On the determination of the intermolecular potential between a tetrahedral molecule and an atom or a linear or a tetrahedral molecule—application to CH₄ molecule

Abstract

A brief summary of the general theory of the long-range potential energy between two molecules, previously developed by Buckingham, is first presented. Then the first detailed expressions of this potential energy are given for the three following molecular pairs : tetrahedral molecule-atom, tetrahedral molecule-linear molecule and tetrahedral molecule-tetrahedral molecule. These expressions are applied to the calculation of the spectral moments of the far infra-red pressure induced absorption band, the second virial coefficient and the intermolecular mean square torque. This allows a discussion of the magnitude of the various terms contributing to this potential energy and leads to a determination, for CH4, of the octupole and hexadecapole moments, and of the hyperpolarizability : f2 = (2"30 + 0"04) x 10 -z4 e.s.u, cm 3, ~ = --(4"55 + 0"55) X 10 -42 e.s.u, cm 4 and A = (2"35 + 0"05) x 10 -32 cm ~.

Interactions between nucleic acid bases in hydrogen bonded and stacked configurations: The role of the molecular charge distribution

“…Thus, for the doubly bonded oxygen atom (as in C=O), Bondi [93] proposes RW (longitudinal) = 1.45 A and R (transversal) = 1. 60 A. In Table IV we have given the results obtained for the most stable hydrogen bonded dimers of nucleic bases using this "longitudinal'' van der Waals radius (1.…”

“…55) as the first-order Eps = ( \kh1)\kh2) I VI \kh1)\kh2)), (1) with \kg) denotes the ground-state eigenfunction of the nonperturbed Hamiltonian ~5 ' ) of molecule i (i = 1~) . It is possible to treat these matrix elements by replacing the potential V by its multipole expansion around a single center for each molecule or equivalently by performing the multipole expansion of each molecular charge density around a single molecular center [56][57][58][59][60]. However this multipole expansion represents exactly the potential of a charge distribution only outside a sphere centered at the origin and containing entirely the charge distribution.…”

Ab initio determination of the electric multipole moments and static (hyper)polarizability of HCCX, X = F, Cl, Br, and I

“…48,50 As for linear molecules, there is only one independent component for any electric multipole moment tensor, we drop the subscript and write ϵ z , ⌰ ϵ ⌰ zz , ⍀ ϭ ⍀ zzz , and ⌽ ϵ ⌽ zzzz . In addition to the Cartesian components of the polarizability tensors we also consider mean values and anisotropies defined as…”

New insights into collision-induced rototranslational absorption and scattering spectra of gaseous methane at different temperatures

“…Proton spin relaxation [100] 0.89 Bond polarizability model [101] 1.0 À1.0 Virial coefficient [102] 2.35 NMR [103] 2.71 Shelton and Tabisz [107] 1.0 2.5…”

“…12. Total anisotropic collision-induced light scattering spectrum of CH 4 -CH 4 at T = 250.5 K using the isotropic EM3SV potential given in Table 1. bond polarizability model [101], Virial coefficient [102], NMR [103] and those calculated ab initio values [82,[104][105][106].…”