theory along with the benchmark third-order algebraic diagrammatic construction [ADC(3)] scheme. A complete breakdown of the orbital picture of ionization is noted at electron binding energies above 22 eV. A comparison with available (e,2e) ionization spectra enables us to identify specific fingerprints of through-space orbital interactions associated with the anomeric effect. At last, based on our 1p-GF/ADC(3) assignment of spectral bands, accurate and spherically averaged (e,2e) electron momentum distributions at an electron impact energy of 1200 eV are computed from the related Dyson orbitals. Very significant discrepancies are observed with momentum distributions obtained for several outer-valence levels using standard Kohn-Sham orbitals. PMID:17566995

Huang, Y R; Knippenberg, S; Hajgató, B; François, J-P; Deng, J K; Deleuze, M S

2007-07-01

292

NOTES ON FEYNMAN DIAGRAMS  

Microsoft Academic Search

We introduce in a pedagogical manner how to compute probability amplitudes from Feynman diagrams, starting with 4 model. We introduce the notion of renormalization in this model at the one-loop level. Then we review the Dirac equation, and introduce QED. We then perform several example calculations in QED. The appendices gives a survey of Gamma matrices and use of Feynman

ALEX NELSON

2009-01-01

293

Hierarchical Hybrid Block Diagrams  

Microsoft Academic Search

Block diagram languages are now commonly used to design and even implement embedded systems. In the design phase, they are used to model both plant and controller, typically with continuous and discrete modeling respectively. The semantics of these lan- guages are often vague and\\/or complex, which is fine for some users but leaves others puzzled by the behav- iors they

Ben Denckla; Pieter J. Mosterman

294

Venn Diagrams and Logic  

NSDL National Science Digital Library

This math lesson from Illuminations uses Venn diagrams to illustrate direct, indirect and transitive reasoning. Students will learn the definitions of direct, indirect and transitive reasoning and give examples of each. Several student activity sheets are included. The material is intended for grades 9-12 and should require 2 and a half class periods to complete.

2011-01-04

295

Simultaneity Spacetime Diagram Model  

NSDL National Science Digital Library

The Simultaneity Spacetime Diagram model uses light-trajectories to show the effect of relative motion when observing (recording) events in special relativity. In the default scenario, an explosion (an event) at the center of a right-moving stick occurs at t=0 and the arrival of the explosion light signal at each end is recorded. The arrival event at the left end occurs before the arrival event at the right end because the stick is moving. How do the location and time of these events change if they are observed in a reference frame (the Other Frame) in which the stick is stationary?   The Simultaneity Spacetime Diagram model was written for the study of special relativity the Lorentz transformation using spacetime diagrams and is a supplemental simulation for an article by Sebastien Cromier and Richard Steinberg "The Twin Twin Paradox: Exploring Student Approaches to Understanding Relativistic Concepts" in the The Physics Teacher 48 (9), 598-601 (2010). Initial conditions, such as the locations of the explosion and the detectors, can be adjusted by dragging before the simulation is run. The slider can be used to change the speed of the stick. A third view shows the stick and the wavefront in space. More importantly, a checkbox allows users to compare the predictions of Galilean and special relativity in order to observe how the assumption of a constant speed of light leads to the relativity of simultaneity.   The Simultaneity Spacetime Diagram model was created using the Easy Java Simulations (EJS) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the ejs_sr_SimultaneitySpacetimeDiagram.jar file will run the program if Java is installed.

Christian, Wolfgang

2010-10-07

296

Molecular cloning and characterization of genes for antibodies generated by orbital tissue-infiltrating B-cells in Graves` ophthalmopathy  

SciTech Connect

Graves` ophthalmopathy is a distressing autoimmune disease of unknown etiology. Analysis of the genes for antibodies secreted by orbital tissue-infiltrating plasma cells might provide insight into the pathogenesis of this disease. The authors, therefore, constructed an immunoglobulin heavy (H) chain and an immunoglobulin k light (L) chain cDNA library from the orbital tissue of a patient with active Graves` ophthalmopathy. Analysis of 15 H (IgG1) and 15 L (k) chains revealed a restricted spectrum of variable region genes. Fourteen of 15 variable k genes were about 94% homologous to the closest known germline gene, KL012. Thirteen of 15 H chain genes were 91% and 90% homologous to the closest germline genes, DP10 and hv1263, respectively. Remarkably, these germline genes also code for other autoantibodies to striated muscle (KL012) and thyroid peridase (KL012 and hv1263). These studies raise the possibility that particular germline genes may be associated with autoimmunity in humans. Further, the present study opens the way to identifying ocular autoantigens that may be the target of an humoral immune response. 29 refs., 4 figs., 1 tab.

Jaume, J.C.; Portolano, S.; Prummel, M.F.; McLachlan, S.M.; Rapoport, B. [Univ. of California, San Francisco, CA (United States)] [Univ. of California, San Francisco, CA (United States)

1994-02-01

297

Molecular orbital (SCF-X??-SW) theory of Fe2+-Mn3+, Fe 3+-Mn 2+, and Fe3+-Mn3+ charge transfer and magnetic exchange in oxides and silicates  

USGS Publications Warehouse

Metal-metal charge-transfer and magnetic exchange interactions have important effects on the optical spectra, crystal chemistry, and physics of minerals. Previous molecular orbital calculations have provided insight on the nature of Fe2+-Fe3+ and Fe2+-Ti4+ charge-transfer transitions in oxides and silicates. In this work, spin-unrestricted molecular orbital calculations on (FeMnO10) clusters are used to study the nature of magnetic exchange and electron delocalization (charge transfer) associated with Fe3+-Mn2+, Fe3+-Mn3+, and Fe2+-Mn3+ interactions in oxides and silicates. -from Author

Sherman, D. M.

1990-01-01

298

Molecular structure, Normal Coordinate Analysis, harmonic vibrational frequencies, Natural Bond Orbital, TD-DFT calculations and biological activity analysis of antioxidant drug 7-hydroxycoumarin  

NASA Astrophysics Data System (ADS)

In this work, we report harmonic vibrational frequencies, molecular structure, NBO and HOMO, LUMO analysis of Umbelliferone also known as 7-hydroxycoumarin (7HC). The optimized geometric bond lengths and bond angles obtained by computation (monomer and dimmer) shows good agreement with experimental XRD data. Harmonic frequencies of 7HC were determined and analyzed by DFT utilizing 6-311+G(d,p) as basis set. The assignments of the vibrational spectra have been carried out with the help of Normal Coordinate Analysis (NCA) following the Scaled Quantum Mechanical Force Field Methodology (SQMFF). The change in electron density (ED) in the ?* and ?* antibonding orbitals and stabilization energies E(2) have been calculated by Natural Bond Orbital (NBO) analysis to give clear evidence of stabilization originating in the hyperconjugation of hydrogen-bonded interaction. The energy and oscillator strength calculated by Time-Dependent Density Functional Theory (TD-DFT) complements with the experimental findings. The simulated spectra satisfactorily coincides with the experimental spectra. Microbial activity of studied compounds was tested against Staphylococcus aureus, Streptococcus pyogenes, Bacillus subtilis, Escherichia coli, Psuedomonas aeruginosa, Klebsiella pneumoniae, Proteus mirabilis, Shigella flexneri, Salmonella typhi and Enterococcus faecalis.

Sebastian, S.; Sylvestre, S.; Jayarajan, D.; Amalanathan, M.; Oudayakumar, K.; Gnanapoongothai, T.; Jayavarthanan, T.

2013-01-01

299

Positron-attachment to acetonitrile, acetaldehyde, and acetone molecules: Vibrational enhancement of positron affinities with configuration interaction level of multi-component molecular orbital approach  

NASA Astrophysics Data System (ADS)

To theoretically demonstrate the binding of a positron to acetonitrile, acetaldehyde, and acetone molecules, we have calculated the vibrational averaged positron affinity (PA) values along the local CN or CO vibrational contribution with the configuration interaction level of multi-component molecular orbital method. This method can take the electron-positron correlation contribution into account through single electronic – single positronic excitation configurations. The PA values are enhanced by including the local vibrational contribution from vertical PA values due to the anharmonicity of the potential. For acetonitrile, acetaldehyde, and acetone molecules, the PA values after averaging over the 1st vibrational state are 136, 55, and 96 meV, which can be compared with the corresponding experimental vlues of 180, 90, and 173 meV, respectively.

Tachikawa, Masanori

2014-04-01

300

The tetrazole-azide tautomerism of some nitrotetrazolo [1,5- a]pyridines studied by NMR, IR spectroscopy and molecular orbital calculations  

NASA Astrophysics Data System (ADS)

The 6-nitro- and 8-nitro- groups in the tetrazolo[1,5- a]pyridine molecule exhibit completely different influences on the tetrazole-azide equilibrium. Introduction of the methyl-, nitro-, azido groups or a bromine atom in positions 5, 6, 7 or 8 of the nitrotetrazolopyridine produce changes in the equilibrium constants. Based on the IR spectra taken in the solid state, the tetrazole structure was assigned for almost all the compounds studied. Only one of them, 2,6-diazido-3-nitropyridine, exists in the diazido-form in the solid. The 1H, 13C, 15N, and 17O NMR spectral parameters (coupling constants, chemical shifts) as well as ab initio molecular orbital calculations were used to describe the tetrazole-azide tautomerism in solutions. The differences in the NMR parameters between the neutral compound (6,8-dinitrotetrazolo[1,5- a]pyridine) and its ?-adducts are also included as data for distinguishing between both molecules.

Cmoch, P.; Wiench, J. W.; Stefaniak, L.; Webb, G. A.

1999-11-01

301

Gradient of molecular Hartree-Fock-Bogoliubov energy with a linear combination of atomic orbital quasiparticle wave functions.  

PubMed

The analytical gradient for the atomic-orbital-based Hartree-Fock-Bogoliubov (HFB) energy functional, the modified form of which was proposed by Staroverov and Scuseria to account for the static electron correlation [J. Chem. Phys. 117, 11107 (2002)], is derived. Interestingly, the Pulay force for the HFB energy is expressed with the same formula as that for the Hartree-Fock method. The efficiency of the present HFB energy gradient is demonstrated in the geometry optimizations of conjugated and biradical systems. The geometries optimized by using the HFB method with the appropriate factor ?, which controls the degree of static correlation included, are found to show good agreement with those obtained by using a complete active-space self-consistent field method, although they are significantly dependent on ?. PMID:24588156

Kobayashi, Masato

2014-02-28

302

Gradient of molecular Hartree-Fock-Bogoliubov energy with a linear combination of atomic orbital quasiparticle wave functions  

NASA Astrophysics Data System (ADS)

The analytical gradient for the atomic-orbital-based Hartree-Fock-Bogoliubov (HFB) energy functional, the modified form of which was proposed by Staroverov and Scuseria to account for the static electron correlation [J. Chem. Phys. 117, 11107 (2002)], is derived. Interestingly, the Pulay force for the HFB energy is expressed with the same formula as that for the Hartree-Fock method. The efficiency of the present HFB energy gradient is demonstrated in the geometry optimizations of conjugated and biradical systems. The geometries optimized by using the HFB method with the appropriate factor ?, which controls the degree of static correlation included, are found to show good agreement with those obtained by using a complete active-space self-consistent field method, although they are significantly dependent on ?.

Kobayashi, Masato

2014-02-01

303

Vibrational spectra and ab initio molecular orbital calculations of the novel anti-cancer drug combretastatin A-4 prodrug  

NASA Astrophysics Data System (ADS)

The NIR-FT Raman and FT-IR spectral studies of the novel antineoplastic and antiangiogenesis substance comprestatin A-4 prodrug (CA4P) were carried out. The equilibrium geometry, various bonding features and harmonic vibrational frequencies of CA4P have been investigated with the help of B3LYP density functional theory (DFT) method. The most preferred cis-configuration for its bioactivity has been demonstrated on the basis of torsional potential energy surface (PES) scan studies. Stability of the molecule arising from hyperconjugative interactions leading to its bioactivity, charge delocalization and mesomeric effects have been analyzed using natural bond orbital (NBO) analysis. Detailed assignments of the vibrational spectra have been made with the aid of theoretically predicted vibrational frequencies. The optimized geometry shows near-planarity of phenyl rings and perpendicular conformation of meta substituted methoxy group. The vibrational analysis confirms the differently acting ring modes, steric repulsion, ? conjugation and back-donation.

James, C.; Pettit, G. R.; Nielsen, O. F.; Jayakumar, V. S.; Joe, I. Hubert

2008-10-01

304

Molecular orbital theory of the hydrogen bond. n ? ?* transitions in monosubstituted by pyridines and their complexes with H 2O  

NASA Astrophysics Data System (ADS)

Ab initio SCF-CI calculations have been performed to investigate substituent and hydrogen bonding effects on n ? ?* transitions in 2- and 4-R-pyridines, with the substituents including CH 3, NH 2, OH, F, C 2H 3, CHO, and CN. Substitution of the saturated ? donating and ? withdrawing groups CH 3, NH 2, OH, and F in the 2 or 4 position of pyridine increases the n ? ?* transition energy, while substitution of the ? and ? electron withdrawing groups CHO and CN decreases the n ? ?* transition energy. Orbital energy differences (? ?* - ? n) and virtual excitation energies tend to correlate with CI n ? ?* transition energies when the substituents are saturated, but these correlations tend to be masked by other effects, including ? conjugation, n orbital interaction, and configurational mixing, when the substituents are unsaturated. Hydrogen bonding with water leads to an increase in the n ? ?* transition energy of monosubstituted pyridines when the pyridine ring is the chromophore. In all hydrogen-bonded dimers except water : 2-aminopyridine, this increase is comparable to, but somewhat greater than, the ground state hydrogen bond energy, suggesting that the hydrogen bond is broken in the excited state, and these complexes dissociate upon vibrational relaxation. For the cyclic water : 2-aminopyridine dimer, the predicted increase in the n ? ?* transition energy is less than the ground state stabilization energy, suggesting that even upon relaxation, this dimer may still remain bound in the excited state. The first excited n ? ?* state of 2- and 4-pyridinecarboxaldehyde, unlike that of the other 2- and 4-R-pyridines, arises when the carbonyl group is the chromophore. Hydrogen bonding of these molecules to water through the pyridine nitrogen leads to a slight decrease in the n ? ?* transition energy, suggesting that these bases form stronger hydrogen bonds in the first excited state than in the

Del Bene, Janet E.

1980-08-01

305

An Introduction to Tree Diagrams  

NSDL National Science Digital Library

This brief article describes the use of tree diagrams in calculating probabilities. The author provides examples of how tree diagrams are used to calculate specific probabilities and why the language chosen relates to the operations used to find the probability.

Cork, Stu

2014-01-01

306

Pattern Recognition of Logic Diagrams.  

National Technical Information Service (NTIS)

This paper presents the development of line following and line analysis pattern recognition routines to automatically computer read hand-drawn logic diagrams. The decision criterion used was based on a tree analysis of segmented lines. The logic diagrams ...

D. A. Naegele

1973-01-01

307

TEP process flow diagram  

Microsoft Academic Search

This presentation describes the development of the proposed Process Flow Diagram (PFD) for the Tokamak Exhaust Processing System (TEP) of ITER. A brief review of design efforts leading up to the PFD is followed by a description of the hydrogen-like, air-like, and waterlike processes. Two new design values are described; the mostcommon and most-demanding design values. The proposed PFD is

R Scott Wilms; Bryan Carlson; James Coons; William Kubic

2008-01-01

308

Development of a Silicon Carbide Molecular Beam Nozzle for Simulation Planetary Flybys and Low-Earth Orbit  

NASA Technical Reports Server (NTRS)

From commercial origins as a molybdenum molecular beam nozzle, a ceramic nozzle of silicon carbide (SiC) was developed for space environment simulation. The nozzle is mechanically stable under extreme conditions of temperature and pressure. A heated, continuous, supersonically-expanded hydrogen beam with a 1% argon seed produced an argon beam component of nearly 4 km/s, with an argon flux exceeding 1x1014 /cm2.s. This nozzle was part of a molecular beam machine used in the Atmospheric Experiments Branch at NASA Goddard Space Flight Center to characterize the performance of the University of Texas at Dallas Ram Wind Sensor (RWS) aboard the Air Force Communications/Navigation Outage Forecasting System (C/NOFS) launched in the Spring of 2008.

Patrick, E. L.; Earle, G. D.; Kasprzak, W. T.; Mahaffy, Paul R.

