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Extending Quantum Mechanical Simulations with HPCx: Melting of Earth's Core

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 Quantum Mechanical Simulations with HPCx: Melting of Earth's Core

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  1. Extending the domain of quantum mechanical simulations with HPCx: Melting Dario Alfè University College London

  2. Why Melting ? • The Earth’s core is mainly iron • Melting temperature of Fe at ICB • Constraint on the temperature of the core

  3. Melting Free energy approach Coexistence approach

  4. Free energy approach

  5. Calculating free energies Thermodynamic integration:

  6. Size and k-points tests

  7. Lidunka Vočadlo & Dario Alfè, PRB, 65, 214105 (2002)

  8. The coexistence approach

  9. 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

  10. Scaling tests (Al, 1000 atoms)

  11. 512 atoms () (~2 weeks HPCx, 64 PEs) 1000 atoms() (~3 weeks HPCx, 128 PEs)

  12. Dario Alfè, Phys. Rev. B, 68, 064423 (2003)

  13. 512 atoms (2x2x1) (~4 weeks SUN-SPARC, 16 PEs) 1728 atoms() (~7 months SUN-SPARC, 16 PEs)

  14. 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).

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