... Title : AB Initio Quantum Chemical Investigations of Solubilities in Supercritical Solutions. Descriptive Note : Conference Paper,. ...
DTIC Science & Technology
... This study involves: Ab-initio crystal orbitals and polymer orbitals; Ab-initio coupled cluster program; Ab-initio quantum chemical calculations and ...
... Abstract : This report describes the development and application of ab initio quantum chemical methods that are especially relevant to the study of ...
... Abstract : Ab-initio quantum chemical investigations of the mechanism of cationic polymerization; Development, implementation testing of ...
... Abstract : Contents: Ab-initio quantum chemical investigations of the mechanism of cationic polymerization; Development of theoretical procedures ...
... (U) DEVELOPMENT OF EFFECTIVE QUANTUM CHEMICAL METHOD FOR ... array of semiempirical approaches and ab initio calculations followed ...
Ab initio quantum chemical techniques have been used to investigate weakly bund complexes of H20 and SO2. An energy gradient program was used to ...
NASA Website
... Accession Number : ADA440631. Title : Ab Initio Quantum Chemical Study of Electron Transfer in Carboranes. Descriptive Note : Journal article. ...
... nightmares for traditional quantum chemical approaches for optimizing structures of such ... an unbiased manner with ab initio forces. ...
... Title : AB Initio Study of the Electronic Magnetic Circular Dichroism ... functions are determined using as initio quantum chemical techniques including ...
quantum chemical method rather than an ab initio one. Although the approximate nature of semiempirical results must be stressed, such methods are reliable ...
In this study we will perform high-level quantum chemical (also called ab initio ) calculations of the rate coefficients for a suite of sulfur reactions and ...
... This is being done by carrying out theoretical high quality three-dimensional ab-initio quantum chemical calculations on the oximes and from these ...
... Abstract : Quantum chemical methods (ab initio, semiempirical, and Hartree-Fock) were used to calculate the energy of several phosphite ...
... predicting known experimental molecular properties as well as properties predicted by other ab initio studies. Quantum chemical calculations are ...
... of ab initio quaru cheiial methtods Lhat are espe,,.ally relevant to the study of high-energy density materials species. Two major quantum chemical ...
... used successfully the strategy for ab-initio MRD-CI ... polymerization; Energetic polymers; Oxetanes; Quantum chemical calculations; Configuration ...
... Energetic polymers, Oxetanes, Quantum Chemical calculations, Configuration ... MRD/CI), Energetic compounds, Ab-initio potential functions, Crystal ...
... We have also calculated further ab-initio atom class-atom class potential functions. Keywords: Quantum chemical electrostatic molecular potential ...
... Abstract : In the research on part I of this project we are carrying out ab-initio quantum chemical calculations and generating electrostatic molecular ...
"An ab initio. Investigation of Possible. Intermediates in the Reaction of the. Hydroxyl ... "A Quantum. Chemical. Investigation of the. 2A 1 Excited ...
... Abstract : Results are presented from ab initio quantum chemical calculations on the ground state potential energy surface for the open shell ...
... We carried out ab-initio quantum chemical calculations on these energetic cyclic ethers and generated the electrostatic molecular potential contour ...
... Rydberg I 'Flu state. Demoulin and Jungen (1974) used an ab initio quantum chemical approach, but only at the SCF level ...
... moment has been cancelled a priori for the electronic transition as a function of R(CC), using ab initio quantum chemical techniques including state ...
... Results of this study substantiate findings from an earlier quantum chemical study using a lower ... for (I) and (II) based on the earlier ab initio study. ...
In the second phase, a ultrafast semi-empirical ab initio method is ... High level quantum chemical calculations are then performed to further narrow down ...
Metal atom clusters are studied based on the application of ab initio quantum mechanical approaches.
NASA Technical Reports Server (NTRS)
... Abstract : This final technical report summarizes research on application of ab initio quantum chemical techniques to enzyme inhibitors such as ...
... index to significant articles, news items, and ... Author : INSTITUTE OF THEORETICAL PHYSICS AND ASTRONOMY VILNIUS (LITHUANIA). ...
with molecular dynamic simulations in combination with high level correlated ab initio quantum chemical the existing minima in the PES. 2. Ab initio quantum-chemical calculations. The lowest energy minima (within surface analysis by metadynamics. Gibbs ...
E-print Network
This report describes the development and application of ab initio quantum chemical methods that are especially relevant to the study of high-energy density materials species. Two major quantum chemical program systems, MESA and BROOKLYN, have been develo...
National Technical Information Service (NTIS)
A initio quantum chemical methods are seeing increased application in a large variety of real-world problems including biomedical applications ranging from drug design to the understanding of environmental mutagens. The vast majority of these quantum chem...
the parameters for a polarizable force field from ab initio quantum-chemical calculations, and a rigorous method initio quantum- chemical calculations have become an increasingly impor- tant source of fitting dataParametrizing a polarizable force field from ...
