van der Waals Constants and Nonadditive Triple-Dipole Force Constants for He and Ne by the Coupled Hartree-Fock Approximation

The dynamic polarizability and the dipole shielding factor at imaginary frequencies are calculated for He and Ne by the coupled Hartree‐Fock approximation. The integrodifferential equations for the perturbed wavefunctions are solved numerically without use of the variational procedure. By using Casimir‐Polder type formulas, the van der Waals constants μ and the nonadditive triple‐dipole force constants ν are computed for He and Ne. Results (in atomic units) are ${\mu }_{\mathrm{HeHe}}{\text{=1.38,\hspace{0.17em}μ}}_{\mathrm{HeNe}}{\text{=2.71,\hspace{0.17em}μ}}_{\mathrm{NeNe}}{\text{=5.44,\hspace{0.17em}ν}}_{\mathrm{HeHeHe}}{\text{=1.33,\hspace{0.17em}ν}}_{\mathrm{HeHeNe}}{\text{=2.51,\hspace{0.17em}ν}}_{\mathrm{HeNeNe}}\text{=4.76}$ , and ${\nu }_{\mathrm{NeNeNe}}\text{=9.10}$ .