The nuclear magnetic resonance chemical shift is one of the most powerful properties available for structure determination at the molecular level. A review of advances made in the ab initio calculation of chemical shielding during the past five years is presented. Specifically, progress in the areas including the ...
NASA Astrophysics Data System (ADS)
In this work we discuss the summation of the Parquet class of diagrams within Green�s function theory as a possible framework for ab initio nuclear structure calculations. The theory is presented and some numerical details are discussed, in particular the approximations employed. We apply the Parquet method to a ...
... Ab initio study on atomic structures and physical properties of CdSe quantum nanodots ... Figure 2. Diagram of covered nanodots. ...
DTIC Science & Technology
... Title : Ab Initio Study on Atomic Structures and Physical Properties of CdSe Quantum Nanodots. Descriptive Note : Final rept. ...
... from federally funded research, testing and training ... agencies for Research Development Test and Evaluation ... Title : Ab Initio Study of the Structure ...
Structural and thermal properties of small lithium clusters are studied using ab initio-based Monte Carlo simulations. The ab initio scheme uses a Hartree-Fock/density functional treatment of the electronic structure combined with a jump-walking Monte Carlo sampling of ...
Energy Citations Database
Ab initio electronic structure methods can supplement CALPHAD in two major ways for subsequent applications to stability in complex alloys. The first one is rather immediate and concerns the direct input of ab initio energetics in CALPHAD databases. The o...
National Technical Information Service (NTIS)
This contribution reviews a number of applications of the ab initio no-core shell model (NCSM) within nuclear physics and beyond. We will highlight a nuclear-structure study of the A = 12 isobar using a chiral NN + 3NF interaction. In the spirit of this workshop we will also mention the new development of the NCSM ...
There has been a significant progress in ab initio approaches to the structure of light nuclei. Starting from realistic two- and three-nucleon interactions the ab initio no-core shell model (NCSM) can predict low-lying levels in p-shell nuclei. It is a challenging task to extend ...
DOE Information Bridge
... Title : Structure of Perfluoromethanimine by Microwave, Infrared, and Raman Spectroscopy, Electron Diffraction, and ab Initio Methods,. ...
... nightmares for traditional quantum chemical approaches for optimizing structures of such ... an unbiased manner with ab initio forces. ...
Structural and spectroscopic properties of hydrazine, H(2)N-NH(2), it being a floppy or fluxional molecule in a vacuum, are investigated by means of ab initio molecular dynamics, ab initio path integral molecular dynamics, and ab initio ring polymer ...
PubMed
Solid State Nuclear Magnetic Resonance (NMR) is a powerful tool in crystallography when combined with theoretical predictions. So far, empirical calculations of spectra have been employed for an unambiguous identification. However, many complex systems are outside the scope of these methods. Our implementation of ultrasoft and projector augmented wave pseudopotentials within ...
The structure and reactions of light nuclei represent fundamental and formidable challenges for microscopic theory based on realistic strong interaction potentials. Several ab initio methods have now emerged that provide nearly exact solutions for some nuclear properties. The ab ...
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 ...
There has been a significant progress in ab initio approaches to the structure of light nuclei. Starting from realistic two- and three-nucleon interactions the ab initio no-core shell model (NCSM) predicts low-lying levels in p-shell nuclei. It is a challenging task to extend ...
Ab initio electronic structure methods can supplement CALPHAD in two major ways for subsequent applications to stability in complex alloys. The first one is rather immediate and concerns the direct input of ab initio energetics in CALPHAD databases. The other way, more involved, is the ...
Recent advances in ab initio quantum many-body methods and growth in computer power now enable highly precise calculations of nuclear structure. The precision has attained a level sufficient to make clear statements on the nature of 3-body forces in nuclear physics. Total binding energies, ...
-2011) and has for its objectives advanced studies in theoretical nuclear structure physics, in strong synergy the fundamental, ab initio studies in nuclear structure physics and experiment. Recently, these basic research of predicted nuclear masses. ...
E-print Network
We report on large-scale applications of the ab initio, no-core shell model with the primary goal of achieving an accurate description of nuclear structure from the fundamental inter-nucleon interactions. In particular, we show that realistic two-nucleon interactions are inadequate to describe the low-lying ...
Many modern scientific applications rely on highly parallel calculations, which scale to 10's of thousands processors. However, most applications do not concentrate on parallelizing input/output operations. In particular, sequential I/O has been identified as a bottleneck for the highly scalable MFDn (Many Fermion Dynamics for nuclear structure) ...
Final report for a research program in theoretical nuclear physics to develop methods and computer programs to perform ab initio calculations for light nuclei ranging from Helium to Oxygen. The method employed is based effective interaction theory within the framework of the shell model. The principal accomplishments were: (1) ...
The detailed molecular structure of methyl phosphonate, the simplest phosphorus ester, was determined by ab initio quantum-chemical calculations in a variety of basis sets. Computed properties include the optimized structure, dipole moment, number and rel...
We report on applications of the ab initio, no-core shell model with the primary goal of achieving an accurate description of nuclear structure and reactions from the fundamental inter-nucleon interactions. We show that realistic two-nucleon interactions are inadequate to describe the low-lying ...
