Long-Range Interactions among He and Be Atoms

Abstract

Long‐range dispersion energies for the atom pairs $\mathrm{He–He}$ , $\mathrm{He–Be}$ , and $\mathrm{Be–Be}$ in their ground states have been calculated in the form $E_{\mathrm{disp}}{\mathrm{=C}}_6{\mathrm{/R}}^6{\mathrm{+C}}_8{\mathrm{/R}}^8{\mathrm{+C}}_{10}{\mathrm{/R}}^{10}{\mathrm{+C}}_{11}{\mathrm{/R}}^{11}{\mathrm{+C}}_{12}{\mathrm{/R}}^{12}$ , the coefficients C_n being obtained from the appropriate dynamic polarizabilities at imaginary frequencies. The needed polarizabilities of imaginary argument have been calculated within the time‐dependent coupled Hartree‐Fock approximation. Three‐body nonadditive contributions to the interaction energies have been also evaluated.