... Abstract : Results are presented from ab initio quantum chemical calculations on the ground state potential energy surface for the open shell ...
DTIC Science & Technology
... Accession Number : ADA351780. Title : Ab Initio and DFT Potential Energy Surfaces for Cyanuric Chloride Reactions. Descriptive Note : Final rept. ...
... 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. ...
We report on the determination of a high quality ab initiu potential energy surface (PES) and dipole
NASA Technical Reports Server (NTRS)
... the potential energy surface provided by modern electronic structure ... screening approach, to determine the equilibrium geometry and composition ...
We have carried out extensive high quality ab initio electronic structure calculations of the ground
The predissociation line broadening in the Schumann-Runge bands of O2 is explained by an ab initio calculation of the pertinent repulsive potential energy curves and spin-orbit matrix elements. The ab initio results provide an overall qualitative picture ...
National Technical Information Service (NTIS)
Examples of transition metal complexes containing dihydrogen ligands are investigated using ab initio electronic structure calculations employing effective core potentials. Calculated geometrical structures and relative energies of various forms of WL(sub...
with molecular dynamic simulations in combination with high level correlated ab initio quantum chemical the existing minima in the PES. 2. Ab initio quantum-chemical calculations. The lowest energy minima (within surface analysis by metadynamics. Gibbs energies and ...
E-print Network
A simple method is described to adjust a potential energy surface to improve agreement with experiment. An application is made to the ab initio HCO potential energy surface.(AIP)
Energy Citations Database
The results of an ab initio calculation of the potential energy surface governing atomic hydrogen recombination in the presence of helium atoms are presented. (auth)
... eg, SiHl6= has a negative ionization potential. ... V. POTENTIAL ENERGY SURFACES AND DYNAMICS ... initio with effective core potentials, ab initio ...
A classical Lennard-Jones potential is derived from a fit to the ab initio energies obtained from an all-electron mixed-basis calculation for methane in zeolite LTA. The potential predicts the heat of adsorption, adsorption isotherm, and self-diffusivity of methane in excellent agreement with ...
PubMed
In the present work we shall discuss recent advances in quantum chemical methodology that have improved the reliability of ab initio electronic structure ...
NASA Website
control of molecular dynamics; grid methods in the solution of time-dependent problems in quantum mechanics; ab initio calculation of potential energy surfaces and vibronic...
Science.gov Websites
... The structures of the entrance channel transition states show the four-body intermediates ... Campus Box 427 Boulder, CO 80309-0427 ...
... Title : A Comparative Study of Nonlocal Density Functional Theory and ab initio Methods: The Potential Energy Surface of sym-Triazine Reactions. ...
An approach is developed to enhance sampling for ab initio Monte Carlo and ab initio path integral Monte Carlo calculations of molecular clusters by utilizing an approximate potential as a guide to move in the configuration space more efficiently. The interpolated potential ...
The lowest two ab initio potential energy surfaces (PES), and the corresponding nonadiabatic couplings between them, have been obtained for the H{sub 3}{sup +} system; the molecular data are compared to those calculated with the diatomic in molecules (DIM) method. The form of the couplings is discussed in terms of ...
Results are presented from ab initio quantum chemical calculations on the ground state potential energy surface for the open shell doublet reaction: HNO + NO right arrow N2O + OH. (I) This reaction is thought to be Important in the sustained combustion of...
Accurate quartet- and doublet-state potential-energy surfaces for the interaction of a hydrogen atom and an oxygen molecule in their ground states have been determined from an ab initio calculation using large-basis sets and the internally contracted mult...
Ab initio calculations using extended basis sets are presented for the potential energy surface (PES) of H + OCS. There are two major reaction channels on the PES; Reaction (I) is H(2S) + OCS(1(Sigma)) yields OH(2(Pi)) + CS(1(Sigma)), and Reaction (II) is...
The recombination dynamics for the SiH2 +SiH2 = SiH2 reaction are studied by quasiclassical trajectory methods using a global potential-energy surface fitted to the available experimental data and the results of various ab initio calculations. The potenti...
We perform ab initio molecular dynamics simulations to study the dissociation of NaCl in water. The potential of mean force (PMF) between the two ions is determined using the constrained-force method. The simulation windows corresponding to the contact and solvent-separated minima, and the transition state in between, are further ...
NASA Astrophysics Data System (ADS)
We report a highly correlated multireference configuration interaction calculation of the near-equilibrium potential energy surface of ozone using a large correlation consistent basis set. Three-dimensional analytical expressions are obtained for the potential energy and dipole moment functions using least-squares ...
