Ab initio calculations of many-body interactions for compressed solid argon

An investigation on many-body effects of solid argon at high pressure was conducted based on a many-body expansion of interaction energy. The three-and four-body terms in the expansion were calculated using the coupled-cluster method with single, double, and noniterative triple theory and incremental method, in which the configurations of argon trimers and tetramers were chosen as the same as those in the actual lattice. The four-body interactions in compressed solid argon were estimated for the first time, and the three-body interaction ab initio calculations were extended to a small distance. It shows that the four-body contribution is repulsive at high densities and effectively cancels the three-body lattice energy. The dimer potential plus three-body interaction can well reproduce the measurements of equation of state at pressure approximately lower than similar to 60 GPa, when including the four-body effects extends the agreement up to the maximum experimental pressure of 114 GPa. (C) 2015 AIP Publishing LLC.