Abstract: Due to the developments in high-performance computing, and advances in first principles methods, 2017 is the era of the temperature-dependent ab initio prediction. In this talk we present recent high-temperature ab initio predictions on prototypical ultra-high-temperature ceramic, cubic zirconium carbide (ZrC).
Ultra-high-temperature ceramics are a class of refractory materials with remarkable properties. High melting-points (TC > 3000 K) are accompanied by exceptional stiffness values (E ≈ 0.5 TPa), moderate-to-high conductivities (κ = 101-2 W/mK), and a range of volumetric mass densities (ρ = 3-13 g/cm3). As a result, ultra-high-temperature ceramics are a source of excitement for certain blocs within the engineering community, in particular for aerospace and nuclear applications.
Our recent work on ZrC addresses transport, thermodynamics and mechanical properties. Predictions extend to the higher end of the solid-state temperature scale, where measurements are difficult. Our simulations on defect thermodynamics predict unprecedented concentrations of Frenkel pairs. In transport calculations we explore a coupling of strain and strong anharmonicity to conductivity that is specific to high temperatures. Furthermore, we have sufficient knowledge of anharmonicity in ZrC,[1] to consider it a reference system to test and develop tractable means of anharmonic computation.
[1] A.I. Duff et al., Physical Review B, 91, 214311, 2015