Journal ArticleDOI
Potential model for diatomic molecules including the united-atom limit and its use in a multiproperty fit for argon
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In this article, the Coulombic behavior at the collapsed diatomic limit for vanishingly small interatomic separations, R→∞, has been investigated for 13 chemically stable diatomics and the Ar2 van der Waals molecule.Abstract:
The extended Hartree–Fock approximate correlation energy potential model recently reported for diatomics has been improved to account for the Coulombic behaviour at the collapsed diatomic limit for vanishingly small interatomic separations, R→ 0. Also discussed is how to impose the appropriate inverse exponential dependence on R into the extended Hartree–Fock energy contribution as R→∞. Test results are presented for the ground states of 13 chemically stable diatomics and the Ar2 van der Waals molecule. For Ar2, the potential-energy function is obtained from a multiproperty fit including spectroscopic, scattering, and second virial coefficient data. For the remaining diatomics, the calibration procedure uses only spectroscopic Rydberg–Klein–Rees (RKR) data. The new Ar2 potential is then used to calculate the thermophysical properties of gaseous argon over the temperature range 102⩽T/K⩽ 105. In all cases, the potential-energy function of the present work has been found to be very accurate.read more
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Equations of state valid continuously from zero to extreme pressures for h2o and co2
TL;DR: In this article, a new form of equation of state is proposed for use over extremely wide ranges of pressure where conventional equations fail, where fluids including H2O and CO2 remain more compressible at very high densities than can be represented by typical equations with van der Waals or Carnahan and Starling repulsive terms.
Journal ArticleDOI
Energy switching approach to potential surfaces: An accurate single‐valued function for the water molecule
TL;DR: In this article, a novel scheme is suggested to construct a global potential energy surface by switching between representations which are optimal for different energy regimes, which is illustrated for the electronic ground state of water for which we use as switched functions the manybody expansion potential of Murrell and Carter [J Chem Phys 88, 4887 (1984) and the polynomial form of Polyansky, Jensen, and Tennyson, [J Phys 101, 7651 (1994)] by also modifying the former to reproduce the Coulombic behavior at the collapsed molecular limits for vanishingly small interatomic
Journal ArticleDOI
Bonding Conundrums in the C2 Molecule: A Valence Bond Study.
TL;DR: The ab initio VB study for the electronic structure of the C2 molecule in the ground state shows that a triply bonded structure is the major one in terms of weights, and the lowest in energy at the equilibrium distance, and with the corresponding "in situ" bond strengths are estimated.
Journal ArticleDOI
Accurate ab initio based multisheeted double many-body expansion potential energy surface for the three lowest electronic singlet states of H3+.
TL;DR: The authors present diabatic and adiabatic potential energy surfaces for the three lowest electronic singlet states of H3+.
Journal ArticleDOI
Accurate DMBE Potential Energy Surface For the N( 2 D) + H 2 ( 1 Σ g + ) Reaction Using an Improved Switching Function Formalism
TL;DR: In this article, a single-sheeted double many-body expansion (DMBE) potential energy surface is reported for the NH2 state of NH2, which is shown to fit with high accuracy an extensive set of new ab initio points (calculated at the multi-reference configuration interaction level using the full valence complete active space as reference and aug-cc-pVQZ and aug -pV5Z basis sets) that have been semiempirically corrected at the valence regions.
References
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Journal ArticleDOI
An improved eigenvalue corrector formula for solving the Schrödinger equation for central fields
TL;DR: In this article, an accurate method for calculating the nuclear wave functions and vibrational-rotational energies of diatomic molecules with some economy in the number of values of the internuclear potential required is presented.
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Potential‐Energy Curves for the X 1Σg+, b3Σu+, and C 1Πu States of the Hydrogen Molecule
W. Kol,L. Wolniewicz +1 more
TL;DR: In this article, the ground-state energy of H2 has been extended to include large internuclear distances and accurate potential energy curve for 0.4≤R≤4.0 a.u.
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Liquid argon: Monte carlo and molecular dynamics calculations
TL;DR: In this paper, the Axilrod-Teller three-body interaction was used to calculate the pair-potential functions of solid and gaseous argon and liquid argon.
Journal ArticleDOI
Intermolecular forces in simple systems
TL;DR: In this paper, a semi-empirical method for the prediction of intermolecular forces was proposed for systems with a small number of electrons and leads to the conclusion that those systems behave as the internal atomic correlation energy was almost independent from the interatomic distance.
Journal ArticleDOI
Isotherms of argon between 0°c and 150°c and pressures up to 2900 atmospheres
A. Michels,Hub Wijker,Hk Wijker +2 more
TL;DR: In this paper, the compressibility isotherms of argon at seven temperatures from 0° to 150°C and pressures up to 2900 atmospheres were investigated. But the results were limited.