The interaction of CO{sub 2} and water is investigated by a combination of ab initio and SOLDRI-MM2 techniques. Ab initio results at levels of theory as high as MP2/6-311+G**//6-31G** are found to be in reasonable agreement with experiment. The R.{theta} potential energy ...
The comprehensive study of the ab initio pair potentials and prediction of properties for acetonitrile and methanol [J. Chem. Phys. 116, 7627 (2002), preceding paper] is extended to examine the vapor-liquid equilibria of their mixture. An ab initio pair interaction ...
Both ab initio MO--LCAO--SCF and the electron-gas (or Gordon--Kim) methods have been used to compute the intermolecular potential (Phi) of N/sub 2/ molecules for seven different N/sub 2/--N/sub 2/ orientations. The ab initio calculations were carried out using a (4s3p) contracted Gaussian basis ...
Results of ab initio Hartree-Fock calculations are presented for the nine-coordination-shell cluster Be{sub 69}. Binding energy, ionization potential, electrical field gradient, nuclear-electrostatic potential, diamagnetic shielding constant, second moments of charge, and Mulliken populations ...
. In the present context it is particularly the oxygen environment which acts as such a reservoir, because it can oxygen chemical potential. 2.2 Calculating Gibbs free energies As apparent from eqs. (3) and (5 as the chemical potential of the oxygen environment. Since the RTO-EN-AVT-142 2 - 3 Ab ...
A practical method of calculating the intrinsic reaction coordinate starting at a saddle point is proposed. The method has been used in combination with the analytical evaluation of the energy gradient for the calculation of the reaction coordinate on an ab initio potential energy surface. The ...
Ab Initio electronic structure calculations using analytical energy derivative methods and automated potential energy surface walking techniques have been carried out on the tautomerization reaction path connecting formamide (F) H2N-CHO, through a transit...
The potential energy surfaces for the doublet pi and doublet sigma states in the collinear F+HH reaction have been calculated with ab initio restricted Hartree-Fock (GRHF) and GRHF-CI (configuration interaction) methods. The doublet pi state in the CI cal...
Dynamical calculations are performed on an ab initio potential energy surface for KCN. Approximate variational solutions of the vibrational Eckart hamiltonian are presented for several states. Fundamental vibrations are found to lie at 302�7 cm-1 and 119�7 cm-1. An effective rotational hamiltonian is solved for ...
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...
We present pair potentials for Cu and Al obtained by using the method of Moebius transform introduced by Chen (Phys. Rev. Lett. 64, 1193 (1990)) to invert the cohesive energy. Calculations of the cohesive energy have been done both in the fcc and bcc stru...
The potential energy surface for trimers of hydrogen fluoride is examined for multiple arrangements of the three-molecule cluster. Several established approaches to model the potential energy are examined, including a strictly pairwise additive potential, an established polarizable ...
For the equilibrium immiscible Fe-Cu system, ab initio calculations using the projector augmented wave method identify the relatively stable structures of the metastable Fe25Cu75 and Fe50Cu50 alloys to be both of fcc and determine their corresponding lattice constants and cohesive energies. Some of the ab ...
... Ab initio Energies Calculated Using 3 ... of the Transition States (TS ... Descriptors : *TRANSITIONS, *MOLECULES, COMPUTATIONS, COMPARISON ...
A new exchange-Coulomb semiempirical model potential energy surface for the He-N2 interaction has been developed. Together with two recent high-level ab initio potential energy surfaces, it has been tested for the reliability of its predictions of second-virial coefficients ...
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 carried out self-consistent reaction field (SCRF) calculations on the bacteriochlorophyll (BChl) and bacteriopheophytin (BPh) molecules at the Hartree-Fock level using the ab initio electronic structure code PSGVB together with an accurate numerical Poisson-Boltzmann solver. These are by far the largest ab ...
... We carried out ab-initio quantum chemical calculations on these energetic cyclic ethers and generated the electrostatic molecular potential contour ...
... from federally funded research, testing and training ... for Research Development Test and Evaluation ... Title : Ab Initio Calculation of Intermolecular ...
We present pair potentials for fluorinated methanes and their dimers with CO2 based on ab initio potential energy surfaces. These potentials reproduce the experimental second virial coefficients of the pure fluorinated methanes and their mixtures with CO2 without ...
The interaction potential energy surface (PES) of H4 is of great importance for quantum chemistry as a test case for molecule-molecule interactions. It is also required for a detailed understanding of certain astrophysical processes, namely collisional excitation and dissociation of H2 in molecular clouds, at densities too low to be accessible ...
