Structural and elastic properties of beta-brass

First-principles calculations have been made for the 50-50 ordered alloy Cu Zn, B-brass, of the energy per atom in tetragonal structure as a function o f the tetragonal, lattice parameters a and c. A full-potential electronic-s tructure program was used with both the local-density approximation (LDA) a nd the generalized gradient approximation (GGA). Both formulations confirm the existence of a shallow energy minimum (the ground state) at cia (beta - brass has CsCl structure), and reveal the occurrence of a shallow secondary minimum at approximately c/a = 1.26. With decreasing electronic charge on the Zn atom this minimum becomes deeper, and moves toward larger cia values , reaching the value c/a = root2 when one full electron is taken away from Zn, i.e., when Zn is replaced with Cu. The three elastic constants of B-bra ss have been calculated and compared with experiment. The large elastic she ar anisotropy of B-brass discussed by Clarence Zener in 1947 has been confi rmed in this work, although the anisotropy is not quite as large as the the n available experimental data indicate.