Ab initio (MP2/6-31G**//MP2/3-21G) calculations yield a value of about 729 kJ/ mole, ... Quantum chemical; Lubricants; Modelling; Semiempirical; Lubrication; ...

May 31, 2011 ... Ab initio (MP2/6-31G**//MP2/3-21G) calculations yield a value of about 729 kJ/ mole, in agreement with the chemical ionization experiments. ...

Conformational topology of ribose: A computational study Abraham F. Jalbout *, Ludwik Adamowicz the theoretical study of the configurational topology of the ribose molecule. MP2/6-31G** geometry optimiza- tions.V. Keywords: Ribose; MP2; Coupled cluster theory; Ab initio; ...

Ab initio and nonlocal density functional theory (DFT) calculations were performed to determine reaction mechanisms for formation of the six- membered ring C3N3Cl3 (cyanuric chloride) from the monomer, cyanogen chloride (ClCN). MP2 geometry optimizations ...

Ab initio calculations were performed to investigate reaction mechanisms for formation and decomposition of the six-membered ring C3N3H3, known as sym-triazine. MP2 geometry optimizations with QCISD(T) energy refinements for critical points on the potenti...

This paper reports ab initio calculations of rare gas (RG=Kr, Ar, Ne, and He) dimer quadrupoles at the second order of Moeller-Plesset perturbation theory (MP2). The study reveals the crucial role of the dispersion contribution to the RG{sub 2} quadrupole in the neighborhood of the equilibrium dimer separation. The ...

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 ...

Ab initio and density functional theory (DFT) methods at the HF/6-31G*, B3LYP/6-31G*, MP2/6-31G*, and MP2/TZVP levels of theory were applied to the investigation of the relative stability of six fullerene isomers of C32. Full geometry optimization of the systems was carried out and electrostatic potential ...

The energies and molecular structures of the highly coordinated species PH5, SH4, SH6, C1H3, and C1H5 have been derived by ab initio computations. Of particular interest are C1H3, which is of C2v symmetry, and C1H5, which is C4v. MP2 vibrational frequenci...

By using correlated ab initio (MP2, CCSD(T)) and multi-level (G3, CBS-QB3) methods we have studied unimolecular and bimolecular reactions of n-butanol in the gas phase. The specific processes investigated include H2O elimination and hydrogen abstraction by the hydroxy (HO) and hydroperoxy (HO2) radicals from this ...

of the formation of naphthalene and its substituted derivatives have been in- vestigated by ab initio G3(MP2,CC)/B3 to a second ring closure and the formation of naphthalene, they are not competitive with the direct H loss addition of the ethynyl radical to ultimately produce substituted naphthalene derivatives. - ...

Correlated ab initio wave function calculations using MP2/aug-cc-pVTZ model chemistry have been performed for three test sets of gas phase saccharide conformations to provide reference values for their relative energies. The test sets consist of 15 conformers of alpha and beta-D-allopyranose, 15 of ...

Geometry optimizations and normal-mode analyses of three conformers of 1,3,5-trinitro-s-triazine (RDX) are performed using second-order Moller-Plesset (MP2) and nonlocal density functional theory (DFT) methods. The density function used in this study is B...

We employ ab initio calculations of van der Waals complexes to study the potential energy parameters (C(6) coefficients) of van der Waals interactions for modeling of the adsorption of silver clusters on the graphite surface. Electronic structure calculations of the (Ag(2))(2), Ag(2)-H(2), and Ag(2)-C(6)H(6) complexes are performed using a coupled-cluster ...

Intermolecular interaction potentials of the trifluoromethane dimer in 15 orientations have been calculated using the Hartree-Fock (HF) self-consistent theory and the second-order M�ller-Plesset (MP2) perturbation theory. Single point energies at important geometries were also calibrated by the coupled cluster with single and double and perturbative ...

The framework of ab initio density-functional theory (DFT) has been introduced as a way to provide a seamless connection between the Kohn-Sham (KS) formulation of DFT and wave-function based ab initio approaches [R. J. Bartlett, I. Grabowski, S. Hirata, and S. Ivanov, J. Chem. Phys. 122, 034104 (2005)]. Recently, ...

We have studied how the calculation of electronic and vibrational contributions to nonlinear optical properties of three representative ?-conjugated organic molecules is affected by the choice of basis set and the inclusion of electron correlation effects. The 6-31G basis does not always provide even qualitative accuracy. For semiquantitative accuracy a 6-31+G(d) basis is sufficient. Although, as ...

We report full-dimensional, ab initio potential energy (PES) and dipole moment surfaces (DMS) for water. The PES is a sum of one-, two- and three-body terms. The three-body potential is a fit, reported here, to roughly 30,000 intrinsic three-body energies obtained with second-order M�ller-Plesset perturbation theory ...

Molecular mechanics valence force field parameters for the sulfonamide group, SO[sub 2]NH, have been derived from ab initio calculations at the RHF/6-31G* level of theory. The force field parameters were designed to be used in conjunction with existing parameters from the MM2/MMP2 force field. The new parameters are demonstrated to accurately reproduce the ...

