Using the coreless Hartree-Fock (CHF) pseudopotential approach we have generated pseudopotentials for the atoms K through Zn. Atomic calculations indicate that excitation energies and orbital energies using these pseudopotentials are in excellent agreement with ab initio Hartree-Fock calculations. Optimized small ...
Energy Citations Database
The catalytic properties of cobalt oxide (Co0) were investigated theoretically. The interactions of atomic hydrogen with small clusters of atoms, representing cobalt oxide surfaces, were calculated using the ab initio Unrestricted Hartree-Fock (UHF) metho...
National Technical Information Service (NTIS)
The nature of the bonding between halogen atoms (F, CI and Br) and the Ag (111) surface has been investigated by analyzing ab initio Hartree- Fock wave functions for cluster models of the Ag surface and a halogen atom. Using a variety of criteria, we conc...
An earlier calculation of hydrocarbon radical hyperfine coupling constants, using the spin-projected unrestricted Hartree Fock (PuHF) method is updated. Unprojected uHF calculations are performed for all the systems studied before. (AIP)
The coreless Hartree--Fock effective potential (CHFEP) method is used to replace the core orbitals for atoms of the first three rows of the periodic table. Self-consistent field (SCF) calculations indicate that these effective potentials give Hartree--Fock quality orbitals and orbital energies. Optimized small basis sets for use with these effective ...
We present a time-dependent localized Hartree-Fock density-functional linear response approach for the treatment of photoionization of atomic systems. This approach employs a spin-dependent localized Hartree-Fock exchange potential to calculate electron orbitals and kernel functions, and thus can be used to study the photoionization from atomic excited ...
An ab initio Hartree-Fock approach aimed at directly obtaining the localized orthogonal orbitals (Wannier functions) of a crystalline insulator is described in detail. The method is used to perform all-electron calculations on the ground states of crystalline lithium fluoride and lithium chloride, without the use of any ...
NASA Astrophysics Data System (ADS)
Ground state properties of crystalline ice Ih are investigated by combining periodic Hartree-Fock calculations with a many-body expansion for the electron correlation energy using second-order many-body perturbation theory and coupled-cluster techniques. Very good agreement with experimental data can already be achieved by considering two-body correlation contributions up to ...
PubMed
We have calculated the static polarizabilities of polymers with small linear and medium-size cyclic elementary cells and their constituent molecules. The basis set dependence has been investigated for the average and the longitudinal polarizabilities. The influence on the results of the selected method for the calculation (finite field or coupled perturbed Hartree-Fock) was ...
Ab initio Hartree--Fock calculations were performed on FeAr and FeAr/sup +/ in order to determine the interaction of both neutral and singly-ionized Fe atoms trapped in Ar, and on ArFeCO and FeCOAr in order to ascertain the effect of an Ar matrix on the FeCO molecule. Quadrupole splittings and isomer shifts are computed using ...
Gaussian 76 is a general-purpose computer program for ab initio Hartree-Fock molecular orbital calculations. It can handle basis sets involving s, p and d-type gaussian functions. Certain standard sets (STO-3G, 4-31G, 6-31G*, etc.) are stored internally f...
Techniques for applying ab-initio calculations to the analysis of atomic spectra are investigated, along with the relationship between the semi-empirical and ab-initio forms of Slater-Condon theory. Slater-Condon theory is reviewed with a focus on the ess...
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 ...
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 potential energy surfaces for the doublet pi and doublet sigma states in the collinear F+HH reaction have been calculated with ab initio restricted Hartree-Fock (GRHF) and GRHF-CI (configuration interaction) methods. The doublet pi state in the CI cal...
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...
The results of valence-only self-consistent field calculations on Hgn+ (n = 0, 1, 2) and HgHn+ (n = 0, 1) using nonrelativistic and quasirelativistic energy-adjusted ab initio pseudopotentials for Hg are compared with corresponding all-electron values from nonrelativistic (Hartree-Fock) and relativistic (Dirac-Fock) atomic as well as ...
The linear and nonlinear optical (NLO) properties of the cis and trans isomers of diphenylbenzobisoxazole (PBO) and diphenylbenzobisthiazole (PBT) have been calculated by ab initio time-dependent coupled perturbed Hartree-Fock method using a split-valence basis set. The second-order NLO susceptibilities of the trans isomers are ...
Geometry optimization, energy calculation, and ab initio vibrational analysis were carried out on different conformers of singlet and triplet hydroxyethynylcarbene and 3-hydroxypropadienylidene. They are probable products of the reaction C{sub 3} + H{sub 2}O. Theoretical methods used include restricted Hartree-Fock, unrestricted ...
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 to give phonon ...
Ab initio calculations are reported for the isotropic hyperfine coupling constants arising from contact spin density distributions in hydrocarbon radicals. Representative sigma radicals (vinyl and ethynyl), nonconjugated pi radicals (methyl and ethyl), and conjugated pi radicals (allyl and cyclohexadienyl) are examined in the unrestricted ...
The X-NO2 rotational energy barriers of nitromethane, nitroethylene, nitrobenzene and and a group of nitramines have been computed using a density functional (LDF) procedure, using ab initio Hartree-Fock (HF)-optimized structures of the ground and rotatio...
Simple orbital ideas are used to describe the lowest two states of the peroxyformyl radical, and ab initio Hartree-Fock calculations in these states are reported. It is found that both states may be formed exothermically by association of O2 and HCO in their ground states; however, the excited state may decompose readily to OH and CO2. ...
Interrelations between the local and the global aspects of the stability, continuity, and symmetry properties of variational wave functions are discussed. The spherical limit of one-electron diatomic molecules and the Hartree-Fock approximation of the ground state of the two-electron atom are shown to exhibit the various concepts involved in an ab initio, ...
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 ...
Improved estimates of the nonrelativistic stationary nucleus correlation energies of the ground-state atomic ions with three to ten electrons and {ital Z} up to 20 are derived by combining experimental data and improved {ital ab} {ital initio} calculations. Unlike previous work in this area, we focus on the correlation contribution to individual ionization ...
Hydrogen bonding in DNA bases was investigated using reliable nonempirical ab initio computational methods. Gradient optimization was carried out on 30 DNA base pairs using the Hartree Fock (HF) approximation and the 6-31G basis set. The optimizations wer...
The structures and relative stabilities of furoxan and some of its isomers, e.g. the 1,2-dinitrosoethylenes, have been determined by means of ab initio Hartree-Fock and Moller-Plesset calculations. Geometries were optimized at the HF/3-21G, HF/6-31G* and ...