2008-01-01

309

Conventions for Block Diagram Representations  

Microsoft Academic Search

Although the use of block diagrams to represent various systems is very widespread, there are no standard conventions for the drawing of block diagrams. This is particularly true when such diagrams are used to represent complex nonlinear systems, and most practical systems of interest are of this type. The purpose of this paper is to suggest an approach to the

A. Bose; P. M. Anderson; C. Concordia; A. A. Fouad; P. Kundur; R. P. Schulz

1986-01-01

310

Modeling process flow using diagrams  

Microsoft Academic Search

In the practice of process improvement, tools such as the flowchart, the value-stream map (VSM), and a variety of ad hoc variants of such diagrams are commonly used. The purpose of this paper is to present a clear, precise, and consistent framework for the use of such flow diagrams in process improvement projects. The paper finds that traditional diagrams, such

Benjamin Kemper; Jeroen de Mast; Michel Mandjes

2010-01-01

311

Symmetry and broken symmetries in molecular orbital descriptions of unstable molecules II. Alignment, flustration and tunneling of spins in mesoscopic molecular magnets  

Microsoft Academic Search

.   As an extention of previous work [Yamaguchi K (1983) J Mol Structure (Theochem) 103:101], our theoretical efforts toward molecular materials are briefly reviewed. Axial, helical and general (cone, tetrahedron,\\u000a etc) spin structures of carbon clusters, manganese oxide clusters and iron-sulfur clusters were investigated using the classical\\u000a Heisenberg model and generalized Hartree-Fock theory. The spin flustrations in the clusters were

K. Yamaguchi; S. Yamanaka; M. Nishino; Y. Takano; Y. Kitagawa; H. Nagao; Y. Yoshioka

1999-01-01

312

The molecular structure of benzene derivatives part 1. 4-Fluorobenzaldehyde by joint analysis of gas electron diffraction, microwave spectroscopy and ab initio molecular orbital calculations  

Microsoft Academic Search

The molecular structure of gaseous 4-fluorobenzaldehyde has been determined by a joint analysis of gas electron diffraction data, rotational constants from microwave spectroscopy, and constrained by results from ab initio calculations. The ab initio calculations have been performed at the HF6-311G?? and MP26-31G? levels of theory. The planar Cs symmetry structure was found to be the only stable conformation. The

Svein Samdal; Tor G. Strand; Maxim A. Tafipolsky; Lev V. Vilkov; M. V. Popik; Hans Vidar Volden

1997-01-01

313

Kepler's Orbit  

NASA Video Gallery

Kepler does not orbit the Earth, rather it orbits the Sun in concert with the Earth, slowly drifting away from Earth. Every 61 Earth years, Kepler and Earth will pass by each other. Throughout the ...

314

Vinyl dichlorosilane and vinyl dibromosilane ( H 2C?CH–SiHX 2 , X=Cl, Br ): conformational structure and vibrational properties determined by gas-phase electron diffraction, ab initio molecular orbital calculations, and variable-temperature Raman spectroscopy  

Microsoft Academic Search

The molecular structures, conformations, vibrational spectra, and torsional potentials of vinyl dichlorosilane (VDC) H2C?CH–SiHCl2, and vinyl dibromosilane (VDB) H2C?CH–SiHBr2, have been studied using gas-phase electron diffraction (GED) data at 23–25°C and variable-temperature Raman spectroscopy, together with ab initio molecular orbital calculations. The GED data were handled by a dynamic theoretical model using a cosine Fourier potential function in describing the

T. H. Johansen; K. Hagen; K. Hassler; A. D. Richardson; U. Pätzold; R. Stølevik

2000-01-01

315

Hexachloroacetone (Cl 3C–C(?O)–CCl 3): conformational structure, and the matter of C 2 equilibrium symmetry, reinvestigated by gas-phase electron diffraction and ab initio molecular orbital calculations  

Microsoft Academic Search

The molecular and conformational structure of hexachloroacetone, Cl3C–CO–CCl3, has been studied using gas-phase electron diffraction (GED) data at a temperature of 300°C, and ab initio molecular orbital calculations. The title compound exists in the gas phase as a single conformer with C2 symmetry, with a twist angle about the C–CCl3 bonds of ?=31.6 (12)° obtained from a quartic potential function

Tore H Johansen; Stig Muren; Kolbjørn Hagen

2001-01-01

316

1,2-Dibromoethyl-trichlorosilane (CH 2Br CHBr SiCl 3): conformational structure and vibrational properties by gas-phase electron diffraction, infrared and Raman spectroscopy, and ab initio molecular orbital and density functional theory calculations  

Microsoft Academic Search

The molecular structure and conformational properties of 1,2-dibromoethyl-trichlorosilane (CH2BrCHBrSiCl3) have been investigated using gas-phase electron diffraction (GED) data recorded at a temperature of 100°C, together with ab initio molecular orbital (MO) and density functional theory (DFT) calculations, infrared (IR) and Raman spectroscopy in the liquid and solid phases, and normal coordinate analysis (NCA). The molecule exists in the gas- and

Tore H. Johansen; Karl Hassler; Alan D. Richardson; Günther Tekautz; Kolbjørn Hagen

2005-01-01

317

Diffusion-controlled detection of trinitrotoluene: interior nanoporous structure and low highest occupied molecular orbital level of building blocks enhance selectivity and sensitivity.  

PubMed

Development of simple, cost-effective, and sensitive fluorescence-based sensors for explosives implies broad applications in homeland security, military operations, and environmental and industrial safety control. However, the reported fluorescence sensory materials (e.g., polymers) usually respond to a class of analytes (e.g., nitroaromatics), rather than a single specific target. Hence, the selective detection of trace amounts of trinitrotoluene (TNT) still remains a big challenge for fluorescence-based sensors. Here we report the selective detection of TNT vapor using the nanoporous fibers fabricated by self-assembly of carbazole-based macrocyclic molecules. The nanoporosity allows for time-dependent diffusion of TNT molecules inside the material, resulting in further fluorescence quenching of the material after removal from the TNT vapor source. Under the same testing conditions, other common nitroaromatic explosives and oxidizing reagents did not demonstrate this postexposure fluorescence quenching; rather, a recovery of fluorescence was observed. The postexposure fluorescence quenching as well as the sensitivity is further enhanced by lowering the highest occupied molecular orbital (HOMO) level of the nanofiber building blocks. This in turn reduces the affinity for oxygen, thus allocating more interaction sites for TNT. Our results present a simple and novel way to achieve detection selectivity for TNT by creating nanoporosity and tuning molecular electronic structure, which when combined may be applied to other fluorescence sensor materials for selective detection of vapor analytes. PMID:22339204

Che, Yanke; Gross, Dustin E; Huang, Helin; Yang, Dongjiang; Yang, Xiaomei; Discekici, Emre; Xue, Zheng; Zhao, Huijun; Moore, Jeffrey S; Zang, Ling

2012-03-14

318

Orbital pathology  

Microsoft Academic Search

This overview of orbital pathology deals with different kinds of tumors, inflammatory, vascular, and traumatic diseases, which may involve the orbit. Depending on the respective orbital compartment of the globe, the intrakonal, extrakonal and optic nerve the most important and most frequent lesions are presented with their specific clinical symptoms. Their specific presentation on CT- and MR-imaging is discussed in

W Müller-Forell; S Pitz

2004-01-01

319

An ab initio molecular orbital study comparing the bonding of the NH3 and the H2O in the monoammines and the monohydrates of main group and transition metal ions  

Microsoft Academic Search

It is common knowledge that some metal ions prefer to bond to nitrogen atoms, others prefer oxygen and others select sulfur, although the mechanistic origin of this behaviour is not well understood. To provide quantitative data that can illuminate this characteristic difference, we have been performing ab initio molecular orbital calculations on complexes of a wide variety of main group

PHILIP GEORGE; JENNY P. GLUSKER; GEORGE D. MARKHAM; MENDEL TRACHTMAN; CHARLES W. BOCK

2003-01-01

320

Molecular determinants for drug-receptor interactions. Part 2. An ab initio molecular orbital and dipole moment study of the novel nootropic agent piracetam (2-oxopyrrolidin-1-ylacetamide)  

NASA Astrophysics Data System (ADS)

From the ab initio molecular energies of the possible conformers and from a classical dipole moment analysis of 2-oxopyrrolidin-l-ylacetamide (? = 4.02 D in dioxan at 30.0°C), the preferred conformation in solution of this novel nootropic agent has been determined. The exocyclic N-CH 2 bond is rotated in one sense by 90° and the exocyclic CH 2-C bond rotated in the same sense by 120° from the "planar" ( OO)- cis conformation. The structures of the two enantiomers in solution differ from that of the crystalline molecule.

Lumbroso, H.; Liégeois, C.; Pappalardo, G. C.; Grassi, A.

321

Preparation and Characterization of [pi]-Stacking Quinodimethane Oligothiophenes. Predicting Semiconductor Behavior and Bandwidths from Crystal Structures and Molecular Orbital Calculations  

SciTech Connect

A series of new quinodimethane-substituted terthiophene and quaterthiophene oligomers has been investigated for comparison with a previously studied quinoid oligothiophene that has demonstrated high mobilities and ambipolar transport behavior in thin-film transistor devices. Each new quinoidal thiophene derivative shows a reversible one-electron oxidation between 0.85 and 1.32 V, a quasi-reversible one-electron second oxidation between 1.37 and 1.96 V, and a reversible two-electron reduction between -0.05 and -0.23 V. The solution UV-vis-NIR spectrum of each compound is dominated by an intense epsilon congruent with 100,000 M{sup -1} cm{sup -1} low energy pi-pi transition that has a lambda(max) ranging between 648 and 790 nm. All X-ray crystal structures exhibit very planar quinoidal backbones and short intermolecular pi-stacking distances (3.335-3.492 A). Structures exhibit a single pi-stacking distance with parallel cofacial stacking (sulfur atoms of equivalent rings pointed in the same direction) or with alternating distances and antiparallel cofacial stacking (sulfur atoms of equivalent rings pointed in the opposite direction). Examples of the layered and herringbone-packing motifs are observed for both the parallel and the antiparallel cofacial stacking. Analysis of the X-ray structures and molecular orbital calculations indicates that all of these compounds have one-dimensional electronic band structures as a result of the pi-stacking. For structures with a unique pi-stacking distance, a simple geometric overlap parameter calculated from the shape of the molecule and the slip from perfect registry in the pi-stack correlates well with the transfer integrals (t) calculated using molecular orbital theory. The calculated valence (633 meV) and conduction (834 meV) bandwidths for a quinoid quaterthiophene structure are similar to those calculated for the benchmark pentacene and indicate that both hole and electron mobilities could be significant.

Janzen, Daron E.; Burand, Michael W.; Ewbank, Paul C.; Pappenfus, Ted M.; Higuchi, Hiroyuki; da Silva, Demetrio A.; Young, Victor G.; Bredas, Jean-Luc; Mann, Kent R. (GIT); (Minnesota); (Toyama)

2010-11-16

322

Argument Diagramming: The Araucaria Project  

NASA Astrophysics Data System (ADS)

Formal arguments, such as those used in science, medicine and law to establish a conclusion by providing supporting evidence, are frequently represented by diagrams such as trees and graphs. We describe the software package Araucaria which allows textual arguments to be marked up and represented as standard, Toulmin or Wigmore diagrams. Since each of these diagramming techniques was devised for a particular domain or argumentation, we discuss some of the issues involved in translating between diagrams. The exercise of translating between different diagramming types illustrates that any one diagramming system often cannot capture all of the nuances inherent in an argument. Finally, we describe some areas, such as critical thinking courses in colleges and universities and the analysis of evidence in court cases, where Araucaria has been put to practical use.

Rowe, Glenn; Reed, Chris

323

Orbital inflammation  

Microsoft Academic Search

Orbital inflammation is a common problem in adults and children, accounting for the majority of all orbital processes. The\\u000a presentation may be acute, subacute, or insidious. When the onset is acute, the process can be mistaken for orbital cellulitis.\\u000a In insidious cases, such as the sclerosing subtype of inflammation, the chronic painless course may prompt concerns about\\u000a a neoplastic infiltration

Kimberly P. Cockerham; Sang H. Hong; Ellen E. Browne

2003-01-01

324

Many-body exchange-repulsion in polarizable molecular mechanics. I. Orbital-based approximations and applications to hydrated metal cation complexes.  

PubMed

We have quantified the extent of the nonadditivity of the short-range exchange-repulsion energy, E(exch-rep), in several polycoordinated complexes of alkali, alkaline-earth, transition, and metal cations. This was done by performing ab initio energy decomposition analyses of interaction energies in these complexes. The magnitude of E(exch-rep(n-body, n > 2)) was found to be strongly cation-dependent, ranging from close to zero for some alkali metal complexes to about 6 kcal/mol for the hexahydrated Zn(2+) complex. In all cases, the cation-water molecules, E(exch-rep(three-body)), has been found to be the dominant contribution to many-body exchange-repulsion effects, higher order terms being negligible. As the physical basis of this effect is discussed, a three-center exponential term was introduced in the SIBFA (Sum of Interactions Between Fragments Ab initio computed) polarizable molecular mechanics procedure to model such effects. The three-body correction is added to the two-center (two-body) overlap-like formulation of the short-range repulsion contribution, E(rep), which is grounded on simplified integrals obtained from localized molecular orbital theory. The present term is computed on using mostly precomputed two-body terms and, therefore, does not increase significantly the computational cost of the method. It was shown to match closely E(three-body) in a series of test cases bearing on the complexes of Ca(2+), Zn(2+), and Hg(2+). For example, its introduction enabled to restore the correct tetrahedral versus square planar preference found from quantum chemistry calculations on the tetrahydrate of Hg(2+) and [Hg(H(2)O)(4)](2+). PMID:21793002

Chaudret, Robin; Gresh, Nohad; Parisel, Olivier; Piquemal, Jean-Philip

2011-11-15

325

Orbiting Earth  

NSDL National Science Digital Library

This Flash animation contrasts the geostationary versus polar orbits for satellites. For a geostationary orbit, the satellite remains directly above a fixed point at all times; in time with the Earth's rotation, the satellite circles the earth once every 24 hours, continually viewing the same part of Earth. For the polar orbit, the satellite circles over both poles in a constant plane while earth rotates beneath. Earth's rotation exposes different parts of the surface on each orbit. The animation is useful for a discussion on how remote sensing imagery and Global Positioning Systems (GPS) signals are derived. The animation can be paused and rewound to stress important points.

Loomis, Jennifer; Nasa; Earth, Exploring

326

Atomic Orbitals  

NSDL National Science Digital Library

The Atomic Orbitals Web site "was established as part of an (ongoing) project at Purdue University to develop 'visualization modules' for general chemistry students." Using the Chime plug-in, which allows unique and stunning visualizations, visitors can learn what an atomic orbital is; what the 1s, 2s, 3s, 2p, 3p, and 3d orbitals are; what hybrid orbitals are; and more. The combination of easy-to-read descriptions and educational graphics make the site a great learning resource for high school and even college level chemistry students.

1969-12-31

327

Behind the folding funnel diagram.  

PubMed

This Commentary clarifies the meaning of the funnel diagram, which has been widely cited in papers on protein folding. To aid in the analysis of the funnel diagram, this Commentary reviews historical approaches to understanding the mechanism of protein folding. The primary role of free energy in protein folding is discussed, and it is pointed out that the decrease [corrected] in the configurational entropy as the native state is approached hinders folding, rather than guiding it. Diagrams are introduced that provide a less ambiguous representation of the factors governing the protein folding reaction than the funnel diagram. PMID:21685880

Karplus, Martin

2011-07-01

328

Bound states of positron with simple carbonyl and aldehyde species with configuration interaction multi-component molecular orbital and local vibrational approaches  

NASA Astrophysics Data System (ADS)

Characteristic features of the positron-binding structure of some carbonyl and aldehyde species such as formaldehyde, acetaldehyde, acetone and propionaldehyde are discussed with the configuration interaction scheme of multi-component molecular orbital (MC_MO) calculations. This method can take the electron-positron correlation contribution into account through single electronic-single positronic excitation configurations. Our vertical positron affinity (PA) values of acetaldehyde and acetone with electronic 6-31 + +G(2df,2pd) and positronic [15s15p3d2f1g] basis sets are as 52 and 92 meV, which can be compared to the recent experimental values of 90 and 173 meV by Danielson et al (2010 Phys. Rev. Lett. 104 233201). For formaldehyde we have also found that the PA values are enhanced by including the local C= \\!\\! =O vibrational contribution from the vertical PA value of 15 meV to 17, 21 and 25 meV after averaging over the zeroth, first and second vibrational states, respectively, due to the anharmonicity of the potential.