The production of OH and HO(2) in Cl-initiated oxidation of cyclohexane has been measured using pulsed-laser photolytic initiation and continuous-laser absorption detection. The experimental data are modeled by master equation calculations that employ new G2(MP2)-like ab initio characterizations of important ...

Ab initio calculations demonstrate that specific zwitterionic molecules which have a {sigma}-bonded donor-acceptor system show an enhanced hyperpolarizability ({beta}) value when the effects of electron correlations are considered. Ab initio second-order Moeller-Plesset perturbation theory ...

Gas-phase activation energies were calculated for three lithium enolate reactions by using several different ab initio and density functional theory (DFT) methods to determine which levels of theory generate acceptable results. The reactions included an aldol-type addition of an enolate to an aldehyde, a proton transfer from an alcohol to a lithium ...

We report here a direct ab initio molecular dynamics study of the p-/o-H2+HOC+ reaction on the basis of the accurate SAC-MP2 potential energy surface. The quasi-classical trajectory method was employed. This work largely focuses on the study of reaction mechanisms. A roaming mechanism was identified for this ...

Intermolecular interaction potentials of the silane dimer in 12 orientations have been calculated by using the Hartree-Fock (HF) self-consistent theory and the second-order M�ller-Plesset (MP2) perturbation theory. We employed basis sets from Pople's medium-size basis sets [up to 6-311++G(3df, 3pd)] and Dunning's correlation consistent basis sets (up to ...

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 ...

MP2/6-31G*//MP2/6-31G* structures, energies, and vibrational frequencies have been calculated for six N[sub 6]/isomers. These isomers are the nitrogen analogues of the following carbon structures: benzene, Dewar benzene, benzvalene, triprismane, bicyclopropenyl, and a diazide. They are of interest because there are ...

Structural and spectroscopic properties of hydrazine, H(2)N-NH(2), it being a floppy or fluxional molecule in a vacuum, are investigated by means of ab initio molecular dynamics, ab initio path integral molecular dynamics, and ab initio ring polymer molecular dynamics ...

The nature of chalcogen{hor ellipsis}chalcogen contact interactions in organic donor-molecule salts was examined by performing ab initio SCF-MO/MP2 calculations on H{sub 2}X{hor ellipsis}XH{sub 2}(X = O, S, SE, Te) and MM2 calculations on donor dimers (TXF){sub 2} (X = S, SE, Te) and (BEDX-TTF){sub 2} (X = O, S). ...

Structural properties of energetically low-lying isomers of the isolated Al O molecular system have been investigated by theoretical ab initio techniques within the Hartree-Fock HF and second-order Moller-Plesset MP2 frozen core level of approximation and density functional methods DFT employing the ...

A series of complexes between ethylene and ozone have been examined at the SCF, MP2, and MP4(SDTQ) levels of theory within a split-valence-plus-polarization basis. The conformational nature of the primary ozonide (PO) is determined to be an O-envelope, and the theoretically predicted geometry is in excellent agreement with a recently reported microwave ...

Dispersion is well known to be important in biological systems, but the effect of electron correlation in such systems remains unclear. In order to assess the relationship between the structure of a protein and its electron correlation energy, we employed both full system Hartree-Fock (HF) and second-order M�ller-Plesset perturbation (MP2) calculations ...

Accurate benchmark calculations of gas-phase basicities of small molecules are presented and compared with available experimental results. The optimized geometries and thermochemical analyses were obtained from MP2/aug-cc-pVTZ calculations. Two different ab initio electron-correlated methods ...

The ab initio/classical free energy perturbation (ABC-FEP) method proposed previously by Wood et al. [J. Chem. Phys. 110, 1329 (1999)] uses classical simulations to calculate solvation free energies within an empirical potential model, then applies free energy perturbation theory to determine the effect of changing the empirical solute-solvent interactions ...

We report full-dimensional, ab initio potential energy and dipole moment surfaces, denoted PES and DMS, respectively, for arbitrary numbers of water monomers. The PES is a sum of 1-, 2-, and 3-body potentials which can also be augmented by semiempirical long-range higher-body interactions. The 1-body potential is a spectroscopically accurate monomer ...

We carried out full ab initio molecular orbital calculations on complexes between neuraminidase-1 (N1-NA) in the influenza A virus and a series of eight sialic acid analogues including oseltamivir (Tamiflu) in order to quantitatively examine the binding mechanism and variation in the inhibitory potency at the atomic and electronic levels. ...

The infrared (3200-30 cm(-1) spectra of gaseous and solid and the Raman spectra of liquid (3200-30 cm(-1), with quantitative depolarization values, and solid vinyldichlorosilane, CH2=CHSiHCl2, have been recorded. Both the gauche and the cis conformers have been identified in the fluid phases. Variable temperature (105-150 degrees C) studies of the infrared spectra of the sample dissolved in liquid ...

