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

The CCSD(T) method, singles and doubles coupled-cluster theory plus a perturbational estimate of the

This study involves: Ab-initio crystal orbitals and polymer orbitals; Ab-initio coupled cluster program; Ab-initio quantum chemical calculations and electrostatic molecular potential contour maps for cationic polymerization; Prediction of crystal density;...

Very efficient computer codes to perform many-body perturbation theory (MBPT) and coupled cluster method (CCM) calculations have been written and employed for the first time in large-scale ab initio calculations of potential energy surfaces.

Very efficient computer codes to perform many-body perturbation theory (MBPT) and coupled cluster method (CCM) calculations have been written and employed for the first time in large-scale ab initio calculations of potential energy surfaces. (Author)

Under AFOSR support over several years, coupled-cluster (CC) and many-body perturbation theory (MBPT) methods for the accurate inclusion of electron correlation in ab initio quantum chemical calculations of molecules have been definitively established as ...

We report preliminary large scale ab initio calculations of ground and excited states of {sup 16}O using quantum chemistry inspired coupled cluster methods and realistic two-body interactions. By using the renormalized Hamiltonians obtained with a no-core G-matrix approach, we obtain the virtually converged results ...

Structural and energetic properties of small, deceptively simple anionic clusters of lithium, Li(n)(-), n = 3-7, were determined using a combination of anion photoelectron spectroscopy and ab initio calculations. The most stable isomers of each of these anions, the ones most likely to contribute to the photoelectron spectra, were found using the gradient ...

Structural and energetic properties of small, deceptively simple anionic clusters of lithium, Lin-, n = 3-7, were determined using a combination of anion photoelectron spectroscopy and ab initio calculations. The most stable isomers of each of these anions, the ones most likely to contribute to the photoelectron spectra, were found using the gradient ...

The reaction of C(3P) with H2S to HCS/HSC isomers is investigated with high level ab initio methods. Besides reaction energies to form HCS/HSC, the energetics and properties of different singlet/triplet H2CS reaction intermediates are studied. The combination of ab initio theory and crossed molecular beams ...

The formation of spiropentane, by addition of singlet (1A1) methylene to methylenecyclopropane, and the unimolecular reactions of spiropentane have all been studied computationally. Benchmark calculations on two key biradicals were conducted by the multireference Mukherjee's coupled-cluster (MkCC) method. Various single-reference coupled-cluster methods ...

The ability to describe properties of molecular system in realistic environment is important for many applications. To address this issue we recently combined [M. Valiev, K. Kowalski, J. Chem. Phys. 2006, 125, 211101] classical molecular mechanics (MM) and ab initio coupled-cluster (CC) modules of NWChem. This paper reports the results ...

We present ab initio calculations for {sup 3}H, {sup 4}He, {sup 16}O, and {sup 40}Ca based on two-nucleon low-momentum interactions V{sub lowk} within coupled-cluster theory. For {sup 3}H and {sup 4}He, our results are within 70 and 10 keV of the corresponding Faddeev and Faddeev-Yakubovsky energies. We study in detail the convergence ...

To assist the proposed search for the electric dipole moment of the electron with the thorium oxide, converged ab initio coupled cluster calculations are performed on the interaction energy, dipole moment, anisotropic static dipole polarizability, and quadrupole moment of the ThO(X 1?+) molecule as functions of ...

High-level quantum-chemical ab initio coupled-cluster and multiconfigurational perturbation methods have been used to compute the vertical and adiabatic electron affinities of the five canonical DNA and RNA nucleobases: uracil, thymine, cytosine, adenine, and guanine. The present results aim for the accurate determination of the ...

To assist the proposed search for the electric dipole moment of the electron with the thorium oxide, converged ab initio coupled cluster calculations are performed on the interaction energy, dipole moment, anisotropic static dipole polarizability, and quadrupole moment of the ThO(X (1)Sigma(+)) molecule as ...

A new ab initio potential energy surface of the Ne�CO complex is developed using single and double excitation coupled-cluster theory with noniterative treatment of triple excitations [CCSD(T)]. The potential has a minimum value of ?49.396 cm?1 at Re = 6.40a0 with approximately T-shaped geometry (?e = 82.5�). Bound state energies ...

We perform coupled-cluster and diffusion Monte Carlo calculations of the energies of circular quantum dots up to 20 electrons. The coupled-cluster calculations include triples corrections and a renormalized Coulomb interaction defined for a given number of low-lying oscillator shells. Using such a renormalized Coulomb interaction brings the coupled-cluster calculations with ...

