High-precision calculation of the equation of state and crystallographic phase stability for aluminum

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Abstract
High-precision, all-electron, full-potential, local-density approximation (LDA) calculations are used to determine the static lattice equation of state (EOS) and crystalline phase stability of Al to 1 TPa. The low-pressure properties found here are consistent with the results of other nonrelativistic LDA calculations, but differ significantly from the results of relativistic LDA or gradient-dependent approximation calculations. The theoretical 300-K isotherm for fcc Al, obtained by adding phonon effects to the static lattice EOS, is in reasonable agreement with room temperature data up to 220 GPa. The predicted static-lattice phase sequence for Al is fcc→hcp→bcc with the transitions occurring at 205±20 GPa and 565±60 GPa. Estimation of the possible impact of phonons on the fcc→hcp transition produces a fairly firm upper bound of 290 GPa (282) on the room-temperature (zero temperature) fcc→hcp transition pressure. This result suggests that a recent diamond-anvil-cell experiment came very close to achieving the fcc→hcp transition. © 1996 The American Physical Society.