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Explore the melting temperature of iron at the Earth's core using free energy and coexistence approaches with high-performance computing. This study provides insights into constraint temperatures and opens possibilities for calculating free energies efficiently.
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Extending the domain of quantum mechanical simulations with HPCx: Melting Dario Alfè University College London
Why Melting ? • The Earth’s core is mainly iron • Melting temperature of Fe at ICB • Constraint on the temperature of the core
Melting Free energy approach Coexistence approach
Calculating free energies Thermodynamic integration:
Density Functional Theory Generalized Gradient Approximation (PW91) VASP code(Kresse and Furthmuller, PRB 54, 11169 (1996)) USPP (130 eV PW-cutoff) Finite temperature Fermi smearing K-points sampling Efficient charge density extrapolation (Alfe`, Comp. Phys. Comm. 118, 31 (1999)) Ab-initio technical details
512 atoms () (~2 weeks HPCx, 64 PEs) 1000 atoms() (~3 weeks HPCx, 128 PEs)
512 atoms (2x2x1) (~4 weeks SUN-SPARC, 16 PEs) 1728 atoms() (~7 months SUN-SPARC, 16 PEs)
Conclusions • Coexistence of phases for melting is now possible even with first principles techniques (though still very expensive). • Next step: Iron ? (One order of magnitude more expensive than Aluminium).