We have calculated the melting temperature of tungsten by two ab initio approaches. The first approach can be divided into two steps. In the first step, we simulate a large coexisting solid and liquid system by the classical embedded-atom method potential and obtain an approximate melting temperature. In the second step, we compute the ...
An accurate and efficient molecular alignment technique is presented based on first principle electronic structure calculations. This new scheme maximizes quantum similarity matrices in the relative orientation of the molecules and uses Fourier transform techniques for two purposes. First, building up the numerical representation of true ab initio ...
PubMed Central
The unimolecular dissociation dynamics of disilane are investigated using classical trajectory methods with a global potential-energy surface fitted to the available experimental data and the results of various ab initio calculations. The potential surfac...
The objectives of this work which were fulfilled were to (1) use high level ab initio molecular orbital theory to predict the structures and energies of potential energetic molecules and to guide the synthesis of the more promising candidate molecules, (2...
Ab initio quantum chemical techniques have been used to investigate weakly bund complexes of H20 and SO2. An energy gradient program was used to ...
A biased potential molecular dynamics simulation approach, accelerated molecular dynamics (AMD), has been implemented in the framework of ab initio molecular dynamics for the study of chemical reactions. Using two examples, the double proton transfer reaction in formic acid dimer and the hypothetical adiabatic ring opening and ...
The nature of intermolecular interactions between aromatic amino acid residues has been investigated by a combination of molecular dynamics and ab initio methods. The potential energy surface of various interacting pairs, including tryptophan, phenilalanine, and tyrosine, was scanned for determining all the ...
Point defects in Fe and dilute FeCu alloys are investigated by ab initio calculations based on density functional theory. The relaxed vacancy and interstitial and substitutional Cu atom formation energies are determined as well as some migration energies. The binding energies of various Cu ...
Ab initio molecular orbital calculations on the structure and stability of the nitrate and sulfate complexes of uranyl (UO{sub 2}{sup 2+}) and plutonyl (PuO{sub 2}{sup 2+}) using effective core potentials are reported. It is found that the binding energy of sulfate is greater than that of nitrate to both uranyl and ...
Structural and thermal properties of small lithium clusters are studied using ab initio-based Monte Carlo simulations. The ab initio scheme uses a Hartree-Fock/density functional treatment of the electronic structure combined with a jump-walking Monte Carlo sampling of nuclear configurations. Structural forms of ...
The lattice constants and cohesive energies of some possible metastable Cu-W compounds are obtained by ab initio calculation and the formation of a metastable phase at Cu75W25 is predicted for the equilibrium immiscible Cu-W system. The prediction is in agreement with the fact that a metastable hcp phase was indeed observed in the ...
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 ...
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 ...
Potential energy curves for electronic states of Hg/sub 2/ and TlHg are presented and analyzed. They are derived using large scale configuration interaction procedures for the valence electrons, with the core electrons represented by ab initio relativistic effective potentials. The effect of ...
X. Huang, B.J. Braams, J.M. Bowman, R.E.A. Kelly, J. Tennyson, G.C. Groenenboom, and Ad van der Avoird : New ab initio potential energy surface and ...
The dynamics of the formation and dissociation of Si3 complexes in atom-dimer collisions have been investigated using quasiclassical trajectories on a potential-energy surface that is a global fit to the available experimental data and ab initio CI and MP...
We present a method for the computation of cohesive and structural properties of solids. The method is based on a local orbital description of the wavefunctions, an ab initio pseudopotential construction for the ion-core potential, and a local density tre...
Rich reactive resonances are found in a 3D quantum dynamics study of the N + N2 exchange reaction using a recently developed ab initio potential energy surface. This surface is characterized by a feature in the interaction region called Lake Eyring , that...
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)
The addition and abstraction reaction pathways on the potential energy surface for H + HCO have been characterized by an ab initio four electron, complete active space, self-consistent field electronic structure calculation. The elimination pathway to go ...
A theoretical research investigation of materials that are potential additives for solid hydrogen rocket fuels is investigated. The ab initio calculations show that mixed clusters of boron and lithium prefer to have an electronegative boron atom at the mi...
The HNO molecule is of interest in both combustion and atmospheric chemistry. For example, Guadagnini et al. have recently presented ab initio potential energy surfaces for the three lowest lying electronic states of HNO and then used these in examining s...