The chemical structure and bonding of the hypermetallic Al5C and Al5C- species have been studied by photoelectron spectroscopy and ab initio calculations.
Examples of transition metal complexes containing dihydrogen ligands are investigated using ab initio electronic structure calculations employing effective core potentials. Calculated geometrical structures and relative energies of various forms of WL(sub...
Ab initio density functional theory calculations are carried out in order to predict the evolution of structural materials under aggressive working conditions such as cases with exposure to corrosion and irradiation, as well as to predict and investigate the properties of functional materials for photovoltaic energy applications. ...
... goals of this program have been to develop new, more effective methods for performing accurate ab initio electronic structure calculations and to ...
Metal atom clusters are studied based on the application of ab initio quantum mechanical approaches.
NASA Technical Reports Server (NTRS)
We have carried out extensive high quality ab initio electronic structure calculations of the ground
The equilibrium structure, dipole moment, harmonic vibrational frequencies, and infrared intensities
... the potential energy surface provided by modern electronic structure ... screening approach, to determine the equilibrium geometry and composition ...
The hyperfine-structure constants of the lowest s and p1/2 states of superheavy elements Z=119 and Z=120+ are calculated using ab initio approach. Core polarization and dominating correlation effects are included to all orders. Breit and quantum electrodynamic effects are also considered. Similar calculations for Cs, Fr, Ba+ , ...
A fundamental understanding of radiation damage effects in solids is of great importance in assisting the development of structural materials with improved mechanical properties for nuclear energy applications. In this presentation, we discuss our recent theoretical investigation on the magnetic structure evolution in bulk Fe after an ...
Quantum mechanical-based (or ab initio) methods are used to predict the stability properties of materials although their application is limited to relatively simple systems in terms of structures and number of alloy components. However thermodynamics of c...
We have carried out ab initio electronic structure calculations of the spin-orbit and rotation-orbit
Ab initio quantum chemical techniques are used to investigate covalently-bonded and hydrogen-bonded species that may be important intermediates in the reaction of hydroxyl and hydroperoxyl radicals. Stable structures of both types are identified. Basis se...
General procedures for computing alloy phase equilibria from ab initio electronic structure calculations are reviewed and applied to the Al-Li phase diagram. Free energies were calculated by the cluster variation method (CVM) in the tetrahedron approximat...
Lattice gauge theory provides our only means of performing ab initio calculations in the nonperturbative regime. It has thus become an increasingly important component of the Jefferson Lab physics program. In this paper, we describe the contributions of lattice QCD to our understanding of hadronic and nuclear physics, focusing on the ...
A global search for possible LiF cluster structures is performed up to (LiF)(8). The method is based on simulated annealing, where all the energies are evaluated on the ab initio level. In addition, the threshold algorithm is employed to determine the energy barriers for the transitions among these structures, for ...
Structural and thermal properties of small lithium clusters are studied using ab initio-based Monte Carlo simulations. The ab initio scheme uses a Hartree-Fock/density functional treatment of the electronic structure combined with a jump-walking Monte Car...
We present an algorithm for calculating the conformational thermodynamics of large, flexible molecules that combines ab initio electronic structure theory calculations with a torsional path integral Monte Carlo (TPIMC) simulation. The new algorithm overcomes the previous limitations of the TPIMC method by including the thermodynamic ...
SnO2: BULK AND SURFACE SIMULATIONS BY AN AB INITIO NUMERICAL LOCAL ORBITALS METHOD A.V. POSTNIKOVa structure of ideal bulk SnO2 is well studied by ab initio calculations (Peltzer y Blanc�a, Svane study of several SnO2 surfaces, com- paring their energies of formation, and started to look
There has been a significant progress in ab initio approaches to the structure of light nuclei. Starting from realistic two- and three-nucleon interactions the ab initio no-core shell model (NCSM) predicts low-lying levels in p-shell nuclei. It is a chall...
The hyperfine coupling of the electron spin to the nuclear spins nearby contains information on the local environment such as the chemical composition, distances, or bond angles. A correct interpretation of this information requires a comparison to a theoretical model. In this work, we employ spin-density-functional theory and ab ...
Rotational spectra for the five naturally occurring germanium isotopologues of the anti-anti conformer of n-butylgermane have been measured using a Fourier-transform microwave spectrometer operating in the 4-18 GHz range. This conformer, determined by ab initio calculations at the MP2/6-311++G(2d,2p) level to be the most stable of five possible ...
The pure rotational spectrum of the complex Kr-AgCl has been measured between 8-15 GHz using a cavity pulsed-jet Fourier transform microwave spectrometer. The complex was found to be linear and relatively rigid, with a Kr-Ag bond length of ~2.641 �. The Kr-Ag stretching frequency was estimated to be 117 cm-1. Ab initio calculations performed at the MP2 ...
Approach for interpretation of nuclear magnetic resonance (NMR) spectra in magnetic materials is presented, consisting in employing the anisotropy of hyperfine interaction. The anisotropic parts of hyperfine magnetic fields on (57)Fe nuclei are calculated ab initio for a model example of lithium ferrite and utilized to assign the ...
