Frozen-core full-CI calculation of imaginary frequency-dependent dipole polarizabilities of ground state BeH2 and the C6 dispersion coefficients of its homodimer

Frozen-core full-CI calculations of frequency-dependent dipole polarizabilities (FDPs) of ground state BeH2 at the experimental distance of R = 2.506a0 have been performed using an extended set of 208 contracted GTO functions [9s9p5d3f] on Be and [9s8p6d] on H involving about 58 × 106 symmetry-adapted Slater determinants. The Casimir-Polder integral was then evaluated analytically using eight optimized imaginary frequencies chosen according to a recently developed interpolation technique which allows for the evaluation of the three dipole dispersion constants for the BeH2-BeH2 homodimer, from which isotropic C6 and anisotropy γ6 coefficients are derived for the first time.