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-...
This study involves: Ab-initio crystal orbitals and polymer orbitals; Ab-initio coupled cluster program; Ab-initio quantum chemical calculations and electrostatic molecular potential contour maps for cationic polymerization; Prediction of crystal density;...
In the research on part I of this project we are carrying out ab-initio quantum chemical calculations and generating electrostatic molecular potential maps for cationic polymerization: on energetic monomers, on their interaction with catalysts and on the ...
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...
Formalisms suitable for calculating the rate of electron exchange between transition metal complexes in aqueous solution are reviewed and implemented in conjunction with ab initio quantum chemical calculations which provide crucial off-diagonal Hamiltonia...
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...
Ab initio quantum chemical calculations have been aimed at elucidating the biradical intermediates formed during the electrophilic addition of ground and ...
... artifacts. 3 Miyoshi and Sakai concluded from their ab initio CI ... Quantum chemical calculations (DVM-Xt) of the nonmetallic ...
... Abstract : Ab initio quantum chemical simulations were coupled with variational transition state theory in estimating rate constants for the H + C3H3 ...
... known GAMESS suite of computer codes [2]. Accurate ab initio methods pro- ... to the systematic improvement of standard quantum-chemical methods ...
... The interactions for DTP, DTC and Fe2O3 are evaluated based on a force field derived from fitting to ab initio quantum chemical calculations of ...
... system organized around a common data structure. ... molecular structures; optimize structures using molecul ... ab initio quantum chemical tech- niques ...
beyond the practical range of the standard ab-initio methods of quantum chemistry because of the large numbers of electrons involved. If one could ...
... For example, ab initio quantum chemical calculations when combined with reaction rate theory and kinetics modeling can, in principle, be capable ...
Aug 24, 2011 ... We have performed high-level ab initio calculations of the ground state and ... can be accurately treated by quantum chemical methods. ...
... Stabilities of Low-Coordinated pi-Bonded Phosphorus Systems. An ab initio Quantum Chemical Investigation. p9 and 10. ...
In the present work we shall discuss recent advances in quantum chemical methodology that have improved the reliability of ab initio electronic structure ...
... 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 ...
... and many-body perturbation theory (MBPT) methods for the accurate inclusion of electron correlation in ab initio quantum chemical calculations of ...
Electronic studies were carried out by several quantum-chemical ... second is a self-consistent-field approximation of an ab initio ...
... The interaction-induced dipole moment of the Ar-H2 van der Waals dimer was computed using ab initio quantum chemical methods in order to ...
... profiles and three-dimensional quantitative structure-activity relationship pharmacophores using ab initio quantum chemical and pharmacophore ...
... fuels requires an interdisciplinary approach involving ab initio modeling, synthesis ... value of high speed video and quantum chemical calculations to ...
... phosphorus species have not been previously determined and were estimated from the results of ab initio quantum chemical calculations available ...
This report presents ab initio quantum chemical studies of DR for molecular ions that are likely to be important in the atmospheric shock layer. ...
... Beta-(1-methyl-2-pyridinium) - alpha-cyano-4-styryldicyanomethanide was optimized using semi-empirical and ab initio quantum chemical methods ...
... Detailed analyses, including 6-31G' and MP2/6-31G* ab initio calculations, were performed for ... formed comparative quantum chemical calculations ...
... generally applicable procedure for carrying out ab initio calculations employing ... were also made in describing quantum-chemical results obtained ...
... have potential applications in medicinal drug design as hydrophobic pharmacophores [1 ... 7]. Due to their axially direc- ted terminal bonds and rigid ...
... 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
... derivatives (first and second) calculated by ab initio quantum chemical techniques (Maple, Dinur, and Hagler 1988; Hagler et al. ...
Using a theoretical quantum chemical approach, we .... completion of the ab initio calculation of the Rydberg and valence potential ...
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 ...
used, and reliable stabilization energies are only obtainable at high quantum- chemical ab initio support quantum-chemical calculations. This re- view focuses on the current status of (poly)amino acids or dispersion energy would have to be included to properly describe them. Therefore, ...
such as H2 (see ref. 11 and references therein), to the best of our knowledge, the only quantum-chemical ab as an Advance Article on the web 16th April 2009 DOI: 10.1039/b822262b By means of non-perturbative ab initio antiaromatic rings with less than one hundred carbon atoms. I. Introduction The full ...
Ab initio (MP2/6-31G**//MP2/3-21G) calculations yield a value of about 729 kJ/ mole, ... Quantum chemical; Lubricants; Modelling; Semiempirical; Lubrication; ...