Tachikawa, Masanori; Kita, Yukiumi; Buenker, Robert J.

2012-03-01

329

Monte Carlo simulations on atropisomerism of thienotriazolodiazepines applicable to slow transition phenomena using potential energy surfaces by ab initio molecular orbital calculations.  

PubMed

Compounds with a medium-sized flexible ring often show atropisomerism that is caused by the high-energy barriers between long-lived conformers that can be isolated and often have different biological properties to each other. In this study, the frequency of the transition between the two stable conformers, aS and aR, of thienotriazolodiazepine compounds with flexible 7-membered rings was estimated computationally by Monte Carlo (MC) simulations and validated experimentally by NMR experiments. To estimate the energy barriers for transitions as precisely as possible, the potential energy (PE) surfaces used in the MC simulations were calculated by molecular orbital (MO) methods. To accomplish the MC simulations with the MO-based PE surfaces in a practical central processing unit (CPU) time, the MO-based PE of each conformer was pre-calculated and stored before the MC simulations, and then only referred to during the MC simulations. The activation energies for transitions calculated by the MC simulations agreed well with the experimental ?G determined by the NMR experiments. The analysis of the transition trajectories of the MC simulations revealed that the transition occurred not only through the transition states, but also through many different transition paths. Our computational methods gave us quantitative estimates of atropisomerism of the thienotriazolodiazepine compounds in a practical period of time, and the method could be applicable for other slow-dynamics phenomena that cannot be investigated by other atomistic simulations. PMID:24583777

Morikami, Kenji; Itezono, Yoshiko; Nishimoto, Masahiro; Ohta, Masateru

2014-01-01

330

Structures, molecular orbitals and UV-vis spectra investigations on methyl 1-benzyl-1H-1,2,3-triazole-4-carboxylate: A computational study.  

PubMed

The methyl 1-benzyl-1H-1,2,3-triazole-4-carboxylate (C11H11N3O2) has been studied by theoretically methods. The structure of this compound is optimized by density functional theory (DFT), the second-order Møller-Plesset perturbation theory (MP2) and G3 theory (G3(MP2)) levels. Our calculation results are in very good agreement with experimental values. Compared to a perfect pentagonal structure, the geometrical structures of C11H11N3O2 show a little distortion of 1,2,3-triazole ring due to the highly electronegativity of substitution groups. In addition, dipole moment and frontier molecular orbitals (FMOs) of the C11H11N3O2 are calculated as well. Because of solvent effect, the HOMO-LUMO energy gap in methanol is predicted to be smaller than in gas phase by 0.367eV. The simulated UV-vis spectra are investigated by time-dependent density functional theory (TD-DFT), and two obviously absorption features have been predicted. These two absorption features are located between 170nm and 210nm, which is in ultraviolet C range. Moreover, the UV absorption features in methanol are predicted to be more intense than in gas phase; besides, the red shift is predicted in methanol as well. PMID:24835928

Wang, Tsang-Hsiu; Chu, Hsing-Yu; Wang, I-Teng

2014-10-15

331

Spectroscopic (FT-IR, FT-Raman, NMR and UV-Visible) and quantum chemical studies of molecular geometry, Frontier molecular orbital, NLO, NBO and thermodynamic properties of salicylic acid.  

PubMed

The solid phase FT-IR and FT-Raman spectra of 2-hydroxybenzoic acid (salicylic acid) have been recorded in the region 4000-400 and 4000-100cm(-)(1) respectively. The optimized molecular geometry and fundamental vibrational frequencies are interpreted with the aid of structure optimizations and normal coordinate force field calculations based on density functional theory (DFT) method and a comparative study between Hartree Fork (HF) method at 6-311++G(d,p) level basis set. The calculated harmonic vibrational frequencies are scaled and they are compared with experimentally obtained FT-IR and FT-Raman spectra. A detailed interpretation of the vibrational spectra of this compound has been made on the basis of the calculated potential energy distribution (PED). The time dependent DFT method is employed to predict its absorption energy and oscillator strength. The linear polarizability (?) and the first order hyper polarizability (?) values of the investigated molecule have been computed. The electronic properties, such as HOMO and LUMO energies, molecular electrostatic potential (MEP) are also performed. Stability of the molecule arising from hyper conjugative interaction, charge delocalization has been analyzed using natural bond orbital (NBO) analysis. PMID:24858354

Suresh, S; Gunasekaran, S; Srinivasan, S

2014-11-11

332

Physiology Flow-Diagram Models  

NSDL National Science Digital Library

A set of physiology flow-diagrams for the cardiovascular system, cardiac auto-rhythmic cell, cardiac contractile cell, respiratory system, coagulation/hemostasis, digestive system, excretion, and autonomic nervous system. These flow-diagrams show cause-and-effect markup and have accompanying tutorials.

PhD Sandra J Bruner (Polk Community College Biology)

2005-10-04

333

Potential-pH Diagrams.  

ERIC Educational Resources Information Center

Potential-pH diagrams show the domains of redoxpotential and pH in which major species are most stable. Constructing such diagrams provides students with opportunities to decide what species must be considered, search literature for equilibrium constants and free energies of formation, and practice in using the Nernst equation. (Author/JN)

Barnum, Dennis W.

1982-01-01

334

Quantum phases of atomic Fermi gases with anisotropic spin-orbit coupling  

SciTech Connect

We consider a general anisotropic spin-orbit coupling and analyze the phase diagrams of both balanced and imbalanced Fermi gases for the entire BCS-BEC evolution. In the first part, we use the self-consistent mean-field theory at zero temperature, and show that the topological structure of the ground-state phase diagrams is quite robust against the effects of anisotropy. In the second part, we go beyond the mean-field description, and investigate the effects of Gaussian fluctuations near the critical temperature. This allows us to derive the time-dependent Ginzburg-Landau theory, from which we extract the effective mass of the Cooper pairs and their critical condensation temperature in the molecular BEC limit.

Iskin, M. [Department of Physics, Koc University, Rumelifeneri Yolu, 34450 Saryer, Istanbul (Turkey); Subasi, A. L. [Department of Physics, Faculty of Science and Letters, Istanbul Technical University, 34469 Maslak, Istanbul (Turkey)

2011-10-15

335

Theoretical phase diagrams for solid H{sub 2}  

SciTech Connect

Possible phase diagrams for solid molecular para-hydrogen in the 0-200 GPa pressure regime are constructed on the basis of ab initio calculations. Structures for the broken symmetry phase (BSP) and H-A phase have recently been proposed under the assumption that the molecules are centered on sites of a hexagonal close-packed lattice with the ideal c/a ratio, i.e., only molecular orientational and electronic changes are allowed. Symmetry considerations then dictate the simplest phase diagrams consistent with experimental observations, although the possibility of additional transitions cannot be ruled out. A simple model is introduced to describe the BSP and H-A transitions.

Surh, M.P.; Runge, K.J.

1993-07-01

336

Orbiter Autoland reliability analysis  

NASA Technical Reports Server (NTRS)

The Space Shuttle Orbiter is the only space reentry vehicle in which the crew is seated upright. This position presents some physiological effects requiring countermeasures to prevent a crewmember from becoming incapacitated. This also introduces a potential need for automated vehicle landing capability. Autoland is a primary procedure that was identified as a requirement for landing following and extended duration orbiter mission. This report documents the results of the reliability analysis performed on the hardware required for an automated landing. A reliability block diagram was used to evaluate system reliability. The analysis considers the manual and automated landing modes currently available on the Orbiter. (Autoland is presently a backup system only.) Results of this study indicate a +/- 36 percent probability of successfully extending a nominal mission to 30 days. Enough variations were evaluated to verify that the reliability could be altered with missions planning and procedures. If the crew is modeled as being fully capable after 30 days, the probability of a successful manual landing is comparable to that of Autoland because much of the hardware is used for both manual and automated landing modes. The analysis indicates that the reliability for the manual mode is limited by the hardware and depends greatly on crew capability. Crew capability for a successful landing after 30 days has not been determined yet.

Welch, D. Phillip

1993-01-01

337

The Hot Orbit: Orbital Cellulitis  

PubMed Central

Orbital cellulitis is an uncommon condition previously associated with severe complications. If untreated, orbital cellulitis can be potentially sight and life threatening. It can affect both adults and children but has a greater tendency to occur in the pediatric age group. The infection most commonly originates from sinuses, eyelids or face, retained foreign bodies, or distant soources by hematogenous spread. It is characterized by eyelid edema, erythema, chemosis, proptosis, blurred vision, fever, headache, and double vision. A history of upper respiratory tract infection prior to the onset is very common especially in children. In the era prior to antibiotics, vision loss from orbital cellulitis was a dreaded complication. Currently, imaging studies for detection of orbital abcess, the use of antibiotics and early drainage have mitigated visual morbidity significantly. The purpose of this review is to describe current investigative strategies and management options in the treatment of orbital cellulitis, establish their effectiveness and possible complications due to late intervention.

Chaudhry, Imtiaz A.; Al-Rashed, Waleed; Arat, Yonca O.

2012-01-01

338

Molecular orbital cluster calculation study of electron correlation and local lattice instability in La2-2xSr1+2xMn2O7  

Microsoft Academic Search

In order to examine covalence and polaron effects in the bilayer manganite La2-2xSr1+2xMn2O7 , we have performed molecular orbital cluster calculations. Two types of (Mn2O11)15- clusters, one with the manganese aligned in the a direction and the other in the c direction, were embedded in a point charge environment that mimicked the crystal environment of the bilayer manganite at x=0.40

Satoru Miyaki; Shinji Uzuhara; Kazuto Terada; Kenji Makoshi; Hiroyasu Koizumi

2005-01-01

339

Molecular orbital cluster calculation study of electron correlation and local lattice instability in La{sub 2-2x}Sr{sub 1+2x}MnâOâ  

Microsoft Academic Search

In order to examine covalence and polaron effects in the bilayer manganite La{sub 2-2x}Sr{sub 1+2x}MnâOâ, we have performed molecular orbital cluster calculations. Two types of (MnâOââ)¹⁵⁻ clusters, one with the manganese aligned in the a direction and the other in the c direction, were embedded in a point charge environment that mimicked the crystal environment of the bilayer manganite at

Satoru Miyaki; Shinji Uzuhara; Kazuto Terada; Kenji Makoshi; Hiroyasu Koizumi

2005-01-01

340

Predicting Allostery Wiring Diagrams within Motor Proteins  

NASA Astrophysics Data System (ADS)

Motor proteins are intricate molecular machines that make use of allostery as a basis of their function. Fundamental questions in trying to understand the operational mechanism of the motors is, therefore, how allostery communicated is within the proteins, what are the pathways that transmit allosteric signals, how to model and predict them. We have proposed a normal-mode analysis based perturbation model that predicts the pathways based on the structure and chemical composition of the molecules. We use the model to investigate allosteric pathways (allostery wiring diagrams) within motor proteins myosin V and VI.

Tehver, Riina

2013-03-01

341

Silver(I) Cation Complexation with 3?,3'?-Bis(pyridine-n-carboxy) Lithocholic Acid 1,2-Ethanediol Diesters (n = 2–4): 1H, 13C and 15N NMR Spectral Studies and Molecular Orbital Calculations  

Microsoft Academic Search

Three isomeric molecular clefts: 3a,3'a-bis(pyridine-n-carboxy) lithocholic acid 1,2-ethanediol diesters (n = 2–4) 1–3 have been synthesized and their structures ascertained by 1H, 13C NMR and MALDI TOF MS. Their complex formation with Ag+-cation (added as AgO3 SCF3) have been investigated by means of NMR and molecular orbital calculations. The coordination behaviour of the silver(I) cation is dependent on the isomerism

Erkki Kolehmainen; Jari Tamminen; Reijo Kauppinen; Juha Linnanto

1999-01-01

342

Valence Band Density of States of Cu3Si Studied by Soft X-Ray Emission Spectroscopy and a First-Principle Molecular Orbital Calculation  

NASA Astrophysics Data System (ADS)

A systematic study of the valence band structure of Cu3Si has been performed by soft X-ray emission spectroscopy and a first-principle molecular orbital calculation using the discrete-variational (DV)-X? cluster model. The existence of Cu 4s, 4p states in the valence band and their important contributions to the valence band as that of Cu 3d are indicated together with previously reported ones. The high-binding energy peak in the Si L2,3 emission spectrum is considered to originate mainly from the Si-Si 3s bonding state but also have a certain contribution of Si 3s bonding state with Cu 4s, 4p. On the other hand, the low-binding energy peaks in the Si L2,3 emission band are attributed to both the antibonding states of Si 3s and the bonding states of Si 3d with Cu 4s, 4p and Cu 3d. The bonding states of Si 3s with Cu 4s, 4p and Cu 3d are expected to exist in the lower part of the valence band for ?\\prime-Cu3Si on the basis of the theoretical calculations. As for Si p states, the high-binding energy peak and the low-binding energy peak in the Si K? emission spectrum should be attributed to the Si 3p bonding state and antibonding state with Cu 3d and Cu 4s, 4p, respectively, according to the theoretical calculations. A comparison is made between experimental spectra and theoretical density of states.

An, Zhenlian; Kamezawa, Chihiro; Hirai, Masaaki; Kusaka, Masahiko; Iwami, Motohiro

2002-12-01

343

Orbital Decompression  

MedlinePLUS

... appearance. One of the most common indications is Graves’ disease, an autoimmune disorder that primarily affects the thyroid gland and the eye. If the eye is affected (Grave’s orbitopathy), there is an enlargement of the orbital ...

344

Orbital Motion  

NSDL National Science Digital Library

Authored by Eleanor Kopsian of Franklin Frazier, this is an activity intended to help students understand orbital motion and Kepler's Laws through a comparison of a circle and an ellipse and the application of Kepler's Law of Elliptical Orbits. The lesson contains objectives, vocabulary, needed materials, strategies, handouts, conclusions, evaluation questions and references. Although simple in design, this can still be a very useful resource for an instructor looking to enhance or create new curriculum.

Kopsian, Eleanor

2009-05-27

345

New Working Diagram for Membrane Separation Processes.  

National Technical Information Service (NTIS)

First a short presentation of the work diagram for rectification processes (McCabe-Thiele-diagram) is given. Then a new work diagram suitable for membrane separation processes is developed. The application in pervaporation and gas separation under cross f...

K. Hattenbach

1985-01-01

346

Particles, Feynman Diagrams and All That  

ERIC Educational Resources Information Center

Quantum fields are introduced in order to give students an accurate qualitative understanding of the origin of Feynman diagrams as representations of particle interactions. Elementary diagrams are combined to produce diagrams representing the main features of the Standard Model.

Daniel, Michael

2006-01-01

347

Charge and magnetic-ordering in a two-orbital double-exchange model for manganites  

Microsoft Academic Search

The phase diagram of half-doped perovskite manganites is studied within the extended double-exchange model. To demonstrate the role of orbital degrees of freedom both one- and two-orbital models are examined. A rich phase diagram is obtained in the mean-filed theory at zero temperature as a function of J [antiferromagnetic (AFM) superexchange interaction] and V (intersite Coulomb repulsion). For the one-orbital

G. Jackeli; N. B. Perkins; N. M. Plakida

2000-01-01

348

Disorder and the extent of polymerization in calcium silicate and aluminosilicate glasses: O-17 NMR results and quantum chemical molecular orbital calculations  

NASA Astrophysics Data System (ADS)

Estimation of the framework connectivity and the atomic structure of depolymerized silicate melts and glasses (NBO/T > 0) remains a difficult question in high-temperature geochemistry relevant to magmatic processes and glass science. Here, we explore the extent of disorder and the nature of polymerization in binary Ca-silicate and ternary Ca-aluminosilicate glasses with varying NBO/T (from 0 to 2.67) using O-17 NMR at two different magnetic fields of 9.4 and 14.1 T in conjunction with quantum chemical calculations. Non-random distributions among framework cations (Si and Al) are demonstrated in the variation of relative populations of oxygen sites with NBO/T. The proportion of non-bridging oxygen (NBO, Ca-O-Si) in the binary and ternary aluminosilicate glasses increases with NBO/T. While the trend is consistent with predictions from composition, the detailed fractions apparently deviate from the predicted values, suggesting further complications in the nature of polymerization. The proportion of each bridging oxygen in the glasses also varies with NBO/T. The fractions of Al-O-Si and Al-O-Al increase with increasing polymerization as CaO is replaced with Al 2O 3, while that of Si-O-Si seems to decrease, implying that activity of silica may decrease from calcium silicate to polymerized aluminosilicates (X=constant). Quantum chemical molecular orbital calculations based on density functional theory show that a silicate chain with Al-NBO (Ca-O-Al) has an energy penalty (calculated cluster energy difference) of about 108 kJ/mol compared with the cluster with Ca-O-Si, consistent with preferential depolymerization of Si-networks, reported in an earlier O-17 NMR study [Allwardt, J., Lee, S.K., Stebbins, J.F., 2003. Bonding preferences of non-bridging oxygens in calcium aluminosilicate glass: Evidence from O-17 MAS and 3QMAS NMR on calcium aluminate glass. Am. Mineral.88, 949-954]. These prominent types of non-randomness in the distributions suggest significant chemical order in silicate glasses that leads to a decrease in silica activity coefficient and will be useful in modeling transport properties of melts.

