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A critical test of the diagonal variation-perturbation technique for the partition function of anharmonic oscillators (1992)

Witschel, W. ; Murmann, K. ; Taubmann, G.

College Park, Md. : American Institute of Physics (AIP)

The Journal of Chemical Physics 97 (1992), S. 8637-8643

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ISSN: 1089-7690

Source: AIP Digital Archive

Topics: Physics , Chemistry and Pharmacology

Notes: The diagonal variation-perturbation technique to fourth order is applied to the partition function of asymmetric anharmonic oscillators. Their constants are taken from spectroscopic constants of diatomic molecules. In contrast to thermodynamic perturbation theory the series does not diverge for very low and high temperatures over a wide range of anharmonicities, but it oscillates slightly around the second order result. The approximation is excellent, differing only 10−3 to 10−4 from the exact numerical results. This technique can be extended to systems of coupled anharmonic oscillators with polynomial anharmonicity and interactions.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1063/1.463382

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Second virial coefficients in closed form for a Kihara (2m-m)-potential (1990)

Witschel, W.

Springer

International journal of thermophysics 11 (1990), S. 1075-1085

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ISSN: 1572-9567

Keywords: Kihara intermolecular potential ; second virial coefficient

Source: Springer Online Journal Archives 1860-2000

Topics: Physics

Notes: Abstract In the literature second virial coefficients are calculated by series expansions or by direct numerical integration. For thermodynamic quantities such as thermodynamic functions, analytical expressions are wanted. This paper gives closed formulas for the second virial coefficient for a convex-body Kihara potential of the type U(ρ)= U 0[(ρ 0/ρ)2m -2(ρ 0/ρ) m ], where m can be a rational number n〉3. Furthermore, a number of related problems such as dielectric virial coefficients and Buckingham-Pople integrals are reduced to the same Laplace-transformation-type technique.