Ab initiocoupled-cluster calculations for the fcc and hcp structures of rare-gas solids

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Abstract
In order to gain more insight into factors governing the relative stability of the fcc and hcp structures of the rare-gas solids Ne through Xe, we performed ab initio coupled-cluster calculations for the most important three- and four-body terms in the many-body expansion of the cohesive energy. These terms are combined with empirical two-body potentials derived from dimer data and with a multipole expansion for the long-range three-body terms. In addition, we calculated phonon spectra, in harmonic approximation, for the two structures. Including zero-point energies, our results agree very well with experimental data for the fcc structure. The hypothetical hcp structure, which is lower in energy with two-body potentials, is destabilized by short-range three-body terms and, even more important, by the contribution of zero-point vibration.