Lee, Sung Keun; Stebbins, Jonathan F.

2006-08-01

349

Molecular orbital calculations on the vibrational spectra of Q 3 T-(OH) species and the hydrolysis of a three-membered aluminosilicate ring  

NASA Astrophysics Data System (ADS)

Force constant analyses of the molecules [(H 3SiO) 3Al-(OH)] 1-, Na +[(H 3SiO) 3Al-(OH)] 1-, [((OH) 3SiO) 3Al-(OH)] 1- [(H 3SiO) 3Si-(OH)],[((OH) 3SiO) 3Si-(OH)],[((OH) 3SiO) 2((OH) 3A10)Si(OH)] 1- and Na + [(H 3SiO ) 2 (H 3Al0) Si- (OH)] 1- have been performed with ab initio molecular orbital calculations to determine the frequencies and H-D shifts of T- (OH) vibrations in Q 3 T- (OH) species where T is a So 4+ or Al 3+. Calculated Q 3 Si-(OH) vibrations are close to the observed value in H 2O-bearing Si0 2 glass. The theoretical Al-(OH) stretching frequency in Na +[ (H 3SiO) 3A1-(OH)] 1- matches the 880 cm - shoulder in the vibrational spectra of hydrous albitic glasses within experimental error. Isotopic substitution of deuterium for hydrogen in the T-(OH) bond results in frequency shifts of less than 25 cm -1 in all cases consistent with the small H-D frequency shifts observed in silica (Mysen and Virgo, 1986) and Na-aluminosilicate glasses (McMillan et al., 1993). Hydrolysis of a three-membered aluminosilicate ring into a trimeric chain (i.e., [H 6SiAl 20 9] 2- + H 2O ? [H 8SiAl 20 10] 2-) was also calculated. Hydrolysis occurs through a pentavalent Al 3+ transition state complex. Calculated energies of the reactants and product in the above reaction predict that the chain configuration is in a marginally lower potential energy state (-36 kJ/mol) than the H 2O-ring dimer. An activation energy of + 171 kJ/mol is predicted between the two species for hydrolysis and +207 kJ/mol for the reverse reaction.

Kubicki, J. D.; Sykes, Dan

1995-12-01

350

Achieving Orbit  

NSDL National Science Digital Library

This is an engineering design challenge activity. Learners will use balloons to investigate how a multi-stage rocket, like that used to launch the Interstellar Boundary Explorer, or IBEX, spacecraft, can propel a satellite to a specific orbit. Learners will construct a two-stage balloon rocket that will be required to reach a particular location on the balloon track, simulating the proper orbit around Earth to be reached by the IBEX satellite. This activity complements other IBEX informal education materials. An instructional video explaining how to facilitate this activity is available: http://bit.ly/ZwlFf4.

351

Model for frustrated spin-orbital chains as applied to CaV2O4  

Microsoft Academic Search

Motivated by recent interest in quasi-one-dimensional compound CaV2O4 , we study the ground states of a spin-orbital chain characterized by an Ising-like orbital Hamiltonian and frustrated interactions between S=1 spins. The on-site spin-orbit interaction and the Jahn-Teller effect compete with intersite superexchange leading to a rich phase diagram in which an antiferro-orbital phase is separated from the orbital paramagnet by

Gia-Wei Chern; Natalia Perkins

2009-01-01

352

Orbital coupled dipolar fermions in an asymmetric optical ladder  

NASA Astrophysics Data System (ADS)

We study a quantum ladder of interacting fermions with coupled s and p orbitals. Such a model describes dipolar molecules or atoms loaded into a double-well optical lattice, dipole moments being aligned by an external field. The two orbital components have distinct hoppings. The tunneling between them is equivalent to a partial Rashba spin-orbital coupling when the orbital space (s, p) is identified as spanned by pseudospin 1/2 states. A rich phase diagram, including incommensurate orbital density wave, pair density wave, and other exotic superconducting phases, is proposed with bosonization analysis. In particular, superconductivity is found in the repulsive regime.

Li, Xiaopeng; Liu, W. Vincent

2013-06-01

353

Orbital Elements  

NSDL National Science Digital Library

Coordinates for tracking the International Space Station and the Mir Space Station are available here from NASA's Johnson Space Center Flight Design and Dynamics Division. The Orbital Elements page offers real-time data for use in ground track plotting programs. The site cautions the data are for ground track plotting programs only and "should not be used for precise applications or analysis!"

354

Elliptical Orbits  

NSDL National Science Digital Library

Although not inquiry, this activity is important for students to understand what an ellipse is and what a focus is, and to break misconceptions about Earth's orbit being highly elliptical. This is the perfect place to check to see if students have the mis

Horton, Michael

2009-05-30

355

Orbital Mechanics.  

ERIC Educational Resources Information Center

Three computer programs are presented that allow the high school student to explore and understand the physical forces involved in orbital flight at a greater depth than is usually possible. For each program, introductory material is given including the physics and mathematics involved. This is followed by the computer program in BASIC language.…

Dalton, Joel B.

356

Mars Orbit  

NSDL National Science Digital Library

This geometry lesson from Illuminations uses the model of the orbits of Mars and Earth relative to the sun to illustrate parametric equations. As an interdisciplinary learning activity, the material may be used in conjunction with astronomy lessons. An interactive applet and student questions are also included. The material is intended for grades 9-12 and should require 1 class period to complete.

2010-12-14

357

LISA Orbits  

Microsoft Academic Search

The LISA formation is composed of 3 spacecraft in an equilateral triangle formation. The baseline formation has a 5million km radius and lies in a heliocentric orbit 20deg away from the Earth. Earth's gravity induces a perturbation on the nominal Keplerian motion of the formation, generating a change in the relative ranges and thus a Doppler that can be very

Angelo Povoleri; Stephen Kemble

2006-01-01

358

Automatically Assessing Graph-Based Diagrams  

ERIC Educational Resources Information Center

To date there has been very little work on the machine understanding of imprecise diagrams, such as diagrams drawn by students in response to assessment questions. Imprecise diagrams exhibit faults such as missing, extraneous and incorrectly formed elements. The semantics of imprecise diagrams are difficult to determine. While there have been…

Thomas, Pete; Smith, Neil; Waugh, Kevin

2008-01-01

359

DRAWING DIAGRAMS IN AN ONLINE EXAMINATION  

Microsoft Academic Search

This paper describes a study into the drawing of diagrams in an online examination. The diagrams were produced by students during an on-line examination using a simple drawing tool. The students' examination answers, which included a diagram, were submitted over the Internet to an automatic marking tool for grading and feedback. This paper describes the diagram drawing tool and discusses

Pete Thomas

360

Steps towards a GPSS block diagram system  

Microsoft Academic Search

We first note that block diagrams have been important for the learning of GPSS and have been used in most GPSS text books. The full value of block diagrams is obtained first when they can be automatically generated from program code and that block diagrams in turn can generate code. The computer generation of block diagrams requires, however, very exact

Ingolf Ståhl

2006-01-01

361

4,5-Dicyano-3,6-diethylbenzo-1,2-diselenete, a highly stable 1,2-diselenete: its preparation, structural characterization, calculated molecular orbitals, and complexation with tetrakis(triphenylphosphine)palladium.  

PubMed

The first isolable benzo-1,2-diselenete, 4,5-dicyano-3,6-diethylbenzo-1,2-diselenete (4), was prepared by the reaction of 4,5-(o-xylylenediseleno)-3,6-diethylphthalonitrile (3) with aluminum chloride in toluene. X-ray crystallographic analysis demonstrated that 4 contains a trapezoidal diselenide ring rather than a benzo-1,2-diselenone structure. In crystal form, 4 undergoes self-assembly and generates structures based on layered molecular sheets since the unit cell contains only one molecule. While the cyclic voltammogram of 4 exhibited only one irreversible peak (Ep = 1.59 V) during oxidation and two quasireversible couples during reduction, three peaks were observed in the differential pulse voltammogram of the reduction couples (E1/2 = -1.19, -0.75, and -0.69 V). Although a THF solution of 4 in the presence of sodium metal was EPR silent, various signals were readily observed in its (1)H, (13)C, and (77)Se NMR spectra. Molecular orbital calculations for 4 demonstrated that the HOMO orbital is primarily localized at the two selenium atoms and four of the benzene carbon atoms while the LUMO orbital is situated solely on the diselenete ring. It appears that the HOMO and LUMO orbitals of 4 receive significant stabilization from the nitrile groups compared to the level of stabilization in the unsubstituted benzo-1,2-diselenete (BDS). The reaction of 4 with tetrakis(triphenylphosphine)palladium in benzene was found to produce a dinuclear palladium complex (8), and the structure of this complex was determined by X-ray crystallographic analysis. The central four membered ring of 8 consists of the Pd1, Se2, Pd2, and Se3 atoms and is not planar but rather adopts a folded arrangement. PMID:24724937

Kimura, Takeshi; Nakahodo, Tsukasa; Fujihara, Hisashi; Suzuki, Eiichi

2014-05-01

362

Pseudohaptic interaction with knot diagrams  

NASA Astrophysics Data System (ADS)

To make progress in understanding knot theory, we need to interact with the projected representations of mathematical knots, which are continuous in three dimensions (3-D) but significantly interrupted in the projective images. One way to achieve such a goal is to design an interactive system that allows us to sketch two-dimensional (2-D) knot diagrams by taking advantage of a collision-sensing controller and explore their underlying smooth structures through a continuous motion. Recent advances of interaction techniques have been made that allow progress in this direction. Pseudohaptics that simulate haptic effects using pure visual feedback can be used to develop such an interactive system. We outline one such pseudohaptic knot diagram interface. Our interface derives from the familiar pencil-and-paper process of drawing 2-D knot diagrams and provides haptic-like sensations to facilitate the creation and exploration of knot diagrams. A centerpiece of the interaction model simulates a physically reactive mouse cursor, which is exploited to resolve the apparent conflict between the continuous structure of the actual smooth knot and the visual discontinuities in the knot diagram representation. Another value in exploiting pseudohaptics is that an acceleration (or deceleration) of the mouse cursor (or surface locator) can be used to indicate the slope of the curve (or surface) of which the projective image is being explored. By exploiting these additional visual cues, we proceed to a full-featured extension to a pseudohaptic four-dimensional (4-D) visualization system that simulates the continuous navigation on 4-D objects and allows us to sense the bumps and holes in the fourth dimension. Preliminary tests of the software show that main features of the interface overcome some expected perceptual limitations in our interaction with 2-D knot diagrams of 3-D knots and 3-D projective images of 4-D mathematical objects.

Weng, Jianguang; Zhang, Hui

2012-07-01

363

Vanishing rainbows near orbiting and the energy dependence of rainbow scattering - Relation to properties of the potential. [molecular beam scattering cross sections  

NASA Technical Reports Server (NTRS)

The energy threshold behavior of elastic rainbow scattering near the transition to orbiting is derived. Analysis of the energy dependence of the rainbow angle shows that the full range from high energies down to orbiting can be fitted with two parameters. Thus, measurements of the rainbow angle can give essentially only two pieces of information about the potential. For potentials of common shapes, such measurements are sensitive to regions of the potential just beyond the minimum and give information about the shape of the potential in this range. However, neither a minimum nor a point of inflection in the potential is necessary for rainbow scattering.

Greene, E. F.; Hall, R. B.; Mason, E. A.

1975-01-01

364

Orbiting Hotel  

NSDL National Science Digital Library

It is the year 2025 and a large company, Z-Tech, wants to put a hotel in space having it orbit around one of the planets in our solar system. Our 9th grade class has been given a very important job. We have to search for the perfect location for the hotel. Our job is to report back to the company with the planet that is the best place for an orbiting hotel. The Task: You are to write a report recommending which planet should be chosen. Your report should include pictures of the planet you recommended. Here are the questions you should answer in order to report back to Z-Tech with your recommendation. * Which planet will be the ...

Hicken, Mrs.

2009-10-19

365

Payload/orbiter contamination control requirement study  

NASA Technical Reports Server (NTRS)

A study was conducted to determine and quantify the expected particulate and molecular on-orbit contaminant environment for selected space shuttle payloads as a result of major shuttle orbiter contamination sources. Individual payload susceptibilities to contamination are reviewed. The risk of payload degradation is identified and preliminary recommendations are provided concerning the limiting factors which may depend on operational activities associated with the payload/orbiter interface or upon independent payload functional activities. A basic computer model of the space shuttle orbiter which includes a representative payload configuration is developed. The major orbiter contamination sources, locations, and flux characteristics based upon available data have been defined and modeled.

Bareiss, L. E.; Rantanen, R. O.; Ress, E. B.

1974-01-01

366

The role of orbital dynamics and cloud-cloud collisions in the formation of giant molecular clouds in global spiral structures  

NASA Technical Reports Server (NTRS)

The role of orbit crowding and cloud-cloud collisions in the formation of GMCs and their organization in global spiral structure is investigated. Both N-body simulations of the cloud system and a detailed analysis of individual particle orbits are used to develop a conceptual understanding of how individual clouds participate in the collective density response. Detailed comparisons are made between a representative cloud-particle simulation in which the cloud particles collide inelastically with one another and give birth to and subsequently interact with young star associations and stripped down simulations in which the cloud particles are allowed to follow ballistic orbits in the absence of cloud-cloud collisions or any star formation processes. Orbit crowding is then related to the behavior of individual particle trajectories in the galactic potential field. The conceptual picture of how GMCs are formed in the clumpy ISMs of spiral galaxies is formulated, and the results are compared in detail with those published by other authors.

Roberts, William W., Jr.; Stewart, Glen R.

1987-01-01

367

Voronoi Diagrams and Spring Rain  

ERIC Educational Resources Information Center

The goal of this geometry project is to use Voronoi diagrams, a powerful modeling tool across disciplines, and the integration of technology to analyze spring rainfall from rain gauge data over a region. In their investigation, students use familiar equipment from their mathematical toolbox: triangles and other polygons, circumcenters and…

Perham, Arnold E.; Perham, Faustine L.

2011-01-01

368

Telesynergy V3 Wiring Diagram  

Cancer.gov

Extron 8 port Video/Audio Switch WAVE Camera Telesynergy v3 Wiring Diagram ISDN T1/PRI Module CTRLR 0 Legend: S-Video Audio VGA DVI USB RS-232 Serial Microphone Ethernet Planar C5i AMD Exam Cam Canon Document Camera Olympus BX51 Sony DVD Recorder JVC

369

INCONEL 718: A solidification diagram  

Microsoft Academic Search

As part of a program studying weldability of Ni-base superalloys, results of an integrated analytical approach are used to generate a constitution diagram for INCONEL 718* in the temperature range associated with solidification. Differential thermal analysis of wrought material and optical and scanning electron microscopy, electron probe microanalysis, and analytical electron microscopy of gas tungsten arc welds are used in

G. A. Knorovsky; M. J. Cieslak; T. J. Headley; A. D. Romig; W. F. Hammetter

1989-01-01

370

Hubble's diagram and cosmic expansion  

Microsoft Academic Search

Edwin Hubble's classic article on the expanding universe appeared in PNAS in 1929 [Hubble, E. P. (1929) Proc. Natl. Acad. Sci. USA 15, 168-173]. The chief result, that a galaxy's distance is proportional to its redshift, is so well known and so deeply embedded into the language of astronomy through the Hubble diagram, the Hubble constant, Hubble's Law, and the

Robert P. Kirshner

2004-01-01

371

Concrete and Abstract Voronoi Diagrams  

Microsoft Academic Search

The Voronoi diagram of a set of sites is a partition of the plane into regions, one to each site, such that the region of each site contains all points of the plane that are closer to this site than to the other ones. Such partitions are of great importance to computer science and many other fields. The challenge is

Rolf Klein

1989-01-01

372

Normalization of the Delano Diagram.  

