Lattice dynamical calculation of isotropic negative thermal expansion inZrW2O8over 0–1050 K

Abstract

We report detailed lattice dynamical calculations of the large isotropic negative thermal expansion (NTE) over 0–1050 K in ${\mathrm{ZrW}}_2{\mathrm{O}}_8$ in its cubic phase. The results bring out the unusually dominant quantitative contributions to NTE of the transverse acoustic, and librational and translational optic phonons below 8 meV. The contributions of these phonons are reduced in the high pressure orthorhombic phase which therefore shows NTE only below 270 K. The calculations show a fair agreement with the published thermal expansion data in both phases.