... This study involves: Ab-initio crystal orbitals and polymer orbitals; Ab-initio coupled cluster program; Ab-initio quantum chemical calculations and ...

Dispersion is well-known to be important in biological systems, but the effect of electron correlation in such systems remains unclear. In order to assess the relationship between the structure of a protein and its electron correlation energy, we employed both full system Hartree-Fock (HF) and second-order M�ller-Plesset perturbation (MP2) calculations ...

Various highly accurate ab initio composite methods of Gaussian-n (G1, G2, G3), their variations (G2(MP2), G3(MP2), G3//B3LYP, G3(MP2)//B3LYP), and complete basis set (CBS-Q, CBS-Q//B3LYP) series of models were applied to compute ...

A new method called adaptive force matching (AFM) has been developed that is capable of producing high quality force fields for condensed phase simulations. This procedure involves the parametrization of force fields to reproduce ab initio forces obtained from condensed phase quantum-mechanics/molecular-mechanics (QM/MM) calculations. During the procedure, ...

We report full-dimensional, ab initio potential energy and dipole moment surfaces, denoted PES and DMS, respectively, for arbitrary numbers of water monomers. The PES is a sum of 1-, 2-, and 3-body potentials which can also be augmented by semiempirical long-range higher-body interactions. The 1-body potential is a spectroscopically accurate monomer ...

Ab initio calculations were carried out with Moeller-Plesset second- and fourth-order perturbation theory (MP2 and MP4), and the coupled cluster method, CCSD(T), on the H atom abstraction reaction from dibromomethane by hydroxyl radical attack. Geometry optimization and vibrational frequency calculations at the MP2 ...

Accurate MP2 and CCSD(T) complete basis set (CBS) interaction energy curves (14 points for each curve) have been obtained for 20 of the dimers reported in the S22 set and analytical Morse curves have been fitted that can be used in developing updated density functional theory (DFT) and force field models. The magnitude and the effect of the basis set ...

Accurate MP2 and CCSD(T) complete basis set (CBS) interaction energy curves (14 points for each curve) have been obtained for 20 of the dimers reported in the S22 set and analytical Morse curves have been fitted that can be used in developing updated density functional theory (DFT) and force field models. The magnitude and the effect of the basis set ...

... 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. ...

... Title : AB Initio Quantum Chemical Investigations of Solubilities in Supercritical Solutions. Descriptive Note : Conference Paper,. ...

Ab initio calculations were conducted for both reaction pathways of the CH3Br and OH system. Geometry optimization and vibrational frequencies analysis were performed for reactants, pre-reaction complex, transition states, post-reaction complex and products at the MP2(full)/6-311+G(d,p), MP2(full)/6-311+G(3df,2pd) ...

HOSO2 radical is the key intermediate for the oxidation SO2 to SO3 by OH radical in the atmosphere. The structural aspects and the energetics of the reaction HOSO2+O2-->SO3+HO2 have been studied using M�ller-Plesset (MP2) and density functional (DFT) techniques with 6-31G** and triple-?, quadruple-?, and quintuple-? quality basis sets including ...

The magnitudes of the two- through six-body energy terms and their contribution to the interaction energy of small ring water clusters ([ital n]=2--6) are computed at the Hartree--Fock (HF) and second- through fourth-order many-body perturbation (MP2, MP4) levels of theory. The analysis is performed at the minimum energy geometries reported earlier [J. ...

The ground vibrational state and equilibrium structures of the halogen (F to I) azides, isocyanates and isothiocyanates have been determined, and compared with spectral and diffraction data. We present results from M�ller Plesset (MP2) and DFT (B3LYP) methodologies, with similar basis sets (TZVP and cc-pVTZ), such that detailed comparisons of each with ...

The geometries, harmonic frequencies, elec-tronic excitation levels, and energetic orderings of various conformers of RDX have been computed at the ab initio MP2 and CCSD(T) levels, providing more reliable results than have been previously obtained. We observe that the various local minimum-energy conformers are ...

Variable temperature (-55 to -100�C) studies of the infrared spectra (3500-400 cm(-1)) of fluorocyclobutane, c-C(4)H(7)F, dissolved in liquid xenon have been carried out as well as the infrared spectra of the gas. By utilizing eight pairs of conformers at 10 different temperatures, the enthalpy difference between the more stable equatorial conformer and the axial form has been determined to be ...

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 ...

The conductorlike continuum solvation model, modified for ab initio in the quantum chemistry program GAMESS, implemented at the M�ller-Plesset Order 2 (MP2) level of theory has been applied to a group of push-pull pyrrole systems to illustrate the effects of donor/acceptor and solvation on the stability and ...

The portion of the potential energy surface (PES) of acetylacetone relevant for the intramolecular proton transfer reaction is studied using ab initio and DFT methods. The best estimate of the barrier governing proton transfer was found to be 3.4 kcal mol?1 at the MP4(FC)/6-311 + G(2d,2p)//MP2(FC)/6-311 + G(2d,2p) ...

