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.

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