Negative thermal expansion of ReO3: Neutron diffraction experiments and dynamical lattice calculations

We have investigated the temperature variation of the unit-cell volume of ReO3 by neutron diffraction. The lattice parameter and the unit-cell volume decrease continuously as the temperature is increased from T=2 K to about T=200 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 ReO3 to be the results of rigid antiphase rotations of the neighboring ReO6 octahedra. We have done model lattice dynamical calculation of phonon dispersions, thermal expansion, and atomic displacement parameters in ReO3. The results of these calculations are in agreement with the experimental results.