National Technical Information Service (NTIS)

A normalization of the Delano y, y bar diagram is proposed in which the y heights are normalized by the entrance pupil height, the y bar heights by the image height. The normalization constants are expressed in terms of the system parameters, and it is se...

F. J. Lopez-Lopez

1970-01-01

373

Theory of satellite orbit-orbit resonance  

Microsoft Academic Search

On the basis of the strong mathematical and physical parallels between orbit-orbit and spin-orbit resonances, the dynamics of mutual orbit perturbations between two satellites about a massive planet are examined, exploiting an approach previously adopted in the study of spin-orbit coupling. The satellites are assumed to have arbitrary mass ratio and to move in non-intersecting orbits of arbitrary size and

Leon Blitzer; John D. Anderson

1981-01-01

374

Inflammation of the Orbit  

MedlinePLUS

... Socket Disorders 4 Inflammation of the Orbit (Inflammatory Orbital Pseudotumor) Any or all of the structures within the ... entire orbit and its contents is called inflammatory orbital pseudotumor (which is not really a tumor and is ...

375

Periodic orbits and their bifurcations in a 3-D system  

NASA Astrophysics Data System (ADS)

We study some simple periodic orbits and their bifurcations in the Hamiltonian (H = 1/2 ((x dot)2 + (y dot)2 + (z dot)2 + Ax2 + By2 + Cz2) - epsilon xz2 - eta yz2. We give the forms of the orbits, the characteristics of the main families, and some existence diagrams and stability diagrams. The existence diagram of the family 1a contains regions that are stable (S), simply unstable (U), doubly unstable (DU) and complex unstable (Delta). In the regions S and U there are lines of equal rotation number m/n. Along these lines we have bifurcations of families of periodic orbits of multiplicity n. When these lines reach the boundary of the complex unstable region, they are tangent to it. Inside the region Delta there are lines m/n, along which the orbits 1a, described n-times, are doubly unstable; however, along these lines there are no bifurcations of n-ple periodic orbits. The families bifurcating from 1a exist only in certain regions of the parameter space (epsilon, eta). The limiting lines of these regions join at particular points representing collisions of bifurcations. These collisions of bifurcations produce a nonuniqueness of the various families of periodic orbits. The complicated structure of the various bifurcations can be understood by constructing appropriate stability diagrams.

Contopoulos, G.; Barbanis, B.

1994-07-01

376

A periodic orbit bifurcation analysis of vibrationally excited isotopologues of sulfur dioxide and water molecules: symmetry breaking substitutions.  

PubMed

Theoretical predictions and assignment of highly excited vibrational states and their organization is one of the most important challenges in molecular spectroscopy. A systematic procedure to investigate such problems is locating the principal families of periodic orbits that emanate from the stationary points of the molecule and then following their evolution with the total energy. This results in constructing continuation/bifurcation diagrams that assist in locating the critical bifurcation energies and to discover new types of vibrational modes. Another parameter that may influence the dynamics of a molecule is isotopic mass substitution. In this article, we investigate the effect of symmetry breaking by isotopic mass substitution of triatomic molecules with C(2v) symmetry in classical and quantum dynamics. Sulfur dioxide and water molecules in their ground electronic state are studied by employing accurate potential energy surfaces. Continuation/bifurcation diagrams of periodic orbits are constructed by varying the energy and the mass of one oxygen atom of sulfur dioxide and one hydrogen atom of a water molecule. The transition from normal-to-local mode vibrations is studied in terms of a pitchfork to a center-saddle elementary bifurcation of periodic orbits. The results presented in this article aim to help the assignment of experimentally obtained spectra. PMID:20825241

Mauguiere, Frederic; Rey, Michael; Tyuterev, Vladimir; Suarez, Jaime; Farantos, Stavros C

2010-09-16

377

Risk Mitigation for Managing On-Orbit Anomalies  

NASA Technical Reports Server (NTRS)

This slide presentation reviews strategies for managing risk mitigation that occur with anomalies in on-orbit spacecraft. It reviews the risks associated with mission operations, a diagram of the method used to manage undesirable events that occur which is a closed loop fault analysis and until corrective action is successful. It also reviews the fish bone diagram which is used if greater detail is required and aids in eliminating possible failure factors.

La, Jim

2010-01-01

378

Reliability computation from reliability block diagrams  

NASA Technical Reports Server (NTRS)

Computer program computes system reliability for very general class of reliability block diagrams. Four factors are considered in calculating probability of system success: active block redundancy, standby block redundancy, partial redundancy, and presence of equivalent blocks in the diagram.

Chelson, P. O.; Eckstein, E. Y.

1975-01-01

379

Calculation of Ceramic Phase Diagrams.  

National Technical Information Service (NTIS)

A data base is being developed for calculation of quasibinary and quasiternary phase diagrams of oxide and oxynitride ceramic systems. The current base covers combinations of Cr2O3, MgO, Al2O3, Fe2O3, Fe3O4, FeO, CaO, SiO2, Si3N4 and AlN. Lattice Stabilit...

L. Kaufman

1979-01-01

380

Phase Diagrams and Chemographic Projections  

NSDL National Science Digital Library

This exercise is a good way to get students thinking about the phase rule, metastable and stable reactions and phase diagrams. The exercise contains a lot of reading, and is suitable for in-class work or for homework. The idea is that students can do this on their own with little help from their instructor. The students only answer a few questions making this is more of a tutorial than a worksheet.

Perkins, Dexter

381

INCONEL 718: A solidification diagram  

Microsoft Academic Search

As part of a program studying weldability of Ni-base superalloys, results of an integrated analytical approach are used to\\u000a generate a constitution diagram for INCONEL 718* in the temperature range associated with solidification. Differential thermal analysis of wrought material and optical and\\u000a scanning electron microscopy, electron probe microanalysis, and analytical electron microscopy of gas tungsten arc welds are\\u000a used in

G. A. Knorovsky; M. J. Cieslak; T. J. Headley; A. D. Romig; W. F. Hammetter

1989-01-01

382

Twistor Diagrams and Quantum Field Theory.  

NASA Astrophysics Data System (ADS)

Available from UMI in association with The British Library. Requires signed TDF. This thesis uses twistor diagram theory, as developed by Penrose (1975) and Hodges (1990c), to try to approach some of the difficulties inherent in the standard quantum field theoretic description of particle interactions. The resolution of these issues is the eventual goal of the twistor diagram program. First twistor diagram theory is introduced from a physical view-point, with the aim of studying larger diagrams than have been typically explored. Methods are evolved to tackle the double box and triple box diagrams. These lead to three methods of constructing an amplitude for the double box, and two ways for the triple box. Next this theory is applied to translate the channels of a Yukawa Feynman diagram, which has more than four external states, into various twistor diagrams. This provides a test of the skeleton hypothesis (of Hodges, 1990c) in these cases, and also shows that conformal breaking must enter into twistor diagrams before the translation of loop level Feynman diagrams. The issue of divergent Feynman diagrams is then considered. By using a twistor equivalent of the sum-over -states idea of quantum field theory, twistor translations of loop diagrams are conjectured. The various massless propagator corrections and vacuum diagrams calculated give results consistent with Feynman theory. Two diagrams are also found that give agreement with the finite parts of the Feynman "fish" diagrams of phi^4 -theory. However it is found that a more rigorous translation for the time-like fish requires new boundaries to be added to the twistor sum-over-states. The twistor diagram obtained is found to give the finite part of the relevant Feynman diagram.

O'Donald, Lewis

383

Cut diagrams for high energy scatterings  

SciTech Connect

A new approach is introduced to study QCD amplitudes at high energy and comparatively small momentum transfer. Novel cut diagrams, representing the resummation of Feynman diagrams, are used to simplify the calculation and to avoid delicate cancellations encountered in the usual approach. An explicit calculation to the sixth order is carried out to demonstrate the advantage of cut diagrams over Feynman diagrams. {copyright} {ital 1996 The American Physical Society.}

Feng, Y.J.; Hamidi-Ravari, O.; Lam, C.S. [Department of Physics, McGill University, 3600 University St., Montreal, P.Q., H3A 2T8 (CANADA)] [Department of Physics, McGill University, 3600 University St., Montreal, P.Q., H3A 2T8 (CANADA)

1996-09-01

384

Orbital order of spinless fermions near an optical Feshbach resonance  

SciTech Connect

We study the quantum phases of a three-color Hubbard model that arises in the dynamics of the p-band orbitals of spinless fermions in an optical lattice. Strong, color-dependent interactions are induced by an optical Feshbach resonance. Starting from the microscopic scattering properties of ultracold atoms, we derive the orbital exchange constants at 1/3 filling on the cubic optical lattice. Using this, we compute the phase diagram in a Gutzwiller ansatz. We find phases with ''axial orbital order'' in which p{sub z} and p{sub x}+ip{sub y} (or p{sub x}-ip{sub y}) orbitals alternate.

Hauke, Philipp [ICFO-Institut de Ciencies Fotoniques, Parc Mediterrani de la Tecnologia, E-08860 Castelldefels (Spain); Kavli Institute for Theoretical Physics, University of California, Santa Barbara, California 93106 (United States); Zhao, Erhai [Kavli Institute for Theoretical Physics, University of California, Santa Barbara, California 93106 (United States); Department of Physics and Astronomy, George Mason University, Fairfax, Virginia 22030 (United States); Goyal, Krittika; Deutsch, Ivan H. [Center for Quantum Information and Control (CQuIC), and Department of Physics and Astronomy, University of New Mexico, Albuquerque, New Mexico 87131 (United States); Liu, W. Vincent [Kavli Institute for Theoretical Physics, University of California, Santa Barbara, California 93106 (United States); Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, Pennsylvania 15260 (United States); Lewenstein, Maciej [ICFO-Institut de Ciencies Fotoniques, Parc Mediterrani de la Tecnologia, E-08860 Castelldefels (Spain); Kavli Institute for Theoretical Physics, University of California, Santa Barbara, California 93106 (United States); ICREA-Institucio Catalana de Recerca i Estudis Avancats, Lluis Companys 23, E-08010 Barcelona (Spain)

2011-11-15

385

Causal diagrams in systems epidemiology  

PubMed Central

Methods of diagrammatic modelling have been greatly developed in the past two decades. Outside the context of infectious diseases, systematic use of diagrams in epidemiology has been mainly confined to the analysis of a single link: that between a disease outcome and its proximal determinant(s). Transmitted causes ("causes of causes") tend not to be systematically analysed. The infectious disease epidemiology modelling tradition models the human population in its environment, typically with the exposure-health relationship and the determinants of exposure being considered at individual and group/ecological levels, respectively. Some properties of the resulting systems are quite general, and are seen in unrelated contexts such as biochemical pathways. Confining analysis to a single link misses the opportunity to discover such properties. The structure of a causal diagram is derived from knowledge about how the world works, as well as from statistical evidence. A single diagram can be used to characterise a whole research area, not just a single analysis - although this depends on the degree of consistency of the causal relationships between different populations - and can therefore be used to integrate multiple datasets. Additional advantages of system-wide models include: the use of instrumental variables - now emerging as an important technique in epidemiology in the context of mendelian randomisation, but under-used in the exploitation of "natural experiments"; the explicit use of change models, which have advantages with respect to inferring causation; and in the detection and elucidation of feedback.

2012-01-01

386

INCONEL 718: A solidification diagram  

NASA Astrophysics Data System (ADS)

As part of a program studying weldability of Ni-base superalloys, results of an integrated analytical approach are used to generate a constitution diagram for INCONEL 718* in the temperature range associated with solidification. Differential thermal analysis of wrought material and optical and scanning electron microscopy, electron probe microanalysis, and analytical electron microscopy of gas tungsten arc welds are used in conjunction with solidification theory to generate data points for this diagram. The important features of the diagram are an austenite (?)/Laves phase eutectic which occurs at ?19.1 wt pct Nb between austenite containing ?9.3 wt pct Nb and a Laves phase which contains ?22.4 wt pct Nb. The distribution coefficient for Nb was found to be ?0.5. The solidification sequence of INCONEL 718 was found to be (1) proeutectic ?, followed by (2) a ?/NbC eutectic at ?1250°C, followed by (3) continued ? solidification, followed by (4) a ?/Laves phase eutectic at ?1200°C. An estimate of the volume fraction eutectic is made using the Scheil solidification model, and the fraction of each phase in the eutectic is calculated via the lever rule. These are compared with experimentally determined values and found to be in good agreement.

Knorovsky, G. A.; Cieslak, M. J.; Headley, T. J.; Romig, A. D.; Hammetter, W. F.

1989-10-01

387

Reasoning on temporal class diagrams: Undecidability results  

Microsoft Academic Search

This paper introduces a temporal class diagram language useful to model temporal varying data. The atemporal portion of the language contains the core constructors available in both EER diagrams and UML class diagrams. The temporal part of the language is able to distin- guish between temporal and atemporal constructs, and it has the ability to represent dynamic constraints between classes.

Alessandro Artale

2006-01-01

388

Unjustified Assumptions Based on Diagrams in Geometry  

ERIC Educational Resources Information Center

We investigated unjustified assumptions made by students when proving geometric statements. Geometric statements can be presented with a diagram or without. Diagrams can be accurate or sketchy. Unjustified assumptions may originate in an accompanying diagram. We thus asked whether the way in which a statement is presented has an effect on…

Dvora, Tali; Dreyfus, Tommy

2004-01-01

389

Ion potential diagrams for electrochromic devices  

Microsoft Academic Search

Ion potential diagrams can facilitate the description of systems in which ionic species are mobile. They depict qualitatively the spatial dependence of the potential energy for mobile ions, somewhat akin to band diagrams for electrons. The authors construct ion potential diagrams for the mixed conducting (oxide), optically active electrodes of five-layer electrochromic devices, based on reversible Li{sup +} intercalation. These

Francesca Varsano; D. Cahen; F. Decker; J. F. Guillemoles; E. Masetti

1998-01-01

390

Guelph Physics Tutorials: Free Body Diagrams  

NSDL National Science Digital Library

This website offers a tutorial on free body diagrams. The tutorial includes an introduction to free body diagrams, example problems, a series of self-paced questions, and a free body diagram java applet. This is part of series of tutorials on physics and mathematics used in physics classes.

2007-04-23

391

Extending Reliability Block Diagrams to Software Architectures  

Microsoft Academic Search

Reliability block diagrams focus on components and connectors as do software architectures. However, some architectural styles possess characteristics which make traditional reliability block diagrams unusable as an analysis technique. In order to use the diagrams, they must be extended to reflect common architectural choices such as concurrency, distribution, dynamism, and implicit connectors.

Ahmed Abd-Allah

1997-01-01

392

Flow Diagram Simulator for the Cement Industry  

Microsoft Academic Search

The most important aspect of work performed in a process engineering department is the development of process flow diagrams. These diagrams display the results of energy and material balances and equipment rating calculations for a complex process plant. The development, features, and implementation of a computerized flow diagram simulation program named Fuller's interactive simulator for process engineering calculations (FISPEC) are

Bruce S. Knoll; William J. Berry

1984-01-01

393

Semantics of the Domain of Flow Diagrams  

Microsoft Academic Search

A domain of flow diagrams similar to that proposed by Scott, a domain of linear flow diagrams proposed by Goguen et al , a domain of decision table diagrams involving mfimtary branching, and a domain of processes based on the ideas of Milner and Beklc are each provided with a direct semantics, closely related to partial-function semantics, and a continuation

John C. Reynolds

1977-01-01

394

Retrieving Information from Data Flow Diagrams  

Microsoft Academic Search

For reverse engineering, we need tools that can extract information from documents written before routine digital storage was feasible. Documents contain both text and diagrams; data flow diagrams play a prominent role in software documents. Using current techniques, it is possible to recover the information in a data flow diagram by scanning the printed document and processing the data obtained.

