We have investigated the temperature variation of the unit-cell volume of ${\text{ReO}}_3$ by neutron diffraction. The lattice parameter and the unit-cell volume decrease continuously as the temperature is increased from $T=2\text{K}$ to about $T=200\text{K}$. After exhibiting minima at about 200 K they increase with increasing temperature linearly up to about 305 K, the maximum temperature investigated during the present experiment. We attribute the negative thermal expansion of ${\text{ReO}}_3$ to be the results of rigid antiphase rotations of the neighboring ${\text{ReO}}_6$ octahedra. We have done model lattice dynamical calculation of phonon dispersions, thermal expansion, and atomic displacement parameters in ${\text{ReO}}_3$. The results of these calculations are in agreement with the experimental results.

• Received 30 May 2008

DOI:https://doi.org/10.1103/PhysRevB.78.134105