Low temperature second virial coefficients of H2-He obtained from quantum mechanical pair correlation functions

The previously tested ab initio potential of H2-He has been used for calculating scattering wave functions, diagonal density matrix elements, pair correlation functions, and finally second virial coefficients, for temperatures up to 100 K. Qualitative agreement with experiment has been found at 90 K, but deviations increased with decreasing temperature up to more than a factor two at temperatures below 20 K. The most likely explanation of this strong effect is the neglect of the formation of dimer hydrogen at the very low temperatures. Some aspects concerning the reliability of the theoretical results will be discussed which are at least partly relevant for equivalent methods. (orig.)