Gregory Butler; Peter Grogono; Rajjan Shinghal; Indra A. Tjandra

1995-01-01

395

Small orbits  

NASA Astrophysics Data System (ADS)

We study both the large and small U-duality charge orbits of extremal black holes appearing in D=5 and D=4 Maxwell-Einstein supergravity theories with symmetric scalar manifolds. We exploit a formalism based on cubic Jordan algebras and their associated Freudenthal triple systems, in order to derive the minimal charge representatives, their stabilizers and the associated “moduli spaces.” After recalling N=8 maximal supergravity, we consider N=2 and N=4 theories coupled to an arbitrary number of vector multiplets, as well as N=2 magic, STU, ST2 and T3 models. While the STU model may be considered as part of the general N=2 sequence, albeit with an additional triality symmetry, the ST2 and T3 models demand a separate treatment, since their representative Jordan algebras are Euclidean or only admit nonzero elements of rank 3, respectively. Finally, we also consider minimally coupled N=2, matter-coupled N=3, and pure N=5 theories.

Borsten, L.; Duff, M. J.; Ferrara, S.; Marrani, A.; Rubens, W.

2012-04-01

396

Space shuttle on-orbit flight control software requirements, preliminary version  

NASA Technical Reports Server (NTRS)

Software modules associated with various flight control functions for the space shuttle orbiter are described. Data flow, interface requirements, initialization requirements and module sequencing requirements are considered. Block diagrams and tables are included.

1975-01-01

397

Mass-imbalanced Fermi gases with spin-orbit coupling  

SciTech Connect

We use the mean-field theory to analyze the ground-state phase diagrams of spin-orbit-coupled mass-imbalanced Fermi gases throughout the BCS-BEC evolution, including both the population-balanced and -imbalanced systems. Our calculations show that the competition between the mass and population imbalance and the Rashba-type spin-orbit coupling gives rise to very rich phase diagrams, involving normal, superfluid, and phase-separated regions. In addition, we find quantum phase transitions between the topologically trivial gapped superfluid and the nontrivial gapless superfluid phases, opening the way for the experimental observation of exotic phenomena with cold atom systems.

Iskin, M. [Department of Physics, Koc University, Rumelifeneri Yolu, TR-34450 Sariyer, Istanbul (Turkey); Subasi, A. L. [Department of Physics, Faculty of Science and Letters, Istanbul Technical University, TR-34469 Maslak, Istanbul (Turkey)

2011-10-15

398

Investigation of the distinction between van der Waals interaction and chemical bonding based on the PAEM-MO diagram.  

PubMed

In recent years, the basic problem of understanding chemical bonding, nonbonded, and/or van der Waals interactions has been intensively debated in terms of various theoretical methods. We propose and construct the potential acting on one electron in a molecule-molecular orbital (PAEM-MO) diagram, which draws the PAEM inserted the MO energy levels with their major atomic orbital components. PAEM-MO diagram is able to show clear distinction of chemical bonding from nonbonded and/or vdW interactions. The rule for this is as follows. Along the line connecting two atoms in a molecule or a complex, the existence of chemical bonding between these two atoms needs to satisfy two conditions: (a) a critical point of PAEM exists and (b) PAEM barrier between the two atoms is lower in energy than the occupied major valence-shell bonding MO which contains in-phase atomic components (positive overlap) of the two considered atoms. In contrast to the chemical bonding, for a nonbonded interaction or van der Waals interaction between two atoms, both conditions (a) and (b) do not be satisfied at the same time. This is demonstrated and discussed by various typical cases, particularly those related to helium atom and H?H bonding in phenanthrene. There are helium bonds in HHeF and HeBeO molecules, whereas no H?H bonding in phenanthrene. The validity and limitation for this rule is demonstrated through the investigations of the curves of the PAEM barrier top and MO energies versus the internuclear distances for He2 , H2 , and He2 (+) systems. © 2014 Wiley Periodicals, Inc. PMID:24615750

Zhao, Dong-Xia; Yang, Zhong-Zhi

2014-05-15

399

Shapes of d Orbitals  

NSDL National Science Digital Library

Shapes of d Orbitals shows the d orbitals in an axis set. Running the mouse over an orbital reveals the "name" of that orbital. This is good practice for helping students link the name of an orbital to the orientation.Shapes of d Orbitals has a link to D Orbitals in an Octahedral Ligand Field. Here the user may click on the name of any one of the d orbitals to obtain a larger 3-dimensional image. The images are rotatable and scalable. Orbital phase is shown by the different colors.

400

Network Legos: Building Blocks of Cellular Wiring Diagrams  

Microsoft Academic Search

ABSTRACT Publicly available datasets provide detailed and large-scale information,on multiple types of molecular,interaction networks,in a number,of model,organisms. The wiring diagrams composed,of these interaction networks,capture a static view of cellular state. An important challenge,in systems,biology,is obtaining,a dynamic,perspective on these networks,by integrating,them,with gene,expression,measurements,taken,under,multiple,conditions. We present a top-down,computational,approach,to identify building blocks of molecular interaction networks,by: (i) integrating gene,expression,measurements,for a particular disease state (e.g.,

T. M. Murali; Corban G. Rivera

2008-01-01

401

Orbital Propellant Depot  

NASA Technical Reports Server (NTRS)

In this artist's concept from 1971, an Earth-to orbit fuel tanker approaches the Orbital Propellant Depot. As envisioned by Marshall Space Flight Center Program Devlopment plarners, an orbital modular propellant storage depot, supplied periodically by the Space Shuttle or Earth-to-orbit fuel tankers would be critical in making available large amounts of fuel to various orbital vehicles and spacecraft.

1971-01-01

402

What is orbital pseudotumor?  

Microsoft Academic Search

We have reviewed the literature in order to delineate the clinicopathologic definition of orbital pseudotumor, also called idiopathic nonspecific orbital inflammation. The clinical picture of orbital pseudotumor varies widely, with signs of mass effect, inflammation and\\/or infiltration. On computed tomography, orbital pseudotumor presents as a unilateral focal or diffuse mass. The histopathologic hallmark of orbital pseudotumor is a mixed inflammatory

Ilse Mombaerts; Roel Goldschmeding; Reinier O. Schlingemann; Leo Koornneef

1996-01-01

403

Optical generation of Voronoi diagram.  

PubMed

We present results of experiments of diffraction by an amplitude screen, made of randomly distributed circular holes. By careful selection of the experimental parameters we obtain an intensity pattern strongly connected to the Voronoi diagram (VD) generated by the centers of the apertures. With the help of simulations we give a description of the observed phenomenon and elucidate the optimal parameters for its observation. Finally, we also suggest how it can be used for a fast, all-optical generation of VDs. PMID:18542580

Giavazzi, F; Cerbino, R; Mazzoni, S; Giglio, M; Vailati, A

2008-03-31

404

Qualitative Spatial Interpretation of Course-of-Action Diagrams.  

National Technical Information Service (NTIS)

This paper demonstrates qualitative spatial reasoning techniques in a real-world diagrammatic reasoning task: Course-of-Action (COA) diagrams. COA diagrams are military planning diagrams that depict unit movements and tasks in a given region. COA diagrams...

J. R. Rasch K. D. Forbus R. W. Ferguson W. Turmel

2000-01-01

405

Analysis of One-Bond Se-Se Nuclear Couplings in Diselenides and 1,2-Diselenoles on the Basis of Molecular Orbital Theory: Torsional Angular Dependence, Electron Density Influence, and Origin in 1J(Se, Se)  

PubMed Central

Nuclear couplings for the Se-Se bonds, 1J(Se, Se), are analyzed on the basis of the molecular orbital (MO) theory. The values are calculated by employing the triple ? basis sets of the Slater type at the DFT level. 1J(Se, Se) are calculated modeled by MeSeSeMe (1a), which shows the typical torsional angular dependence on ?(CMeSeSeCMe). The dependence explains well the observed 1Jobsd (Se, Se) of small values (? 64 Hz) for RSeSeR? (1) (simple derivatives of 1a) and large values (330–380 Hz) observed for 4-substituted naphto[1,8-c, d]-1,2-diselenoles (2) which correspond to symperiplanar diselenides. 1J (Se, Se: 2) becomes larger as the electron density on Se increases. The paramagnetic spin-orbit terms contribute predominantly. The contributions are evaluated separately from each MO (?i) and each ?i ? ?a transition, where ?i and ?a are occupied and unoccupied MO's, respectively. The separate evaluation enables us to recognize and visualize the origin and the mechanism of the couplings.

Tanioku, Akito; Hayashi, Satoko; Nakanishi, Waro

2009-01-01

406

Correlation of electronic transitions and redox potentials measured for pyrocatechol, resorcinol, hydroquinone, pyrogallol, and gallic acid with results of semi-empirical molecular orbital computations A useful interpretation tool  

NASA Astrophysics Data System (ADS)

Cyclic voltammogram (CV) electrochemical measurements for pyrocatechol, resorcinol, hydroquinone, pyrogallol, and gallic acid in strong alkaline solution produced observable oxidation-reduction potentials for each hydroxy group present except for resorcinol. UV absorption spectra were also observed for the diluted solutions. Semi-empirical molecular orbital computations were conducted for these molecules of C2 v point group symmetry to determine the character and energies to aid interpretation of the experimental results. CV oxidation removed a ?-electron by a radiationless ?-?* transition followed by an electron shift from a negative oxygen to the positive aromatic ?-system indicated by an observable ?-?* transition. Simple semi-empirical computations correlated with measured excited electronic states during electron transfer.

Carter, Melvin Keith

2007-04-01

407

Characterisation of Maillard reaction products derived from LEKFD--a pentapeptide found in ?-lactoglobulin sequence, glycated with glucose--by tandem mass spectrometry, molecular orbital calculations and gel filtration chromatography coupled with continuous photodiode array.  

PubMed

Maillard reaction peptides (MRPs) contribute to taste, aroma, colour, texture and biological activity. However, peptide degradation or the cross-linking of MRPs in the Maillard reaction has not been investigated clearly. A peptide of LEKFD, a part of ?-lactoglobulin, was heated at 110 °C for 24h with glucose and the reaction products were analysed by HPLC with ODS, ESI-MS, ESI-MS/MS and HPLC with gel-filtration column and DAD detector. In the HPLC fractions, an imminium ion of LEK*FD, a pyrylium ion or a hydroxymethyl furylium ion of LEK*FD, and KFD and EK were detected by ESI-MS. Therefore, those products may be produced by the Maillard reaction. The molecular orbital of glycated LEKFD at the lysine epsilon-amino residue with Schiff base form was calculated by MOPAC. HPLC with gel-filtration column showed cross-linking and degradation of peptides. PMID:24128561

Yamaguchi, Keiko; Homma, Takeshi; Nomi, Yuri; Otsuka, Yuzuru

2014-02-15

408

Spin and orbital magnetic moments of molecular beam epitaxy {gamma}{sup '}-Fe{sub 4}N films on LaAlO{sub 3}(001) and MgO(001) substrates by x-ray magnetic circular dichroism  

SciTech Connect

10-nm-thick {gamma}{sup '}-Fe{sub 4}N films were grown epitaxially on LaAlO{sub 3}(001) and MgO(001) substrates by molecular beam epitaxy using solid Fe and a radio-frequency NH{sub 3} plasma. The lattice mismatch of these substrates to {gamma}{sup '}-Fe{sub 4}N is 0% and 11%, respectively. Spin and orbital magnetic moments of these {gamma}{sup '}-Fe{sub 4}N epitaxial films were deduced by x-ray magnetic circular dichroism measurements at 300 K. The total magnetic moments are almost the same for the two substrates, that is, 2.44{+-}0.06 {mu}{sub B} and 2.47{+-}0.06 {mu}{sub B}, respectively. These values are very close to those predicted theoretically, and distinctively larger than that for {alpha}-Fe.

Ito, K.; Lee, G. H.; Harada, K.; Suzuno, M.; Suemasu, T. [Institute of Applied Physics, University of Tsukuba, Ibaraki 305-8573 (Japan); Takeda, Y.; Saitoh, Y. [Japan Atomic Energy Agency, SPring-8, Hyogo 679-5198 (Japan); Ye, M.; Kimura, A. [Graduate School of Science, Hiroshima University, Hiroshima 739-8526 (Japan); Akinaga, H. [National Institute of Advanced Industrial Science and Technology, Ibaraki 305-8568 (Japan)

2011-03-07

409

Bifurcation Diagrams and Heteroclinic Networks of Octagonal H-Planforms  

NASA Astrophysics Data System (ADS)

This paper completes the classification of bifurcation diagrams for H-planforms in the Poincaré disc {D} whose fundamental domain is a regular octagon. An H-planform is a steady solution of a PDE or integro-differential equation in {D}, which is invariant under the action of a lattice subgroup ? of U(1,1), the group of isometries of {{D}}. In our case ? generates a tiling of {D} with regular octagons. This problem was introduced as an example of spontaneous pattern formation in a model of image feature detection by the visual cortex where the features are assumed to be represented in the space of structure tensors. Under `generic' assumptions the bifurcation problem reduces to an ODE which is invariant by an irreducible representation of the group of automorphisms {G} of the compact Riemann surface {D}/\\varGamma . The irreducible representations of {G} have dimensions one, two, three and four. The bifurcation diagrams for the representations of dimensions less than four have already been described and correspond to well-known group actions. In the present work we compute the bifurcation diagrams for the remaining three irreducible representations of dimension four, thus completing the classification. In one of these cases, there is generic bifurcation of a heteroclinic network connecting equilibria with two different orbit types.

Faye, Grégory; Chossat, Pascal

2012-06-01

410

EXTRACT: a program to extract three-dimensional coordinates from stereo diagrams of proteins.  

PubMed

The program EXTRACT has been developed to extract accurate three-dimensional coordinates from published stereo alpha-carbon diagrams of protein structures. The approach is based on the display of scanned images of the left and right eye views of the diagram on a stereo-equipped workstation, allowing construction of a molecular model using the diagram as a guide. A number of structural checks assess the building, including probability maps derived for alpha-carbon geometry in protein structures. The procedure has also been extended to produce less accurate models from mono images. PMID:7794829

Oldfield, T J; Hubbard, R E

1995-02-01

411

A layout algorithm for data flow diagrams  

SciTech Connect

A layout algorithm is presented that allows the automatic drawing of data flow diagrams, a diagrammatic representation widely used in the functional analysis of information systems. A grid standard is defined for such diagrams, and aesthetics for a good readability are identified. The layout algorithm receives as input an abstract graph, specifying connectivity relations between the elements of the diagram, and produces as output a corresponding diagram according to the aesthetics. The basic strategy is to build incrementally the layout; first, a good topology is constructed with few crossings between edges; subsequently, the shape of the diagram is determined in terms of angles appearing along edges; and finally, dimensions are given to the graph, obtaining a grid skeleton for the diagram.

Batini, C.; Nardelli, E.; Tamassia, R.

1986-04-01

412

Shuttle Orbiter Uplink Text and Graphics System  

NASA Technical Reports Server (NTRS)

This paper presents the definition of requirements for and current design of the Shuttle Orbiter Uplink Text and Graphics System (UT&GS). Beginning in early 1981, the UT&GS will support Shuttle flights by providing the capability of transmitting single-frame imagery from the ground to the orbiting Shuttle vehicle. Such imagery is in the form of maps, text, diagrams, or photographs, and is outputted on the Orbiter as a paper hard copy. Four modes of operation will be provided to minimize the time required to transmit less than full-resolution imagery. This paper discusses the considerations and complications leading to the four modes and associated resolution requirements. The paper also presents the design of the CCD array ground scanner and airborne CRT hardcopier.

Hoover, A. A.; Land, C. K.; Lipoma, P. C.

1978-01-01

413

Process Flow Diagrams for Training and Operations  

Microsoft Academic Search

\\u000a This paper focuses on the use of process flow diagrams for training first responders who execute search and seizure warrants\\u000a at electronic crime scenes. A generic process flow framework is presented, and the design goals and layout characteristics\\u000a of process flow diagrams are discussed. An evaluation of the process flow diagrams used in training courses indicates that\\u000a they are beneficial

Jacobus Venter

2006-01-01

414

Projected seniority-two orbital optimization of the antisymmetric product of one-reference orbital geminal.  

