An Atomistic Understanding of the Unusual Thermal Behavior of the Molecular Oxide Tc2O7.

The thermal behavior of Tc2O7 has been investigated by single-crystal X-ray diffraction of the solid state over a range of 80-280 K and by ab initio molecular dynamics (MD) simulations. The thermal expansion coefficient of the solid was experimentally determined to be 189 × 10-6 Å3 K-1 at 280 K. The simulations accurately reproduce the experimentally determined crystal structures and thermal expansion within a few percent. The experimental melting point and vapor pressure for Tc2O7 are unusually high and low, respectively, in comparison to similar molecular solids. Through investigating the structure and the motion of the solid across a range of temperatures, we provide insights into the thermal behavior of Tc2O7.