Polarisabilities and dispersion coefficients from the weighted exchange-hole model

Abstract

Frequency-dependent polarisabilities and dispersion coefficients are calculated for the molecules HF, CO, H₂O and NH₃ using the recently developed weighted exchange-hole (WXhole) model of the response function. The results are compared to those obtained by time-dependent Hartree–Fock and density functional theory (DFT) calculations. It is shown that the WXhole model yields response properties that can describe both, the isotropic and anisotropic contributions to the polarisabilty and dispersion coefficients with a reasonable accuracy. This result is notable taking into account the fact that the WXhole method is much less expensive than corresponding fully coupled Hartree–Fock and DFT methods and also, as is shown in this work, requires smaller basis sets to obtain converged results.

Keywords:

• intermolecular interactions
• dispersion coefficients
• polarisabilities

Acknowledgement

I have met Trygve the first time at the summer school in Lund. He was giving a lecture about gradient theory which was a very good introduction to the theoretical determination of molecular properties (and has thus also a relation to the current work). While one sees it very often that good scientists are not necessarily good teachers, I would like to remark that Trygve Helgaker is an outstanding exception to this rule. Thank you, Trygve!