State-of-the-art, calibrated ab initio quantum chemical calculations have been performed to obtain accurate structures, energies, and vibrational frequencies of the lowest singlet states of HNS and NSH, which are closed-shell states. Enthalpies of formati...
The energy difference between silaethylene (H2Si=CH2) and methylsilylene (SiHMe) has been determined with ab initio quantum chemical techniques. Large basis sets and a variety of methods for the inclusion of electron correlation effects have been employed...
This final technical report summarizes research on application of ab initio quantum chemical techniques to enzyme inhibitors such as acetylcholinesterase. Computational techniques have been developed, tested and applied to (1) chemically related series of...
Metal atom clusters are studied based on the application of ab initio quantum mechanical approaches. Because these large 'molecular' systems pose special practical computational problems in the application of the quantum mechanical methods, there is a spe...
The application of ab initio quantum mechanical approaches in the study of metal atom clusters requires simplifying techniques that do not compromise the reliability of the calculations. Various aspects of the implementation of the effective core potentia...
Under AFOSR support over several years, coupled-cluster (CC) and many-body perturbation theory (MBPT) methods for the accurate inclusion of electron correlation in ab initio quantum chemical calculations of molecules have been definitively established as ...
... positions signifi- F cantly affects the ab initio quantum chemical calculations or DDF = gk(R) O = (1/ FN,j)Nk(R)J I/d V, the PIXEL ...
The requirements for very accurate ab initio quantum chemical prediction of dissociation energies are examined using a detailed investigation of the nitrogen molecule. Although agreement with experiment to within 1 kcal/mol is not achieved even with the m...
Ab initio quantum chemical calculations are presented for the energy of dimerization of the borane molecule (2BH3 B2H6). The calculations are superior to previous theoretical treatments both in the level of treatment of electron correlation and in the one...
Ab-initio quantum chemical computations have been applied to a set of molecular clusters derived from Si5H12 to model defects in crystalline silicon involving boron, carbon, nitrogen, oxygen, and hydrogen. In computations of defect structure, hydrogen ato...
This report results from a contract tasking Institute of Theoretical Physics and Astronomy as follows: The contractor will investigate quantum mechanical design of light-driven, single supermolecular logically-controlled machines and molecular computing d...
Page 1. Page 2. Page 3. Page 4. Page 5. Page 6. Page 7. Page 8. Page 9. Page 10. Page 11. Page 12. Page 13. Page 14. Page 15. Page 16. Page ...
In this paper we describe how the density matrix renormalization group can be used for quantum chemical calculations for molecules, as an alternative to traditional methods, such as configuration interaction or coupled cluster approaches. As a demonstration of the potential of this approach, we present results for the H{sub 2}O molecule in a standard ...
Energy Citations Database
Quantum chemical methods (ab initio, semiempirical, and Hartree-Fock) were used to calculate the energy of several phosphite-phosphonate tautomers, and thereby determine the position of equilibrium in the gas phase. Unless the phosphorus moiety contains s...
Quantum chemical laboratory investigations aiming at a study of the binding between metal and ligand in biosystems, and electronic aspects governing biochemical reactions, including charge transfer, are addressed. The influence of an aqueous or other surr...
structure of finite-length armchair carbon nanotubes has been studied using several ab-initio properties and the spatially-resolved electronic structure of finite-size nanotubes, quantum-chemical methods-band-gap polymers.12 To compensate for the weaknesses of the various quantum-chemical techniques, we utilized
isomer. Ab initio calculations also were performed to aid in the spectral assignments for neopentyl, t which were based on extensive quantum-chemical calculations. Since there are approximately 170 stable in C5H11O2, rather than needing to rely on ab initio calculations to make predictions
Molecular simulation of the vapour�liquid phase coexistence of neon and argon using ab initio are reported for the vapour�liquid phase coexistence of neon and argon. For neon two dierent quantum chemical interactions. In addition calculations are also reported for neon using a potential that includes three
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 previous ab initio results on lattices of K atoms for coordination numbers z 8, 4, and 2 are analyzed these DFT results for K into contact with a simple and physically appealing quantum-chemical model proposed conclusions are given at the end of the paper. II. THEORETICAL METHOD We have performed the ab ...
Results are presented from ab initio quantum chemical calculations on the ground state potential energy surface for the open shell doublet reaction: HNO + NO right arrow N2O + OH. (I) This reaction is thought to be Important in the sustained combustion of...
The electric dipole transition moment has been cancelled a priori for the electronic transition as a function of R(C-C), using ab initio quantum chemical techniques including state averaged, complete active space MCSCF and multireference CI. The transitio...
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...
In an attempt to better understand the Ultraviolet absorption and emission spectra of hydroxide ion, we have carried out what we believe are the first ab initio quantum chemical calculations on excited electronic states of this ion. Because these excited ...
