On negative volume expansion coefficients

Abstract

It is shown that the Grüneisen constant derived from the elastic properties of a solid can be negative in certain cases. The lattice models examined are (a) ionic lattices with the zinc blende structure, (b) ionic lattices with the rocksalt structure. In the first case it is found that a negative value is obtained over the whole range of parameters examined. In the second, negative values are obtained when the shear modulus of the lattice is sufficiently small. In all these cases the volume expansion coefficient of the cubic lattice would be negative at sufficiently low temperatures.