A conformational analysis of nine macrocyclic thioether musks has been carried out using molecular mechanics (MMFF), density functional theory (DFT) using both B3LYP and M06 functionals, as well as Hartree-Fock and post-Hartree-Fock (MP2) ab initio methods. 6-Thia-, 10-thia- and ...

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 ...

The class of bimetallic clusters, Au(n)M(m) (M = Zn, Cd, Hg), is calculated at the ab initio level using the DFT, RI-MP2, and CCSD(T) methods. For the triatomic Au2M (M = Zn, Cd), the auride-type linear Au-M-Au structures are preferred; for Au2Hg, the linear Au-Au-Hg "amalgam" is preferred. The mixed cation ...

The sign preference of hydrogen bonded aqueous ionic clusters X�(H₂O)_i (n =1�5, X = F; Cl; Br) has been investigated using the Density Functional Theory and ab initio MP2 method. The present study indicates the anomalously large difference in formation free energies ...

The equilibrium geometries, vibrational frequencies, dissociation energies, and populations of the title species were studied at Hartree-Fock (HF), second-order Moeller-Plesset (MP2), and coupled-cluster singles-doubles (triples) [CCSD(T)] levels. The electron correlation effects and relativistic effects on the geometry and stability were investigated at ...

Self-consistent field calculations have been performed on the compounds FNO{sub x} (x = 1, 2, 3) using 4-31G, 6-31G*/MP2, and PDZ/MP2 basis sets. Dipole moments, Koopman's ionization potentials, and predicted geometries are reported. The predicted relative stability for FNO{sub 2} isomers is FNO{sub 2} > c-FONO > t-FONO. FONO{sub 2} is ...

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, ...

The authors investigated the coupling of torsion and OH overtone vibration in hydrogen peroxide by high level ab initio calculations. Within a Born-Oppenheimer framework, the trans barrier and equilibrium torsional angle were calculated as a function of OH stretch and averaged over Morse local-mode wavefunctions for the nine lowest overtone states. Using ...

The harmonic force constants, harmonic wavenumbers and dipole moment derivatives of benzene were calculated at the HF, MP2, MP3, CCD and CCSD levels of theory with several basis sets. It was determined that the signs of the dipole moment derivatives are consistent from all the methods. The MP2, MP3, CCD and CCSD calculations with the cc-pVDZ basis set all ...

In the framework of quantum-chemical methods (RHF, MP2, and DFT), we study the reaction of photoinduced isomerization of biological molecules-retinal in rhodopsin (Rh) and bacteriorhodopsin (BRh)-the key intermediates in the vision process. The charge redistribution in the retinal chromophore of these biological molecules as the mechanism of 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, ...

The values of combustion and formation enthalpy for glycolic acid ( I) and glycolide ( II) were determined by calorimetry. The temperature dependence of vapor pressures of I and II was obtained using the transpiration method, and the sublimation enthalpies were obtained. The enthalpy of melting of I was found by differential scanning calorimetry. Stable conformers were determined by the ...

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 HF/6-31G* level with molecular models for the ...

Neutral and anionic 13-atom aluminum clusters are studied with high-level, fully ab initio methods: second-order perturbation theory (MP2) and coupled cluster theory with singles, doubles, and perturbative triples (CCSD(T)). Energies and vibrational frequencies are reported for icosahedral and decahedral isomers, ...

MP2/6-31++G(d,p) ab initio calculations have been performed to estimate the effect of the H-bond on the vibrational properties of HF due to its complexation with aromatic azines (CnN6-nHn, with n = 5, 4 or 3). Our calculations have revealed that the greater is the number of nitrogen atoms in the aromatic ring, the ...

Peptide N-acetyl-L-alanine-N'-methylamide (AD) provides a model of the basic elements of secondary structure (one flexible backbone dihedral angle of each type, J and ?) in the simplest possible form. Accordingly, AD has become a standard test case for all models of peptide solvation, and it has been the subject of many theoretical and experimental studies. Starting from the B3LYP/6-31G* optimized ...

An ab initio study (at G2[MP2]) level shows that deprotonated 2-methyl-3,4-epoxybutan-2-ol (A) and 3-methyl-2,3-epoxybutan-1-ol (B) should interconvert via modest barriers (A --> B [47 kJ mol-1]; B --> A [33 kJ mol-1]) by three-centre Payne rearrangements. The competing four-centre rearrangements of A and B ...

Theoretical studies on BC(n) (n=1-6) clusters are carried out using density functional theory, M�ller-Plesset second-order perturbation theory (MP2), coupled-cluster calculations including up to triple excitations (CCSD(T)), and higher-level approaches. All possible isomers depending on the positions of the boron atom are generated and the lowest-energy ...

Standard molar enthalpies of formation in the gaseous state of a series of alkyl 3-methylbut-2-enoates have been obtained from combustion calorimetry and results from the temperature dependence of the vapor pressure measured by the transpiration method. To verify the experimental data, we have performed ab initio calculations of all compounds. Enthalpies ...

