Ab initio study of ultra-incompressible ternary BeCN2 polymorph

The structural, mechanical, thermodynamic, and electronic properties calculated by projector-augmented wave method are presented for BeCN2 in chalcopyrite and wurtzite-like structures. The calculated high bulk modulus (321 and 309 GPa) and large shear modulus (302 and 298 GPa) suggest that they are ultra-incompressible and hard materials. The ultra-incompressibility is attributed to a stacking of strongly three-dimensional covalent bonded CN4 and BeN4 tetrahedrons connected by corners. Thermodynamic study demonstrates that these two structures can be synthesized at ambient condition. Furthermore, the structural transformation from the wurtzite-like to the chalcopyrite phase was predicted at about 17 GPa according to the enthalpy difference calculations.

► The structural, mechanical, thermodynamic, and electronic properties of BeCN2 in CH and WU structures have been studied.
► Both structures may be ultra-incompressible and potential candidates for superhard materials.
► Thermodynamic assessment establishes that these two phases could be experimentally synthesized at readily attainable pressures.