Ab initio Correlation Calculations for the Lattice Structures of Zn, Cd and Hg

Abstract

Mercury condenses at 233 K into the rhombohedral structure with a bond length a = 3.005Å and an angle of 70.53o . In contrast, zinc and cadmium adopt the hexagonal close-packed (hcp) structure, but with an anomolous c/a ratio which is far from ideal hcp. Density functional methods fail to describe either of these structures accurately. An application of the method of increments to these metals, including correlation via coupled cluster calculations on finite fragments of the solid, allows the systematic inclusion and comparison of the competing effects that leads to the observed structures.