Ideal strength of Mg2X (X = Si, Ge, Sn and Pb) from first-principles

First-principles calculations within generalized gradient approximation have been performed to investigate ideal strengths of anti-fluorite structured Mg2X (X = Si, Ge, Sn and Pb) compounds. The present calculations showed that the ideal tensile strengths of Mg2X occur in the [111] directions while the ideal shear strengths appear in the (111) [11-2] systems. Both ideal tensile strength and shear strength of Mg2X (X = Si, Ge, Sn and Pb) decreased gradually with the increase of atomic number of X. The microscopic process and inherent mechanisms of mechanical properties were discussed from the evolution of electronic structures during strain.