Dynamics of the O( ) + HCl reaction on the electronic state: A new ab initio potential energy for the lowest electronic state of the O( ) + HCl system is presented. This surface is based on electronic the reactants O( ) + HCl() to the products OH() + Cl( ). The reaction barrier on this surface lies at an O
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We present a new technique which allows the fully {\\em ab initio} calculationof the chemical potential of a substitutional impurity in a high-temperaturecrystal, including harmonic and anharmonic lattice vibrations. The techniqueuses the combination of thermodynamic integration and reference modelsdeveloped recently for the {\\em ...
Structure and dynamics of HeI2 van der Waals (vdW) complex are analyzed from first principles. Ab initio technology, at CCSD(T) and MRCI level of theories, was employed for constructing potential energy surfaces of the ground and excited electronic states, and a full quantum mechanical treatment for studying its ...
We report full ab initio Hartree-Fock calculation to compute quantum mechanical interaction energies for ?-trypsin/benzamidine binding complex. In this study, the full quantum mechanical ab initio energy calculation for the entire protein complex with 3238 atoms is made ...
An efficient procedure based on the reproducing kernel Hilbert space interpolation method is presented for constructing intermolecular potential energy surfaces (PES) using not only calculated ab initio data but also a priori information on long-range interactions. Explicitly, use of the reciprocal power ...
The rates of intramolecular proton transfer are calculated on a full-dimensional reactive electronic potential energy surface that incorporates high level ab initio calculations along the reaction path and by using classical Transition State theory, Path-Integral Quantum Transition State Theory, and the Quantum ...
Variational transition state theory calculations with the correction of multidimensional tunneling are performed on a 12-dimensional ab initio potential energy surface for the H+SiH4 abstraction reaction. The surface is constructed using a dual-level strategy. For the temperature range 200-1600 K, thermal rate ...
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 ...
Ga- and As-terminated GaAs(100) surfaces are studied through first-principles density-functional pseudopotential calculations of the energies of surfaces with different stoichiometries and reconstructions. We predict structural transitions as a function of Ga and As chemical potentials within an experimentally accessible range which is shown to be fixed by ...
We regularize the potential distribution framework to calculate the excess free energy of liquid water simulated with the BLYP-D density functional. Assuming classical statistical mechanical simulations at 350 K model the liquid at 298 K, the calculated free energy is found in fair agreement with experiments, but the excess internal ...
Recently presented nonrelativistic and quasirelativistic energy-adjusted ab initio pseudopotentials, semiempirical core polarization potentials and energy-optimized valence basis sets for the elements Hg to Rn have been applied in molecular calculations on selected hydrides of mercury through ...
The desorption potential energies of a hydrogen molecule from hydrogenated diamond C(100) surfaces have been calculated by the ab initio pseudopotential method.We found that a dihydride surface is less stable than a monohydride surface and that hydrogen desorption can be expected to occur from the dihydride instead ...
We present full-dimensional potential energy surfaces (PESs) for hydrated chloride based on the sum of ab initio (H(2)O)Cl(-), (H(2)O)(2), and (H(2)O)(3) potentials. The PESs are shown to predict minima and corresponding harmonic frequencies accurately on the basis of comparisons with previous ...
Ab initio Hartree--Fock calculations were performed on FeAr and FeAr/sup +/ in order to determine the interaction of both neutral and singly-ionized Fe atoms trapped in Ar, and on ArFeCO and FeCOAr in order to ascertain the effect of an Ar matrix on the FeCO molecule. Quadrupole splittings and isomer shifts are computed using ab ...
Recent accurate observations [1] of collision-induced absorption (CIA) in the nitrogen and oxygen fundamentals pointed at the existence of the minimum in its integrated intensity temperature variation. This work aims at simulation of the CIA intensity in N2 using quantum chemical complete potential energy and dipole surfaces for N2-N2 system. The absolute ...
This paper discusses using kinetic, spectroscopic, and ab initio studies of the prooxidant reaction of vitamin E derivatives to determine second-order rate constants for the reaction of six tocopheroxyl radicals with five alkyl hydroperoxides in benzene along with the first adiabatic ionization potentials of the alkyl hydroperoxides. ...
The structures and relative energies of Pt(PH/sub 3/)XY isomers are investigated with use of ab initio molecular orbital theory and effective potentials. In particular, the cis and trans isomers of the dihydride, dichloride, and hydrochloride are studied. In all cases, the trans isomer is the more stable. Available ...
The authors analyze the implications of the recently reported results of ab initio calculations of formation energies of the Fe-Cr alloy. The formation energies show a change in sign from negative to positive as Cr composition increases above {approx}10%. By developing a classic potential to ...
A formula to calculate the charge penetration energy that results when two charge densities overlap has been derived for molecules described by an effective fragment potential (EFP). The method has been compared with the ab initio charge penetration, taken to be the difference between the electrostatic ...