The rotational spectra of the (20)Ne and (22)Ne isotopomers of the Ne-dimethyl sulfide (DMS) rare gas dimer have been measured by Fourier transform microwave spectroscopy. MP2/6-311++G(2d,2p) calculations, and the experimental spectroscopic data, suggest a structure of C(s) symmetry in which the Ne atom lies above the heavy atom plane of the DMS (in the ...

A computer program SURVIB is described for calculating vibrational anharmonicity constants for polyatomic molecules. The program requires as input a grid of calculated energies in the vicinity of a stationary point. This grid is fit, in a least squares sense, to a polynomial function of the internal coordinates. This analytic representation of the energy surface is employed in a normal mode ...

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 ...

Ab initio MP2/aug'-cc-pVTZ calculations have been carried out to determine the structures, binding energies, and bonding of complexes FCl:CNX, with X = CN, NC, NO(2), F, CF(3), Cl, Br, H, CCF, CCH, CH(3), SiH(3), Li, and Na. Equation-of-motion coupled cluster calculations have also been carried out to determine the ...

The IR, Raman and NMR spectra of 3-aminomethylene-2,4-pentanedione (AMP) H2NCHC(COCH3)2 were measured. According to the NMR spectra in chloroform and more polar DMSO at room temperature, the sample exists as single entity. On the other hand vibrational spectra revealed that in less polar solutions AMP exists as two conformers with EZ or ZZ orientation of acetyl groups whereas in more polar solvent ...

The first hydration shell of the deprotonated glycine is built up by the discrete hydration model. The potential energy surfaces (PESs) of the deprotonated glycine and its hydration complexes with different number of water molecules have been scanned by the Monte Carlo multiple minimum (MCMM) conformational search analysis with the MMFFs force field. Then the energy-minimized structures are ...

Thermodynamic properties of phosphorus-containing compounds were investigated using high-level ab initio computations. An extended set of contemporary density functional theory (DFT) procedures was assessed for their ability to accurately predict bond dissociation energies of a set of phosphoranyl radicals. The results of meta- and double-hybrids as well ...

The spectroscopic properties of CuAr, CuAr(+) and CuAr(-) have been studied in detail using ab initio MP2, CCSD and CCSD(T) methods. The effect of basis set on spectroscopic properties of these molecular systems has also been investigated. Among these molecules, CuAr(+) is found to be more strongly bound than CuAr ...

The intermolecular potential energy surface (PES) of the naphthalene-argon (NpAr) complex is constructed using an ab initio method. The molecule-argon interaction energy is computed at the level of the second-order M�ller-Plesset (MP2) theory combined with the augmented correlation consistent polarized valence ...

The intermolecular potential energy surface (PES) of the naphthalene-argon (NpAr) complex is constructed using an ab initio method. The molecule-argon interaction energy is computed at the level of the second-order M�ller-Plesset (MP2) theory combined with the augmented correlation consistent polarized valence ...

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 ...

Ab initio calculations of the geometry and reactivity of 1,2-ketocarbene C6H4O as an intermediate in organic reactions were performed using the second-order Møller-Plesset (MP2) perturbation theory in the 6-311G* basis set. Only the singlet state of the intermediate was considered. An oxirene-like structure (6) ...

... Title : AB Initio Study of the Electronic Magnetic Circular Dichroism ... functions are determined using as initio quantum chemical techniques including ...

The thermochemistry of the formation of Lewis adducts of BH3 in tetrahydrofuran (THF) solution and the gas phase and the kinetics of substitution on ammonia borane (AB) by triethylamine are reported. The dative bond energy of Lewis adducts were predicted using density functional theory at the B3LYP/DZVP2 and B3LYP/6-311+G** levels and correlated ab ...

Due to recent advances in methods and computers, the accuracy of ab calculations has reached a point

Variable temperature (-55 to -100 ^�C) studies of the infrared spectra (4000-400 cm^{-1}) of bromocyclobutane, c-C_4H_7Br dissolved in liquid xenon have been carried out. The infrared spectrum (4000-100 cm^{-1}) of the gas has also been recorded. The enthalpy difference between the more stable equatorial conformer and the axial form, has been determined to be 372 � 34 cm^{-1} . This ...

Matrix isolation spectroscopy in combination with ab initio calculations is a powerful technique for the identification of weakly bound intermolecular complexes. Here, weak complexes between formamide and acetylene are studied, and three 1:1 complexes with binding energies of -2.96, -2.46, and -1.79 kcal/mol have been found at the MP2 level of theory ...

In this work, we examine the performance of a range of local and hybrid DFT functionals (including BLYP, PBE, PW91, B3P86, B3LYP, and TPSS), new generation DFT functionals (including KMLYP, BMK, M05, and M05-2X), and DFT functionals with the explicit empirical correction for dispersion interactions (including BLYP-D, PBE-D, and B3P86-D) in calculating ion-pair binding energies of ...