We report anisotropic collision-induced Raman scattering intensities by the Kr-Xe atomic pair recorded in a gas mixture of Kr and Xe at room temperature. We compare them to quantum-mechanical calculations on the basis of modern incremental polarizability models of either ab initio post-Hartree-Fock or density functional theory methods.
considerably with the equilibrium bond distance, and varies from strongly covalent for the shortest bond to a predominantly ionic interaction for the longest bonds in the MoO 6 octahedron. The degree of covalence structural components, such as the layer orientation, covalent groups, bond lengths and angles, and assess
E-print Network
Accurate calculations for the H-(H20) complex with extended basis sets are reported at the restricted Hartree-Fock (RHF) through the fourth-order Moller-Plesset (MP) perturbation levels of theory. In the equilibrium geometry of the H-(H2O) complex the H- ...
The coreless Hartree--Fock effective potential (CHFEP) method is used to replace the core orbitals for atoms of the first three rows of the periodic table. Self-consistent field (SCF) calculations indicate that these effective potentials give Hartree--Foc...
The effects of the 4f shell of electrons and the relativity of valence electrons are compared. The effect of 4f shell (lanthanide contraction) is estimated from the numerical Hartree-Fock (HF) calculations of pseudo-atoms corresponding to Hf, Re, Au, Hg, ...
We report calculated exciton energies for the cytosine and guanine stacks obtained in the ab initio Hartree-Fock crystal orbital and exciton approximation, which includes the excited electron-hole interaction. This interaction plays an important role in the description of excited electron spectra in the low-energy region. The stacks ...
The authors use simple orbital ideas to describe the lowest two (doublet A" and doublet A') of the peroxyformyl radical and report ab initio Hartree-Fock calculations for these states. It was found that both states may be formed exothermically by association of O2 and HCO in their ground states; however, the excited state may decompose ...
We report anisotropic collision-induced Raman scattering intensities by the Kr-Xe atomic pair recorded in a gas mixture of Kr and Xe at room temperature. We compare them to quantum-mechanical calculations on the basis of modern incremental polarizability models of either ab initio post-Hartree-Fock or density functional theory methods. ...
Accurate binding energies cannot usually be obtained from Hartree-Fock (HF) calculations because the changes in correlation energy are often of the same orders of magnitude as the corresponding changes in the HF energy. The HF binding energies are still o...
We have thoroughly analyzed the electronic structure of stacked DNA Watson-Crick (WC) base pair dimers using ab initio Hartree-Fock and semiempirical Hartree-Fock-configuration-interaction quantum chemistry. We consider all the possible base compositions and sequences at the nucleoside level in vacuo. The results ...
He-atom scattering is a well established and valuable tool for investigating surface structure. The correct interpretation of the experimental data requires an accurate description of the He-surface interaction potential. A quantum-mechanical treatment of the interaction potential is presented using the current dominant methodologies for computing ground state energies ...
Combined ab initio Hartree-Fock quantum mechanical/molecular mechanical (QM/MM) molecular dynamics simulations have been carried out for water at ambient and supercritical conditions. The QM/MM coupling potential is optimized for ambient water by scaling down the original MM charges in the MM potential model. Simulation results show ...
We have studied the mechanical compressibility and band structure of solid nitromethane both in equilibrium and compressed states using Hartree-Fock and density functional theory (DFT) with atom-centered all-electron linear combination of atomic orbitals basis sets. Hartree-Fock calculations with a 6-21G basis set, uncorrected for basis set superposition ...
By means of solid-state linear-dichroic infrared (IR-LD) spectroscopy the stereo-structures of dipeptides methionyl-histidine (Met-His) and histidyl-methionine (His-Met) are predicted, accompanied with a detailed experimental IR-characteristic bands assignment. The experimental results are compared and confirmed with theoretical structural ones, obtained by ab ...
Courses in computational chemistry are increasingly common at the undergraduate level. Excellent user-friendly programs, which make the execution of ab initio calculations quite simple, are available. However, there is a danger that the underlying SCF procedure (usually coupled with contracted Gaussian atomic orbital basis sets) can become a ?black box? ...
NSDL National Science Digital Library
Essential oils that contain large concentrations of germacrene D are typically accompanied by cadinane sesquiterpenoids. The acid-catalyzed cyclization of germacrene D to give cadinane and selinane sesquiterpenes has been computationally investigated using both density functional (B3LYP/6-31G*) and post Hartree-Fock (MP2/6-31G* *) ...
PubMed Central
Gaussian 76 is a general-purpose computer program for ab initio Hartree-Fock molecular orbital calculations. It can handle basis sets involving s, p and d-type gaussian functions. Certain standard sets (STO-3G, 4-31G, 6-31G*, etc.) are stored internally for easy use. Closed shell (RHF) or unrestricted open shell (UHF) wave functions ...
DOE Information Bridge
This study investigates the electronic structure of Group IA cations intercalated into zeolites with the analcime (ANA) framework using ab initio periodic Hartree-Fock theory. The purpose of the study is to gain a better understanding of the role played by electron-donating species in zeolites in general, with specific applications to ...
We report full ab initio Hartree-Fock calculation to compute quantum mechanical interaction energies for ?-trypsin/benzamidine binding complex. In this study, the full quantum mechanical ab initio energy calculation for the entire protein complex with 3238 atoms is made possible by using a ...
A consistent set of ab initio effective core potentials (ECP) has been generated for the main group elements from Na to Bi using the procedure originally developed by Kahn. The ECP's are derived from all-electron numerical Hartree--Fock atomic wave functions and fit to analytical representations for use in molecular ...
Yohimbine hydrochloride (YHCl) is an aphrodisiac and promoted for erectile dysfunction, weight loss and depression. The optimized geometry, total energy, potential energy surface and vibrational wavenumbers of yohimbine hydrochloride have been determined using ab initio, Hartree-Fock (HF) and density functional theory (DFT/B3LYP) ...
The optimized molecular structures, vibrational frequencies, corresponding vibrational assignments, thermodynamic properties, UV-vis spectra and atomic charges of 3-(5-methylthiazol-2-yldiazenyl)-2-phenyl-1H-indole molecule have been investigated using ab initio Hartree-Fock (HF) and density functional theory (B3LYP) methods at 6-31G ...
An ab initio approach to determining the appropriate potential in which to embed a cluster in order to simulate a larger system is proposed. For ionic and covalent systems, simple approximations are presented as obtained by systematic simplifications of the more general theory. It is also seen that for metallic systems such a reduction is not obtained. The ...
We study the role of nonlocality of exchange in a neutral zigzag graphene nanoribbon within the ?-orbital unrestricted Hartree-Fock approximation. Within this theory we find that the magnetic features are further stabilized for both the intraedge and interedge exchange as compared to mean-field theories of zigzag ribbons based on local exchange (such as the Hubbard model or ...
The dispersion coefficients for the van der Waals interactions between the rare gases Ne, Ar, Kr, and Xe and the low-lying states of Li, Na, K, and Rb are estimated using a combination of ab initio and semiempirical methods. The rare-gas oscillator strength distributions for the quadrupole and octupole transitions were derived by using high-quality ...
