Newly synthesized MgAl2Ge2: A first-principles comparison with its silicide and carbide counterparts.

Using plane-wave pseudopotential density functional theory (DFT), the first-principle calculations are performed to investigate the structural aspects, mechanical behaviors and electronic features of the newly synthesized CaAl 2 Si 2 -prototype intermetallic compound, MgAl 2 Ge 2 for the first time and the results are compared with those calculated for its silicide and carbide counterparts MgAl 2 Si 2 and MgAl 2 C 2 . The calculated lattice constants agree fairly well with their corresponding experimental values. The estimated elastic tensors satisfy the mechanical stability conditions for MgAl 2 Ge 2 along with MgAl 2 Si 2 and MgAl 2 C 2 . The level of elastic anisotropy increases following the sequence of X -elements Ge → Si → C. MgAl 2 Ge 2 and MgAl 2 Si 2 are expected to be ductile and damage tolerant, while MgAl 2 C 2 is a brittle one. MgAl 2 Ge 2 and MgAl 2 Si 2 should exhibit better thermal shock resistance and low thermal conductivity and accordingly these can be used as thermal barrier coating (TBC) materials. The Debye temperature of MgAl 2 Ge 2 is lowest among three intermetallic compounds. MgAl 2 Ge 2 and MgAl 2 Si 2 should exhibit metallic conductivity; while the dual characters of weak-metals and semiconductors are expected for MgAl 2 C 2 . The values of theoretical Vickers hardness for MgAl 2 Ge 2 , MgAl 2 Si 2 , and MgAl 2 C 2 are 3.3, 2.7, and 7.7 GPa, respectively, indicating that these three intermetallics are soft and easily machinable. [ABSTRACT FROM AUTHOR]