In this paper we describe how the density matrix renormalization group can be used for quantum chemical calculations for molecules, as an alternative to traditional methods, such as configuration interaction or coupled cluster approaches. As a demonstration of the potential of this approach, we present results for the H{sub 2}O molecule in a standard ...

The Ca3 and Ca4 metallic clusters have been investigated using state-of-the-art ab initio quantum mechanical methods. Large atomic natural orbital basis sets have been used in conjunction with the singles and doubles coupled-cluster (CCSD) method, a coupl...

It is now possible to calculate many properties including the energetics (total bond dissociation energies or heats of formation) of molecules containing light elements to high accuracy by using correlation-consistent basis sets, coupled cluster theory an...

Chances for the existence and detection of interstellar cyanovinylidene, CC(H)CN, the branched isomer of cyanoacetylene, are discussed based on the results of quantum-chemical calculations. Ab-initio (coupled cluster) and density functional theory predictions for CC(H)CN structure, electric dipole moment, rotational spectroscopy, and ...

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; Potential energy surface 1. Introduction

A prediction of four-membered cyclic boranes is presented. Structure and bonding of planar and puckered rings optimized at MBPT(2)/PVDZ level are discussed. Singlet-triplet gaps and thermodynamic stabilities of the rings based on Coupled Cluster calculations are given.

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, ...

The interaction-induced contribution to the NMR shielding constants in homonuclear A2 and heteronuclear AB (A,B=He,Ne,Ar) dimers is obtained ab initio by employing a coupled cluster singles and doubles with perturbative treatment of triples wave function model and extended ...

We report the result of our ab initio calculation of the 6s{sup 2}S{sub 1/2}{yields}5d{sup 2}D{sub 3/2} parity nonconserving electric dipole transition amplitude in {sup 137}Ba{sup +} based on relativistic coupled-cluster theory. Considering single, double, and partial triple excitations, we have achieved an accuracy of less than 1%. ...

Ab initio quantum mechanical methods, including the self-consistent field (SCF), two-configuration SCF (TCSCF), single and double excitation configuration interaction (CISD), two-reference CISD with the TCSCF optimized molecular orbitals (TCSCCF-CISD), single and double excitation coupled cluster (CCSD), and the ...

Ab initio electronic structure calculations are reported for OPO, its ions OPO+ and OPO-. Geometric parameters and rotational constants are calculated using the singles and doubles coupled cluster method, including a perturbational correction for connected triple excitations, CCSD(T), together with systematic ...

The following final report summarizes four years of research for ONR on the topic of 'Many-Body Quantum Mechanical Studies of Molecular Clusters.' There are two primary aspects of this effort, a methodological part focusing on new first principle (i.e. ab initio) multi-reference coupled-cluster methods for obtaining improved solutions ...

We report the development of a general order relativistic coupled-cluster (CC) code. Our implementation is based on Kramers-paired molecular spinors, utilizes double group symmetry, and is applicable with the full Dirac-Coulomb and several approximate relativistic Hamiltonians. The available methods include iterative and perturbative single-reference CC approaches with ...

The potential energy surfaces (PESs) of the two lowest excited singlet states of furan [correlating with the Rydberg (1)A(2)(3s) and valence (1)B(2)(V) states at the C(2v) ground-state molecular configuration] have been studied in some detail with regard to the photoinduced ring-opening reaction. The surfaces have been characterized in terms of their stationary points and points of minimum energy ...

The potential energy surfaces (PESs) of the two lowest excited singlet states of furan [correlating with the Rydberg 1A2(3s) and valence 1B2(V) states at the C2v ground-state molecular configuration] have been studied in some detail with regard to the photoinduced ring-opening reaction. The surfaces have been characterized in terms of their stationary points and points of minimum energy conical ...

The available experimental rotational constants of cis,trans-1,4-difluorobutadiene do not permit a determination of a complete structure. However, this problem, rather frequent in finding structures, may be solved by the mixed estimation method. The experimental ground state rotational constants are corrected for the rovibrational contribution calculated from an ab ...

Interaction potentials of the iodine atom, atomic cation, and anion with light rare-gas atoms from He to Ar are calculated within the unified ab initio approach using the unrestricted coupled-cluster with singles and doubles and perturbative treatment of triples correlation treatment, relativistic small-core pseudopotential, and an ...

