High precision first principles prediction of the aluminum equation of state
- Los Alamos National Lab., NM (United States)
- Univ. of Florida, Gainesville, FL (United States)
To resolve drastic differences in predictions among earlier calculations and to interpret new diamond anvil cell results, the authors have recalculated the T = 0 K equation of state (EOS) of Al from equilibrium through P {approx} 600 GPa. The experiment found no fcc-hcp phase transition at pressures up through 220 GPa (V/V{sub 0} = 0.50). Three DFT-LSDA calculations a decade ago gave widely divergent predictions for that transition pressure: MM (spherical LMTO) 120 GPa, MM (generalized pseudopotential) 360 GPa, LC (ab initio pseudopotential) 220 GPa. The only all-electron, full-potential calculation back then was restricted to cubic symmetries; it found the fcc-bcc transition at P = 330 GPa, V/V{sub 0} = 0.446. LC`s calculation was consistent (P = 300 GPa, V/V{sub 0} = 0.45), allowing for model dependencies, hence seemed to be confirmed. The calculations were done with a new code, {open_quotes}GTOFF{close_quotes} developed recently by one of the authors (JCB). GTOFF generalizes the linear combination of Gaussian Orbitals, Fitting Function algorithms and techniques used successfully for all-electron full-potential calculations in thin films to systems 1-, 2- or 3-D Bloch periodicity. Its implementation allows careful determination of calculational imprecision. The authors find the equilibrium fcc lattice constant to be 7.596 au (experiment: 7.60 au), the equilibrium bulk modulus to be 79.7 GPa (experiment: 72.7 GPa), and predict the fcc-hcp pressure at 205{+-}20 GPa. Detailed analysis of omitted contributions enables determination of conservative upper bound to that transition pressure as 290 GPa.
- OSTI ID:
- 146543
- Report Number(s):
- CONF-950231-; TRN: 95:005716-0008
- Resource Relation:
- Conference: 35. Sanibel symposium on atomic, molecular, and condensed matter theory, computational methods, and the application of fundamental theory to problems of biology and pharmacology, St. Augustine, FL (United States), 25 Feb - 4 Mar 1995; Other Information: PBD: 1995; Related Information: Is Part Of Thirty-fifth Sanibel symposium; PB: 335 p.
- Country of Publication:
- United States
- Language:
- English
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