Following our recent studies of the thermodynamic properties of azaspiropentane and borospiropentane, in consideration of their usefulness as new potential high energy materials, we follow up with ab initio calculations on the thermodynamic properties of azaborospiropentanes. Properties reported in this study ...
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 ...
Quantum chemical calculations of energies, geometrical structure and vibrational wave numbers of 3,4-dimethoxybenzonitrile (DMBN) were carried out by the ab initio Hartree-Fock (HF) and density functional theory (DFT) with complete relaxation in the potential energy surface using 6-311++G(d,p) ...
Ab initio molecular electronic structure theory has now progressed to the point where it is capable of making genuine contributions to the understanding of simple chemical reactions. Especially noteworthy examples are the elementary fluorine hydrogen reactions pertinent to the HF chemical laser. The reactions F + H/sub 2/ ..-->.. FH + H, H + FH ...
The study and prediction of chemical reactivity is one of the most influential contributions of quantum chemistry. A central concept in the theoretical treatment of chemical reactions is the reaction pathway, which can be quite difficult to integrate accurately and efficiently. This talk will outline our developments in the integration of these pathways on ab ...
Ab initio molecular orbital theory has been used to calculate accurate enthalpies of formation and adiabatic electron affinities or ionization potentials for N3, N3(-), N5(+), and N5(-) from total atomization energies. Born-Haber cycle calculations, using...
The quantum dynamics of the rotational quenching of the Mg24H+(X1?+) molecular cation interacting with He4(1S) as a buffer gas, at relative temperatures ranging from 1 K down to millikelvins, is described by accurate close coupling scattering calculations on an ab initio potential energy surface. The efficiency of ...
The photoelectron spectra of the weakly bound KrO- anion are simulated using a theory which combines the atoms-in-molecule model for molecular electronic wave functions and the Rau-Fano model for photodetachment intensities [J. Chem. Phys. 112, 5852 (2000)]. The nonrelativistic potential energy curves of the anion are obtained from ab ...
Mass tensor molecular dynamics method was first introduced by Bennett [J. Comput. Phys. 19, 267 (1975)] for efficient sampling of phase space through the use of generalized atomic masses. Here, we show how to apply this method to ab initio molecular dynamics simulations with minimal computational overhead. Test calculations on liquid water show a threefold ...
The ferroelectric [001], [011], and [111] instabilities in KNbO3 with up to 12.5 mol% Cu on K or Nb sites, respectively, are investigated using both ab initio density-functional theory and classical interatomic potentials. A doping level of only about 2�4 mol% Cu on K sites enhances the ferroelectric instabilities and induces a ...
We study the potential energy landscape underlying the motion of monatomic liquids by quenching from random initial configurations (stochastic configurations) to the nearest local minimum of the potential energy. We show that this procedure reveals the underlying potential ...
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 stationary points on the cyclo-C(6)H(11)O(2) ...
We have applied the ab initio path integral molecular dynamics simulation to study hydronium ion and its isotopes, which are the simplest systems for hydrated proton and deuteron. In this simulation, all the rotational and vibrational degrees of freedom are treated fully quantum mechanically, while the potential ...
Computational materials science based on ab initio calculations has become an important partner to experiment. This is demonstrated here for the effect of impurities and alloying elements on the strength of a Zr twist grain boundary, the dissociative adsorption and diffusion of iodine on a zirconium surface, the diffusion of oxygen atoms in a Ni twist ...
This study address the adequacy of ab initio pair interaction energy potentials for the prediction of macroscopic properties. Recently, Bukowski et al. [J. Phys. Chem. A 103, 7322 (1999)] performed a comprehensive study of the potential energy surfaces for several pairs of ...
The potential energy surface of the ground state of the He-MnH(X (7)Sigma(+)) van der Waals complex is presented. Within the supermolecular approach of intermolecular energy calculations, a grid of ab initio points was computed at the multireference configuration interaction level using the ...
Molybdenum's and tantalum's high strength and high-temperature stability makes these refractory metals very attractive for use in advanced process technologies; however, the pure metals are very brittle. To describe plastic deformation requires knowledge of how dislocations--the defects responsible for crystal plasticity--evolve under stress. A classical potential for ...
... Corporate Author : NATIONAL STANDARD REFERENCE DATA SYSTEM. ... observable properties including the total energy, dissociation energy ...
... agencies for Research Development Test and Evaluation ... Potentials of Mixed Systems: Testing the Lorentz ... Mixing Rules with Ab Initio Calculations. ...
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 ...