Oscillator strengths for several lines of astrophysical interest arising from some configurations and some levels radiative lifetimes of Pb IV have been calculated. These values were obtained in intermediate coupling (IC) and using ab initio relativistic Hartree-Fock calculations. We use for the IC calculations the standard method of ...
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 ...
Energy-optimized geometries of 15 isomeric (CH){sub 12} hydrocarbons are presented. Geometries were optimized with ab initio restricted Hartree-Fock calculations with the split-valence 3-21G basis set. Energies were calculated at those geometries with the polarized 6-31G{sup *} basis. Compound 8 is suggested as the most stable isomer ...
Van der Waals interaction potentials of the square planar D{sub 4h} and regular tetrahedral T{sub d} configurations of He{sub 4} were examined at the matrix Hartree-Fock, many-body perturbation theory, coupled-cluster theory, and configuration interaction levels of ab initio theory. Potential energy minima, pairwise and nonpairwise ...
The {l brace}D,H{r brace}{sup +} complex in silicon, with D=P or As, is studied near the {ital ab} {ital initio} Hartree--Fock level. The results show that the transitions between {l brace}D,H{r brace}{sup 0} and {l brace}D,H{r brace}{sup +} involve a drastic change in the equilibrium geometry and electronic structure of the complex. ...
The total energy of ZnS as a function of unit-cell volume has been calculated for the zinc-blende and rocksalt structures by the first-principles Hartree-Fock linear-combination-of-atomic-orbitals method. The calculated structural properties of both phases and the transition pressure between them agree very well with experiment. The band structure of the high-pressure phase is ...
The (/sup 19/F) magnetic hyperfine interaction tensor in F/sub 2//sup -/ is calculated from the spin density distribution obtained through a variational configuration mixing procedure. All spin-adapted configurations arising from single and double replacements in the unrestricted Hartree-Fock determinant within a polarized triple-zeta basis are considered. The estimated ...
The band structure of tetraza porphin nickel(II) is investigated using semiempirical crystal orbital (CO) calculations for transition metal systems that are based on the INDO approximation. The model Hamiltonian is designed to reproduce the results of ab initio calculations of double-zeta quality at low computational expense. Results show that the various ...
The scattering length for electron-argon scattering is calculated very accurately by an [ital ab] [ital initio] method with wave functions computed exactly at zero energy. The multiconfiguration Hartree-Fock method, which takes into account the effects of target polarization and electron correlation through the ...
In order to apply ab initio wave-function-based correlation methods to metals, it is desirable to split the calculation into a mean-field part and a correlation part. Whereas the mean-field part (here Hartree-Fock) is performed in the extended periodic system, it is necessary to use for the correlation part local wave-function-based ...
The results of ab initio Hartree--Fock calculations of the orientationally averaged, elastic electron scattering cross section of C/sub 2/H/sub 4/ with six different basis sets are reported. The averaging and Fourier transform were calculated by the approach of Kohl, Pulay, and Fink. Six different basis sets, ranging from 6-31G to ...
Molecular orbital theory is used in the context of ab initio Hartree-Fock calculations to study the origin of quantum confinement effects in layered Pb{sub 7}I{sub 14} clusters. As the cluster geometry is energy optimized in several steps, the structure distends into two quasi-hemispherical iodine layers sandwiching a hexagonal lead ...
We present and discuss the results of the large scale Hartree-Fock calculations of Nb impurities substituting for Ti ions in SrTiO3 using ab initio computer code CRYSTAL and several supercells containing up to 135 atoms. The local structure optimisation, the electronic charge redistribution, chemical bond covalence and the ...
Energy gaps between the highest-occupied molecular orbital and lowest-unoccupied molecular orbital ({Delta}E{sub HOMO-LUMO}) for a suite of common polycyclic aromatic hydrocarbons (PAHs) in the gas-phase were calculated with three different molecular modeling methods: semiempirical, ab initio Hartree-Fock, and density functional ...
The vibrational frequencies and molecular geometry of (R)- and (rac)-4-phenly-1,3-oxazolidin-2-one (4-POO) in the ground state have been calculated using the Hartree-Fock and density functional method (B3LYP) with 6-31G(d) basis set. The optimized geometric bond lengths are described better by HF while bond angles are reproduced more accurately by DFT (B3LYP). Comparison of the observed ...
The geometrical structure and vibrational frequencies of the ground triplet electronic state of HCCN have been examined at a wide range of levels of ab initio electronic structure theory. The potential energy surface of HCC bending is very flat for HCCN owing to a competition between linear allene HC=C=N and bent carbene HCC=N valence structures. Evidence ...
The geometrical structure and vibrational frequencies of the ground triplet electronic state of HCCN have been examined at a wide range of levels of ab initio electronic structure theory. The potential energy surface of HCC bending is very flat for HCCN owing to a competition between linear allene OHC=C=N and bent carbene HCC=N valence structures. Evidence ...
The pure quantum mechanics method, called Local Self-Consistent Field (LSCF), that allows to optimize a wave function within the constraint that some predefined spinorbitals are kept frozen, is discussed. These spinorbitals can be of any shape, and their occupation numbers can be 0 or 1. Any post-Hartree-Fock method, based on the restricted or unrestricted ...
Relativistic pseudopotentials (PPs) of the energy-consistent variety have been generated for the post-d group 13-15 elements, by adjustment to multiconfiguration Dirac-Hartree-Fock data based on the Dirac-Coulomb-Breit Hamiltonian. The outer-core (n-1)spd shells are explicitly treated together with the nsp valence shell, with these PPs, and the implications of the small-core ...
Ab initio values of the absolute shielding constants of phosphorus and hydrogen in PH(3) were determined, and their accuracy is discussed. In particular, we analyzed the relativistic corrections to nuclear magnetic resonance (NMR) shielding constants, comparing the constants computed using the four-component Dirac-Hartree-Fock ...
Symmetry methods employed in the ab initio polyatomic program HONDO are extended to the analytic computation of the energy Hessian matrix. A ''skeleton'' Hessian matrix is calculated from the unique blocks of electron repulsion integrals. The true Hessian matrix is generated by projecting the symmetric component out of ...
The ability to perform ab initio electronic structure calculations that scales linearly with the system size is one of the central aims in theoretical chemistry. In this study, the implementation of the divide-and-conquer (DC) algorithm, an algorithm with the potential to aid the achievement of true linear scaling within Hartree-Fock ...
Hybrid density functionals, which replace a fraction of density functional theory exchange with exact Hartree-Fock exchange has been used to study the electronic, geometric, and magnetic properties of ? -- Pu. Different fractions of Hartree-Fock exchange have been used and the computations have been performed using the all-electron full-potential linearized augmented plane ...
The effects of the 4f shell of electrons and the relativity of valence electrons are compared. The effect of 4f shell (lanthanide contraction) is estimated from the numerical Hartree-Fock (HF) calculations of pseudo-atoms corresponding to Hf, Re, Au, Hg, Tl, Pb and Bi without 4f electrons and with atomic numbers reduced by 14. The relativistic effect estimated from the ...
