HR: 09:45h
AN: V21A-08    [PDF]
TI: A determination of the melting slope of MgO from first principles
AU: * Tangney, P
EM: tangney@civet.berkeley.edu
AF: Physics Department, University of California at Berkeley, 366 LeConte Hall #7300, Berkeley, CA 94720 United States
AU: Scandolo, S
EM: scandolo@ictp.trieste.it
AF: The Abdus Salam ICTP, Strada Costiera 11, Trieste, 34014 Italy
AB: Using a combination of density functional theory (DFT) and molecular dynamics simulations we have calculated the low pressure melting slope of MgO. Our molecular dynamics simulations are performed on both the DFT potential energy surface and a potential energy surface calculated with a new class of highly accurate classical potentials which closely reproduce the DFT results. With these tools we have reduced the error in our evaluation of the melting slope to that intrinsic to the DFT energy functionals that we use. Our results suggest that the melting temperature of MgO increases much more rapidly with pressure than has been found by diamond-anvil cell experiments[1]. Previous theoretical determinations of the melting slope using empirical potentials have also disagreed strongly with experimental results. However, by testing different DFT energy functionals we conclude that the uncertainty in our results cannot explain the large discrepancy between theory and experiment and that a new experimental determination of the MgO melting line may be in order. The melting slope that we calculate, if extrapolated to higher pressures, has strong implications for the composition of the earth's lower mantle. [1] A. Zerr and R. Boehler, Nature 371, 506 (1994).
DE: 1025 Composition of the mantle
DE: 1099 General or miscellaneous
DE: 3210 Modeling
DE: 3230 Numerical solutions
DE: 3924 High-pressure behavior
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2003 Fall Meeting