PadéApproximant Calculation of the Nonretarded van der Waals Coefficients for Two and Three Helium Atoms
Abstract
The longrange (nonretarded) van der Waals coefficients for two and three helium atoms are determined by an integration over imaginary frequencies of helium dynamic polarizabilities. An analytic form for the dynamic polarizability as a function of frequency is generated by the Padéapproximant method from accurate numerical values calculated by Schwartz. The coefficient C_{AB} of the van der Waals energy (the C_{AB}R_{AB}^{6} term) between two He atoms is calculated to be 1.460 a.u., and the coefficient D_{ABC} of the nonadditive contribution [the D_{ABC}(3 θ_{A} θ_{B} θ_{C}+1) R_{AB}^{ 3}R_{BC}^{3}R_{CA}^{3} term] between three He atoms is calculated to be 1.481 a.u.
 Publication:

Physical Review
 Pub Date:
 July 1968
 DOI:
 10.1103/PhysRev.171.70
 Bibcode:
 1968PhRv..171...70T