Molecular geometry, vibrational wavenumbers and gauge including atomic orbital (GIAO) 13C NMR and 1H NMR chemical shift values of 1,3-phenylenediacetic acid (C10H10O4), in the ground state have been calculated by using ab initio Hartree-Fock (HF) and density functional theory (DFT/B3LYP) methods with 6-311++G(d,p) basis set for the ...
The total energy of ZnO as a function of unit cell volume has been calculated for the zinc-blende, wurtzite, and rocksalt structures by the [ital ab] [ital initio] all-electron periodic Hartree-Fock linear-combination-of-atomic-orbitals method using a large Gaussian basis set that was variationally optimized for the solid state. ...
The FTIR and FT Raman vibrational spectra of o-tolunitrile have been recorded using Perkin-Elmer 180 Spectrometer in the range 3100-100 cm(-1). A detailed vibrational spectral analysis has been carried out and assignments of the observed fundamental bands have been proposed on the basis of peak positions and relative intensities. The optimized geometrical parameters, force constants, true ...
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 computed values of ...
The direct application of ab-initio methods (Hartree-Fock or density functional theory) to study complete biomolecules has been impossible due to the huge computational cost of fully quantum mechanical calculations. As an initial step towards overcoming this problem, we implemented an ab-initio-based method to predict geometric ...
The multiconfiguration Hartree-Fock method has been applied to study low-energy scattering of electrons from argon atoms. The polarization of the argon atoms due to the scattered electron and the electron-correlation effects that are very important in the calculation are taken into account in the {ital ab} {ital nitio} way more accurately through the ...
Three novel theoretical approaches are proposed as a means by which the atomic many body effects can be taken into account. A V{sup N-1}/Hartree-Fock starting potential is chosen for the basis set. This basis set is then used to determine electric dipole PNC transition amplitudes in three distinct calculations: (1) a configuration interaction (CI) calculation where the atomic ...
In two recent articles a method has been described for calculating the total energy of large molecules. The method is called the kernel energy method (KEM) and requires knowledge of the crystal structure of interest. Calculations are simplified by adopting the approximation that a full molecule could be represented by smaller kernels of atoms. The KEM was illustrated with peptides ranging in size ...
Calculations of the electronic and vibrational second hyperpolarizabilities of various quadrupolar ?-conjugated molecules performed at the ab initio Hartree-Fock level of approximation show that the vibrational contribution is large for most nonlinear optical phenomena. As for unsubstituted ?-conjugated compounds, the Raman term which ...
{ital Ab} {ital initio} Hartree-Fock effective-core-potential calculations have been performed to determine the binding-energy trends of the transition-metal--argon diatomic positive ions. The interaction in these systems is mainly governed by charge-induced dipole forces, with the metal carrying the charge. It is found that all the ...
This work is an ab initio study of the 2p34S3/2o, and 2D3/2,5/2o states of C- and 2p23P0,1,2, 1D2, and 1S0 states of neutral carbon. We use the multiconfiguration Hartree-Fock approach, focusing on the accuracy of the wave function itself. We obtain all C- detachment thresholds, including correlation effects to about 0.5%. Isotope ...
The molecular geometry and electronic structure of formylcobalt tricarbonyl, (eta-ethylene)hydridocobalt tricarbonyl, and ethylcobalt tricarbonyl were investigated by means of ab initio Hartree-Fock and configuration-interaction calculations in a Gaussian basis set. Several stable conformations of each of the complexes were found, and ...
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 ...
The thermodynamic and quantum-chemical aspects of hydrogenation of coal organic matter in the presence of iron and nickel compounds as catalysts were considered. A thermodynamic analysis of the formation reaction of catalytically active catalyst entities under hydrogenation conditions was performed. The electronic structure of FeO, FeS, FeS{sub 2}, NiO, and NiS with the minimal number of iron and ...
The authors examined the effect of solvation on the conformational preferences (e.g., {alpha}-helix versus {beta}-sheet) of tripeptides using ab initio quantum mechanics (Hartree-Fock 6-31G**) with solvation in the Poisson-Boltzmann continuum solvent approximation. It was found that aqueous solvent preferentially stabilizes the ...
Experimental total cross sections for direct electron-impact ionization of the valence electron of several Li-like ions are seen to follow a new ab initio scaling law which is inspired by a Coulomb-Born model and the frozen-core Hartree-Fock approximation. The predictive character of this scaling law should be very useful to ...
The infinite-order regular approximation (IORA) and IORA with modified metric (IORAmm) is used to develop an algorithm for calculating relativistically corrected isotropic hyperfine structure (HFS) constants. The new method is applied to the calculation of alkali atoms Li-Fr, coinage metal atoms Cu, Ag, and Au, the Hg+ radical ion, and the mercury containing radicals HgH, HgCH3, HgCN, and HgF. By ...
Redox potentials for two stepwise anodic oxidations of a series of carbamates in methanolic solution have been calculated using ab initio and DFT quantum mechanical methods. Hartree-Fock method and Density Functional Theory at the B3LYP level, together with 6-31G(d), 6-31G(d,p) and 6-311++G(2df,2p) basis sets have been used for the ...
We have designed and analyzed a molecular model of a generic triple helix DNA base structure - the cytosine-guanine-cytosine (CGC+) assembly. The complex has been investigated for the ability of a concerted proton transfer from cytosine to guanine. Ab initio calculations have been preformed using Unrestricted Hartree-Fock (UHF) method ...
The vibrational frequencies of three substituted 4-thioflavones in the ground state have been calculated using the Hartree-Fock and density functional method (B3LYP) with 6-31G* and 6-31+G** basis sets. The structural analysis shows that there exists H-bonding in the selected compounds and the hydrogen bond lengths increase with the augment of the conjugate parameters of the substituent group on ...
The molecular geometry, the normal mode frequencies and corresponding vibrational assignment of melaminium phthalate (C3H7N6+.C8H5O4(-)) in the ground state were performed by HF and B3LYP levels of theory using the 6-31G(d) basis set. The optimized bond length numbers with bond angles are in good agreement with the X-ray data. The vibrational spectra of melaminium phthalate which is calculated by ...
In order to understand the physics of radiation-induced proton density decay in thin SiO{sub 2} films, the authors performed ab initio Hartree-Fock calculations of the potential energy curves for the interaction between model oxide clusters and H in two charge states. The calculated results led to two separate proposed mechanisms for ...
The structures, energies, and charges of uranyl cation complexes with water molecules, nitrate ion, and carbonate ions were determined using Hartree-Fock, second-order Moeller-Plesset (MP2) perturbation theory, and density functional theory (DFT) ab initio quantum chemical methods. Reasonable agreement with experimentally determined ...
