Theoretical strength and structural response of Cu crystal

The theoretical strength and structural response of FCC crystal Cu under uniaxial loading along one edge of a unit cell have been investigated with MAEAM. The stability criteria of the tetragonal system are extended to the generally stressed orthogonal system. The results show that, even if an orthorhombic path is applied, the deformation is spontaneously along the tetragonal Bain path till tensile elastic limit at stretch λ1 = 1.085 where the Born criterion is violated. The branched orthogonal path is preferred over the conventional tetragonal Bain path from minimization of the stress σ1 or the energy E. Although a stress-free BCC phase with the local maximum energy of −3.460 eV appearing either in compressive region or in tensile region is unstable and would slip spontaneously into a near neighbor stress-free mBCT phase with the local minimum energy of −3.461 eV, the initial FCC phase with the lowest energy of −3.489 eV is the most stable in correspondence with the actual behavior of pure Cu. Furthermore, the calculated elastic moduli of FCC phase are in good agreement with the experimental values. The stable region ranges from −2.89 GPa to 7.252 GPa in the theoretical strength or from 0.912 to 1.085 in the stretch λ1 correspondingly.