The electron transfer (ET) properties of 10- and 12-vertex carboranes are investigated by the ab initio Hartree-Fock method within the Marcus-Hush (MH) two-state model and the Koopman theorem (KT) approach. The calculated value of the ET coupling matrix e...
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 ...
NASA Astrophysics Data System (ADS)
We investigate the dynamical mean-field theory (DMFT) from a quantum chemical perspective. Dynamical mean-field theory offers a formalism to extend quantum chemical methods for finite systems to infinite periodic problems within a local correlation approximation. In addition, quantum ...
PubMed
The distonic dimer radical cation of the 2,3-dihydrofuran was radiolytically generated in Freon matrix and studied by low-temperature EPR spectroscopy. The structure of the dimer radical cation was also investigated using different quantum chemical methods. The BH&HLYP, similarly as ab initio HF and MP2 ...
We describe large scale ab initio quantum chemical and mixed quantum mechanics/molecular mechanics (QM/MM) methods for studying enzymatic reactions. First, technical aspects of the methodology are reviewed, including the hybrid density functional theory (DFT) methods that are typically employed for the QM aspect of ...
The results of systematic theoretical studies of molecular structure, charge distribution and bond characteristics (bond lengths and bond orders) of potassium - magnesium aspartates ((Asp�)3 K+ Mg2+) in aqueous solution obtained by ab initio quantum-chemical method are presented. The supermolecules including (Asp�)3 K+ Mg2+ + nH2O ...
CsCl-NbCl{sub 5}-NbOCl{sub 3} melts were studied by Raman spectroscopy for the temperature range 340 and 650{degrees}C. Bonding modes for Nb-O and various niobium anion species. Interpretations of the Raman spectra based on ab initio calculations were performed.
Experimental single-molecule stretching curves for three backbone architectures (single-stranded DNA, various types of peptides, polyvinylamine) are quantitatively compared with corresponding quantum-chemical (zero-temperature) ab-initio calculations in the high-force range of up to two nanonewtons. For high forces, quantitative agreement is obtained with ...
High-level quantum-chemical ab initio coupled-cluster and multiconfigurational perturbation methods have been used to compute the vertical and adiabatic electron affinities of the five canonical DNA and RNA nucleobases: uracil, thymine, cytosine, adenine, and guanine. The present results aim for the accurate determination of the ...
Recent accurate observations [1] of collision-induced absorption (CIA) in the nitrogen and oxygen fundamentals pointed at the existence of the minimum in its integrated intensity temperature variation. This work aims at simulation of the CIA intensity in N2 using quantum chemical complete potential energy and dipole surfaces for N2-N2 system. The absolute ...
Ab initio molecular orbital calculations on the structure and stability of the nitrate and sulfate complexes of uranyl (UO{sub 2}{sup 2+}) and plutonyl (PuO{sub 2}{sup 2+}) using effective core potentials are reported. It is found that the binding energy of sulfate is greater than that of nitrate to both uranyl and plutonyl, with a slight preference for ...
The report discusses modeling gas-grain chemistry with ab initio quantum chemical cluster calculations which include heterogeneous hydrogenation of CO and H2CO on icy grain mantles, and ammonia-catalyzed, water-enhanced polymerization of formaldehyde in laboratory studies of astrophysical ices.
Ab initio quantum chemical simulations were coupled with variational transition state theory in estimating rate constants for the H + C3H3 and H + C3H5 recombination reactions. The energy of interaction between the H atom and each of the radicals was eval...
Studies of ring-saturated pyrimidine base lesions are used to illustrate an integrated modeling approach that combines quantum-chemical calculations with molecular dynamics simulation. Electronic-structure calculations on the lesions in Isolation reveal s...
The ab-initio calculation of resonance lifetimes of metastable anions challenges modern quantum-chemical methods. The exact lifetime of the lowest-energy resonance is encoded into a complex ``density'' that can be obtained via complex-coordinate scaling. Using one and two electron examples, we illustrate a method for extracting the lifetime from the ...
This paper discusses: Program Enhancements and New Program Developments on the CRAY Supercomputer; MRD-CI Calculations for Cationic Polymerization of Energetic Oxetanes; Ab-Initio MRD-CI Calculations for Breaking a Chemical Bond in a Molecule in a Crystal...
Contents of this report include: Conversion of Our Programs to CRAY Vector Supercomputers; Calculations for Cationic Polymerization of Energetic Monomers; MRD-CI Calculations on Decomposition Pathways of Energetic Nitrocompounds; POLY-CRYST; Ab-Initio Ato...
GRAPHICS&MODELING DESCRIPTORS v) -besides computed molecular descriptors by some quantum chemical or QSAR&QSAR Methodology: other methods Methodology: selected molecular descriptors Results: chemometrics for set I Results and modeling of progestogen-receptor was performed. Besides DFT ab initio computed ...