Water at elevated temperatures and pressures in attracting interest as a reaction medium and an environmentally benign alternative to organic solvents. The fugacity coefficients of the hydroperoxyl radical in supercritical water are estimated through molecular simulations. A potential function for the radical is first derived from ab initio self-consistent ...
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 Hamiltonians ...
The optimized structure and electronic properties of neutral and singly charged magnesium clusters have been investigated using ab initio theoretical methods based on density-functional theory and systematic post-Hartree-Fock many-body perturbation theory accounting for all electrons in the system. We have systematically calculated the ...
The periodic ab initio Hartree-Fock linear combination of atomic orbitals program CRYSTAL has been used to investigate the electronic structure of the wurtzite-type phase of SiC. Binding energy, lattice parameters (a,c), and the internal coordinate have been optimized. Inclusion of polarization functions, which has been shown to be ...
We report quantum mechanical calculations of the differential, momentum transfer, and integral cross sections for electron-CH/sub 4/ elastic scattering in the energy range 20--500 eV. The e/sup -/-CH/sub 4/ interaction term is composed of three local spherical potentials, namely, the static, the exchange, and the polarization. The static potential is generated without additional approximations ...
We report on large ab initio calculation for the 4s^2- 4s4p transitions in the Zinc-like sequence, using the multi-configuration Dirac-Hartree-Fock method. Results for fine-structure energy levels, the wavelengths, transition rates and lifetimes between Z = 70 (Yb) and Z= 92 (U) are presented and compared with other theories and ...
Skyrme-like energy density functionals are built upon new ab initio calculations of nuclear matter which reproduce the empirical saturation properties. These calculations are performed in the framework of the Brueckner-Hartree-Fock approximation with consistent two- and three-body forces. The Skyrme parametrizations are obtained from a simultaneous fit of ...
The authors have performed high-level ab initio calculations using both Hartree-Fock (HF) and Moller-Plesset perturbation theory (MP2) to study the geometry and energetics of the adsorption complex involving H{sub 2}O and the Bronsted acid site in the zeolite H-ZSM-5. In these calculations, which use aluminosilicate cluster models for ...
We perform ab initio calculations of isotope shifts for isotopes of cesium (from A=123 to A=137) and francium (from A=207 to A=228). These calculations start from the relativistic Hartree-Fock method and make use of several techniques to include correlations. The field (volume) isotope shift is calculated by means of an all-order ...
We perform ab initio calculations of isotope shifts for isotopes of cesium (from A=123 to A=137 ) and francium (from A=207 to A=228 ). These calculations start from the relativistic Hartree-Fock method and make use of several techniques to include correlations. The field (volume) isotope shift is calculated by means of an ...
This chapter discusses recent progress in the investigation and use of 13C, 15N, and 19F nuclear magnetic resonance (NMR) chemical shifts and chemical shift tensors in proteins and model systems primarily using quantum chemical (ab initio Hartree-Fock and density functional theory) techniques. Correlations between spectra and structure ...
A description for the program-user is provided to enable the execution of a suite of atomic-structure programs translated from the Cowan-CDC-Los Alamos version and now operational under CMS on the Rutherford and Appleton Laboratory central mainframe computer. Wavelengths, atomic energy levels and oscillator strengths are computed 'ab ...
We present highly correlated multi-configuration Hartree�Fock (MCHF) calculations of the hyperfine structure of the 3p5 2PoJ levels of 33S? and 35, 37Cl. We obtain good agreement with observation. The hyperfine structure of the neutral sulphur 33S 3p4 3PJ lowest multiplet that has never been measured to the knowledge of the authors is also estimated theoretically. We discuss ...
Unrestricted Hartree-Fock molecular orbital calculations have been conducted on the molecules LiOH/sub 2/, Li(OH/sub 2/)/sub 2/, and LiNH/sub 3/, using 6-31G** and larger basis sets. Equilibrium have been determined, and electron spin densities have been calculated which are in good agreement with experimental data. Harmonic vibrational frequencies have been predicted for the ...
Ab initio Hartree-Fock and second-order Moeller-Plesset theory calculations have been performed to investigate the stability of triply-coordinated O{sup +} centers in the Si-O-Si network of amorphous SiO{sub 2}. The calculations reveal that the H{sup +} ion binds with a bridging O center to form a very stable (D{sub e} > 6 eV) ...
We have performed fully periodic ab initio post-Hartree-Fock calculations on three low-temperature molecular phases of solid nitrogen, namely ?, ?, and ?. The aim is to characterize the pressure-induced transitions among these phases, which are prototypical molecular crystals, through a periodic local-MP2 method, implemented in the ...
We have performed fully periodic ab initio post-Hartree-Fock calculations on three low-temperature molecular phases of solid nitrogen, namely ?, ?, and V. The aim is to characterize the pressure-induced transitions among these phases, which are prototypical molecular crystals, through a periodic local-MP2 method, implemented in the ...
We propose a new long-range correction scheme that combines generalized-gradient-approximation (GGA) exchange functionals in density-functional theory (DFT) with the ab initio Hartree-Fock exchange integral by using the standard error function. To develop this scheme, we suggest a new technique that constructs an approximate ...
The procedures developed in this paper have been employed to calculate theoretical free energies of formation of ion-water clusters for comparison with experiment. Gibbs free energies were calculated for the gas phase reaction, ion(H2O)N-1+H2O(vapor)=ion(H2O)N, for the Li+, Na+, K+, Cl-, and F- ions and for N=1-6. The standard state for all calculations was taken as 298 �K and 1 atm. The Monte ...
The title terpene, C30H46O3, is a 28,13?-lactone of oleanolic acid prepared with bis�muth trifluoro�methane�sulfonate (OTf), Bi(OTf)3�xH2O. All rings are trans-fused. The X-ray study shows the inversion of the orientation of 18-H in the lactonization reaction. A quantum ...
Unscreened Hartree-Fock approximation (HFA) calculations for metallic Fe, Co, Ni, and Cu are presented, by using a quantum-chemical approach. To the best of our knowledge these are the first HFA results to have been done for crystalline 3d transition metals. Our approach uses a linearized muffin-tin orbital calculation to determine Bloch functions for the Hartree one-particle ...
The FT-IR and FT-Raman spectra of 3-Bromo phenol (3-BP) molecule have been recorded using Bruker IFS 66V spectrometer in the range of 4000-100 cm(-1). The molecular geometry and vibrational frequencies in the ground state are calculated by using the ab initio Hartree-fock (HF) and DFT (B3LYP) methods with 6-31G (d, p) and 6-311G (d, p) ...
Methodology is discussed for mixed ab initio quantum mechanics/molecular mechanics modeling of systems where the quantum mechanics (QM) and molecular mechanics (MM) regions are within the same molecule. The ab initio QM calculations are at the restricted Hartree-Fock level using the ...