The ab initio fragment molecular orbital calculations were performed for the alpha-subtype of the human retinoid X receptor (hRXRalpha) complex with its natural ligand 9- cis retinoic acid (9cRA) to quantitatively specify the key residues with important roles for the ligand inducible information transmission of RXR. In the RXR-9cRA complex, the ...

Many Divide-and-Conquer based approaches are being developed to overcome the high scaling problem of the ab initio methods. In this work, one such method, Molecular Tailoring Approach (MTA) has been interfaced with recently developed efficient M�ller-Plesset second order perturbation theory (MP2) codes viz. ...

Geometrical parameters of tetraatomic carbonyl molecules X2CO and XYCO (X, Y = H, F, Cl) in the ground (S0) and lowest excited singlet (S1) and triplet (T1) electronic states as well as values of barriers to inversion in S1 and T1 states and S1 larr S0 and T1 larr S0 adiabatic transition energies were systematically investigated by means of various quantum-chemical techniques. The following ...

Correlated ab initio quantum chemical methods based on second-order perturbation theory and density functional theory (DFT) together with large atomic orbital (AO) basis sets are used to calculate the structures of four cyclophanes with two aromatic rings and one sulphur-containing phane with one aromatic ring. The calculated geometrical data for ...

The mechanism for the deamination of guanine with H(2)O, OH(-), H(2)O/OH(-) and for GuaH(+) with H(2)O has been investigated using ab initio calculations. Optimized geometries of the reactants, transition states, intermediates, and products were determined at RHF/6-31G(d), MP2/6-31G(d), B3LYP/6-31G(d), and ...

The anomeric effect of 2-substituted 1,4-dioxane derivatives was calculated and compared with the values for substituted cyclohexane. The bond lengths, bond angles, torsion angles, and relative energies of axial and equatorial conformers of 2-substituted 1,4-dioxanes were calculated by the second-order M�ller-Plesset (MP2), density functional theory ...

The separation, capture and storage of carbon dioxide from the flue gas is an environmental and economical problem of significant importance. Zeolites and activated carbons have been used from the industries in order to reduce the emissions of CO2. A new family of materials, the metal-organic frameworks (MOFs), has been recently proposed as an efficient substitute of the abovementioned materials. ...

Energy and free energy barriers for acetaldehyde conversion in aldehyde oxidoreductase are determined for three reaction pathways using quantum mechanical/molecular mechanical (QM/MM) calculations on the solvated enzyme. Ab initio single-point QM/MM energies are obtained at the stationary points optimized at the DFT(B3LYP)/MM level. These ...

Benzene - methanol cluster structures were investigated with theoretical chemistry methods to describe the microsolvation of benzene and the benzene-methanol azeotrope. Benzene - methanol (MeOH) clusters containing up to 6 methanol molecules have been calculated by ab initio ...

An ab initio molecular dynamics study performed with the projector augmented wave method (PAW) on proton motion and (double) proton transfer in the formamidine-formic acid complex is reported. The PAW trajectories were calculated with a time interval of 0.12 fs, for a total evolution time period of 36ps, and for temperatures in the range 500-600 K. All ...

The infrared (3200-30 cm(-1) spectra of gaseous and solid, the Raman spectra (3200-30 cm(-1)) of the liquid and solid vinyl silyl bromide, CH2CHSiH2Br, have been recorded. Additionally, quantitative depolarization values have been obtained. Both the gauche and cis conformers have been identified in the fluid phases but only the gauche conformer remains in the solid. Variable temperature studies ...

Ab initio calculations using the 6-311G**, cc-pVDZ, and (valence) double-zeta pseudopotential (DZP) basis sets, with (MP2, QCISD, CCSD(T)) and without (UHF) the inclusion of electron correlation, and density functional (BHandHLYP, B3LYP) calculations predict that homolytic substitution reactions of acetyl radicals at the silicon atoms in disilane can ...

We have investigated the feasibility of using ab initio molecular orbital methods for predicting the global warming potential of the proposed chlorofluorocarbon (CFC) substitute CF{sub 3}CH{sub 2}F, HFC-134a. Various levels of theory and basis sets were used to optimize geometry and calculate harmonic vibrational frequencies and infrared intensities for ...

The results of a uniform set of ab initio quantum-chemical calculations for 10 carbon/nitrogen cubanoids are presented. There are 22 possible C/N cubanoids with formulas (CH)[sub 8[minus]n]N[sub n], where 0 [le] n [le] 8. We give results for one cubanoid for each value of n; for n = 4 both the T[sub d] and C[sub 4v] structures are discussed. The geometries ...

Ab initio calculations at the CCSD(T) level of theory were performed to characterize the Ar + CF4 intermolecular potential. Potential energy curves were calculated with the aug-cc-pVTZ basis set, and with and without a correction for basis set superposition error (BSSE). Additional calculations were performed with other correlation consistent basis sets to ...

... AB-INITIO SIMULATION OF a/2110> ... 4. TITLE AND SUBTITLE AB-INITIO SIMULATION OF a/2110> SCREW DISLOCATIONS γ-TiAl 5c. ...