Hydrogen bonding in infinite (HF)_infinity and (HCl)_infinity bent (zig-zag) chains is studied using the ab initio coupled-cluster singles and doubles (CCSD) correlation method. The correlation contribution to the binding energy is decomposed in terms of non-additive many-body interactions between the monomers in the chains, the ...

The gas phase reaction of Th(+) with H(2)O to produce HThO(+) + H and ThO(+) + H(2) was investigated using density functional theory and coupled cluster methods. RRKM calculations of the branching ratio favor the H atomic elimination channel in disagreement with experiment. Ab initio classical trajectory ...

We discuss peculiarities of open-quantum systems, as compared to closed-quantum systems. We emphasize the importance of taking continuum degrees of freedom into account when dealing with systems with a tendency to decay through emission of fragments. In this context, we introduce the coupled-cluster theory and argue that this method allows for an accurate description of such systems starting from ...

A theoretical study of the potential energy surface and bound states is performed for the ground state of the NeI2 van der Waals (vdW) complex. The three-dimensional interaction energies are obtained from ab initio coupled-cluster, coupled-cluster single double (triple)/complete basis set, calculations using large ...

Implementation of very accurate ab initio methods on the one hand and improvements in computer facilities on the other hand allow the determination of structural, thermochemical, and spectroscopic properties of small- to medium-sized molecules to a very high accuracy. The predictive capabilities have become so high that theoretical calculations can guide, ...

We present ab-initio calculations for ³H, ⁴He, ¹⁶O, and ⁴⁰Ca based on two-nucleon low-momentum interactions V_{low k} within coupled-cluster theory. For ³H and ⁴He, our reesults are within 70 keV and 10 keV of the ...

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 ...

A theoretical study of the potential energy surface and bound states is performed for the ground state of the NeI(2) van der Waals (vdW) complex. The three-dimensional interaction energies are obtained from ab initio coupled-cluster, coupled-cluster single double (triple)/complete basis set, calculations using ...

High-level ab initio calculations were carried out to evaluate the interaction between the hydroquinone and benzene molecules. The intermolecular interaction energy was calculated using the M�ller-Plesset second-order perturbation theory at the complete basis set limit and also at the coupled cluster theory with ...

The heats of formation of CF3, its cation and anion, CF4, C2F4, and :CFCF3 have been calculated at high levels of ab initio molecular orbital theory. Geometries and frequencies were determined, in general, with second-order perturbation theory. Total energies based on coupled cluster calculations with perturbative ...

Zinc crystallizes in the hcp structure, but with an anomalously large c/a ratio, indicating a strong distortion away from ideal packing. Coupled cluster calculations within the framework of the method of increments, improved by an embedding scheme for metals, were performed to explore the potential energy surface of zinc with respect to the hexagonal ...

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 ...

We study the ground and low-lying excited states of {sup 15}O, {sup 17}O, {sup 15}N, and {sup 17}F using modern two-body nucleon-nucleon interactions and the suitably designed variants of the ab initio equation-of-motion coupled-cluster theory aimed at an accurate description of systems with valence particles and holes. A number of ...

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 ...

Three-dimensional quantum mechanical calculations on the vibrational predissociation dynamics of HeI2 B state complex are performed using a potential energy surface accurately fitted to unrestricted open-shell coupled cluster ab initio data, further enabling extrapolation for large I2 bond lengths. A Lanczos ...

In continuing pursuit of thermochemical accuracy to the level of 0.1 kcal mol(-1), the heats of formation of NCO, HNCO, HOCN, HCNO, and HONC have been rigorously determined using state-of-the-art ab initio electronic structure theory, including conventional coupled cluster methods [coupled ...

Two new schemes for computing molecular total atomization energies (TAEs) and/or heats of formation (?Hf?) of first- and second-row compounds to very high accuracy are presented. The more affordable scheme, W1 (Weizmann-1) theory, yields a mean absolute error of 0.30 kcal/mol and includes only a single, molecule-independent, empirical parameter. It requires CCSD (coupled ...

A new ab initio method for calculating transition strengths and orbital-unrelaxed first-order properties of singlet ground and excited states of extended molecular systems is presented. It is based on coupled cluster response theory at the level of the CC2 model with local approximations introduced to the ...

