Investigation on composition-dependent properties of Mg5xAl23−5xO27+5xN5−5x (0 ≤ x ≤ 1): Part II. Mechanical properties via first-principles calculations combined with bond valence models

Abstract

Due to the application in transparent windows, armors and domes, it is essential to have a deep insight into the mechanical properties of spinel-type MgAlON solid solution. Mg5xAl23−5xO27+5xN5−5x were chosen for the investigation of composition-dependent mechanical properties via combining first-principles calculations with bond valence models. The calculated mechanical properties showed a consistence with experimental values, supporting the validity of the investigation. The simulated elastic constants were used to check the mechanical stability and analyze the shear modulus of Mg5xAl23−5xO27+5xN5−5x. The mechanical properties of Mg5xAl23−5xO27+5xN5−5x weakened with increasing x. The composition-dependent mechanical properties were explored from the perspective of chemical bonds. The results demonstrated that decline trend of the mechanical properties, including hardness, bulk modulus and shear modulus of Mg5xAl23−5xO27+5xN5−5x is mainly impacted by the bonds in tetrahedra, since the linear density of bond valence and bond force constant in tetrahedra decreased dramatically, while those in octahedra were almost unchanged.