Ab initio molecular dynamics study on thermal expansion of solid-solution compounds in MAX phase

The thermal expansion (CTE) of the Cr-based solid-solution compounds in M(n+1)AX(n) phases is explored by ab initio molecular dynamics (AIMD) method. The calculated CTE and thermal expansion anisotropy (TEA) agree well with experimental measurement. The anisotropy is reduced considerably as exemplified in the case of Cr-2(Al0.667Ge0.333)C where the CTE of c axis is reduced from 11.2 x 10(-6)/K to 10.3 x 10(-6)/K. For (Cr1.833Ti0.167)AlC and (Cr1.333Ti0.667)AlC, the calculated results show that the Ti doping does reduce the average CTE of Cr2AlC from 12 to 11. This study demonstrates that a solid-solution approach is a route for tuning a physical property like the thermal expansion.