We report the development of a general order relativistic coupled-cluster (CC) code. Our implementation is based on Kramers-paired molecular spinors, utilizes double group symmetry, and is applicable with the full Dirac-Coulomb and several approximate relativistic Hamiltonians. The available methods include iterative and perturbative single-reference CC approaches with ...

Ab initio quantum mechanical methods, including the self-consistent field (SCF), single and double excitation configuration interaction (CISD), the single and double excitation coupled cluster (CCSD), and the single, double, and perturbative triple excitation coupled ...

The recently developed reduced multireference coupled-cluster method with singles and doubles (RMR CCSD), which is perturbatively corrected for triples [RMR CCSD(T)], is employed to compute binding energies of nine transition metal ions with CH2. Unlike analogous compounds involving main-group elements, the MCH2+ (M=Sc to Cu) transition metal complexes often exhibit a ...

The recently developed reduced multireference coupled-cluster method with singles and doubles (RMR CCSD), which is perturbatively corrected for triples [RMR CCSD(T)], is employed to compute binding energies of nine transition metal ions with CH2. Unlike analogous compounds involving main-group elements, the MCH2+ (M=Sc to Cu) transition metal complexes often exhibit a ...

The reaction of ground state ([sup 2][ital A][prime]) CH[sub 3]N[sub 2][r arrow]CH[sub 3]+N[sub 2] was studied using the [ital ab] [ital initio] quantum mechanical techniques, including the self-consistent field (SCF), single and double excitation configuration interaction (CISD), single and double excitation coupled ...

Various ab initio methods are used to compute the six dimensional potential energy surfaces (6D-PESs) of the ground states of the H(2)NSi and H(2)SiN radicals. They include standard coupled cluster (RCCSD(T)) techniques and the newly developed explicitly correlated RCCSD(T)-F12 methods. For H(2)NSi, the explicitly ...

... 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,. ...

Using the ab initio coupled cluster method, correlation energies were calculated for a number of molecules composed of first-row atoms. The results of computations can be fitted rather well with simple analytic formulas. The main result of the present investigation is that intraatomic part of the correlation energy ...

Context: The Herschel Space Observatory with its high-resolution instrument HIFI on board will observe the CH+ 1?0 and 2?1 rotational transitions in a wide range of gas temperatures up to 1000 K. Collisional parameters for such temperatures are thus welcome. Aims: We aim to obtain accurate rate coefficients for the collisional excitation of CH+ by He for high gas temperatures. Methods: The ...

In this article, we report on the ab initio calculation of the static longitudinal second hyperpolarizability (?) of ? conjugated unsaturated oligomer chains using polyacetylene and polyyne as model compounds. The common observation is that the electron correlation enhances ? in these systems. The present study reveals that for extended chain lengths the ...

The potassium trimer is investigated in its lowest electronic doublet states, employing several high-level ab initio methods (coupled cluster with single, double, and noniterative triple excitations, multiconfiguration self-consistent field, and multireference Rayleigh-Schr�dinger perturbation theory of second ...

Electronic circular dichroism (ECD) parameters of the disulphide chromophore have been calculated for dihydrogen disulphide, dimethyl disulphide, and cystine using density-functional theory, coupled-cluster theory, and multiconfigurational self-consistent field theory. The objective is twofold: first, to examine the performance of the Coulomb-attenuated CAM-B3LYP functional ...

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, ...

We present a microscopic calculation of spectroscopic factors for neutron and proton removal from O24 using the coupled-cluster method and a state-of-the-art chiral nucleon-nucleon interaction at next-to-next-to-next-to-leading order. To account for the coupling to the scattering continuum we use a Berggren single-particle basis that treats bound, resonant, and continuum states on an equal ...

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 correlation potential ...

A method and codes for two-step correlation calculations of heavy-atom molecules have been developed, employing the generalized relativistic effective core potential (GRECP) and relativistic coupled cluster (RCC) methods at the first step, followed by nonvariational one-center restoration of proper four-component spinors in the heavy cores. Electron ...

Basis set convergence of the Hartree-Fock and the correlation energy is examined for the hydrogen bonded infinite bent chains (HF)_infinity and (HCl)_infinity. We employ series of correlation consistent basis sets up to quintuple zeta quality together with a coupled cluster method (CCSD) to describe electron correlation on ab ...

