Second‐order polarization propagator calculations of dynamic dipole polarizabilities and C6 coefficients

The frequency‐dependent dipole polarizability, α(E), is calculated using the second‐order polarization propagator approximation (SOPPA). We have shown how to express α(E) as a function of E2 and thus obtained a form of α(E) that can be used to compute C6‐coefficients without invoking complex arithmetic. For He we find that SOPPA recovers a large fraction of the correlation contribution for all frequencies, whereas for H2 where the correlation contributions are much smaller and also basis set‐dependent, we find a less definite trend of SOPPA relative to RPA.