An expression is derived for the charge density susceptibility which, under the Unsold approximations, reduces to the Fourier transforms of electron density functions. When considering uncorrelated wavefunctions, the susceptibility is given simply by static form factors in terms of which the second order Coulomb energy may be calculated. This is equivalent to applying the Unsold approximations directly unto the second order Coulomb energy expression in the usual time independent Rayleigh-Schrodinger perturbation theory. / Using the interactions of hydrogen-hydrogen and helium-helium diatoms as test cases, we evaluated numerically and analytically the various integrals for their second order dispersion energies. The two approaches differ in that while the latter requires analytic form factors, the former can use both analytic as well as the readily available tabulated form factors. Their results are found to be in excellent agreements. / Appropriate choices for the Unsold average excitation energy are made to put the values of the dispersion energy on an absolute scale. Precise potentials at large separations are obtained. By adding to our dispersion energy the first order Coulomb, exchange and second order induction contributions, the whole potential curves too agree remarkably well with previous accurate results. / The present treatment allows the use of the full Coulomb potential without recourse to the multipole expansion. In addition, the formulation in momentum space affords considerable mathematical simplification. / Source: Dissertation Abstracts International, Volume: 42-06, Section: B, page: 2392. / Thesis (Ph.D.)--The Florida State University, 1981.
| Identifer | oai:union.ndltd.org:fsu.edu/oai:fsu.digital.flvc.org:fsu_74546 |
| Contributors | LEE, KER-FONG., Florida State University |
| Source Sets | Florida State University |
| Detected Language | English |
| Type | Text |
| Format | 117 p. |
| Rights | On campus use only. |
| Relation | Dissertation Abstracts International |
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