Thermochemical Ranking and Dynamic Stability of TeO₂Polymorphs from Ab Initio Theory

The ability to predict temperature-dependent properties of solids from ab initio theories alone has marked a fundamental step forward in realistic materials modeling. Here, we use density functional theory (DFT)-based thermochemistry to investigate crystalline tellurium dioxide (TeO2). While the DFT description of its polymorphs is challenging, we demonstrate that the inclusion of suitable dispersion corrections makes a thermochemical analysis and a correct stability ranking possible. Paratellurite (α-TeO2), a technologically most important compound used in optical devices, is lowest in Gibbs free enthalpy in agreement with previous thermochemical experiments. While α-TeO2 exhibits a three-dimensional bonding network, the well-known mineral tellurite (β-TeO2) contains two-dimensional sheets; nonetheless, we demonstrate that both polymorphs are extremely similar in thermodynamic state functions and chemical bonding. The latter is analyzed with the crystal orbital Hamilton population (COHP) method and offered as a possible explanation for the small stability difference (<1 kJ mol–1). Finally, a recently synthesized polymorph (γ-TeO2) is found to be higher in energy as expected (+6 kJ mol–1 at 300 K) but nonetheless dynamically stable. These results shed new light on the TeO2 polymorphs but also provide more general insight into the capabilities of theoretical materials modeling at finite temperatures.