Calculation of  ₀cdifferences for the face-centred cubic and close-packed hexagonal lattices in the ideal inert gas solids

Θ0c(cph) and the ratio K ≡ 100{Θ0c(cph) - Θ0c(fcc)}/Θ0c(fcc) for the ideal inert gas solids was calculated, using the quasi-harmonic approximation and an (m - 6) Lennard-Jones all-neighbour force model; K was found to be about 2%. The neglect of explicit anharmonic contributions to K is discussed. A table of the relevant all-neighbour sums is given. It was found that the use of the ideal axial ratio γI = Θ(8/3) to characterize the close-packed hexagonal lattice limits the accuracy to which K can be calculated to about one decimal place, and Θ0c(cph) to about two decimal places.