The molecular vibrations of xanthine were investigated in polycrystalline sample, at room temperature by Fourier transform infrared (FTIR) and FT-Raman spectroscopies. The spectra of the molecule have been recorded in the regions 4000-50 cm(-1) and 3500-100 cm(-1), respectively. Theoretical information on the optimized geometry, harmonic vibrational frequencies, infrared and Raman intensities were ...
The explicit polarization (X-Pol) method has been examined using ab initio molecular orbital theory and density functional theory. The X-Pol potential was designed to provide a novel theoretical framework for developing next-generation force fields for biomolecular simulations. Importantly, the X-Pol potential is a general method, which can be employed ...
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 quantum-chemical ...
An improved interatomic potential for tetrahedral carbon is presented. This potential is of the Stillinger-Weber (SW) type and has been determined from calculations performed on a select group of small hydrocarbon molecules, chosen for their similarities to the tetrahedral lattice of bulk diamond. Counterpoise corrected Hartree-Fock (HF) and second-order M�ller-Plesset ...
We present ab-initio CCSD calculations of the 3-5 He ground states. We perform these calcula- tions using a mixed basis of oscillator and complex Woods-Saxon states for chosen partial waves. From this starting point, we build a spherical Gamow-Hartree-Fock basis from a renormalized in- teraction of the low-momentum type generated from the N3 LO two-body ...
We present a computational study of hydrostatic compression effects on the pentaerythritol tetranitrate (PETN) energetic material up to 22.7 GPa by means of the ab initio all-electron periodic Hartree-Fock quantum mechanical method with the STO-3G Gaussian basis set. We fitted the calculated volume-energy relation to the energy SJEOS ...
Since the seminal contribution of Roothaan, quantum chemistry methods are traditionally expressed using finite basis sets comprised of smooth and continuous functions (atom-centered Gaussians) to describe the electronic degrees of freedom. Although this approach proved quite powerful, it is not well suited for large basis sets because of linear dependence problems and ill conditioning of the ...
We present an interpretation of the intermolecular transfer integral that is independent from the origin of the energy scale allowing convergence studies of this important parameter of organic molecular materials. We present extensive numerical studies by using an ethylene pi dimer to investigate the dependence of transfer integrals on the level of theory and intermolecular packing. Transfer ...
We investigate theoretically the charge accumulated Q in a three-terminal molecular device in the presence of an external electric field. Our approach is based on ab initio Hartree-Fock and density functional theory methodology contained in Gaussian package. Our main finding is a negative differential resistance (NDR) in the charge Q ...
Time-reversible ab initio molecular dynamics based on a lossless multichannel decomposition for the integration of the electronic degrees of freedom [Phys. Rev. Lett. 97, 123001 (2006)] is explored. The authors present a lossless time-reversible density matrix molecular dynamics scheme. This approach often allows for stable ...
Based on {ital ab initio} quantum-chemical methods, accurate calculations on small boron clusters B{sub n} (n=2{endash}14) were carried out to determine their electronic and geometric structures. The geometry optimization with a linear search of local minima on the potential-energy surface was performed using analytical gradients in the framework of the ...
Phenothiazine and its derivatives have been investigated because of their interesting pharmacological activity and their potential use in solar energy applications. Raman spectra of phenothiazine and its radical cation were obtained. Hartree-Fock (HF) and density functional theory (DFT) ab initio calculations were performed to find ...
The FT-IR and FT-Raman vibrational spectra of 1,3-dichlorobenzene (1,3-DCB) have been recorded using Bruker IFS 66V Spectrometer in the range 4000-100cm(-1). A detailed vibrational spectral analysis has been carried out and assignments of the observed fundamental bands have been proposed on the basis of peak positions and relative intensities. The optimized molecular geometry, vibrational ...
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 chemical techniques can be used to construct new ab initio Hamiltonians ...
The isomer shift for the 23.87 keV M1 resonant transition in the 119Sn nucleus is calibrated with the help of ab initio calculations. The calibration constant ?(119Sn) obtained from Hartree-Fock (HF) calculations (?HF(119Sn)=(0.081+/-0.002)a0-3 mm/s) and from second-order M�ller-Plesset (MP2) calculations ...
A simple but accurate and computationally efficient method for routine ab initio calculations of molecular Rydberg states is described. The method, which can be applied to Rydberg states associated with a nondegenerate ion core, consists in the self-consistent solution of an effective one-electron problem. First, the restricted ...
Isotope fractionation in the U(III)-U(IV) reaction system was investigated by a series of atomic relativistic ab initio calculations using the multiconfigurational Dirac-Coulomb Hartree-Fock method. To evaluate the nuclear volume effect on the fractionation, the Fermi statistical distribution function was adopted for nuclear charge ...
The ab initio structure of disiloxane (H{sub 3}Si-O-SiH{sub 3}) is studied with a series of basis sets of increasing quality, including extended basis sets and explicit electron correlation at the single-reference single-and double-excitation configuration interaction (SDCI) level. The calculated molecular geometry and barrier to linearization of the ...
In this article, as a first step to develop an efficient approximation for predicting the molecular electronic excited state properties at ab initio level, we propose local excitation approximation (LEA). In the LEA scheme, the only local electron excitations within selected substructure (Chromophore) are treated to calculate the targeted excited state ...
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 nuclear quantum effects have ...
Lithium ceramics are one class of materials being considered as tritium breeders for fusion technology,and hydrogen is known to enhance the release of tritium from lithium ceramic materials. Dissociative hydrogen chemisorption on the Li{sub 2}O surfaces of the (100), (110), and (111) planes has been investigated with ab initio ...
The FT-IR and FT-Raman vibrational spectra of alpha-chlorotoluene have been recorded using Perkin-Elmer 180 spectrometer in the range 3600-10 cm(-1) in the solid phase. A detailed vibrational spectral analysis has been carried out and assignments of the observed fundamental bands have been proposed on the basis of peak positions and relative intensities. The optimized molecular geometry, ...
A number of proteins can assemble into chiral structures that display strong nonlinear optical activity. For instance, proteins such as myosin and collagen exhibit intense second harmonic generation (SHG). A large number of experimental studies on the SHG of proteins have been conducted; however few predictive models have been proposed that reliably relate the macroscopic SHG properties to the ...
The ground state of odd-N polyynic oligomers CNH2 features kink solitons in carbon-carbon bond-length alternation (BLA) patterns. We perform a systematic first-principles computational study of neutral and singly charged kinks in long oligomers addressing relationships between BLA patterns, electron energy gaps, and accompanying distributions of spin and charge densities, both in vacuum and in the ...
We apply ab initio quantum-chemical methods to calculate correlation effects on cohesive properties of Mg, thereby extending the method of increments to metallic systems. Metals require special treatment because of two distinct features. Since the conduction bands are only partially filled, we cannot construct well localized orbitals from them. ...