The ground electronic state of the eka-mercury dimer (E112{sub 2}) was studied within the model of generalized relativistic effective core potentials. A combined procedure based on describing correlation effects by the scalar relativistic coupled-cluster method and on taking into account spin-dependent interactions by means of density-functional theory was used in the ...

The ground electronic state of the eka-mercury dimer (E1122) was studied within the model of generalized relativistic effective core potentials. A combined procedure based on describing correlation effects by the scalar relativistic coupled-cluster method and on taking into account spin-dependent interactions by means of density-functional theory was used in the calculations. ...

The low-temperature rotational (de-) excitation of C3 (X1?+g) by collisions with He (1S) is studied using an ab initio potential energy surface (PES). This PES has been calculated using the single- and double-excitation coupled-cluster approach with noniterative perturbational treatment of triple excitations [CCSD(T)] and the augmented ...

Symmetry-Adapted Perturbation Theory (SAPT) provides a reliable method for ab initio calculations of intermolecular interaction energies. This methodology has been extended by including coupled-cluster single and double excitations in the calculation of the second-order polarization energy. The second-order dispersion energy at the ...

Protonated pyrene and coronene have been isolated in 6 K neon matrices. The cations were produced in the reaction of the parent aromatics with protonated ethanol in a hot cathode discharge source, mass-selected and co-deposited with neon. Three electronic transitions of the most stable isomer of protonated pyrene and four of protonated coronene have been recorded. The strongest, ...

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 correlation ...

Optimal control of rovibrational excitations of the CO molecule using picosecond infrared laser pulses is described in the framework of the electric-nuclear Born-Oppenheimer approximation [G. G. Balint-Kurti et al., J. Chem. Phys. 122, 084110 (2005)]. The potential energy surface of the CO molecule in the presence of an electric field is calculated using coupled ...

Two-hydrogen transfer (simultaneous protic and hydridic hydrogen transfer) is examined as a potentially efficient mechanism for the selective reduction of CO(2) to methanol. High-level ab initio CCSD(T) coupled-cluster theory simulations of ammonia-borane (AB), which contains both protic and hydridic hydrogen, show ...

The SC3 H radical is known by experiment to have a linear equilibrium structure, but even rather high-level ab initio computations give a bent equilibrium geometry. A theoretical study of the SCCCH radical has been carried out in order to analyse the influence of several factors in the computed equilibrium structure. Quadratic configuration interaction ...

A relativistic ab initio model potential (AIMP) for Pt, Au, and Hg atoms has been developed using a relativistic scheme by eliminating small components (RESC) in which the 5p, 5d, and 6s electrons are treated explicitly. The quality of new RESC-AIMP has been tested by calculating the spectroscopic properties of the hydrides of these elements using the ...

A six-dimensional interaction potential for the water dimer has been fitted to ab initio interaction energies computed at 2510 dimer configurations. These energies were obtained by combining the supermolecular second-order energies extrapolated to the complete basis set limit from up to quadruple-zeta quality basis sets with the contribution from the ...

The multimode multistate vibronic interactions between the five lowest electronic states of all three isomers of the difluorobenzene radical cation are investigated theoretically, based on ab initio electronic structure data, and employing a well-established vibronic coupling model. The approach rests on the linear vibronic coupling scheme, augmented by ...

Isofulminic acid, HONC, the most energetic stable isomer of isocyanic acid HNCO, higher in energy by 84 kcal/mol, has been detected spectroscopically by rotational spectroscopy supported by coupled cluster electronic structure calculations. The fundamental rotational transitions of the normal, carbon-13, oxygen-18, and deuterium isotopic species have been ...

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 Si-H stretching-bending overtones in SiHCl3 were investigated employing theoretically calculated potential energy surfaces (PES) and dipole moment surfaces (DMS). The coupled cluster method CCSD(T) was utilized to generate both one-dimensional (1D) and three-dimensional (3D) surfaces. An empirical 3D PES was also taken into consideration. The computed ...

Fully relativistic ab initio Dirac-Coulomb Fock-space coupled cluster calculations were performed on Tl and element 113. The calculated polarizabilty of element 113, 29.85 au, is the smallest in group 13, except for B. The estimated atomic and van der Waals radii of element 113 are also the smallest among these ...

The ammonia-hydrogen bromide and ammonia-hydrogen iodide, anionic heterodimers were studied by anion photoelectron spectroscopy. In complementary studies, these anions and their neutral counterparts were also investigated via ab initio theory at the coupled cluster level. In both systems, neutral NH(3)...HX dimers ...