An algorithm for constructing a quasidiabatic, coupled electronic state Hamiltonian, in a localized region of nuclear coordinate space, suitable for determining bound state spectra, is generalized to determine a nonlocal Hamiltonian capable of describing, for example, multichannel nonadiabatic photodissociation. For Nstate coupled electronic states, the Hamiltonian, Hd, is a ...
NMR chemical shifts for an L-alanine molecular crystal are calculated using ab initio plane wave density functional theory. Dynamical effects including anharmonicity may be included by averaging chemical shifts over an ensemble of structural configurations generated using molecular dynamics (MD). The time scales required mean that ...
... system organized around a common data structure. ... molecular structures; optimize structures using molecul ... ab initio quantum chemical tech- niques ...
The goal of this research is to provide increased understanding of the chemistry and reactivity of pentavalent phosphorus compounds by analysis of structures and electronic structures obtained from ab initio molecular orbital calculations. Electronic stru...
Measurements of the relative abundance of anionic species, commonly described as Qn species in silicate glasses are essential for any structure-based model of thermodynamic or transport properties of silicate liquids and magmas. Solid-state 29Si NMR has provided the most convincing evidence that the Qn species distribution in alkali glasses is not random but closer to binary. ...
... cysteinyl form has been further supported by nuclear magnetic resonance and Raman spectra of the 390 nm intermediate (9,10). The ... ...
NBII National Biological Information Infrastructure
Dec 8, 2009 ... We examine different molecular structures of nitrogen based on recent observations for analog systems. A structure with Immm symmetry and ...
NASA Website
The hyperfine-structure constants of the lowest s and p{sub 1/2} states of superheavy elements Z=119 and Z=120{sup +} are calculated using ab initio approach. Core polarization and dominating correlation effects are included to all orders. Breit and quantum electrodynamic effects are also considered. Similar calculations for Cs, Fr, ...
In supernova cores, nuclear "pasta" phases such as a triangular lattice of rodlike nuclei and layered structure of slablike nuclei are considered to exist. However, it is still unclear whether or not they are actually formed in collapsing supernova cores. Using ab initio simulations called quantum molecular ...
... goals of this program have been to develop new, more effective methods for perform in accurate ab initio electronic structure calculations and to ...
... Abstract : The objectives of this work which were fulfilled were to (1) use high level ab initio molecular orbital theory to predict the structures and ...
... known GAMESS suite of computer codes [2]. Accurate ab initio methods pro- ... to the systematic improvement of standard quantum-chemical methods ...
... This allowed her to gain insight into SiGe alloy superlattice structures, etching of Si by fluorine, the rate limiting chemical vapor deposition process ...
Research progress on an alternative method to ab initio variational and perturbative approaches for the electronic structure of molecules is described. Progress in the report year on the evaluation of (1) molecular properties, (2) energy derivatives with ...
In the present work we shall discuss recent advances in quantum chemical methodology that have improved the reliability of ab initio electronic structure ...
Results are reported from SDCI and CPF ab initio computations for the ground and low-lying states of
... crystal structures which are ordered superstructures of a parent disordered phase; a highly reliable statistical mechanical method (CVM) has now ...
... substantial impact; these tools are now incorporated in many ab initio codes ... Most commonly used quantum chemical methods possess one or the ...
on "Quantum Chemical Calculation of the Equilibrium Structures of Small ... based on the application of ab initio quantum mechanical approaches. This ...
... profiles and three-dimensional quantitative structure-activity relationship pharmacophores using ab initio quantum chemical and pharmacophore ...
(either ab initio methods or basis sets) for electronic structure calculations, and a graph theory procedure for identifying instantaneous molecular fragment identities...
Science.gov Websites
... softening of Al-based fcc alloys using ab initio Korringa-Kohn-Rostoker augmented-spherical-wave electronic structure calculations is discussed. ...
... Beta-(1-methyl-2-pyridinium) - alpha-cyano-4-styryldicyanomethanide was optimized using semi-empirical and ab initio quantum chemical methods ...
... previous grant period have been to develop new, more effective methods for performing accurate ab initio electronic structure calculations and to ...
... progress is reported in development of ab initio computational methods for the electronic structures of molecules employing atomic spectral-product ...
... calculations have been performed on the weakly bonded CO-02 complex at the ... In the T-shaped structure, the oxygen is very weakly bonded to the ...
... optimized. Then, with the C4 C6 twist angle still constrained to 00, ... structure on the rotational pathway, yielding a rotational barrier ...
For some simple, but nontrivial molecular systems, the interaction potentials are now well determined from ab initio electronic structure calculations ...
... a transition metal, A is mostly a IIIA or IVA element of periodic table, and X ... the M2AlC formula to address the influence of the M elements (Y, Zr ...
... More recently, extensive calculations on the nitrogen oxides were conducted employing the density functional method (ref 2) in conjunction with a ...
The reaction of some organophosphorus compounds with cholinesterase is thought to proceed by nucleophilic substitution through a pentacoordinate trigonal bypyramidal structure. Recently, Robert Holmes suggested that a hexacoordinate species might be invol...
... The structures of the entrance channel transition states show the four-body intermediates ... Campus Box 427 Boulder, CO 80309-0427 ...