PubMed

We present a new, non-variational orbital-optimization scheme for the antisymmetric product of one-reference orbital geminal wave function. Our approach is motivated by the observation that an orbital-optimized seniority-zero configuration interaction (CI) expansion yields similar results to an orbital-optimized seniority-zero-plus-two CI expansion [L. Bytautas, T. M. Henderson, C. A. Jimenez-Hoyos, J. K. Ellis, and G. E. Scuseria, J. Chem. Phys. 135, 044119 (2011)]. A numerical analysis is performed for the C2 and LiF molecules, for the CH2 singlet diradical as well as for the symmetric stretching of hypothetical (linear) hydrogen chains. For these test cases, the proposed orbital-optimization protocol yields similar results to its variational orbital optimization counterpart, but prevents symmetry-breaking of molecular orbitals in most cases. PMID:24907997

Boguslawski, Katharina; Tecmer, Pawe?; Limacher, Peter A; Johnson, Paul A; Ayers, Paul W; Bultinck, Patrick; De Baerdemacker, Stijn; Van Neck, Dimitri

2014-06-01

415

Projected seniority-two orbital optimization of the antisymmetric product of one-reference orbital geminal  

NASA Astrophysics Data System (ADS)

We present a new, non-variational orbital-optimization scheme for the antisymmetric product of one-reference orbital geminal wave function. Our approach is motivated by the observation that an orbital-optimized seniority-zero configuration interaction (CI) expansion yields similar results to an orbital-optimized seniority-zero-plus-two CI expansion [L. Bytautas, T. M. Henderson, C. A. Jimenez-Hoyos, J. K. Ellis, and G. E. Scuseria, J. Chem. Phys. 135, 044119 (2011)]. A numerical analysis is performed for the C2 and LiF molecules, for the CH2 singlet diradical as well as for the symmetric stretching of hypothetical (linear) hydrogen chains. For these test cases, the proposed orbital-optimization protocol yields similar results to its variational orbital optimization counterpart, but prevents symmetry-breaking of molecular orbitals in most cases.

Boguslawski, Katharina; Tecmer, Pawe?; Limacher, Peter A.; Johnson, Paul A.; Ayers, Paul W.; Bultinck, Patrick; De Baerdemacker, Stijn; Van Neck, Dimitri

2014-06-01

416

Phase diagram of ammonium nitrate.  

PubMed

Ammonium Nitrate (AN) is a fertilizer, yet becomes an explosive upon a small addition of chemical impurities. The origin of enhanced chemical sensitivity in impure AN (or AN mixtures) is not well understood, posing significant safety issues in using AN even today. To remedy the situation, we have carried out an extensive study to investigate the phase stability of AN and its mixtures with hexane (ANFO-AN mixed with fuel oil) and Aluminum (Ammonal) at high pressures and temperatures, using diamond anvil cells (DAC) and micro-Raman spectroscopy. The results indicate that pure AN decomposes to N2, N2O, and H2O at the onset of the melt, whereas the mixtures, ANFO and Ammonal, decompose at substantially lower temperatures. The present results also confirm the recently proposed phase IV-IV' transition above 17 GPa and provide new constraints for the melting and phase diagram of AN to 40 GPa and 400°C. PMID:24320387

Dunuwille, Mihindra; Yoo, Choong-Shik

2013-12-01

417

Phase diagram of ammonium nitrate  

NASA Astrophysics Data System (ADS)

Ammonium Nitrate (AN) has often subjected to uses in improvised explosive devices, due to its wide availability as a fertilizer and its capability of becoming explosive with slight additions of organic and inorganic compounds. Yet, the origin of enhanced energetic properties of impure AN (or AN mixtures) is neither chemically unique nor well understood -resulting in rather catastrophic disasters in the past1 and thereby a significant burden on safety in using ammonium nitrates even today. To remedy this situation, we have carried out an extensive study to investigate the phase stability of AN at high pressure and temperature, using diamond anvil cells and micro-Raman spectroscopy. The present results confirm the recently proposed phase IV-to-IV' transition above 17 GPa2 and provide new constraints for the melting and phase diagram of AN to 40 GPa and 400 °C.

Dunuwille, M.; Yoo, C. S.

2014-05-01

418

Hubble's diagram and cosmic expansion  

NASA Astrophysics Data System (ADS)

Edwin Hubble's classic article on the expanding universe appeared in PNAS in 1929 [Hubble, E. P. (1929) Proc. Natl. Acad. Sci. USA 15, 168-173]. The chief result, that a galaxy's distance is proportional to its redshift, is so well known and so deeply embedded into the language of astronomy through the Hubble diagram, the Hubble constant, Hubble's Law, and the Hubble time, that the article itself is rarely referenced. Even though Hubble's distances have a large systematic error, Hubble's velocities come chiefly from Vesto Melvin Slipher, and the interpretation in terms of the de Sitter effect is out of the mainstream of modern cosmology, this article opened the way to investigation of the expanding, evolving, and accelerating universe that engages today's burgeoning field of cosmology.

Kirshner, Robert P.

2004-01-01

419

Symmetric Monotone Venn Diagrams with Seven Curves  

NASA Astrophysics Data System (ADS)

An n-Venn diagram consists of n curves drawn in the plane in such a way that each of the 2 n possible intersections of the interiors and exteriors of the curves forms a connected non-empty region. A k-region in a diagram is a region that is in the interior of precisely k curves. A n-Venn diagram is symmetric if it has a point of rotation about which rotations of the plane by 2?/n radians leaves the diagram fixed; it is polar symmetric if it is symmetric and its stereographic projection about the infinite outer face is isomorphic to the projection about the innermost face. A Venn diagram is monotone if every k-region is adjacent to both some (k - 1)-region (if k > 0) and also to some k + 1 region (if k < n). A Venn diagram is simple if at most two curves intersect at any point. We prove that the "Grünbaum" encoding uniquely identifies monotone simple symmetric n-Venn diagrams and describe an algorithm that produces an exhaustive list of all of the monotone simple symmetric n-Venn diagrams. There are exactly 23 simple monotone symmetric 7-Venn diagrams, of which 6 are polar symmetric.

Cao, Tao; Mamakani, Khalegh; Ruskey, Frank

420

Ion potential diagrams for electrochromic devices  

SciTech Connect

Ion potential diagrams can facilitate the description of systems in which ionic species are mobile. They depict qualitatively the spatial dependence of the potential energy for mobile ions, somewhat akin to band diagrams for electrons. The authors construct ion potential diagrams for the mixed conducting (oxide), optically active electrodes of five-layer electrochromic devices, based on reversible Li{sup +} intercalation. These serve to analyze stability problems that arise in these systems. The authors then use them as building blocks to arrive at ion diagrams for complete devices. This allows analyses of (dis)coloration kinetics.

Varsano, F. [Weizmann Inst. of Science, Rehovot (Israel). Dept. of Materials and Interfaces]|[Univ. di Roma La Sapienza, Rome (Italy). Dipt. di Chimica; Cahen, D. [Weizmann Inst. of Science, Rehovot (Israel). Dept. of Materials and Interfaces; Decker, F. [Univ. di Roma La Sapienza, Rome (Italy). Dipt. di Chimica; Guillemoles, J.F. [Weizmann Inst. of Science, Rehovot (Israel). Dept. of Materials and Interfaces]|[CNRS, Paris (France). Lab. d`Electrochimie; Masetti, E. [ENEA, Rome (Italy). Sezione Dispositivi Ottici

1998-12-01

421

Effectiveness of Using Computer-Assisted Instruction in Teaching the Shapes of Atomic Orbitals.  

ERIC Educational Resources Information Center

Investigates the effect of computer-assisted instruction (CAI) when used as a supplement to classroom instruction to improve secondary school students' understanding of orbital shapes. Results indicate that the CAI approach enhanced student learning and helped them figure out cues portrayed in diagrams of atomic orbitals. (Contains 22 references.)…

Shubbar, Khalil E.

2003-01-01

422

Statistical initial orbit determination  

Microsoft Academic Search

For the ballistic missile initial orbit determination problem in particular, the concept of 'launch folders' is extended. This allows to decouple the observational data from the initial orbit determination problem per se. The observational data is only used to select among the possible orbital element sets in the group of folders. Monte Carlo simulations using up to 7200 orbital element

L. G. Taff; B. Belkin; G. A. Schweiter; K. Sommar

1992-01-01

423

The voronoi diagram of three lines  

Microsoft Academic Search

We give a complete description of the Voronoi diagram of three lines in R3. In particular, we show that the topology of the Voronoi diagram is invariant for three lines in general position, that is, that are pairwise skew and not all parallel to a common plane. The tri- sector consists of four unbounded branches of either a non-singular quartic

Hazel Everett; Sylvain Lazard; Daniel Lazard; Mohab Safey El Din

2007-01-01

424

Model Checking Activity Diagrams in TCM  

Microsoft Academic Search

We give a brief description of our (prototype) implementation in TCM [4] of an execution al-gorithm for activity diagrams. The execution algorithm translates an activity diagram into its corresponding execution structure. This execution structure is input for a model checker. With a model checker, requirements on the execution structure can be verified. Currently, we only use our own variant of

Rik Eshuis

425

Towards the Automatic Generation of Software Diagrams  

Microsoft Academic Search

The authors formulate the criteria for drawing dataflow diagrams and describe the placement and routing algorithms used in a system called MONDRIAN. A generalized approach to the question of software diagrams is proposed based on the authors' experience with MONDRIAN and a metasystem approach to the creation of CASE (computer-aided software engineering) environments. A formal approach to the definition of

L. Beth Protsko; Paul G. Sorenson; J. Paul Tremblay; Douglas A. Schaefer

1991-01-01

426

Understanding Machines from Text and Diagrams.  

National Technical Information Service (NTIS)

Instructional materials typically use both text and diagrams to explain how machines work. In this paper we give an account of what information is involved in understanding a mechanical device and the role that diagrams might play in communicating this in...

M. Hegarty M. A. Just

1987-01-01

427

Free-Body Diagrams: Necessary or Sufficient?  

Microsoft Academic Search

The Rutgers PAER group is working to help students develop various scientific abilities. One of the abilities is to create, understand and learn to use for qualitative reasoning and problem solving different representations of physical processes such as pictorial representations, motion diagrams, free-body diagrams, and energy bar charts. Physics education literature indicates that using multiple representations is beneficial for student

David Rosengrant; Alan van Heuvelen; Eugenia Etkina

2005-01-01

428

Phase diagram of a random tiling quasicrystal  

Microsoft Academic Search

We study the phase diagram of a two-dimensional random tiling model for quasicrystals. At proper concentrations the model has 8-fold rotational symmetry. Landau theory correctly gives most of the qualitative features of the phase diagram, which is in turn studied in detail numerically using a transfer matrix approach. We find that the system can enter the quasicrystal phase from many

Weixiong Li; Michael Widom

1992-01-01

429

On hardware description from block diagrams  

Microsoft Academic Search

In this paper, we present a systematic way to describe the logical architecture of the system implementing a given algorithm by means of an extended block diagram, and develop a standard notation to describe each block. We then show a technique for correctly transforming a block diagram into a physical circuit description by introducing the notion of time into the

H. Jagadish; T. Kailath; J. Newkirk; R. Mathews

1984-01-01

430

Towards IEC 61499 function blocks diagrams verification  

Microsoft Academic Search

After having sketched the different techniques enabling to check properties of discrete event systems control software, we present in this article a formal method for IEC 61499 function blocks diagrams verification. This method is based on a formal representation of the behaviour of function blocks diagrams and takes benefit of verification tools developed from the SIGNAL synchronous language.

C. Schnakenbourg; J.-M. Faure; J.-J. Lesage

2002-01-01

431

Compiling Data Flow Diagrams into Functional Programs  

Microsoft Academic Search

We suggest a method for compiling an arbitrary visual language V data flow diagrams with loops into a parallel functional language Sisal functions based on token propagation over the diagram and loop collapsing into a system of (mutually) recursive functions. This com- pilation algorithm preserves a concurrence potentially present in the data flow graph.

Mikhail Auguston; Ravindra Mathur

432

Block diagram modeling of quantum laser sources  

Microsoft Academic Search

The paper presents a method for modeling quantum laser sources. Quantum cascaded (QC), quantum dot (QD) and quantum dot cascaded (QDC) lasers are studied. Their block diagram models are devised. VisSim environment is used to achieve this purpose. Block diagram simulation results are validated against experimental published work and full agreements are obtained. Using of graphical user interface allows a

Imbaby I. Mahmoud

2010-01-01

433

Charge and magnetic-ordering in a two-orbital double-exchange model for manganites  

Microsoft Academic Search

Phase diagram of half-doped perovskite manganites is studied within the\\u000aextended double-exchange model. To demonstrate the role of orbital degrees of\\u000afreedom both one- and two-orbital models are examined. A rich phase diagram is\\u000aobtained in the mean-field theory at zero temperature as a function of J\\u000a(antiferromagnetic (AFM) superexchange interaction) and V (intersite Coulomb\\u000arepulsion). For the one-orbital model

G. Jackeli; N. B. Perkins; N. M. Plakida

2000-01-01

434

Free-Body Diagrams: Necessary or Sufficient?  

NSDL National Science Digital Library

The Rutgers PAER group is working to help students develop various scientific abilities. One of the abilities is to create, understand and learn to use for qualitative reasoning and problem solving different representations of physical processes such as pictorial representations, motion diagrams, free-body diagrams, and energy bar charts. Physics education literature indicates that using multiple representations is beneficial for student understanding of physics ideas and for problem solving. We developed a special approach to construct and utilize free-body diagrams for representing physical phenomena and for problem solving. We will examine whether students draw free-body diagrams in solving problems when they know they will not receive credit for it; the consistency of their use in different conceptual areas; and if students who use free-body diagrams while solving problems in different areas of physics are more successful then those who do not.

Rosengrant, David; Van Heuvelen, A.; Etkina, Eugenia

2009-11-30

435

Phase diagram of ammonium nitrate  

SciTech Connect

Ammonium Nitrate (AN) is a fertilizer, yet becomes an explosive upon a small addition of chemical impurities. The origin of enhanced chemical sensitivity in impure AN (or AN mixtures) is not well understood, posing significant safety issues in using AN even today. To remedy the situation, we have carried out an extensive study to investigate the phase stability of AN and its mixtures with hexane (ANFO–AN mixed with fuel oil) and Aluminum (Ammonal) at high pressures and temperatures, using diamond anvil cells (DAC) and micro-Raman spectroscopy. The results indicate that pure AN decomposes to N{sub 2}, N{sub 2}O, and H{sub 2}O at the onset of the melt, whereas the mixtures, ANFO and Ammonal, decompose at substantially lower temperatures. The present results also confirm the recently proposed phase IV-IV{sup ?} transition above 17 GPa and provide new constraints for the melting and phase diagram of AN to 40 GPa and 400°C.

Dunuwille, Mihindra; Yoo, Choong-Shik, E-mail: csyoo@wsu.edu [Department of Chemistry and Institute for Shock Physics, Washington State University, Pullman, Washington 99164 (United States)] [Department of Chemistry and Institute for Shock Physics, Washington State University, Pullman, Washington 99164 (United States)

2013-12-07

436

Molecular orbital calculations, experimental and theoretical UV spectra of granulatimides and didemnimides, biologically active polycyclic heteroaromatic alkaloids from the ascidian Didemnum granulatum  

NASA Astrophysics Data System (ADS)

A detailed computational study was performed for compounds granulatimide, isogranulatimide, and didemnimides A, D, and E, using the semiempirical Austin model 1 quantum chemical method. The electronic features and structural parameters were confronted with the inhibition of the G2 cell cycle checkpoint of mammalian cancer cells. All compounds were submitted to a rigorous conformational analysis using the Tripos 5.2 force field implemented in the Spartan 5.01 program. The electronic density in specific regions of the molecules appears to play a pivotal role towards activity. The molecular planarity creates a broad negative electrostatic potential on the two sides of the active compounds (granulatimide and isogralulatimide) and a positive potential in their central core, while the non-planar compounds (didemnimides A, D, and E, which are inactive) present an asymmetric potential scattered over the molecules. These electrostatic potential features are likely to be the modulator of hydrophobicity or lipophilicity of the compounds, which appear correlated with activity. The hydrogen attached to the N atom of the pyrrole moiety of indole is more positive for active compounds than for the inactive molecules. The theoretical electronic spectra were obtained for all compounds using the configuration interaction method, with the AM1 routine. All transitions present ??? ? nature. The theoretical results are in good agreement with experimental values.

Camargo, A. J.; Oliveira, J. H. H. L.; Trsic, M.; Berlinck, R. G. S.

