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 ų 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.