... Abstract : Electronic structure calculations using theoretical methods based on the linked-diagram theorem are reported for a series of dissociation ...
Mar 1, 2011 ... Conformational Characteristics of Poly(tetrafluoroethylene) (PTFE) Based Upon Ab Initio Electronic Structure Calculations on Model Molecules ...
In this work, we present a study on water acetonitrile (AN) mixtures by molecular dynamics ab initio and X-ray diffraction techniques. Comparison of the experimental total G(r) functions of the mixtures with the results of molecular dynamics simulation shows an overall good agreement. The properties of hydrogen bonded clusters (water clusters, and water AN ...
Quantum mechanical-based (or ab initio) methods are used to predict the stability properties of materials although their application is limited to relatively simple systems in terms of structures and number of alloy components. However thermodynamics of complex multi-component alloys requires a more versatile approach afforded within ...
Research completed during the period 1 Feb. 1990 - 28 Feb. 1994 is summarized in the following included papers: 'Ab Initio Statistical Mechanics of Structural Phase Transition'; 'Ab Initio Molecular Dynamics: Analytically Continued Energy Functionals and Insights into Iterative Solutions'; ...
Temperature dependence of nuclear magnetic resonance (NMR) spectra of (47)Ti and (49)Ti in polycrystalline ilmenite FeTiO(3) was measured in the range from 5 to 300 K under an external magnetic field of 9.401 T. NMR spectra collected between 300 and 77 K exhibit a resolved quadrupole splitting. The electric field gradient (EFG) tensor was evaluated for Ti nuclei and the ratio ...
Temperature dependence of nuclear magnetic resonance (NMR) spectra of 47Ti and 49Ti in polycrystalline ilmenite FeTiO3 was measured in the range from 5 to 300 K under an external magnetic field of 9.401 T. NMR spectra collected between 300 and 77 K exhibit a resolved quadrupole splitting. The electric field gradient (EFG) tensor was evaluated for Ti nuclei and the ratio of ...
The impact of quantum nuclear effects on hydrogen (H-) bond strength has been inferred in earlier work from bond lengths obtained from path integral molecular dynamics (PIMD) simulations. To obtain a direct quantitative assessment of such effects, we use constrained-centroid PIMD simulations to calculate the free energy changes upon breaking the H-bonds in dimers of HF and ...
The generalized two-dimensional Peierls-Nabarro (PN) model7 for studying interfaces is developed further, where an exact generalized stacking fault energy ?-surface obtained from ab initio calculations acts as an input function for the generalized PN model. Using the multiscale modeling techniques, which combines elastic theory with ab ...
The lowest two ab initio potential energy surfaces (PES), and the corresponding nonadiabatic couplings between them, have been obtained for the H{sub 3}{sup +} system; the molecular data are compared to those calculated with the diatomic in molecules (DIM) method. The form of the couplings is discussed in terms of the topology of the molecular ...
Structural and energetic properties of small, deceptively simple anionic clusters of lithium, Li(n)(-), n = 3-7, were determined using a combination of anion photoelectron spectroscopy and ab initio calculations. The most stable isomers of each of these anions, the ones most likely to contribute to the photoelectron spectra, were found ...
Structural and energetic properties of small, deceptively simple anionic clusters of lithium, Lin-, n = 3-7, were determined using a combination of anion photoelectron spectroscopy and ab initio calculations. The most stable isomers of each of these anions, the ones most likely to contribute to the photoelectron spectra, were found ...
The high-pressure induced phase transformation from the zinc blende to rocksalt structure in SiC has been studied by the ab initio molecular dynamics method. The simulations showed that SiC passes through a tetragonal intermediate state before transforming to a monoclinic phase at 160�GPa. The mechanism for this phase transformation ...
A systematic method for approximating the ab initio electronic energy of crystal lattices has been improved by the incorporation of long range electrostatic and dispersion interactions. The effect of these long range interactions on the optimization of the crystal structure is reported. The harmonic lattice dynamics have been evaluated ...
We present results for the static and dynamic structural properties of undercooled liquid Si, at several temperatures between 1550 K and 1100 K, obtained through orbital-free ab-initio molecular dynamics simulations. The local bond angle distributions show a modest increase in the tetrahedral order upon decreasing the temperature. We also analyze the ...
The influence of changes in the contracted Gaussian basis set used for ab initio calculations of nuclear magnetic resonance (NMR) phosphorous chemical shift anisotropy (CSA) tensors was investigated. The isotropic chemical shift and chemical shift anisotr...
The quadrupolar coupling constant Cq and the asymmetry parameter {eta} for the bridging oxygen sites in vitreous silica structures derived via classical molecular dynamics simulation have been calculated using the point-charge lattice summation method. The results of these calculations indicate that while Cq is a function of both the Si-O-Si angle and the associated Si-O ...
Ab initio no-core shell-model solutions for the structure of light nuclei are shown to be dominated by low-spin and high-deformation configurations. This implies that only a small fraction of the full model space is important for a description of bound-state properties of light nuclei. It further points to the fact that the coupling ...
The rotational mechanism of the NH{sub 4}{sup +} ion in water is analyzed by using both semiempirical (AM1) and ab initio (6-31G* SCF level) methods. AM1 predicts rapid rotation at any degree of first solvent shell hydration from n = 1-6. These results are considered artifactual since AM1 favors ion-water structures of a type not found ...
