Pseudo-spectral dipole oscillator strength distributions for the normal alkanes through octane and the evaluation of some related dipole-dipole and triple-dipole dispersion interaction energy coefficients

Abstract

Pseudo-spectral dipole oscillator strength distributions (DOSDs) are reported for ground state C2H6, C3H8 and normal-C4H10, C5H12, C6H14, C7H16 and C8H18. The pseudo DOSDs, which are a discrete representation of original recommended continuous DOSDs, can be used to evaluate the dipole properties of the alkanes in a very efficient and economical way without loss of accuracy. The pseudo DOSDs, together with a previous pseudo DOSD for CH4, are used to evaluate the orientation averaged dipole-dipole dispersion energy coefficient, C6(A, B), the corresponding relativistic coefficient, W 4(A, B), and the triple-dipole dispersion energy coefficients, C 9(A, B, C), for all pairs and triple of molecules taken from CnH 2n+2, n = 1(1)8. The results are used to make self consistent tests of various semiempirical formulae for C6, W 4 and C9.