A semiempirical potential energy surface is obtained for the major isotopologue of the water molecule H2 16O that allows the vibration-rotation energy levels in the range of 0-26000 cm-1 to be calculated with an accuracy almost equal to the average experimental accuracy of measurements in the infrared and visible ranges. Variational ...
Most theoretical calculations of cross sections for low-energy electron- and positron-molecule collisions include the important induced-polarization effects in the interaction potential by means of a semiempirical adiabatic approximation based on the known asymptotic form of the potential. In order to examine the validity of the ...
A new high quality three-dimensional potential energy surface for the Ne-CO van der Waals complex is developed using the CCSD(T) method and avqz/avqz+33221 basis set. The ab initio calculation is performed in a total of 1365 configurations with supermolecule method. There is a single global minimum located in a ...
We have resolved the apparent inconsistency in quantifying the electrochemical surface potential at the liquid-vapor interface when using explicit ab initio electronic charge density and effective atomic partial charge models of liquid water. It is shown that regions of space must be excluded for the evaluation of the electric ...
A new global potential energy surface for the lowest triplet electronic state (a3A'') of HNO has been developed by a three-dimensional cubic spline interpolation of more than 13 000 ab initio points, which were calculated at the multireference configuration interaction level with Davidson correction using the ...
A new global potential energy surface for the lowest triplet electronic state (a(3)A") of HNO has been developed by a three-dimensional cubic spline interpolation of more than 13,000 ab initio points, which were calculated at the multireference configuration interaction level with Davidson correction using the ...
In a previous publication (1997. P. Jensen, J. Mol. Spectrosc. 181, 207-214), rotation-vibration energy levels for the electronic ground state X3B1 of the amidogen ion, NH2+, were predicted using the MORBID Hamiltonian and computer program with an ab initio potential energy surface. In the ...
Ab initio global adiabatic and quasidiabatic potential energy surfaces of lowest four electronic (1-4 3A'') states of the H++O2 system have been computed in the Jacobi coordinates (R,r,?) using Dunning's cc-pVTZ basis set at the internally contracted multireference (single and double) configuration interaction ...
Ab initio global adiabatic and quasidiabatic potential energy surfaces of lowest four electronic (1-4? (3)A(")) states of the H(+)+O(2) system have been computed in the Jacobi coordinates (R,r,?) using Dunning's cc-pVTZ basis set at the internally contracted multireference (single and double) configuration ...
We have resolved the inconsistency in quantifying the surface potential at the liquid-vapor interface when using explicit ab initio electronic charge density and effective atomic partial charge models of liquid water. This is related, in part, to the fact that the resulting electric potentials from partial-charge ...
Molecular dynamics simulations of NO-doped Ar solid upon Rydberg photoexcitation of the impurity have been carried out taking into account angular dependent potential energy surfaces (PESs) in the ground and excited states. To go beyond isotropic potentials simulations, the effects of anisotropy of potentials on ...
Atom-surface potentials entering the calculations of fast atom scattering at surfaces are often taken to be purely repulsive and parameterized by variants of the ZBL potential. However, such surface potentials derived from pairwise superpositions of binary potentials fail to reproduce recent rainbow scattering ...
We report a new ``spectroscopic'' potential energy surface (PES) of formaldehyde (H212C16O) in its ground electronic state, obtained by refining an ab initio PES in a least-squares fitting to the experimental spectroscopic data for formaldehyde currently available in the literature. The ab ...
We report a new "spectroscopic" potential energy surface (PES) of formaldehyde (H(2) (12)C(16)O) in its ground electronic state, obtained by refining an ab initio PES in a least-squares fitting to the experimental spectroscopic data for formaldehyde currently available in the literature. The ab ...
In the present work, all adiabatic potential energy curves, spectroscopic constants and dipole moments of CaH+ molecular ion dissociating below the ionic limit Ca2+H- are presented. These curves are determined by an ab initio approach involving a non-empirical pseudo-potential for the Ca core, ...
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 ...
Ab initio quantum chemistry methods are used to study the energetics of interactions of O atoms with
Harding and Goddardl (HGI) computed accurate ab initio potential ... In order to resolve this uncertainty Harding and Goddard ...
Additivity of Cation- Interactions: An ab Initio Computational Study on -Cation- Sandwich Complexes- sandwiches are the sums of the two corresponding TMA- systems. The contribution of electron correlation- sandwiches and to estimate their binding energies. Morokuma decomposition analysis on the binding energy
Hensley, J.M., S. Green, and G.W. Flynn, 1991: A simple ab initio calculation for energy transfer in collisions of hot hydrogen atoms with carbon dioxide. ...