... ADP012740 TITLE: Ab Initio Study on Spin Polarization of III-V Compound Tips ... Ab initio study on spin polarization of III-V compound tips ...

Ab initio electronic structure methods can supplement CALPHAD in two major ways for subsequent applications to stability in complex alloys. The first one is rather immediate and concerns the direct input of ab initio energetics in CALPHAD databases. The o...

...with this part. The certificate shall be void ab initio for those vehicles causing the...issued, and the certificate may be deemed void ab initio. (C) The manufacturer...with this part. The certificate shall be void ab initio for those vehicles causing...

... ADP023770. Title : ab-Initio Molecular Dynamics Simulations of Molten Ni-Based Superalloys. Descriptive Note : Conference paper. ...

... from federally funded research, testing and training ... for Research Development Test and Evaluation ... of Molecular Modelling and Ab initio Molecular ...

... from federally funded research, testing and training ... agencies for Research Development Test and Evaluation ... Title : New AB Initio Based Density ...

... from federally funded research, testing and training ... for Research Development Test and Evaluation ... Title : Development of Ab-initio Multibody ...

... Ab initio Energies Calculated Using 3 ... of the Transition States (TS ... Descriptors : *TRANSITIONS, *MOLECULES, COMPUTATIONS, COMPARISON ...

... Abstract : Results are presented from ab initio quantum chemical calculations on the ground state potential energy surface for the open shell ...

... from federally funded research, testing and training ... and agencies for Research Development Test and Evaluation ... Title : An Ab Initio Study of Solid ...

... from federally funded research, testing and training ... agencies for Research Development Test and Evaluation ... Title : An AB Initio Study of Dimethyl ...

... Accession Number : ADA523968. Title : Ab-initio Simulations of Molten Ni Alloys. Descriptive Note : Journal article (preprint). ...

... Title : Ab-Initio Molecular Dynamics Simulations of Molten Ni-Based Superalloys. Descriptive Note : Conference paper (preprint). ...

... from federally funded research, testing and training ... for Research Development Test and Evaluation ... Title : Ab-Initio Molecular Dynamics Simulations ...

... We carried out ab-initio quantum chemical calculations on these energetic cyclic ethers and generated the electrostatic molecular potential contour ...

Ab initio quantum chemical techniques have been used to investigate weakly bund complexes of H20 and SO2. An energy gradient program was used to ...

... Accession Number : ADA351780. Title : Ab Initio and DFT Potential Energy Surfaces for Cyanuric Chloride Reactions. Descriptive Note : Final rept. ...

... Ab initio study on atomic structures and physical properties of CdSe quantum nanodots ... Figure 2. Diagram of covered nanodots. ...

... Title : Ab Initio Study on Atomic Structures and Physical Properties of CdSe Quantum Nanodots. Descriptive Note : Final rept. ...

... from federally funded research, testing and training ... agencies for Research Development Test and Evaluation ... Title : Ab Initio Study of the Structure ...

... 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 ...

... from federally funded research, testing and training ... and agencies for Research Development Test and Evaluation ... Title : Ab Initio Study of Ultracold ...

1 AB INITIO STUDIES ON HEXAVALENT PHOSPHORUS COMPOUNDS Ashley L. Wilson* Aberdeen High School Aberdeen, Maryland 21001 ...

... Accession Number : ADA436055. Title : Ab Initio Studies on Hexavalent Phosphorus Compounds. Descriptive Note : Conference paper. ...

... from federally funded research, testing and training ... agencies for Research Development Test and Evaluation ... Title : Ab Initio Relativistic Study of ...

... Accession Number : ADA440631. Title : Ab Initio Quantum Chemical Study of Electron Transfer in Carboranes. Descriptive Note : Journal article. ...

... Accession Number : ADA270577. Title : Ab Initio Potential Energy Surface for the H + OCS Reaction. Descriptive Note : Final rept. ...

... [2"- ARMY RESEARCH LABORATORY [C Ab Initio Potential Energy Surface for H + OCS Reactions: Extended Basis Sets ...

... 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. ...

... Ab initio direct trajectory simulation on hydrogen atom transfer in 7-azaindole in the electronic excited state with assist of water molecules ...

... from federally funded research, testing and training ... for Research Development Test and Evaluation ... Title : Ab Initio Direct Trajectory Simulation on ...

... Title : Ab Initio Calculation of Vibrational Circular Dichroism Spectra Using Accurate Post-Self-Consistent-Field Force Fields: trans-2,3 ...

... from federally funded research, testing and training ... for Research Development Test and Evaluation ... Title : Ab Initio Calculation of Intermolecular ...

... from federally funded research, testing and training ... agencies for Research Development Test and Evaluation ... Title : AB Initio Propagator Theory of ...

To improve upon non-bonded force fields for hydrocarbons, a "toolbox" providing the link between the potentials and experimentally or computationally available observables has been developed. The relevant properties obtained by the programs in the toolbox are as follows: (i) ab initio potential energies of hydrocarbon dimers using Moller-Piesset ...