Hartree-Fock ab initio Raman spectra calculations and Raman spectroscopic measurements were carried out on amorphous selenium in order to identify the characteristic vibrational mode due to sigma bonds. Variations in measured peak intensity were observed as a consequence of band gap light illumination. Based on our previous theoretical investigations we ...
Quantum chemical calculations of the structure and stability of MNg{4/2+} (M = Cu, Ag and Au; Ng = He and Ne) series at the CCSD(T) theoretical level are performed. The interaction mechanism is investigated using the natural bond orbital (NBO) and electron density analyses. The analyses of the electron density show the weak electrostatic interaction in the ...
The fluorescence properties of 2-phenylindole, 2-naphthylindole and 2-anthracenylindole were investigated. 2-Anthracenylindole was newly synthesized by Suzuki-Miyaura's coupling. The fluorescence quantum yield of 2-phenylindole was the highest and the fluorescence emission maximum wavelength of 2-anthracenylindole was the longest. The ab initio ...
. All ab initio molecular dynamics simulations were performed with the CPMD program.13 Density func and Ernzerhof.14 Core electrons on all atoms were represented by norm- conserving pseudopotentials15). 13 J. H�utter et al., CPMD, Copyright IBM Z�urich Research Laboratory and MPI f�ur Festk
The geometry of Z-Beta-(1-methyl-2-pyridinium) - alpha-cyano-4- styryldicyanomethanide was optimized using semi-empirical and ab initio quantum chemical methods. The predicted geometries using a one determinant description do not compare well with the obs...
packages, including MOLDEN for general model building, Gaussian, PC GAMESS, and Dalton for quantum chemical Lab: Monte Carlo Oct 20 M Foundations of the MO theory Oct 22 W Semi-empirical MO theory Second assignment due Oct 24 F Computer Lab: semi-empirical methods Oct 27 M Ab Initio MO Theory: Basis Sets Oct 29
Using the same level of [ital ab] [ital initio] quantum chemical theory as that applied by Becker [ital et] [ital al]. [J. Chem. Phys. [bold 100], 1759 (1994)], we have reexamined the structures of SF[sub 5] and SF[sup +][sub 5]. Contrary to their report, we find that the SF[sub 5]/([ital D][sub 3[ital h
We report differential scattering experiments on the laser excitation of Na + M collision pairs with M = N(2), CO, C(2)H(2), and CO(2). The collision event is probed by the laser polarization revealing geometric and electronic properties of the collision pair. The experimental data are compared to the results of a Monte Carlo trajectory simulation using ab ...
Quantum chemical calculations of the structures and stabilities of the title series at the CCSD(T) theoretical level are performed. Laplacian, electron density deformation, electron localization function and reduced density gradient analysis are investigated to explore the nature of the interaction. The results show that a covalent contribution occurs in ...
Published data on the prototropic tautomerism of some carbonyl and nitrogen-containing acyclic and heterocyclic compounds are systematised. Mechanisms of intramolecular and intermolecular proton transfer in tautomerisation reactions are considered. On the basis of the results of semiempirical and ab initio quantum-chemical ...
This report pertains to: New Program Developments on the CRAY Supercomputer, MRD-CI Calculations for Cationic Polymerization of Energetic Oxetanes, Ab-Initio MRD-CI Calculations for Breaking a Chemical Bond in a Molecule in a Crystal or Other Solid Enviro...
of the chromophore and its surroundings, enabling us to describe reactions involving chemical bond breaking ab initio amu here. When the QM/MM border was in between two chemically bonded atoms, a link hydrogen atom25. Although the difference with experiment is smaller, the quantum chemical simulations show larger ...
Multiple emissions have been observed from benzil under different conditions in solutions at room temperature as well as in low temperature glass matrices at 77 K. Low temperature emission has been monitored in rigid matrices frozen under different conditions of illumination. Steady state and time-resolved results together with the ab initio ...
We have applied the ab initio path integral molecular dynamics simulation to study hydronium ion and its isotopes, which are the simplest systems for hydrated proton and deuteron. In this simulation, all the rotational and vibrational degrees of freedom are treated fully quantum mechanically, while the potential energies of the respective atomic ...
Quantum chemical calculations of energies, geometrical structure and vibrational wave numbers of 3,4-dimethoxybenzonitrile (DMBN) were carried out by the ab initio Hartree-Fock (HF) and density functional theory (DFT) with complete relaxation in the potential energy surface using 6-311++G(d,p) basis set. The ...
The complete set of 134 isolated-pentagon-rule isomers of C94 has been first investigated by various quantum-chemical approaches. Twenty low-energy cage structures are computed by the ab initio Hartree-Fock self-consistent field method and hybrid density functional theory treatment. All the methods point out a C2 species as the system ...
