Thermal equation of state of silicon carbide

A large volume press coupled with in-situ energy-dispersive synchrotron X-ray was used to probe the change of silicon carbide (SiC) under high pressure and temperature (P-T) up to 8.1 GPa and 1100 K. The obtained pressure-volume-temperature data were fitted to a modified high-T BirchMurnaghan equation of state, yielding values of a series of thermo-elastic parameters, such as the ambient bulk modulus K-To = 237(2) GPa, temperature derivative of the bulk modulus at a constant pressure (partial derivative K/partial derivative T)(P) = -0.037(4) GPa K-1, volumetric thermal expansivity alpha(0, T) = a + bT with a = 5.77(1) x 10(-6) K-1 and b = 1.36(2) x 10(-8) K-2, and pressure derivative of the thermal expansion at a constant temperature (partial derivative alpha/partial derivative P)(T) = 6.53 +/- 0.64 x 10(-7) K-1 GPa(-1). Furthermore, we found the temperature derivative of the bulk modulus at a constant volume, (partial derivative K-T/partial derivative T)(V), equal to -0.028(4) GPa K-1 by using a thermal pressure approach. In addition, the elastic properties of SiC were determined by density functional theory through the calculation of Helmholtz free energy. The computed results generally agree well with the experimentally determined values.