The high accuracy extrapolated ab initio thermochemistry (HEAT) protocol is applied to compute the total atomization energy (TAE) and the heat of formation of benzene. Large-scale coupled-cluster calculations with more than 1500 basis functions and 42 correlated electrons as well as zero-point energies based on full cubic and ...

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 isomers are ...

Ab initio calculations (coupled cluster with single and double excitations; CCSD) have been used to investigate the model redox systems ethylene:M(0) (M = Li, Na, K, Rb, Cs) and ethylene:M(I) (M = Be, Mg, Ca, Sr, Ba, Zn, Cd, Hg). Within C2v symmetry, the ground (2A1) states correspond to the charge distribution ...

Excited-state reaction paths and the corresponding energy profiles of 2-(2'-hydroxyphenyl)benzotriazole (TIN-H) have been determined with the CC2 (simplified singles-and-doubles coupled-cluster) ab initio method. Hydrogen transfer along the intramolecular hydrogen bond, torsion of the aromatic rings and pyramidization of the central ...

New ab initio potential energy surfaces for the ground (X?1A') and excited (�1A?) electronic states of HSiCl were obtained by using the single and double excitation coupled-cluster theory with a noniterative perturbation treatment of triple excitations and the multi-reference configuration interaction with Davidson correction, ...

We report ab initio correlated relativistic calculations of the effective electric field W{sub d} acting on the electron in two excited electronic states of PbO, required for extracting the electric dipole moment of the electron from an ongoing experiment at Yale, which has the potential of improving accuracy for this elusive property by several orders of ...

Using linear response approach to the M�ssbauer isomer shift, the calibration constant alpha((57)Fe) was obtained from high level ab initio calculations carried out for a representative set of iron compounds. The importance of the effects of relativity and electron correlation for an accurate description of the (57)Fe isomer shift is demonstrated on the ...

Hydrogen abstraction reactions play a key role in many thermal and catalytic processes involved in the production of fuels and chemicals. In this paper, the hydrogen abstraction reactions on toluene and tetralin by the benzyl radical are investigated by ab initio methods. These reactions are representatives of similar reactions occurring in the thermolysis ...

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 double-? basis set. The analytical PES ...

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 double-? basis set. The analytical PES ...

Using state-of-the-art theoretical methods, we investigate the stable isomers of C- 4, C4H and C4H-. Three of them are relevant for astrophysics and astrochemistry. These computations are performed using highly correlated ab initio methods and the aug-cc-pVXZ (X = T,Q) basis sets. In addition to the linear isomers, we predict the existence of several ...

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

The quantum mechanical theory for the scattering of two identical rigid rotors is reviewed and applied to the collision of O2(3?g-) molecules using a new accurate ab initio potential energy surface (PES) for the quintet state of the composite system. The PES is based on calculations using restricted coupled-cluster theory with singles, ...

Highly accurate analytical intermolecular potential energy surfaces (PESs) of the complexes composed of the water molecule and the rare gas (Rg) atom are presented for Rg=He, Ne, Ar, and Kr. These PESs were scanned using the supermolecule coupled cluster singles and doubles including connected triples method [CCSD(T)]. Efficient basis sets including the ...

The quantum mechanical theory for the scattering of two identical rigid rotors is reviewed and applied to the collision of O2(3Sigma(g)-) molecules using a new accurate ab initio potential energy surface (PES) for the quintet state of the composite system. The PES is based on calculations using restricted coupled-cluster theory with ...

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

PSI3 is a program system and development platform for ab initio molecular electronic structure computations. The package includes mature programming interfaces for parsing user input, accessing commonly used data such as basis-set information or molecular orbital coefficients, and retrieving and storing binary data (with no software limitations on file ...

In this work a reliable full nine-dimensional potential energy surface for studying the dynamics of H5+ is constructed, which is completely symmetric under any permutation of the nuclei. For this purpose, we develop a triatoms-in-molecules method as an extension of the more common diatoms-in-molecules one, which allows a very accurate description of the asymptotic regions by including correctly ...

In this work a reliable full nine-dimensional potential energy surface for studying the dynamics of H(5)(+) is constructed, which is completely symmetric under any permutation of the nuclei. For this purpose, we develop a triatoms-in-molecules method as an extension of the more common diatoms-in-molecules one, which allows a very accurate description of the asymptotic regions by including ...

