Theoretical study of FCC–HCP phase coexistence and phase stability in Al by FP-LAPW method with GGA for exchange and correlation

Abstract

Zero pressure properties, phase stability and phase coexistence have been studied for Al. Possible high pressure phases of Al are examined by comparing the total internal energies and enthalpies for three structures:FCC, BCC and HCP. The energies are calculated using the density function formalism and the full potential linear augmented plane wave (FPLAPW) method. Perdew-Burke-Ernzerhof 96 parameterization of Generalized Gradient Approximation (GGA) is used for exchange and correlation. Zero pressure lattice constants and the bulk modulus have been calculated for three phases of Al, and show good agreement with published experimental results. Our results for the minimum energy c/ a ratio for hcp match well with the experimental value. Coexistence of FCC–HCP phases for a wide range of pressures near phase transformation is indicated by volume–energy curves, in agreement with a recent powder X-ray diffraction experiment. The calculated lattice parameters at high pressures show good agreement with reported experimental values. The computed transition pressure and volume for FCC–HCP phase transition is also in reasonable agreement with experiment. Finally, we have also calculated the FCC–BCC and BCC–HCP transition pressures and compared our results with reported theoretical results. These results show that the Perdew-Burke–Ernzerhof GGA, along with FP-LAPW, gives reasonably accurate results for aluminum over a large range of pressures.