2001-01-01

437

1,1,1,3,3,3-Hexabromotrisilane: structure and conformation determined by gas-phase electron diffraction, ab initio molecular orbital and molecular mechanics calculations, and vibrational spectroscopy  

Microsoft Academic Search

The molecular structure of 1,1,1,3,3,3-hexabromotrisilane at 140°C has been studied using gas-phase electron diffraction. The two SiBr3 groups are both staggered relative to the central SiH2 group, but a twist of about 13° of the SiBr3 groups relative to the exactly staggered position reduces the symmetry to C2. From the vibrational spectra a distinction between C2 or C2v symmetry is

Tore H. Johansen; Kolbjørn Hagen; Reidar Stølevik; Margot Ernst; Karl Hassler

1995-01-01

438

Ab initio molecular orbital study on the excited states of [2.2]-, [3.3]-, and siloxane-bridged paracyclophanes.  

PubMed

Paracyclophanes are simple idealized model molecules for the study of interacting ?-stacking systems. In this study, the excited states of [2.2]paracyclophane ([2.2]PCP), [3.3]paracyclophane ([3.3]PCP), and siloxane-bridged paracyclophane (SiPCP) are systematically investigated using the multiconfiguration quasi-degenerated perturbation theory (MCQDPT) method. The excited states of the alkyl- and silyl-substituted benzene monomers and benzene dimer, which can be regarded as the building blocks of paracyclophanes, are also examined at the same level of theory for more detailed understanding. The accuracy of the time-dependent density functional theory (TD-DFT) method required for excited state geometry optimization of the paracyclophanes is confirmed from calculations of the benzene dimer. The equilibrium distances between the benzene rings of the paracyclophanes in the first excited states are shorter than those in the ground state, and the benzene rings at the excited state optimized geometries are in an almost eclipsed parallel configuration, which indicates excimer formation. The calculated transition energies and oscillator strengths are generally in good agreement with the corresponding experimental results. A clear correlation between the excited state properties and the molecular structures is systematically demonstrated based on the calculation results for the substituted benzene monomers and benzene dimer. The transition energies of SiPCP are close to the corresponding absorption and fluorescence energies of the experimentally studied phenylene-silica hybrids, which indicates that the electronic properties of organic-silica hybrids, which is a new class of material with potential in photofunctional applications, can be approximated by simple siloxane-bridged cyclophane derivatives. PMID:23046357

Shirai, Soichi; Iwata, Suehiro; Maegawa, Yoshifumi; Tani, Takao; Inagaki, Shinji

2012-10-18

439

Exploring the forbidden zone in the Lieber diagram  

NASA Astrophysics Data System (ADS)

The ``Lieber diagram''(M. Lieber (unpublished), but see the article by J.H. McGuire, et al.) in Atomic, Molecular and Optical Physics Handbook, Ed. by G.W.F. Drake (AIP Press, 1996). shows the regions where varieties of the Thomas double-collision mechanism for particle capture in the process 1 + (23) arrow (12) + 3 are kinematically allowed, in terms of the masses of the three particles. The Thomas process, when allowed, is the dominant process in high energy collisions, because the Green's function denominator in the scattering amplitude is allowed to go on shell. However, for certain mass ratios, we recently showed that where the double-collision capture was kinematically forbidden, nevertheless triple-collision capture was possible.( John H. Carter and M. Lieber, APS Centennial Bulletin) 44, No. 1, Part I, p. 139, Abstract DP01 54, (1999) We have now demonstrated that when neither double nor triple collision captures are possible, capture by quadruple collisions may be possible. The boundary curves in the Lieber diagram are quadratic for double, cubic for triple, and quartic for quadruple collisions. We therefore conjecture that the forbidden region in the Lieber diagram breaks up into infinitely many bands, where successively higher order collisions are required, bounded by algebraic curves of successively higher degrees.

Carter, John H.; Lieber, M.

2000-06-01

440

Fibrolipoma of the orbit.  

PubMed

A 47-year-old woman presented with a growing mass on the lateral rim of orbit. Orbital CT revealed a well-circumscribed soft tissue mass in the right lateral orbit, with focal hyperostosis of the adjacent zygomatic bone. MRI showed a lesion of mixed T1-signal intensity, which became hypointense after fat suppression. The lesion was excised, and the diagnosis of orbital fibrolipoma was made by histopathologic examination. There was no evidence of tumor after 12 months of follow-up. Orbital fibrolipoma is a rare variant of lipoma, with only 1 case described previously. It should be considered in the differential diagnosis of orbital mass. PMID:20700070

Kim, Myung Hun; Sa, Ho Seok; Woo, Kyung; Kim, Yoon-Duck

2011-01-01

441

The atomic orbitals of the topological atom.  

PubMed

The effective atomic orbitals have been realized in the framework of Bader's atoms in molecules theory for a general wavefunction. This formalism can be used to retrieve from any type of calculation a proper set of orthonormalized numerical atomic orbitals, with occupation numbers that sum up to the respective Quantum Theory of Atoms in Molecules (QTAIM) atomic populations. Experience shows that only a limited number of effective atomic orbitals exhibit significant occupation numbers. These correspond to atomic hybrids that closely resemble the core and valence shells of the atom. The occupation numbers of the remaining effective orbitals are almost negligible, except for atoms with hypervalent character. In addition, the molecular orbitals of a calculation can be exactly expressed as a linear combination of this orthonormalized set of numerical atomic orbitals, and the Mulliken population analysis carried out on this basis set exactly reproduces the original QTAIM atomic populations of the atoms. Approximate expansion of the molecular orbitals over a much reduced set of orthogonal atomic basis functions can also be accomplished to a very good accuracy with a singular value decomposition procedure. PMID:23758358

Ramos-Cordoba, Eloy; Salvador, Pedro; Mayer, István

2013-06-01

442

Dynamical evolution of active detached binaries on the logJo-logM diagram and contact binary formation  

NASA Astrophysics Data System (ADS)

Orbital angular momentum (OAM, Jo), systemic mass (M) and orbital period (P) distributions of chromospherically active binaries (CAB) and W Ursae Majoris (W UMa) systems were investigated. The diagrams of and logJo-logM were formed from 119 CAB and 102 W UMa stars. The logJo-logM diagram is found to be most meaningful in demonstrating dynamical evolution of binary star orbits. A slightly curved borderline (contact border) separating the detached and the contact systems was discovered on the logJo-logM diagram. Since the orbital size (a) and period (P) of binaries are determined by their current Jo, M and mass ratio, q, the rates of OAM loss (dlogJo/dt) and mass loss (dlogM/dt) are primary parameters to determine the direction and the speed of the dynamical evolution. A detached system becomes a contact system if its own dynamical evolution enables it to pass the contact border on the logJo-logM diagram. The evolution of q for a mass-losing detached system is unknown unless the mass-loss rate for each component is known. Assuming q is constant in the first approximation and using the mean decreasing rates of Jo and M from the kinematical ages of CAB stars, it has been predicted that 11, 23 and 39 per cent of current CAB stars would transform to W UMa systems if their nuclear evolution permits them to live 2, 4 and 6 Gyr, respectively.

Eker, Z.; Demircan, O.; Bilir, S.; Karata?, Y.

2006-12-01

443

Spectroscopic (FT-IR, FT-Raman, and UV-visible) and quantum chemical studies on molecular geometry, Frontier molecular orbitals, NBO, NLO and thermodynamic properties of 1-acetylindole.  

PubMed

Quantum chemical calculations of ground state energy, geometrical structure and vibrational wavenumbers of 1-acetylindole were carried out using density functional (DFT/B3LYP) method with 6-311++G(d,p) basis set. The FT-IR and FT-Raman spectra were recorded in the condensed state. The fundamental vibrational wavenumbers were calculated and a good correlation between experimental and scaled calculated wavenumbers has been accomplished. Electric dipole moment, polarizability and first static hyperpolarizability values of 1-acetylindole have been calculated at the same level of theory and basis set. The results show that the 1-acetylindole molecule possesses nonlinear optical (NLO) behavior with non-zero values. Stability of the molecule arising from hyper-conjugative interactions and charge delocalization has been analyzed using natural bond orbital (NBO) analysis. UV-Visible spectrum of the molecule was recorded in the region 200-500nm and the electronic properties like HOMO and LUMO energies and composition were obtained using TD-DFT method. The calculated energies and oscillator strengths are in good correspondence with the experimental data. The thermodynamic properties of the compound under investigation were calculated at different temperatures. PMID:24996206

Shukla, Vikas K; Al-Abdullah, Ebtehal S; El-Emam, Ali A; Sachan, Alok K; Pathak, Shilendra K; Kumar, Amarendra; Prasad, Onkar; Bishnoi, Abha; Sinha, Leena

2014-12-10

444

Physics Classroom: Drawing Free-Body Diagrams  

NSDL National Science Digital Library

This tutorial explains how free body diagrams are used in solving problems involving Newton's Second Law. This tutorials demonstrates how to draw free body diagrams, what the diagram means to Physics, and includes practice problems for the student. This tutorial also includes other tutorials, animations, and student activities in other concepts of Physics. The Physics Classroom is a set of resources created for learners and teachers of high school physics. It includes comprehensive tutorials, problem sets with solutions, extra help for struggling students, Shockwave animations, multimedia learning modules, labs, and photo gallery.

Henderson, Tom

2011-10-03

445

Near threshold expansion of Feynman diagrams  

SciTech Connect

The near threshold expansion of Feynman diagrams is derived from their configuration space representation, by performing all x integrations. The general scalar Feynman diagram is considered, with an arbitrary number of external momenta, an arbitrary number of internal lines and an arbitrary number of loops, in n dimensions and all masses may be different. The expansions are considered both below and above threshold. Rules, giving real and imaginary part, are derived. Unitarity of a sunset diagram with I internal lines is checked in a direct way by showing that its imaginary part is equal to the phase space integral of I particles.

Mendels, E. [Schenkkade 221, The Hague, 2595 AT Den Haag (Netherlands)

2005-07-01

446

Quantum Monte Carlo and high-level ab initio molecular orbital investigation of dissociation channels of the positronic alkali-metal hydrides, [XH;e+] (X = Li, Na, and K)  

NASA Astrophysics Data System (ADS)

Energy thresholds for dissociation channels of positronic alkali-metal hydrides, [XH;e+] (X = Li, Na, and K), to XH + e+(positron dissociation), XH+ + Ps (positronium dissociation), and X+ + [H-;e+] (positronic hydride ion dissociation) have been calculated using quantum Monte Carlo and high-level ab initio molecular orbital methods, and including quantum zero-point vibrational energy of all of the particles. As the atomic number of X increases from Li to K, the dissociation energy to XH + e+ increases because the dipole moment of XH increases with the atomic number of X, while the dissociation energy to XH+ + Ps decreases. The energy threshold for the ionic dissociation to X+ + [H-;e+] is also reduced, and we obtain 0.975 (3) eV, 0.573 (12) eV, and 0.472 (19) eV for [LiH;e+], [NaH;e+], and [KH;e+], respectively, for this channel. Our results strongly support the conclusion that, among these three channels, the lowest energy dissociation for [XH;e+] is the pathway to X+ + [H-;e+], where X = Li, Na, and K.

Yamada, Yurika; Kita, Yukiumi; Tachikawa, Masanori; Towler, Mike D.; Needs, Richard J.

2014-03-01

447

Lunar orbiting prospector  

NASA Technical Reports Server (NTRS)

One of the prime reasons for establishing a manned lunar presence is the possibility of using the potential lunar resources. The Lunar Orbital Prospector (LOP) is a lunar orbiting platform whose mission is to prospect and explore the Moon from orbit in support of early lunar colonization and exploitation efforts. The LOP mission is divided into three primary phases: transport from Earth to low lunar orbit (LLO), operation in lunar orbit, and platform servicing in lunar orbit. The platform alters its orbit to obtain the desired surface viewing, and the orbit can be changed periodically as needed. After completion of the inital remote sensing mission, more ambitious and/or complicated prospecting and exploration missions can be contemplated. A refueled propulsion module, updated instruments, or additional remote sensing packages can be flown up from the lunar base to the platform.

1988-01-01

448

Atomic Orbital Shapes  

NSDL National Science Digital Library

This applet shows 3-dimensional representations of hydrogenic orbital surfaces. Orbital phase is shown by the different colors. The images are rotatable and scalable. This applet will run very slowly on older, slower machines.

449

Harmonically Excited Orbital Variations.  

National Technical Information Service (NTIS)

Rephrasing the equations of motion for orbital maneuvers in terms of Lagrangian generalized coordinates instead of Newtonian rectangular cartesian coordinates can make certain harmonic terms in the orbital angular momentum vector more readily apparent. In...

T. Morgan

1985-01-01

450

Orbiting Binary Stars  

NSDL National Science Digital Library

This simulation demonstrates the path of binary stars' orbit. The user is able to set the masses, orbital separation, orbital eccentricity, the inclination angle to our line of sight, and the angle of the nodes of two orbiting stars. The observed velocities of the two stars, and the Doppler shifted spectral lines are also shown in the upper right box. The site also includes definitions of terms used, instructions on how to use the simulation and a few examples.

Kolena, John

2007-12-11

451

Mars orbit selection  

NASA Technical Reports Server (NTRS)

Parking orbits for a manned Mars mission are examined for ease of access to the Martian moons. Delta V plots for a variety of burns versus elliptical orbit apoapsis are included. A high elliptical orbit (24 hour period, 500 km periapsis, 20 to 30 deg. inclination) minimizes delta V to the Martian moons and Mars orbit insertion (MOI) and trans-Earth injection (TEI) delta Vs.

Babb, Gus R.; Stump, William R.

1986-01-01

452

Pathologies of the Orbit  

Microsoft Academic Search

Pathologic lesions of the orbit continue to be a great challenge to the diagnostic radiologist. The complex anatomy of the\\u000a orbit on the one hand and the multitude of disease entities that may affect the orbit on the other hand demand a simple, well-structured\\u000a approach to diagnostic imaging. Subdividing the orbit into four (or five) distinct spaces, i.e., the eyeball,

Ullrich G. Mueller-Lisse; JuerGen Lutz

453

Arietid Meteor Orbits Measurements  

NASA Astrophysics Data System (ADS)

The Arietid meteor shower is one of the strongest of the year. The origin of this daytime shower is unknown; the orbit is therefore of great interest, since an accurate orbit distribution is needed to integrate the shower backward in time to test associations with comets or asteroids. The orbital parameters of the Arietid shower as a function of time, with errors, have been generated using 415 radar orbits gathered at the CMOR facility in Tavistock, Canada.

Campbell-Brown, M. D.

2004-12-01

454

Orbits of Photographic Meteors  

Microsoft Academic Search

New photographic observations of meterors in the brightness range-5 > Mp > -18 (?) and with a median value of M = -8.5 have yielded orbits with a precision of better than 1° in the angular elements and of about 0.05 in e and 1\\/a. A comparison of 100 of these fireball orbits with Super-Schmidt orbits shows: A. A class

R. E. McCrosky

1967-01-01

455

Orbital-Lifetime Program  

NASA Technical Reports Server (NTRS)

Orbital Lifetime Program (OL) analyzes long-term motion of Earthorbiting spacecraft at altitudes of up to 2,500 km. Models perturbations to orbit caused by solar-radiation pressure, atmospheric drag, and gravitational effects of Sun, Moon, and oblate Earth. Used to predict orbital lifetime and decay rate of satellites. OL written in FORTRAN 77.

Orr, L. H.

1986-01-01

456

SEASAT B orbit synthesis  

NASA Technical Reports Server (NTRS)

Addition were made to Battelle's Interactive Graphics Orbit Selection (IGOS) program; IGOS was exercised via telephone lines from JPL, and candidate SEASAT orbits were analyzed by Battelle. The additions to the program enable clear understanding of the implications of a specific orbit to the diverse desires of the SEASAT user community.

Rea, F. G.; Warmke, J. M.

1976-01-01

457

Statistical initial orbit determination  

Microsoft Academic Search

The computation of a meaningful initial orbital element set based on angles- only data is abandoned as a futile endeavor. Rather, for the ballistic missile initial orbit determination problem in particular, the concept of 'launch folders' is extended. This allows one to decouple the observational data from the initial orbit determination problem per se. The observational data is only used

Laurence G. Taff; Barry Belkin; G. A. Schweiter; K. Sommar

1991-01-01