In this work, the experimental and theoretical vibrational spectra of 1-bromonaphthalene (1-BN) were studied. FTIR and FT Raman spectra were recorded in the region 4000-400cm(-1) and 3500-50cm(-1), respectively. The structural and spectroscopic data of the molecule in the ground state were calculated by using ab initio Hartree-Fock and ...
The bottleneck in conventional ab initio Hartree -Fock calculations is the storage of the electron repulsion integrals because their number increases with the fourth power of the number of basis functions. This problem can be solved by a combination of the multiplicative integral approximation (MIA) and the direct ...
The ab initio determination of the leading long-range term of pairwise additive dispersive interactions, based on the independent analysis of the response properties of the interacting objects, is here considered in the case where these are part of a periodic system. The interaction of a nitrogen molecule with a thin film of hexagonal BN has been chosen as ...
This work is devoted to the elucidation of the applicability of the jellium model to the description of alkali cluster properties. We compare the jellium model results with those derived within ab initio theoretical approaches and with experiments. On the basis of Hartree-Fock and local-density approximations we have calculated the binding energies per ...
Structural and dynamical properties of Ge (II) in aqueous solution have been investigated using the novel ab initio quantum mechanical charge field (QMCF) molecular dynamics (MD) formalism. The first and second hydration shells were treated by ab initio quantum mechanics at restricted ...
The FTIR and FT Raman vibrational spectra of 1,5-methylnaphthalene (1,5-MN) have been recorded using Brunker IFS 66 V Spectrometer in the range 3600-10 cm(-1) in the solid phase. A detailed vibrational spectral analysis has been carried out and assignments of the observed fundamental bands have been proposed on the basis of peak positions and relative intensities. The Optimized molecular geometry, ...
On-the-fly, ab initio classical molecular dynamics are demonstrated with an underlying dual basis set potential energy surface. Dual-basis self-consistent field (Hartree-Fock and density functional theory) and resolution-of-the-identity second-order M�ller-Plesset perturbation theory (RI-MP2) dynamics are tested for small systems, ...
High-level ab initio molecular orbital calculations have been carried out on a series of C{sub 6}H{sub 6}{sup 2+} isomers. Optimized geometrical structures have been obtained, and characterized via normal mode and frequency analysis, at the single-determinant Hartree-Fock level with a basis set of split valence plus polarization ...
Ab initio calculations of the isotropic hyperfine coupling constants in the electronic ground states of some diatomic hydride radicals and their radical cations are reported using highly correlated wave functions. An augmented coupled-cluster doubles procedure, including an approximate account of the effects of the inclusion of amplitudes due to single and ...
We describe an ab initio approach to compute the optical absorption spectra of molecules and solids, which is suitable for the study of large systems and gives access to spectra within a wide energy range. In this approach, the quantum Liouville equation is solved iteratively within first order perturbation theory, with a Hamiltonian containing a static ...
The effects of applied electric fields on the magnetic parameters of a nitroxide spin label have been calculated using an intermediate level of Rayleigh-Schr�dinger perturbation theory based on unrestricted Hartree-Fock ab initio calculations. The theory is tested for selected simple model organic radicals and gives electronic ...
... Title : THE PROJECTED HARTREE - FOCK METHOD, AN EXTENSION OF THE INDEPENDENT-PARTICLE SCHEME. ...
DTIC Science & Technology
Conventional density functional theory (DFT) fails for materials with strongly correlated electrons, such as late transition metal oxides. Large errors in the intra-atomic Coulomb and exchange interactions are the source of this failure. The DFT+U method has provided a means, through empirical parameters, to correct these errors. Here, we present a systematic ab ...
Ab initio calculations of the optical activity in chiral complexes of Co(III) were performed. The complex ions studied were tris(ethylenediamine)cobalt(III), tris(1,3 -diaminopropane)cobalt(III), tris(oxalato)cobaltate(III) and hexaamminecobalt(III). The Restricted Hartree-Fock/Random Phase Approximation was used for the calculation of ...
Ab initio quantum chemical studies of various adsorbate-surface interactions are presented. 1. Aluminum adsorption on the basal plane of graphite is studied using the cluster model approach. One layer clusters find the Al prefers to adsorb at the center of the carbon rings. A two layer cluster determines the most stable Al adsorption site to be above the ...
The title hydrated tetrol, C19H32O4�3H2O, was synthesized by stereoselective reduction of the compound 3?,5?,6?-trihy�droxy�androstan-17-one. All rings are fused trans. The organic mol�ecules are connected head-to-tail along the c axis via O�H?O hydrogen bonds. Layers of water mol�ecules in the ...
The title hydrated tetrol, C(19)H(32)O(4)�3H(2)O, was synthesized by stereoselective reduction of the compound 3?,5?,6?-trihy-droxy-androstan-17-one. All rings are fused trans. The organic mol-ecules are connected head-to-tail along the c axis via O-H?O hydrogen bonds. Layers of water mol-ecules in the ab plane inter-connect these chains. A quantum chemical ...
The simplest variational method for treating electronic excited states, configuration interaction with single excitations (CIS), has been interfaced with the effective fragment potential (EFP) method to provide an effective and computationally efficient approach for studying the qualitative effects of solvents on the electronic spectra of molecules. Three different approaches for interfacing a ...
Hartree--Fock cluster calculations have been carried out for the ground 3d and excited 3dZ4s configurations of the Cu ion in a NaCl host. Special emphasis has been given to providing an accurate representation of the Coulomb potential due to the remainder of the lattice. Configuration coordinate curves were determined for the symmetric displacement of the nearest-neighbor Cl ...
The static polarizability and second hyperpolarizability of increasingly large polydiacetylene and polybutatriene (PBT) chains have been evaluated using the optimized effective potential for exact exchange (OEP-EXX) method developed by Yang and Wu [Phys. Rev. Lett. 89, 143002 (2002)], where the unknown part of the effective potential is expressed as a linear combination of Gaussian functions. ...
A composite coupled cluster methodology is used with systematic sequences of correlation consistent basis sets to accurately determine the structure, vibrational frequencies, and isotopic shifts for trans-HNNO ((2)A'), cis-HNNO ((2)A'), and ONHN ((2)A'). Anharmonic corrections to the vibrational frequencies and rotational constants are obtained using density functional theory. With basis sets ...
A method for calculating the EPR g-tensor based on coupled perturbed Hartree-Fock (HF) and density functional theory (DFT) is presented. The one-electron molecular orbitals of a spin- unrestricted Slater determinant are calculated up to first order in the applied magnetic field. The g-tensor is evaluated as a mixed second derivative property with respect to the applied field ...
A composite coupled cluster methodology is used with systematic sequences of correlation consistent basis sets to accurately determine the structure, vibrational frequencies, and isotopic shifts for trans-HNNO (2A'), cis-HNNO (2A'), and ONHN (2A'). Anharmonic corrections to the vibrational frequencies and rotational constants are obtained using density functional theory. With basis sets larger ...
