FULL-POTENTIAL CALCULATIONS USING THE GENERALIZED GRADIENT APPROXIMATION - STRUCTURAL-PROPERTIES OF TRANSITION-METALS

The equilibrium volumes and bulk moduli of nonmagnetic 3d, 4d, and 5d transition metals have been calculated using a full-potential linear-m uffin-tin-orbitals (FP-LMTO) method and the generalized gradient appro ximation (PW91) of Perdew and Wang [in Electronic Structure of Solids 1991, edited by P. Ziesche and H. Eschrig (Akademie Verlag, Berlin, 19 91), Vol. 11]. The gradient-corrected FP-LMTO results are found to be superior to the corresponding local-density approximation (LDA) result s in all transition-metal series. Furthermore, the atomic-spheres appr oximation (ASA) is found to yield larger equilibrium volumes and small er bulk moduli than the FP method. The inaccuracies introduced by the ASA are of the same magnitude as the gradient-corrections, suggesting that a FP treatment is important for gradient-corrected calculations. Excellent agreement with experiment is found for the cia ratios of the hcp metals using both the LDA and the PW91, while for the fcc-bcc str uctural energy differences of 4d metals disagreement with semiempirica l estimates remains.