Angle and bond-length dependent C6 coefficients for H2 interacting with H, Li, Be and rare gas atoms

Thakkar, Ajit J.; Hu, Zhe-Ming; Chuaqui, Claudio; Carley, J. Scott; LeRoy, Robert J.

doi:10.1007/bf01113130

Cited by 19 publications

(11 citation statements)

References 43 publications

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“…Many of the early He-H 2 surfaces were intended only to describe the He + H 2 van der Waals potential well and the outer (low-energy) part of the He-H 2 repulsive wall [10][11][12][13][14][15][16]18,19,23 , and were valid only for equilibrium H 2 molecules. However, several analytic He-H 2 surfaces were intended to be valid in the higher-energy interaction region.…”

Section: B Previous Surfacesmentioning

confidence: 99%

“…available ab initio potential energy surfaces for H 3 (molecule plus open-shell atom) [1][2][3][4][5] or H 4 (two molecules) [6][7][8][9] . Previous analytic He-H 2 surfaces [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24] were based on only a few dozen ab initio energies, which provided highly inadequate coverage of all but a very restricted region in the conformation space of He-H 2 . This paper reports a greatly-expanded set of ab initio energies, and a greatly improved He-H 2 PES fitted to these energies.…”

Section: Introductionmentioning

confidence: 99%

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Accurate analytic He–H2 potential energy surface from a greatly expanded set of ab initio energies

Boothroyd

Martín

Peterson

2003

The Journal of Chemical Physics

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The interaction potential energy surface (PES) of He-H 2 is of great importance for quantum chemistry, as the simplest test case for interactions between a molecule and a closed-shell atom. It is also required for a detailed understanding of certain astrophysical processes, namely collisional excitation and dissociation of H 2 in molecular clouds, at densities too low to be accessible experimentally. A new set of 23 703 ab initio energies was computed, for He-H 2 geometries where the interaction energy was expected to be nonnegligible. These have an estimated rms "random" error of ∼ 0.2 millihartree and a systematic error of ∼ 0.6 millihartree (0.4 kcal/mol). A new analytic He-H 2 PES, with 112 parameters, was fitted to 20 203 of these new ab initio energies (and to an additional 4862 points generated at large separations). This yielded an improvement by better than an order of magnitude in the fit to the interaction region, relative to the best previous surfaces (which were accurate only for near-equilibrium H 2 molecule sizes). This new PES has an rms error of 0.95 millihartree (0.60 kcal/mole) relative to the the 14 585 ab initio energies that lie below twice the H 2 dissociation energy, and 2.97 millihartree (1.87 kcal/mole) relative to the full set of 20 203 ab initio energies (the fitting procedure used a reduced weight for high energies, yielding a weighted rms error of 1.42 millihartree, i.e., 0.89 kcal/mole). These rms errors are comparable to the estimated error in the ab initio energies themselves; the conical intersection between the ground state and the first excited state is the largest source of error in the PES.

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Section: B Previous Surfacesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Accurate analytic He–H2 potential energy surface from a greatly expanded set of ab initio energies

Boothroyd

Martín

Peterson

2003

The Journal of Chemical Physics

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“…5 Recently, an improved version of that S semiempirical calculation was published. 6 However, the higher order dispersion coefficients for H 2 -rare gas interactions are much less well known. Accurate values are available for H 2 -He at three bond lengths 7 -9 of H 2 .…”

Section: Intramolecular Bond Length Dependence Of the Anisotropic Dismentioning

confidence: 99%

Intramolecular bond length dependence of the anisotropic dispersion coefficients for H2–rare gas interactions

Wormer

Hettema

Thakkar

1993

The Journal of Chemical Physics

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Effective states arising from variational perturbation calculations in a full configuration interaction basis are used to calculate dynamic multipole polarizabilities for H2 at seven different bond lengths. These are combined with previously calculated dynamic polarizabilities for rare gas atoms to obtain the intramolecular bond length dependence of the anisotropic C 6 , Cg, and C lO dispersion coefficients for H 2 -X (X=He, Ne, Ar, Kr, Xe) interactions. The results are generally in good agreement with previous semiempirical estimates where available.

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“…In parentheses the corresponding values from Refs. [22] and [25] (Ho ) p are given (in Ry atomic units). theory provides a physically correct form for the densityfunctional in the separated fragment limit.…”

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confidence: 99%

van der Waals Interactions in Density-Functional Theory

1996

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We present a framework for long-range density-functional theory which is valid for interactions between isolated fragments of matter at large separation. The van der Waals coefficients for interactions between a large number of pairs of atoms are calculated and compared to available first-principles calculations. The success in this test case shows a way of extending density-functional theory calculations with local or semilocal approximations to include van der Waals forces.

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Angle and bond-length dependent C6 coefficients for H2 interacting with H, Li, Be and rare gas atoms

Cited by 19 publications

References 43 publications

Accurate analytic He–H2 potential energy surface from a greatly expanded set of ab initio energies

Accurate analytic He–H2 potential energy surface from a greatly expanded set of ab initio energies

Intramolecular bond length dependence of the anisotropic dispersion coefficients for H2–rare gas interactions

van der Waals Interactions in Density-Functional Theory

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