NIR FT-Raman and FT-IR spectra of the non linear optic (NLO) material, Bis (4-Nitrophenyl) carbonate (BNPC) have been recorded and analyzed. Ab initio quantum chemical computations have been performed at HF/6-31G(d) level to compute the optimized geometry, vibrational wavenumbers, intensities and first ...
Semiempirical (modified neglect of differential overlap) and ab initio (in STO-3G basis set) quantum chemical calculations were carried out on the electronic structure and geometry of alkoxy groups on the surface of zeolites with a high silica content. The net positive charge of the alkyl fragments was found to be ...
In this feature article, we provide a side-by-side introduction for two research fields: quantum chemical calculations of molecular interaction in nucleic acids and RNA structural bioinformatics. Our main aim is to demonstrate that these research areas, while largely separated in contemporary literature, have substantial potential to complement each other ...
A quantum chemical study of the binding of Li+ cation to polyalkyloxides has been carried out. The lithium cation interaction with three polyalkyloxides (polyethylene oxide (PEO), polytrimethylene oxide (PTMO), and polypropylene oxide (PPO)) has been investigated using ab initio molecular orbital theory at the ...
A pair of peptide groups in space, as modeled by formamide dimer, was used to evaluate vibrational coupling between the amide-I modes and the spatial behavior of the coupling using ab initio quantum chemical calculations. It was found that the coupling between two C=O groups, which is electrostatic in nature, is ...
An NMR structure refinement method for the NMR crystallography of zeolites is presented and demonstrated to give an NMR-determined crystal structure for the zeolite Sigma-2 that is in very good agreement with the single-crystal X-ray diffraction structure. The Si coordinates of the zeolite framework were solved from 29Si double-quantum NMR data obtained at a low magnetic field strength (7.0 T) and ...
In this work, the molar enthalpies of formation of the ionic liquids [C2MIM][NO3] and [C4MIM][NO3] were measured by means of combustion calorimetry. The molar enthalpy of fusion of [C2MIM][NO3] was measured using differential scanning calorimetry. Ab initio calculations of the enthalpy of formation in the gaseous phase have been performed for the ionic ...
Raman spectra of binary sodium silicates are calculated by self-consistent field (SCF) molecular orbital ab initio calculation of the quantum chemical method with several poly silicon-oxygen tetrahedral model clusters when both the basis sets of 6-31 G and 6-31 G(d) are applied. The symmetric stretching vibrational ...
The complex formed by isopentane, as a model for the isoleucine residue present in the wild-type thymidylate synthase, with 4-mercaptopyridine as a fragment of the thymidylate synthase inhibitor Thymitaq (AG337) is investigated with ab initio quantum chemical calculations at Hartree-Fock and MP2 levels, using the ...
We study how the Mott metal-insulator transition (MIT) is affected when we have to deal with electrons with different angular momentum quantum numbers. For that purpose we apply ab initio quantum-chemical methods to lithium rings in order to investigate the analog of a MIT. By changing the interatomic distance we analyze the character ...
We investigate a reaction of boron trichloride (BCl3) with iron(III) hydroxide (Fe(OH)3) by ab initio quantum chemical calculation as a simple model for a reaction of iron impurities in BCl3 gas. We also examine a reaction with water. We find that compounds such as Fe(Cl)(OBCl2)2(OHBCl2) and Fe(Cl)2(OBCl2)(OHBCl2) ...
We observed the microwave spectrum of ethyl isovalerate by molecular beam Fourier transform microwave spectroscopy. The rotational and centrifugal distortion constants of the most abundant conformer were determined. Its structure was investigated by comparison of the experimental rotational constants with those obtained by ab initio methods. In a first ...
A fully ab initio scheme based on quantum chemical wavefunction methods is used to investigate the correlated multiorbital electronic structure of a 3d-metal compound, LaCoO3. The strong short-range electron correlations, involving both Co and O orbitals, are treated by multireference techniques. The use of ...
Quantum chemical molecular models are used to interpret the IR spectra of methoxy species formed in methanol adsorption on silica and zeolites. The calculations are carried out by the ab initio SCF MO method with 3-21G basis set, using a scaling procedure to correct the ab ...
Using a diabatic state formalism and pseudospectral numerical methods, we have developed an efficient {ital ab initio} quantum chemical approach to the calculation of electron transfer matrix elements for large molecules. The theory is developed at the Hartree{endash}Fock level and validated by comparison with ...
Vibrational properties of inclusion complexes with cyclodextrins are studied by means of Raman spectroscopy and numerical simulation. In particular, Raman spectra of the nonsteroidal, anti-inflammatory drug indomethacin undergo notable changes in the energy range between 1600 and 1700 cm-1 when inclusion complexes with cyclodextrins are formed. By using both ab ...
