An improved self-consistent phonon approximation including four-phonon processes

An improved self-consistent phonon theory (ISC) including three- and four-phonon processes has been used to calculate the zero-pressure lattice parameters and the zero-pressure thermal expansion for Kr. The results indicate that, however limited ISC theory with three-phonon processes may be, trying to supplement this theory with higher-order phonon terms will make the convergence of the theory less satisfactory. In the light of our results we discuss earlier related work as well as a paper by Van Doren and Henkel.