A coupled cluster expansion was used to direct an ab initio search for stable ordered structures on the cubic fluorite lattice across the ZrO2-Y2O3 composition range. The energies of 453 arrangements of (Zr, Y) cations and (O, vacancy) anions on the fluorite lattice were calculated by using density functional ...

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 ...

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 ...

Large basis set coupled cluster calculations through noniterative triple excitations were used to compute optimized structures, harmonic vibrational frequencies, atomization energies at 0 K and heats of formation at 298 K for hydroxylamine (NH2OH) and three related compounds (NH3, HNO and H2O2). The use of basis sets as large as augmented sextuple zeta ...

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 ...

The electronic structure of the ScN and ScP molecules is a subject of controversy and turns out to be a challenging problem in quantum chemistry. We show that the ground-state electronic structure for both molecules depends critically on the choice of methods used which incorporate different ways of accounting for electron correlation. A parallel ab ...

Four potential energy surfaces are of current interest for the Ne-CO interaction. Two are high-level fully ab initio surfaces obtained a decade ago using symmetry-adapted perturbation theory and supermolecule coupled-cluster methods. The other two are very recent exchange-Coulomb (XC) model potential energy surfaces constructed by ...

Four potential energy surfaces are of current interest for the Ne-CO interaction. Two are high-level fully ab initio surfaces obtained a decade ago using symmetry-adapted perturbation theory and supermolecule coupled-cluster methods. The other two are very recent exchange-Coulomb (XC) model potential energy surfaces constructed by ...

The absorption cross section of HOOH, a starting point for larger ROOH, was calculated using the "Wigner method." Calculations use the Wigner transform of ground state wave functions and classical approximations for excited state wave functions. Potential energy and transition dipole moment surfaces were calculated using the equation-of-motion coupled-cluster singles and ...

The absorption cross section of HOOH, a starting point for larger ROOH, was calculated using the ``Wigner method.'' Calculations use the Wigner transform of ground state wave functions and classical approximations for excited state wave functions. Potential energy and transition dipole moment surfaces were calculated using the equation-of-motion coupled-cluster singles and ...

The potential energy surface of H(5)(+) is characterized using density functional theory. The hypersurface is evaluated at selected configurations employing different functionals, and compared with results obtained from ab initio CCSD(T) calculations. The lowest ten stationary points (minima and saddle-points) on the surface are located, and the features ...

The equilibrium structures of FNO, ClNO, HONO, and FNO2 have been determined using three different, somewhat complementary methods: a completely experimental, a semi-experimental (where the equilibrium rotational constants are derived from the experimental effective ground-state rotational constants and an ab initio cubic force field), and an ...

The performance of current density functionals is analyzed in detail for the electric field gradients (EFG) of hydrogen chloride and copper chloride by comparison with ab initio methods and available experimental data. The range of density functionals applied shows good agreement with coupled cluster H and Cl field ...

The structural, electronic, vibrational, optical, magnetic, and aromatic characteristics of Sin, Sin1-, Sin2-, and Sin1+, clusters have been calculated very accurately with a variety of high level ab initio techniques. These calculations have been performed with the aim to clarify existing ambiguities in the literature and to bring up the fluxional and ...

A new ab initio interaction potential for the electronic ground state of argon dimer has been developed. The potential is a sum of contributions corresponding to various levels of the coupled-cluster theory up to the full coupled-cluster method with single, double, triple, and quadruple excitations. All contributions have been ...

A new ab initio interaction potential for the electronic ground state of argon dimer has been developed. The potential is a sum of contributions corresponding to various levels of the coupled-cluster theory up to the full coupled-cluster method with single, double, triple, and quadruple excitations. All contributions have been ...

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 ...

The photophysical and dynamical properties of the donor-(?-bridge)-acceptor molecule N-phenylpiperindone-malondinitrile are investigated by second-order approximate coupled cluster (CC2) and time-dependent density functional theory (TDDFT). The study is based on optimized equilibrium geometries for ground and excited states as well as on ...

... 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...

The minimum energy path for isomerization of HO(3) has been explored in detail using accurate high-level ab initio methods and techniques for extrapolation to the complete basis set limit. In agreement with other reports, the best estimates from both valence-only and all-electron single-reference methods here utilized predict the minimum of the cis-HO(3) ...

... 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 ... 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 ...

... 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). ...

... 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. ...

... 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 ...

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. ...

... 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 ...

... 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 ...