The ab initio no-core shell model (NCSM) is a well-established theoretical framework aimed at an exact description of nuclear structure starting from high-precision interactions between the nucleons. In the NCSM we consider a system of A point-like, non-relativistic nucleons that interact by realistic inter-nucleon ...
We recently proposed a multistage ab initio wavepacket dynamics (MS-AIWD) treatment for the study of delocalized electronic systems as well as electron transport through donor-bridge-acceptor systems such as those found in molecular-wire/electrode networks. In this method, the full donor-bridge-acceptor open system is treated through a rigorous ...
Deuterium isotope effects measure the change in chemical shift on substitution of a proton by deuterium. They have been calculated by direct treatment of the H/D nuclear quantum effect using a multicomponent ab initio molecular orbital method based on a non-Born-Oppenheimer approximation. This method enables the determination of both ...
We have investigated the electronic structure of TTF-TCNQ under uniaxial compression with ab initio plane-wave pseudopotential calculations within the local-density approximation and generalized gradient approximation. Depending on the compression direction, the constituent molecules are deformed in different ways. Along with these ...
An ab initio quantum-chemical study has been made of the possible existence in terms of structural and thermodynamic stabilities of the pentacoordinated nitrogen hydrides and fluorides, NF(n)H(5-n) for n=0 to 5. Three structurally stable species have been...
The complex hyperfine structures in the J = 1 ? 0, and J = 2 ? 1 ground state rotational transitions of 35Cl3CH and 35Cl237ClCH were resolved and measured at conditions of supersonic expansion. Accurate spectroscopic constants for the two isotopomers have been derived from global fits of the hyperfine structure together with hyperfine-free high-J ...
Intramolecular hydrogen bonding (IHB) interactions and molecular structures of 2-nitrosophenol, nitrosonaphthols, and their quinone-monooxime tautomers were investigated at ab initio and density functional theory (DFT) levels. The geometry optimization of the structures studied was performed without any geometrical ...
Results of ab initio Hartree-Fock calculations are presented for the nine-coordination-shell cluster Be{sub 69}. Binding energy, ionization potential, electrical field gradient, nuclear-electrostatic potential, diamagnetic shielding constant, second moments of charge, and Mulliken populations are reported for several electronic states. ...
the possible existence of high mass neutron star observations favors a stiff EoS. Ab initio calculations initio calculations of the nuclear many�body problem predict a density and isospin behavior of the Eo. The predictive power of such density functionals at supra�normal densities is restricted. Ab ...
A combination of high-level ab initio electronic-structure calculations and empirical bond-additivity corrections are used to calculate thermochemical properties of gas-phase molecules. A self-consistent set of heats of formation for molecules in the SiH,...
A combination of high-level ab initio electronic-structure calculations and empirical bond-additivity corrections are used to calculate thermochemical properties of gas-phase molecules. A self-consistent set of heats of formation for molecules in the SiH, Si--H--Cl, Si--H--F, Si--N--H and Si--N--H--F systems is presented.
The results of ab initio multi-configuration self-consistent field (MSCF) calculations on 1,2-cyclohexadiene are reported. These calculations support the contention that the compound's equilibrium geometry is strongly bent and chiral but can easily racemize. Structures are proposed for the ground state, diradical, and ...
- tion was at best able to produce reasonable struc- tures for only very small alpha-helical proteins. Acad. Sci. USA 97(21), 11221�11226. Holm, L., and Sander, C. (1995) Dali: A network tool for proteinFunctional Inferences from Blind ab Initio Protein Structure Predictions Richard Bonneau, Jerry
Results of ab initio molecular orbital calculations are reported for complexes of eleven anions with a water molecule. Optimized geometries obtained with the 6-31G(d) basis set were used in calculations including diffuse functions and the correlation energy. The present structural and energetic results complement and extend ...
We have studied structural and dynamical properties of Mg2Sn by employing an ab-initio pseudopotential method and a linear response scheme, within the generalised gradient approximation. The calculated lattice constant, bulk modulus and pressure derivative of bulk modulus are in agreement with previous ab-initio calculations and available experimental ...
In this work, the structure of symmetric N2O3 was investigated using ab initio methods. Bond lengths and bond angles were determined using the 6-31 G* and the 6-311 G* basis sets using both SCF and MP2 theory. At the highest level of theory considered in ...
The detailed molecular structures including the equilibrium conformations and energies of the four prototype phosphorus compounds exhibiting a phosphorus oxygen phosphorous(P-O-P) interconnection, H4P2O2n-1 for n=1 to 4, were determined by ab initio quant...
The structures of Al sub 2 F sub 7- and Al sub 2 Cl sub 7- have been investigated using ab initio molecular orbital theory including the effects of polarization functions in the basis sets. The Al sub 2 F sub 7- ion has a linear or nearly linear Al-F-Al b...
We present a theoretical investigation of the electronic structure of an InAs monomolecular plane inserted in bulk GaAs. Our calculations are based on the ab initio self-consistent pseudopotential method. Both electrons and holes are found to be strongly ...