A quantum mechanical investigation of the vibrational and rotational deactivation of NO(+) in collisions with He atoms in the cold and ultracold regime is presented. Ab initio potential energy calculations are carried out at BCCD(T) level and a new global 3D potential ...
We report a full dimensional, ab initio-based global potential energy surface (PES) and dipole moment surface for Cl-H2O. Both surfaces are symmetric with respect to interchange of the H atoms. The PES is a fit to thousands of electronic energies calculated using the coupled-cluster method ...
A quantum mechanical investigation of the vibrational and rotational deactivation of NO+ in collisions with He atoms in the cold and ultracold regime is presented. Ab initio potential energy calculations are carried out at BCCD(T) level and a new global 3D potential energy ...
We present elastic and inelastic spin-changing cross sections for cold and ultracold NH(X (3)?(-)) + NH(X (3)?(-)) collisions, obtained from full quantum scattering calculations on an accurate ab initio quintet potential-energy surface. Although we consider only collisions in zero field, we focus on the cross sections relevant for ...
We present elastic and inelastic spin-changing cross sections for cold and ultracold NH(X 3?-) + NH(X 3?-) collisions, obtained from full quantum scattering calculations on an accurate ab initio quintet potential-energy surface. Although we consider only collisions in zero field, we focus on the cross sections relevant for magnetic ...
... Abstract : This report describes the development and application of ab initio quantum chemical methods that are especially relevant to the study of ...
An ab initio model is developed for the potentials in ionic molecular solids in which the electron covalenc within the molecular ions substantially affects the interionic interactions. By treating the intermolecular and intramolecular interactions on the ...
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 ...
BackgroundNative structures of proteins are formed essentially due to the combining effects of local and distant (in the sense of sequence) interactions among residues. These interaction information are, explicitly or implicitly, encoded into the scoring function in protein structure prediction approaches�threading approaches usually measure an alignment in the sense that how well a sequence ...
A general set of methods is presented for calculating chemical potentials in solid and liquid mixtures using {\\em ab initio} techniques based on density functional theory (DFT). The methods are designed to give an {\\em ab initio} approach to treating chemical equilibrium between coexisting ...
Ab initio molecular orbital calculations on phosphites, protonated phosphites, and protonated phosphates reveal important stereoelectronic effects. In the phosphites, an antiperiplanar lone pair on oxygen to the phosphite lone pair raises the energy of th...
The number of ab initio molecular electronic calculations has increased dramatically in the last few years. Both the practitioners and other interested students of the results of the calculations have found it increasingly difficult to determine the prese...
The adsorption energies of methane and ethane in zeolites are investigated with ab initio molecular orbital theory and density functional theory. In this work we have used zeolite cluster models containing two, three, and five tetrahedral (Si, Al) atoms a...
General procedures for computing alloy phase equilibria from ab initio electronic structure calculations are reviewed and applied to the Al-Li phase diagram. Free energies were calculated by the cluster variation method (CVM) in the tetrahedron approximat...
A global search for possible LiF cluster structures is performed up to (LiF)(8). The method is based on simulated annealing, where all the energies are evaluated on the ab initio level. In addition, the threshold algorithm is employed to determine the energy barriers for the transitions among these structures, for ...
Non-covalent interactions involving aromatic rings contribute significantly to the stability of three-dimensional structures of biological macromolecules. Therefore, accurate descriptions of such interactions are crucial in understanding the functional mechanisms of biological molecules. However, it is also well known that, for some cases where van der Waals interactions make a dominant ...
The molecular vibrations of xanthine were investigated in polycrystalline sample, at room temperature by Fourier transform infrared (FTIR) and FT-Raman spectroscopies. The spectra of the molecule have been recorded in the regions 4000-50 cm(-1) and 3500-100 cm(-1), respectively. Theoretical information on the optimized geometry, harmonic vibrational frequencies, infrared and Raman intensities were ...
Results are presented of a fully ab initio calculation of impact ionization rates in GaAs within the density functional theory framework, using a screened-exchange formalism and the highly precise all-electron full-potential linearized augmented plane wave method. The calculated impact ionization rates show a marked orientation ...
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Fourteen conformers of 3-amino-1-propanol as the minima on the potential energy surface are examined at the MP2/6-311++G** level. Their relative energies calculated at B3LYP, MP3 and MP4 levels of theory indicated that two most stable conformers display the intramolecular OH���N hydrogen bonds. The vertical ionization ...