The infrared (3100-40 cm(-1)) spectra of gaseous and solid and Raman (3200-20 cm(-1)) spectra of liquid with qualitative depolarization values and solid n-propyltrifluorosilane, CH(3)CH(2)CH(2)SiF(3), have been recorded. Additionally the infrared spectra of the sample in nitrogen and argon matrices have been recorded. Both the anti and gauche conformers have been identified in the fluid phases but ...

We report on the determination of a high quality ab initiu potential energy surface (PES) and dipole

We report on a major update (version 2) of the original SHort Read Mapping Program (SHRiMP). SHRiMP2 primarily targets mapping sensitivity, and is able to achieve high accuracy at a very reasonable speed. SHRiMP2 supports both letter space and color space (AB/SOLiD) reads, enables for direct ...

The infrared (3100 40 cm?1) spectra of gaseous and solid and Raman (3200 20 cm?1) spectra of liquid 2-chloroethylsilyl chloride, ClCH2CH2SiH2Cl, have been recorded. There are five possible stable conformers, Gg, Tg, Gt, Tt and Gg? for this molecule where the capital letter G (gauche) or T (trans) refer to rotation around the C C bond and the lower case letters to rotation around the Si C bond. ...

The thermal decomposition of formyl, acetyl, and benzoyl azides to the corresponding isocyanate and nitrogen has been treated theoretically using ab initio molecular orbital calculations at the M�ller-Plesset type 2 (MP2)(full)/6-31G* level. The reaction is stimulated by elongation of N bond N bond and is ...

To investigate the microscopic second-order nonlinear optical (NLO) behavior of the 1-salicylidene-3-thio-semicarbazone Schiff base compound, the electric dipole moments (?), linear static polarizabilities (?) and first static hyperpolarizabilites (?) have been calculated using finite field second-order M�ller-Plesset perturbation (FF MP2) theory. The ...

Glyoxal, methylglyoxal, and 2,3-butanedione (diacetyl) are all known biomass burning effluents and suspected aerosol precursors. Pressure-broadened quantitative infrared spectra of glyoxal, methylglyoxal, and diacetyl vapors covering the 520-6500 cm(-1) range are reported at 0.112 cm(-1) resolution, each with a composite spectrum derived from a minimum of 10 different sample pressures for the ...

Glyoxal, methylglyoxal and 2,3-butanedione (diacetyl) are all known biomass burning effluents and suspected aerosol precursors. Pressure-broadened quantitative infrared spectra of glyoxal, methylglyoxal and diacetyl vapors covering the 520�6500 cm�1 range are reported at 0.11 cm�1 resolution, each with a composite spectrum derived from a minimum of ten different sample pressures for the ...

Density functional theory (DFT), HF and MP2 calculations have been carried out to investigate thioxanthone molecule using the standard 6-31+G(d,p) basis set. The results of MP2 calculations show a butterfly structure for thioxanthone. The calculated results show that the predicted geometry can well reproduce the structural parameters. The predicted vibrational frequencies were assigned and ...

To provide physicochemical insight into the role of each residue in the ligand-binding pocket (LBP) of the vitamin D receptor (VDR), we evaluated the energies of the interactions between the LBP residues and 1alpha,25(OH)2D3 by using an ab initio fragment molecular orbital (FMO) method at the M�ller-Plesset second-order perturbation ...

For the first time the coexistence of a sigma- and a pi-complex in the C(4)H(4)O:HCl system has been observed, in the same supersonic expansion of a molecular jet seeded with argon (or helium) or in a flow-cooled cell at 240 K. This is an exception to the third of the Legon-Miller rules which claims the sigma-structure to be the only one to exist. On the grounds of energetic considerations and ...

Thermochemical reactions for boron hydrides can be constructed relative to BH{sub 3} and H{sub 2} where x and y are varied in the reaction xBH{sub 3} {yields} boron hydride + yH{sub 2}. From calculated relative energies (MP2/6-31G{sup *}//3-21G) and the experimental heat of formation of H{sub 2} and the adjusted heat of formation of BH{sub 3}, heats of ...

Monohydrates of halogen monoxides ClO.H2O and BrO.H2O have been studied by means of DFT (B3LYP) and ab initio (MP2) correlated calculations with aug-cc-pVnZ basis sets ranging from triple- up to quintuple-zeta. These complexes might be formed in the troposphere and stratosphere and participate in chemical reactions ...

In this paper the accuracy of the q-Integral method is evaluated in several molecular properties of the H2 system using the Density Functional Theory (DFT). The q-Integral method is an alternative approach to evaluate two-electron integrals where the CPU time is substantially less than usual. For this purpose, we evaluated potential energy curves, rovibrational spectroscopy constants, ...

The structural stability of phenylacetic acid and mandelic acid was investigated by the DFT-B3LYP and the ab initio MP2 calculations with the 6-311G** basis set. The two molecules were predicted at the DFT and MP2 levels of calculation to have the non-planar (Np) forms as their lowest energy structures. The ...