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Phase diagram of MgO from density-functional theory and molecular-dynamics simulations

Strachan, Alejandro and Çağin, Tahir and Goddard, William A., III (1999) Phase diagram of MgO from density-functional theory and molecular-dynamics simulations. Physical Review B, 60 (22). pp. 15084-15093. ISSN 0163-1829.

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We use first-principles methods (no empirical parameters) to establish the phase diagram for the B1(NaCl), B2(CsCl), and liquid phases of MgO. We used density-functional theory with the generalized gradient approximation to predict the equation-of-state [volume versus pressure (V(P))] at 0 K for MgO in the low-density B1 (NaCl) phase and the high-density B2 (CsCl) phase. We find a pressure-induced phase transition at P=400 GPa. We then fitted an MS-Q type force field (FF) to the quantum results. This FF, denoted as qMS-Q FF, was then used in molecular dynamics (MD) simulations to investigate the phase coexistence curves of the B1-B2 and B1-liquid phases. This leads to a first-principles phase diagram for MgO for pressures up to 500 GPa and temperatures up to 8000 K. The accuracy of the fit of the qMS-Q FF to the quantum mechanics validates the functional form of the qMS-Q FF in which the charges are obtained from charge equilibration (QEq) and the nonelectrostatic forces are described with simple two-body Morse potentials. Such qMS-Q FF using no empirical data should be useful for MD or Monte Carlo simulations of many other materials.

Item Type:Article
Çağin, Tahir0000-0002-3665-0932
Goddard, William A., III0000-0003-0097-5716
Additional Information:© 1999 The American Physical Society. Received 13 May 1999. We thank Dr. Ersan Demiralp for useful discussions. This research was funded by a grant from DOE-ASCI. A.S. acknowledges financial support from FOMEC (Argentina). The facilities of the MSC are also supported by grants from NSF (CHE 95-22179), ARO (MURI), ARO (DURIP), BP Chemical, Exxon, Dow Chemical, Owens-Corning, Avery Dennison, Chevron Petroleum Technology Co., Asahi Chemical, Chevron Chemical Co., Chevron Research Technology Co., and Beckman Institute.
Issue or Number:22
Record Number:CaltechAUTHORS:STRAprb99
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ID Code:2159
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Deposited On:12 Mar 2006
Last Modified:02 Oct 2019 22:50

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