Single-determinant ab initio molecular-orbital calculations have been carried out on the series of donor-acceptor complexes A-OH/sub 2/ (A = Li, Be, B, C, Na, Mg, Al) in their ground and certain excited states. Equilibrium A-O distances, dissociation energies, dipole moments, and some vibrational frequencies have been determined. ...
Extensive ab initio calculations using a complete active space second-order perturbation theory wavefunction, including scalar and spin-orbit relativistic effects with a quadruple-zeta quality basis set were used to construct an analytical potential energy surface (PES) of the ground state of the [H, O, I] system. ...
In this paper, we further develop the molecular fractionation with conjugate caps (MFCC) scheme for quantum mechanical computation of DNA-ligand interaction energy. We study three oligonuclear acid interaction systems: dinucleotide dCG/water, trinucleotide dCGT/water, and a Watson-Crick paired DNA segment, dCGT/dGCA. Using the basic MFCC approach, the nucleotide chains are cut ...
The pseudofunction energy-band method is a full potential, ab initio technique with no adjustable parameters. The basis function is related to the pseudofunction used to create ab initio pseudopotentials. Orthogonalization of the pseudofunction to the core states is ...
We have tested approaches for molecular-dynamics simulations of the ion properties in high-energy-density matter. The scheme incorporates quantum corrections within the potentials used in the classical molecular-dynamics simulation. Thus, a significantly larger number of particles in the simulation box as in ab ...
The vertical ionization potentials from 9-22 eV for ethylene, cyclopropene, cyclobutene and methylene cyclopropane are correlated with the ab initio 4-31G molecular orbital energies with an rms error of 0.2 eV. The result is related to the reorganization ...
Critical points on the potential energy surface (PES) for sym-triazine (C3N3H3) have been calculated using nonlocal density functional (NDFT) methods. The two decomposition mechanisms for sym-triazine investigated are a concerted triple dissociation of th...
A detailed study of methods for generating the minimum energy path of a chemical reaction using ab initio electronic structure calculations is presented; the convergence with respect to step size of the geometry and energy along this path is studied with several algorithms. The investigations are extended to the ...
We perform ab initio calculation using quantum chemistry package (MOLPRO) on the excited states of Na3 cluster and present the adiabatic PESs for the electronic states 22E' and 12A1', and the non-adiabatic coupling (NAC) terms among those states. Since the ab initio calculated NAC elements for the states 22E' and ...
We perform ab initio calculation using quantum chemistry package (MOLPRO) on the excited states of Na(3) cluster and present the adiabatic PESs for the electronic states 2(2)E' and 1(2)A(1)', and the non-adiabatic coupling (NAC) terms among those states. Since the ab initio calculated NAC elements for the states ...
A global 12-dimensional ab initio interpolated potential energy surface (PES) for the SiH4+H-->SiH3+H2 reaction is presented. The ab initio calculations are based on the unrestricted quadratic configuration interaction treatment with all single and double excitations ...
, HMMSTR-CM, for protein contact map predictions. Contact potentials were calculated by using HMMSTR potentials then were used to evaluate these templates. An ab initio method based on the target contact compactness scores. Each C was scored by using the "contact free energy" (CFE). The ...
We use the method of Moebius transform introduced by one of us (Chen, Phys. Rev. Lett. 64, 1193 (1990)) to obtain pair potentials for fcc metals from first principles total energy calculations. The derivation is exact for radial potentials and it converge...
Misfolded metallo-proteins are potential causal agents in the onset of neuro-degenerative diseases, such as Alzheimer's and Parkinson's Diseases (PD). Experimental results involving metal chelation have shown significant promise in symptom reduction and misfolding reversal. We explore, through atomistic simulations, potential reaction pathways for the ...
The explicit polarization (X-Pol) method has been examined using ab initio molecular orbital theory and density functional theory. The X-Pol potential was designed to provide a novel theoretical framework for developing next-generation force fields for biomolecular simulations. Importantly, the X-Pol potential is a ...
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 ...
We employ recent flexible ab initio potential energy and dipole surfaces [Y. Wang, X. Huang, B. C. Shepler, B. J. Braams, and J. M. Bowman, J. Chem. Phys. 134, 094509 (2011)] to the calculation of IR spectra of the intramolecular modes of water clusters. We use a quantum approach that begins with a partitioned ...
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 ...
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 ...
Long range interactions between the ground state alkali diatomics Na(2)-Na(2), K(2)-K(2), Na(2)-K(2), and NaK-NaK are examined. Interaction energies are first determined from ab initio calculations at the coupled-cluster with singles, doubles, and perturbative triples [CCSD(T)] level of theory, including counterpoise corrections. Long ...
