Thermodynamic and elastic properties of hexagonal ZnO under high temperature

Studies on thermodynamic and elastic properties of hexagonal ZnO (wurtzite structure) under high temperature have not been reported usually from no matter experimental or theoretic methods. In this work, we study these properties by ab-initio together with quasi-harmonic Debye model. The value of Cv tends to the Petit and Dulong limit at high temperature under any pressure, 49.73 J/mol K. And Cv is greatly limited by pressure at intermediate temperatures. Nevertheless, the limit effect on Cv caused by pressure is not obvious under low as well as very high temperature. The thermal expansions along a or c axis are almost same under temperature, which increase with temperature like a parabola. C11, C33, C12 and C13 decrease with temperature a little, which means that mechanics properties are weakened respectively.