High precision first principles prediction of the aluminum equation of state

Conference · Fri Dec 01 04:00:00 EST 1995

OSTI ID:146543

Boettger, J C ^[1]; Trickey, S B ^[2]

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1. Los Alamos National Lab., NM (United States)
2. 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--
• Country of Publication: United States
• Language: English

Related Subjects

66 PHYSICS
ALUMINIUM
CALCULATION METHODS
EQUATIONS OF STATE
G CODES
LCAO METHOD
TEMPERATURE RANGE 0000-0013 K
VERY HIGH PRESSURE