Bulk moduli of solid and liquid metals

Abstract

The ability of Shaw (1968, 1969, 1970) and Ashcroft (1966, 1967, 1970) pseudopotentials to yield accurate bulk moduli (for solids and liquids) by each of the homogeneous deformation (HD) and long wave (LW) methods is tested. The HD method, though more accurate in principle, is in practice not yet properly applicable; refinement of the present theory of non-local pseudopotentials must be awaited. Ashcroft-Langreth fitting to the observed (zero) pressure may be viewed as a device for circumventing this difficulty and is the most accurate method available; even so, it is only semi-quantitatively successful. The LW method avoids the main uncertainty (the theory of the depletion hole) associated with non-local pseudopotentials and can give semi-quantitative results for Shaw pseudopotentials. It will also give results of rather similar quality for the simpler metals (e.g. Na, Mg, Al) using Ashcroft pseudopotentials but fails for such higher polyvalents as Pb.