To further understand the catalytic role of the protein environment in the enzymatic process, the author has analyzed the reaction mechanism of the Claisen rearrangement of Bacillus subtilis chorismate mutase (BsCM). By introducing a new computational strategy that combines all-electron QM calculations with ab initio QM/MM modelings, it was possible to ...
Comparative analysis of the electronic structure of molybdenum sulfides and their catalytic activity in hydrogenation reactions was performed from the results of Hartree-Fock ab initio quantum-chemical calculations using the STO 3-21G and 6-311G basis sets with geometry optimization. The model reactions of hydrogenation of aromatic and ...
The local structure of sixfold oxygen coordinated silicon (Si[6]) in sodium phosphosilicate glasses has been investigated using MAS NMR spectroscopy and ab initio quantum-chemical techniques. It has been demonstrated that Si[6] is interconnected by six PO4 tetrahedral units by sharing only their corners, forming a nearly regular ...
This paper is aimed at combining quantum-chemical calculations of the frequency spectra of clusters and spectroscopic studies of vibrational spectra of GeS2 glasses, obtained at different conditions, and films, prepared on their base. The optimized geometries and Raman spectra of edge- and corner-sharing, and ethane-like Ge-S clusters have been obtained from ...
A theoretical study of rotational profiles of molecular absorption bands is essential for direct comparison with observations of diffuse interstellar bands. Applications using a Gaussian quantum-chemical approach within density functional theory are presented. Structural and vibrational properties of the polycyclic aromatic hydrocarbon ovalene cation (C32H14+) are obtained. We ...
A theoretical study of rotational profiles of molecular absorption bands is essential for direct comparison with observations of diffuse interstellar bands. Applications using gaussian quantum-chemical approach within DFT are presented. Structural and vibrational properties of the polycyclic aromatic hydrocarbon ovalene cation (C32H14+) are obtained. We discuss the expected ...
We present results of theoretical studies of the photoabsorption band corresponding to the vertical electronic transition S(0)-S(1) between first two singlet states of the model chromophore from the green fluorescent protein (GFP) in its neutral form. Predictions of quantum chemical approaches including ab initio ...
Vibrational spectral analysis aided by ab initio computations at HF/6-31G (d) level of an anti-inflammatory drag, ethenzamide, has been carried out using NIR FT-RAMAN and FT-IR spectra. The present investigation deals with the analysis of structural and bonding features responsible for biological activities, nature of hydrogen bonding, vibrational ...
The electron-correlation effects on the ground-state properties of CeO2 are studied by ab initio quantum-chemical methods. For this purpose the method of increments is applied. It combines Hartree-Fock calculations for periodic systems with correlation calculations requiring only information of the corresponding finite-cluster ...
A recently proposed computational scheme based on local increments has been applied to the calculation of correlation contributions to the cohesive energy of the CaO crystal. Using {ital ab} {ital initio} quantum-chemical methods for evaluating individual increments, we obtain {approximately}80{percent} of the difference between the ...
Comments are presented on a few aspects of computational chemistry, considering its evolution and eventual future developments. We also discuss in some detail two topics: first, a new quantum chemical approach that proposes the combination of Hartree-Fock and Heitler-London approximations at the ab initio and at ...
The ion-molecule reaction of C + H3(+) - CH(+) + H2 has not been studied in the laboratory but is thought to be important in the gas phase synthesis of organic molecules in dense interstellar clouds. This reaction was studied theoretically by performing quantum chemical ab initio calculations on the potential ...
Heroin, morphine and narcotine are very large molecules having 50, 40 and 53 atoms respectively. Moderately high resolution photoacoustic (PA) spectra have been recorded in 9.6 mum and 10.6 mum regions of CO_2 laser. It is very difficult to assign the modes of vibrations for PA bands by comparison with conventional low resolution IR spectra. The ab initio ...
The proton transfer between imidazole and water was studied by quantum chemical calculations in the presence of further ligand water molecules. In particular, we investigated the effect of the position of secondary waters relative to the proton transfer system. It is shown that the energy surface of transfer can be well reproduced when these waters are ...
-1,7-dicarbado- decaborane (metacarborane, C2B10H12), which have important applications as solid.elsevier.com/locate/cplett Chemical Physics Letters 406 (2005) 483�488 #12;decaborane (H2C-CB8H8C-CH2), and 1,12-dimethylene- 1
This paper presents the thermochemical properties of 42 energetic materials commonly used in explosives and/or propellants. The standard enthalpies of formation at 298.15 K and heat capacities and entropies in the temperature range of 300-5000 K have been computed by means of the density functional theory in quantum chemistry along with a protocol developed for these energetic compounds. The ...
The possibility of calculating the molecular structure, vibrational frequencies, and electrooptical parameters of the silane molecule SiH4 and the silicon tetrafluoride molecule SiF4 is analyzed by using the ab initio quantum-chemical method (the MP2 perturbation theory) and the density functional theory (the B3LYP functional) with a ...
