Third-order elastic constants and the low-temperature limit of the Grüneisen parameter of magnesium stannide on axe's shell model

Abstract

The third-order elastic constants and the pressure derivatives of the second-order elastic constants of magnesium stannide are calculated. The Grüneisen parameters of the acoustic modes in six symmetry directions are then computed. It is significant that most of the transverse elastic modes have negative Grüneisen parameters. The low-temperature limit of the Grüneisen parameter is then evaluated. Its relevance to the low-temperature thermal expansion of magnesium stannide is discussed.