Mechanical properties and atomistic deformation mechanism of spinel-type BeP2N4

•The elastic moduli as a function of crystal orientations have been investigated.•The ideal strengths of the γ-BeP2N4 and γ-Si3N4 were systematically studied.•The origin of deformation mechanism of the γ-BeP2N4 under shear strain is revealed.

The anisotropic mechanical properties and atomistic deformation mechanism of incompressible γ-BeP2N4 were comprehensively investigated by first-principles calculations. According to the dependence of the Young’s modulus on different directions in crystal, the γ-BeP2N4 exhibits a well-pronounced anisotropy which may impose certain limitations and restrictions on its applications. The ideal strength calculations demonstrated that γ-BeP2N4 shows substantially lower ideal shear strength than superhard c-BN and diamond, suggesting that it cannot be intrinsically superhard as claimed in the previous studies. Furthermore, the origin of the lattice instability of γ-BeP2N4 under large shear strain that occurs at the atomic level during plastic deformation can be attributed to the breaking of P–N bonds in PN6 octahedrons.

Graphical abstractCalculated bond lengths as a function of strain for γ-BeP2N4 under shear deformation along (110)〈11¯0〉 directions.Figure optionsDownload full-size imageDownload as PowerPoint slide