Ab initio calculations of mechanical stability of bcc Cu under pressure

The ground state properties, elastic constants and moduli and electronic structure of the bcc structured Cu under pressure were calculated by ab initio method based on the projector augmented wave pseudopotential and generalized gradient approximation. The results show that the elastic constants of the bcc Cu increase with increasing pressure. The tetragonal shear modulus C' also increases from negative to positive with increasing pressure and the critical pressure is about 7.5 GPa. The increase of the mechanical stability of the bcc Cu under pressure can be interpreted by the change of the electronic structure. Based on the calculated results, it can be concluded that the bcc structured Cu precipitates can be stabilized by the strain imposed by the constraint of coherency with the matrix of ferritic steels.