The VOH and VOD centers in MgO, CaO, and SrO have been investigated at the ab initio quantum-mechanical level, by using the CRYSTAL98 periodic program, the Hartree-Fock Hamiltonian, the supercell scheme, and a localized basis set. The defects, formally obtained by substituting a hydrogen atom for a cation, exhibit a large relaxation of H from the perfect ...
For reasons of computational efficiency, so far most ab initio molecular dynamics simulations of liquid water have been based on semi-local density functional approximations, such as PBE and BLYP. These approaches yield a liquid structure that, albeit qualitatively correct, is overstructured compared to experiment, even after ...
Deleterious effects of radiation in nuclear reactor systems cause material degradation and the potential for component failure. Radiation damage is fundamentally due to freely migrating point defects produced in collision cascades. A reduction in the freely migrating point defect population should, then, reduce radiation damage and increase component lifetime. The addition of ...
For the equilibrium immiscible Fe-Cu system, ab initio calculations using the projector augmented wave method identify the relatively stable structures of the metastable Fe25Cu75 and Fe50Cu50 alloys to be both of fcc and determine their corresponding lattice constants and cohesive energies. Some of the ab ...
Ab initio electronic-structure calculations are combined with empirical bond-additivity corrections to yield thermochemical properties of gas-phase molecules. A self-consistent set of heats of formation for molecules in the Si-H, Si-H-Cl, Si-H-F, Si-N-H a...
scaling DFT code (see Peter Haynes) Other codes used in TCM for applications ffl CPMD � DFT ab initio? (MT/RN) ffl non�collinear spins in QMC (MT) ffl Pseudopotentials for many�body calculations (Lee, Mostofi, Di'eguez) Applications etc..(CASTEP, CPMD) ffl ab initio molecular dynamics (various projects
Ab-initio quantum chemical investigations of the mechanism of cationic polymerization; Development, implementation testing of theoretical procedures for prediction of crystal structures and densities; Ab-initio quantum chemical MODPOT/VRDDO/MERGE calculat...
Contents: Ab-initio quantum chemical investigations of the mechanism of cationic polymerization; Development of theoretical procedures for prediction of crystal structures and densities; Ab-initio quantum chemical MODPOT/VRDDO/MERGE calculations on nitro-...
Non-ionic and zwitterionic forms of neutral arginine � an ab initio study Piotr Skurski a January 2001 Abstract Six low-energy structures of arginine were studied at the zero-point corrected CCSD with an excess electron [10] and it was via this route that we began our exploration of various arginine isomer
Sch�ffel Ab initio Quantum Chemical Calculations with GAMESS-UK and GAUSSIAN90 Program Packages: ~ . , ISSN 0933-789X #12;Ab initio Quantum Chemical Calculations with GAMESS-UK and GAUSSIAN90 Program Packages Berlin 31 w Abstract Two commercial available molecular electronic structure ...
We present an ab initio quantum theory of the finite-temperature magnetism of iron and nickel. A recently developed technique which combines dynamical mean-field theory with realistic electronic structure methods successfully describes the many-body features of the one electron spectra and the observed magnetic moments below and above ...
The reaction SiH4 + H(-) to SiH5(-) is investigated by employing ab initio quantum chemical techniques. With respect to silane and a hydride ion, a trigonal-bipyramidal form of SiH5(-) is found to be stable by 16.9 kcal/mol and a tetragonal-pyramidal form...
The Raman and neutron scattering spectra of 46 mol% AlCl(sub 3) -54 mol% 1-ethyl-3-methyl imidazolium chloride (EMIC) and 67 mol% AlCl(sub 3) - 33 mol% EMIC melts are presented. Ab initio molecular orbital calculations have been carried out on structures ...
The Raman and neutron scattering spectra of 46 mol% AlCl[sub 3] -54 mol% 1-ethyl-3-methyl imidazolium chloride (EMIC) and 67 mol% AlCl[sub 3] - 33 mol% EMIC melts are presented. Ab initio molecular orbital calculations have been carried out on structures of chloroaluminate anion and EMI cation and the interaction between anion and ...
The Raman and neutron scattering spectra of 46 mol% AlCl{sub 3} -54 mol% 1-ethyl-3-methyl imidazolium chloride (EMIC) and 67 mol% AlCl{sub 3} - 33 mol% EMIC melts are presented. Ab initio molecular orbital calculations have been carried out on structures of chloroaluminate anion and EMI cation and the interaction between anion and ...
The recent literature on the determination of minimum energy conformations by ab initio quantum mechanical techniques is reviewed. The availability of computer-coded analytical first and second derivatives of the Hartree-Fock energy makes possible calculations that will be of significant assistance in structure determination of ...
PubMed Central
Atomistic and ab initio methods are used to study structural and electronic properties of perfect and defective chalcopyrites, specifically, ZnGeP2 and CdGeAs2. These materials are important due to their suitability for nonlinear optical applications in t...
The potential barriers for the internal rotation of silole dimers are studied theoretically using the ab initio molecular orbital method at the RHF/6-31G** level of calculations. In 2,2{prime}-bisilole, it is found that the anti-conformation is the most stable structure in the ground state and that the potential barrier height for ...
