Theoretical Study on the Mechanism of Anisotropic Thermal Properties ofTi2AlCandCr2AlC

Abstract

Temperature dependences of thermal and elastic properties, such as the Grüneisen parameters, thermal expansion, bulk modulus, and heat capacity ofTi2AlCandCr2AlC, are studied by combining first‐principles method and lattice dynamic calculation based on the quasi‐harmonic model. Experimental thermal expansion coefficient is also measured for comparison. Thermal expansion coefficients ofTi2AlCandCr2AlCshow different trends:Ti2AlCexhibits anisotropic thermal expansion whileCr2AlCshows generally isotropic character. The mechanism is explored by investigating the isotropy or anisotropy of Grüneisen parameters (phonon anharmonicity and thermal pressure) and elastic stiffness (response to thermal pressure) ofTi2AlCandCr2AlC. In addition, the calculated bulk modulus ofCr2AlCis higher at ambient temperature but decreases faster than the value ofTi2AlCas temperature increasing.