This report describes the development and application of ab initio quantum chemical methods that are especially relevant to the study of high-energy density materials species. Two major quantum chemical program systems, MESA and BROOKLYN, have been developed during the ...
Ab initio DFT quantum chemical methods are applied to study intermediates in the catalytic cycle of soluble methane monooxygenase hydroxylase (MMOH), a dinuclear iron-containing enzyme that converts methane and dioxygen selectively to methanol and water. The quantum ...
The structure of dimeric SiO is reexamined by a study of the IR spectra of the matrix-isolated species. Spectra of isotopomers from experiments with {sup 29}Si- and {sup 18}O-enriched samples are discussed with the help of normal-coordinate analysis. The results are in line with data of the geometrical and electronic structure obtained by ab initio SCF ...
A theory of quantum electron wavepacket dynamics that nonadiabatically couples with classical nuclear motions in intense optical fields is studied. The formalism is intended to track the laser-driven electron wavepackets in terms of the linear combination of configuration-state functions generated with ab initio molecular orbitals. Beginning with the total ...
The Fourier transform infrared (FTIR) and FT-Raman spectra of p-cyanobenzoic acid (CBA) have been recorded in the range 4000-400 and 4000-100 cm(-1), respectively. The complete vibrational assignment and analysis of the fundamental modes of the compound were carried out using the observed FTIR and FT-Raman data. The vibrational frequencies determined experimentally were compared with theoretical ...
The authors have performed ab initio quantum mechanical calculations in monomeric clusters modeling the 12 different T sites of zeolite ZSM-5. By comparing the results of calculations that use minimum basis sets with those that employ valence double-[zeta] bases, the authors conclude that minimum basis sets are unreliable for predicting relative ...
Terahertz spectroscopy, which investigates the electromagnetic spectrum of samples between 0.1 and 10 THz, allows not only for exploration of molecular structures but also of molecular dynamics. One difficulty in performing THz spectroscopy is that the data can be noisy and difficult to interpret. Ab initio molecular modelling has recently become more and ...
In this paper we report a theoretical study of the static dipole polarizability of two one-dimensional structures: (a) linear carbon chains Cn (n=2-10) and (b) ladderlike planar boron chains Bn (n=4-14). The polarizabilities of these chains are calculated both at the Hartree-Fock and the correlated levels by applying accurate ab initio ...
A initio quantum chemical methods are seeing increased application in a large variety of real-world problems including biomedical applications ranging from drug design to the understanding of environmental mutagens. The vast majority of these quantum chemical methods are ...
DOE Information Bridge
... Title : Chalcopyrite Magnetic Semiconductors: An Ab-Initio Study of Their Structural, Electronic and Magnetic Properties. ...
... from federally funded research, testing and training ... for Research Development Test and Evaluation ... COMPENDIUM OF AB INITIO CALCULATIONS ...
... Accession Number : ADA219907. Title : An Ab Initio Study of the Geometry and Rotational Barrier of 4- Phenylimidazole. ...
... from federally funded research, testing and training ... and agencies for Research Development Test and Evaluation ... Title : Ab Initio Calculations of the ...
... Title : Ab Initio Calculation of Vibrational Absorption and Circular Dichroism Spectra Using Density Functional Force Fields. ...
The S/sub N/2 reaction between ammonia and formic acid has been studied as a model reaction for peptide bond formation using the semiempirical MNDO and ab initio molecular orbital methods. Two reaction mechanisms have been examined, i.e., a stepwise and a concerted reaction. The stationary points of each reaction including intermediate and transition ...
High level ab initio quantum chemical calculations have been performed on the association of chloroform with ammonia in the gas phase (counterpoise corrected MP2 and coupled-cluster CCSD(T) calculations with 6-311++G(d,p) basis functions). Minimum energy equilibrium structures have been found for CHCl(3)-NH(3) ...
One of the most prominent aims in Computational Chemistry is the modeling of chemical reactions and the prediction of molecular properties. Quantum chemical methods are used for the calculation of molecular structures, spectra, reaction energy profiles and many other interesting quantities. Nowadays, the accuracy of the theoretical calculations can compete ...
A new band system of C2, e 3?g-c 3?u+ was studied by ab initio quantum chemical and experimental methods. The calculations were carried out at the multireference configuration interaction level of theory with Davidson's correction using aug-cc-pV6Z basis set and include core and core-valence correlation as well as ...
The five-membered heterocyclic pyrrole moiety is an important structure in coals and derived tars, and the thermal decomposition reactions of pyrrole are important for production of precursors of the oxides of nitrogen, NO{sub x}, in the combustion of coals. The kinetics of pyrolysis of pyrrole have been investigated theoretically by ab initio ...
Due to recent advances in methods and computers, the accuracy of ab calculations has reached a point