We report the results of a large-scale ab initio simulation of an intergranular glassy film (IGF) model in ?-Si3N4. It is shown that the stress-strain behavior under uniaxial load in the model with prismatic surfaces and few defective bonds is very different from an earlier IGF model with basal planes. The results are explained by the fundamental ...
We use ab initio crystalline calculations to explore the role of iodine in determining the properties of 1,4-diiodobenzene. The results strongly suggest that the large halogen is an important or perhaps the dominant determinant of the ability of diiodobenzene to transport holes. We conjecture that the high mobility of diiodobenzene is due to a combination ...
The GaAs(100) surface is modeled by using atomic clusters in order to study the effects of passivation with sulfur. Both the Ga- and the As-terminated surfaces are tied off with S atoms in a 2 {times} 1 reconstruction. The most stable structure is established on the basis of ab initio Hartree-Fock calculations. It is found that after ...
The authors have calculated the band structures of organic conductors TTF-TCNQ and {beta}-(BEDT-TTF){sub 2}I{sub 3} using the ab initio plane-wave pseudopotential method within the local-density approximation (LDA). The Fermi-surface shape and the origin of bands near the Fermi level are investigated for each compound.
We present a formulation of ab initio electronic structure calculations in a finite magnetic field, which retains the simplicity and efficiency of techniques widely used in first principles molecular dynamics simulations, based on plane-wave basis sets and Fourier transforms. In addition we discuss results obtained with this method for ...
We have performed ab initio calculations of positron distribution, ACAR and lifetime in the quasi-one-dimensional organic conductor TTF-TCNQ. The electronic structure is obtained within the LDA, while the positron state is calculated either with the LDA or with the GGA. Except the positron lifetime, differences between the LDA and GGA ...
Ab initio calculations were used to determine the equilibrium geometries and energies of lithium dimethylaminoborohydride. Relative energies of the monomeric and dimeric species were calculated in the gas phase and for the dimethyl ether microsolvated molecules. The most stable structure was a dimer in which the lithium and boron atoms ...
Electronic properties have an important role in the metabolism of benzo(a)pyrene (BP) and the mutagenic action of its metabolites. In this paper, the ground electronic state of BP is characterized by the ab initio molecular fragment floating spherical Gaussian orbital method, and a speculative structural-electronic mechanism is ...
There has been an interest in the study of hydrogen ion clusters. However, only positive clusters, Hn +, where n = 3m 5, 7, ..., have been discovered and successfully analyzed by meand of both experimental and ab initio theoretical methods (cf. Hirao and ...
Ab Initio electronic structure calculations using analytical energy derivative methods and automated potential energy surface walking techniques have been carried out on the tautomerization reaction path connecting formamide (F) H2N-CHO, through a transit...
The use of ab initio molecular orbital calculations to aid in the characterization, i.e., structures and energies, of metal halide complexes present in high temperature salt vapors has been investigated. Standard LCAO-SCF methods were used and calculation...
Ab initio molecular dynamics is used to compute the thermal conductivity of hydrogen at 80 g cm{sup -3} and temperature up to 800 eV. Pressures and ionic structure are compared with orbital-free calculations. Thermal conductivity is evaluated using the Kubo-Greenwood formula and is compared with models currently used in hydrodynamical ...
The hyperfine structure of the long-lived 5D3/2 and 5D5/2 levels of Ba+ ion is analyzed. A procedure for extracting relatively unexplored nuclear magnetic moments ? is presented. The relevant electronic matrix elements are computed in the framework of the ab initio relativistic many-body perturbation theory. ...
Perturbed angular correlation of ?-ray (PAC) spectroscopy performed on a single crystal of Ag(imidazole)2NO3 doped with radioactive 111Ag(I) reveals that one nuclear quadrupole interaction (NQI) characterizes the resulting PAC spectra. This implies a unique coordination geometry for Cd(II) after the decay of 111Ag(I). The full NQI tensor was determined in the experiment. The ...
As an extension of previous works in sulphur-substituted biphenyls, a complete pulsed 35Cl nuclear quadrupole resonance (NQR) study of the bis(4-chlorophenyl) sulphide compound is presented. In order to characterize the structural thermal behaviour of the solid phase, the NQR spectra and spin-lattice relaxation times were recorded from 80 K to 330 K. In ...
We present the first ab initio structure investigation of the loosely bound {sup 11}Be nucleus, together with a study of the lighter isotope {sup 9}Be. The nuclear structure of these isotopes is particularly interesting because of the appearance of a parity-inverted ground state in {sup 11}Be. ...
We are presenting the first ab initio structure investigation of the loosely bound {sup 11}Be nucleus, together with a study of the lighter isotope {sup 9}Be. The nuclear structure of these isotopes is particularly interesting due to the appearance of a parity-inverted ground state in {sup ...
An accurate and efficient molecular alignment technique is presented based on first principle electronic structure calculations. This new scheme maximizes quantum similarity matrices in the relative orientation of the molecules and uses Fourier transform techniques for two purposes. First, building up the numerical representation of true ab ...
Ab initio self-consistent-field calculations are reported for electronic states of beryllium clusters comprised of 93, 105, 111, and 123 atoms. The respective clusters correspond to coordination shells 12-15 of a central Be atom with internuclear separations derived from the lattice constants of the bulk metal. Ab ...
