Structural, electronic and elastic properties of wurtzite-structured TlxAl1−xN alloys from first principles

Structural, electronic and elastic properties of wurtzite-structured thallium aluminum nitride (TlxAl1−xN) across the entire alloy composition range have been studied using first-principles pesudopotential plane-wave density functional calculations. The alloy's lattice constants obey Vegard's law well. Band-gap bowing coefficients show very strong composition dependence. Elastic constants and their aggregate elastic modulus change continuously with Tl-concentrations varying from 0 up to 100%. A transition from brittle fracture to plastic flow occurs in TlxAl1−xN alloys at about x=0.33. Further, elastic wave velocity and Debye temperature all monotonically decrease with increasing Tl concentration. Our calculated results for the binary cases, aluminum nitride (AlN) and thallium nitride (TlN), are in good agreement with previously reported data.