High Pressure Behavior ofZrW2O8: Grüneisen Parameter and Thermal Properties

Abstract

High pressure Raman spectroscopic studies are carried out on negative thermal expansion material ${\mathrm{ZrW}}_2{\mathrm{O}}_8$. The system exhibits amorphization at $2.2\pm 0.3\mathrm{GPa}$ via an intermediate orthorhombic phase. In the cubic phase most modes below 50 meV are found to have negative Grüneisen parameter. Using the reported phonon density of states thermal properties are calculated and compared with the reported results. In contrast to the earlier belief, the present results show that modes of energies much higher than 10 meV also contribute substantially to the negative thermal expansion.