The magnetic ground state of the Heusler compound Mn2CoSn was predicted to be nearly half-metallic ferrimagnetic with a high spin polarization by ab initio electronic structure calculations. Mn2CoSn was synthesized, and the magnetic behavior of the compound was studied using a superconducting quantum interference device and x-ray ...
The quadratic, cubic and semi-diagonal quartic force field of propene has been calculated at the MP2 level of theory employing a basis set of triple-? quality. A semi-experimental equilibrium structure has been derived from experimental ground state rotational constants and rovibrational interaction parameters calculated from the ab ...
Owing to their small mass, hydrogen atoms exhibit strong quantum behavior even at room temperature. Including these effects in first-principles calculations is challenging because of the huge computational effort required by conventional techniques. Here we present the first ab initio application of a recently developed stochastic scheme, which allows to ...
The structural, electronic and dynamic properties of cesium chloride, ZrRu and ZrZn were studied by employing an ab initio pseudopotential method and a linear response scheme, within the generalized gradient approximation. The calculated lattice constant, bulk modulus and first-order pressure derivative of the bulk modulus were ...
A novel technique combining the advantages of the laser-rf double-resonance scheme and a fast-beam collinear laser spectroscopy has been applied to a detailed study of the hyperfine structure of /sup 235/U II. The experimental results are analyzed with use of ab initio Dirac-Fock calculations of the reduced radial parameters of ...
It is essential to know the arrangement of the atoms in a material in order to compute and understand its properties. Searching for stable structures of materials using first-principles electronic structure methods, such as density-functional-theory (DFT), is a rapidly growing field. Here we describe our simple, elegant and powerful approach to searching ...
We present a combined computational and experimental study on structural and electric properties of recently synthesized heteroaromatic dyes and their simple aggregates. Ab initio and density functional theory calculations are carried out to investigate ground state and excited state properties along with their modulation induced by ...
We present the result of ab initio modeling of the Ge(111)-(2 � 1) surface electronic structure in the presence of donor doping atom at certain position in the surface bilayer of (2 � 1) reconstruction. We briefly compare these results with the data of experimental low temperature STM investigations. Ab ...
An ab initio density functional theory-based study of the electronic band structure, the elastic, electric, elastoelectric, and linear and nonlinear optical properties of the new ion conductor LiB6O9F, has been performed. The computed band structure reveals a wide direct band gap. The coefficients of the second ...
Dynamics of molecules in an intense laser field is studied in terms of the quantum electronic wave packet coupled with classical nuclear motions. The equations of motion are derived taking a proper account of molecular interactions with the vector potential of a classical electromagnetic field, along with the nonadiabatic interaction due to the breakdown of the ...
The paramagnetic F center in LiF is investigated at a quantum mechanical level with the CRYSTAL98 periodic code by using a supercell scheme. The isotropic and anisotropic components of the hyperfine coupling tensor describing the interaction between the unpaired electron and the nuclear spins up to the seventh nearest neighbors of the defect are computed by using two different ...
This paper uses chemical shift surfaces to simulate experimental 13C cross polarization magic angle spinning spectra for amorphous solid state disaccharides, paying particular attention to the glycosidic linkage atoms in trehalose, sucrose, and lactose. The combination of molecular mechanics with density functional theory/gauge invariant atomic orbital ab ...
My efforts in the Density Functional Theory (DFT) project of Dr. Bartlett's research group have been limited to the implementation of analytical energy gradients with respect to nuclear displacement in ACES2. The most immediate benefit of this work is ana...
Ab initio, the point reactor kinetics has been derivd systematically with an assumption of separation of neutron number density, into a shape-function and a time-function. The understanding of the actual approach of the phenomena is aimed at by a systemat...
The structure of atomic clusters is investigated using methods of ab initio quantum chemistry in conjunction with scanning tunneling microscopy (STM). Gold sols are imaged via STM and their sizes characterized. Atomic resolution reveals facets, steps, and...
The main goals of this program have been to develop new, more effective methods for perform in accurate ab initio electronic structure calculations and to use these methods for the prediction of molecular structure, bonding and reactivity, especially for ...
The main goals of this program have been to develop new, more effective methods for performing accurate ab initio electronic structure calculations and to use these methods for the prediction of molecular structure, bonding and reactivity, especially for ...
Progress is reported in development, implementation, and application of a spectral method for ab initio studies of the electronic structure of matter. In this approach, antisymmetry restrictions are enforced subsequent to construction of the many-electron...
Ab initio molecular orbital theory is used to characterize a series of metal-substituted benzene and cyclopentadiene structures, with the heteroatom taken from the block in the periodic table bounded by groups IV-VI and periods 2-5. Structures are predict...
We describe an implementation of the benchmark ab initio electronic structure full configuration interaction model on the Intel Touchstone Delta. Its performance is demonstrated with several calculations, the largest of which (95 million configurations, 4...
The main goals in the previous grant period have been to develop new, more effective methods for performing accurate ab initio electronic structure calculations and to use these methods for the prediction of molecular structure, bonding and reactivity, es...