The fragment molecular orbital method (FMO) has been used with a large number of wave functions for single-point calculations, and its high accuracy in comparison to ab initio methods has been well established. We have developed the analytic derivative of the electrostatic interaction between far separated fragments and performed a number of restricted ...
We describe a complete set of algorithms for ab initio molecular simulations based on numerically tabulated atom-centered orbitals (NAOs) to capture a wide range of molecular and materials properties from quantum-mechanical first principles. The full algorithmic framework described here is embodied in the Fritz Haber Institute "ab ...
We present refinements of the SIBFA molecular mechanics procedure to represent the intermolecular interaction energies of Zn(II). The two first-order contributions, electrostatic (E(MTP)), and short-range repulsion (E(rep)), are refined following the recent developments due to Piquemal et al. (Piquemal et al. J Phys Chem A 2003, 107, 9800; and Piquemal et al., submitted). Thus, E(MTP) is augmented ...
We present an ab initio (quasirelativistic) two-component approach to the computation of molecular parity-violating effects which is based on the zeroth-order regular approximation (ZORA). As a first application, we compute the parity-violating energy differences between various P and M conformations of C{sub 2}-symmetric molecules belonging to the series ...
Charge exchange collisions at 105 keV between Ar7+ ions and lithium atoms have been studied by photon spectroscopy in the 2000-6000 � wavelength range. A large number of new lines in Ar VII have been identified with the help of ab initio pseudo-relativistic Hartree-Fock calculations taking into account electrostatic interactions ...
The pressure-induced phase transition in CdS was investigated using picosecond time-resolved electronic spectroscopy in plate impact shock wave experiments. Real-time changes in the electronic spectra were observed, with 100 ps time resolution, in single crystals of CdS shocked along the c and a axes to peak stresses between 35 and 90 kbar (above the phase transition stress of approximately 30 ...
According to recent works, the self-trapped excitons (STE) in alkali halides are grouped in three different types. In some (e.g. RbI), a population transfer is observed among coexisting types as temperature is raised. In others (NaBr and NaI) extra type emission bands have been observed under dilational strain. We studied the adiabatic potential energy surface (APES) of the STE under the effect of ...
A relativistic pseudopotentional (RPP) for use in ab initio molecular electronic structure calculations is derived in the context of the relativistic effective core potential (REP) method of Lee et al. The resulting atom-specific RPP has salient features of the REP imbedded within it while retaining the form of a functional that is dynamically defined at ...
Quantum chemistry calculations have been performed using Gaussian03 program to compute optimized geometry, harmonic vibrational frequency along with intensities in IR and Raman spectra and atomic charges at RHF/6-31+G*, B3LYP/6-31+G* and B3LYP/6-31++G* levels for 2-mercaptobenzothiazole (MBT, C(7)H(5)NS(2)) and 2-mercaptobenzoxazole (MBO, C(7)H(5)NOS) in the ground state. The scaled harmonic ...
Vibrational frequencies and gauge including atomic orbital (GIAO) 13C NMR and 1H NMR chemical shift values of 2,6 distyrylpyridine (C21H17N) in the ground state have been calculated by using the Hartree-Fock (HF) and density functional method (B3LYP) with 6-31G(d) basis set. These methods are proposed as a tool to be applied in the structural characterization of 2,6 distyrylpyridine (C21H17N). The ...
The kernel energy method (KEM) is applied to the vesicular stomatitis virus (VSV) nucleoprotein (PDB ID code 2QVJ). The calculations employ atomic coordinates from the crystal structure at 2.8-? resolution, except for the hydrogen atoms, whose positions were modeled by using the computer program HYPERCHEM. The calculated KEM ab initio limited basis ...
Photofragmentation of thymine and 5-bromouracil into cation and neutral fragments following the core ionization by soft x-rays using photoelectron-photoion-photoion coincidence technique has been studied. The fragment ion mass spectra were recorded in coincidence with the C 1s photoelectron spectra. In the case of thymine, deuterated samples were used to identify fragments. Deuteration or ...
Experimental and theoretical vibrational spectra of ?-2-aminopyridinium dihydrogenphosphate (?-2APDP) have been investigated. The FT-IR spectrum of ?-2APDP was recorded in the region 4000-400 cm(-1). The optimized molecular structure and theoretical vibrational frequencies of ?-2APDP have been investigated using ab initio Hartree-Fock ...
Peptide nanorings (PNRs) has a closed ring form composed of alternating D- and L-?-amino acid residues. Much interest has been attracted owing to their function as a selective ion receptor. Here, based on ab initio molecular orbital theory, the excited as well as the ground state structures have been theoretically studied and discussed how the ...
We offer a new theoretical interpretation for the effect of enhanced electron density at the {sup 7}Be nucleus encapsulated in fullerene C{sub 60}. Our ab initio Hartree-Fock calculations show that the electron density at the {sup 7}Be nucleus in {sup 7}Be-C{sub 60} increases due to the attractive effective potential well generated by ...
Our ab initio all-electron fully relativistic Dirac-Fock (DF) and nonrelativistic (NR) Hartree-Fock (HF) self-consistent field (SCF) calculations predict the superheavy diatomic ekaplutonium fluoride E126F to be bound with the calculated dissociation energy of 7.44 and 10.46 eV at the predicted E126-F bond lengths of 2.03 and 2.18 ...
Semiempirical and ab initio Hartree Fock computational results indicate that the highly reactive dienophile tetramethyldisilene, Me{sub 2}Si=SiMe{sub 2}, is an excellent candidate for a novel functionalization of the equator of C{sub 70} via a [2+4] cycloaddition to the 21, 22, 23, 42 carbons. Thermal or ...
Density functional theory (DFT) and ab initio (Hartree-Fock) calculations employing the 6-31G* basis set are used to determine gas-phase proton microaffinities (PA(n,i)) of two bulky symmetrical tripodal tetraamine ligands N[(CH2)(4)NH2]3, trbn, and N[(CH2)(5)NH2]3, trpa. The corresponding proton macroaffinities (PA(n)) are calculated ...
Ab initio Hartree-Fock (HF), density functional theory (DFT) and second-order M�ller-Plesset (MP2) methods were used to perform harmonic and anharmonic calculations for the biomolecule cytosine and its deuterated derivative. The anharmonic vibrational spectra were computed using the vibrational self-consistent field (VSCF) and ...
The approach used to calculate the two-electron integral by many electronic structure packages including generalized atomic and molecular electronic structure system-UK has been designed for CPU-based compute units. We redesigned the two-electron compute algorithm for acceleration on a graphical processing unit (GPU). We report the acceleration strategy and illustrate it on the (ss|ss) type ...
Dimethyl phosphorothioate (DMPS) was investigated using FTIR and Raman spectroscopies. DMPS is a model compound for the backbone of single-stranded phosphorothioate DNA, a powerful anti-sense drug. Ab initio calculations of the infrared and Raman frequencies and intensities, and the interatomic force constants were performed using ...
