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The 6th School on Simulation and Modeling Physics "Ab-initio methods and their applications"

The 6th School on Simulation and Modeling Physics "Ab-initio methods and their applications" Hanoi, 27 - 29 November 2007. Exploring planetary interiors by ab-initio molecular dynamics. 6 th SMP, Hanoi, Nov 27-29, 2007 Sandro Scandolo (the Abdus Salam ICTP, Trieste, Italy).

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The 6th School on Simulation and Modeling Physics "Ab-initio methods and their applications"

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  1. The 6th School on Simulation and Modeling Physics"Ab-initio methods and their applications" Hanoi, 27 - 29 November 2007

  2. Exploring planetary interiors by ab-initio molecular dynamics 6th SMP, Hanoi, Nov 27-29, 2007 Sandro Scandolo (the Abdus Salam ICTP, Trieste, Italy)

  3. The Abdus Salam International Centre for Theoretical Physics (under UNESCO / IAEA), Trieste, Italy www.ictp.it ICTP’s mission: To foster the growth of advanced studies and research in physics and mathematics, especially among researchers from developing countries Opportunities - Conferences / Schools throughout the year - Associates (our faculty “in the field”) - Visitors (junior, STEP, TRIL, etc) - Diploma Course

  4. High pressure in Materials Science Planetary Science 1991: Earth’s core conditions reproduced in the laboratory 1951: the first man-made diamonds

  5. Shock waves Diamond anvil cell

  6. from “first principles” Approximations - Born-Oppenheimer - Classical nuclei - Density functional theory Variable-cell molecular dynamics [Parrinello & Rahman, 1981]

  7. Outline High Pressure in Materials Science: + “Carbonia”: a silica-like CO2 amorph + Novel transition metal nitrides High pressure in Planetary Science: + Carbon in planetary interiors + Melting of iron

  8. Experimental confirmation of silica-like CO2 Yoo et al, Science 283, 1510 (1999) Silica-like CO2 : the crystal phases Serra, Cavazzoni, Chiarotti, Scandolo, Tosatti, Science 284, 788 (1999) Molecular CO2 Candidate theoretical structures for silica-like CO2 Crystal structure of silica-like CO2 not yet determined Is there a glass analog? + Molecular CO2 predicted to tranform into a silica-like crystal at high pressure + Silica-like phases of CO2 predicted to be ultrahard

  9. “Carbonia”: the silica-like CO2 glass Experimental evidence for amorphous CO2 Santoro, Gorelli, Bini, Ruocco, Scandolo, Crichton, Nature, in press (2006) Tetrahedral CO4 Octahedral CO6 Compression by ab-initio molecular dynamics gives: At 1000 K and 100 GPa: a crystalline phase At 2000 K and 80 GPa: an amorphous phase

  10. Platinum nitride: PtN or PtN2? Polymeric N Molecular N2 Raman shift (cm-1) Single-bonded polymeric nitrogen Gregoryanz et al, Nature Mat. (2004) Crowhurst et al, Science (2006) Eremets et al, Nature Mat. (2004) Ab-initio calculations on structures with 1:1 stoichiometry fail to reproduce the experimental Raman spectra

  11. Platinum nitride: PtN2 pyrite Young, Montoya, Lazzeri, Sanloup, Gregoryanz, Scandolo, PRB 2006 Raman spectra X-ray diffraction

  12. MN2 with interstitial N2 units: a new class of transition metal nitrides? New “heavy” metal nitrides are superhard Bulk modulus: 428 GPa (IrN2), 358 GPa (OsN2) PtN2 pyrite IrN2 Single bonded N-N Young, Sanloup, Gregoryanz, Scandolo, Hemley, Mao, PRL 96, 155501 (2006)

  13. Scandolo & Jeanloz, American Scientist (2003) H2O+CH4+NH3 Marvin Ross, “Diamonds in the sky” Nature (1981) Methane was found to dissociate under a shock wave

  14. Methane dissociation: what do simulations say Compressed methane Compressed methane heated up to 4000 K F. Ancilotto et al., Science 275, 1288 (1997)

  15. Methane dissociation: the experimental confirmation L.R. Benedetti et al., Science 283, 100 (1999) Before compression After compression

  16. Melting of Carbon X. Wang, S. Scandolo, R. Car, Phys. Rev. Lett 2005 Coordination number BC8, SC ?? 5.3-5.8 5.2 diamond liquid 4.7 4.3 Neptune and Uranus isentrope 3.8

  17. Accuracy of DFT?: Melting of silicon Liquid Solid Tm(LDA) = 1380 K Tm(GGA) = 1520 K Tm(meta-GGA) = 1700 K Tm(experiment) = 1687 K X. Wang, S. Scandolo, R. Car

  18. How hot is the centre of the Earth? liquid solid The temperature at the inner core boundary coincides with the melting temperature of Fe at 330 GPa Inner core (solid Fe) Mantle Outer core (liquid Fe)

  19. The “optimized” potential method “Optimized” potential at P,T A. Laio et al, Science 287, 1027 (2000)

  20. Melting of Iron at Earth’s core pressures A. Laio et al, Science 287, 1027 (2000) Shock wave experiments DFT-based calculation by Alfe’ et al Our results Inner-Outer core boundary Static experiments

  21. D. Stevenson, Nature 423, 239 (2003)

  22. The crew: J. Montoya A. Young R. Rousseau C. Cavazzoni Y. Liang X. Wang A. Laio R. Car …. www.quantum-espresso.org

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