Elastic and electronic properties of select M2AX phases

In this letter we report on the low-temperature specific heat of several M(2)AX phases: Ti2AlC, V2AlC, V2AsC, Nb2SnC, Ti2AlN, Hf2InC, Nb2AlC, and Cr2AlC. The Debye temperatures are quite high. The density of states at the Fermi level, N(E-F) varies from approximate to1.4 (eV formula unit)-1 to 6 (eV formula unit)-1. Ab initio calculations show that N(E-F) is dictated by the transition metal d-d bands; the A-group element has little effect. We also measured the velocity of sound in V2AlC, V2AsC, Ti2AlC, and Ti2AlN. The average bulk modulus of these materials is over 100 GPa, with a high of approximate to140 GPa for Ti2AlN. Our theoretical calculations correctly predict the trend in both the density of states and the bulk modulus, although there is some disagreement in the actual values. (C) 2004 American Institute of Physics.