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北大新材料论坛（深圳， 2012 ）

北大新材料论坛（深圳， 2012 ）. 新能源材料性质的全量子模拟. 李新征 1 , 陈基 1 , Chris Pickard 2 , Richard Needs 3 , Angelos Michaelides 2. 1 School of Physics, Peking University, China 2 University College London, U. K. 3 University of Cambridge, U. K. 理解材料性质时的关键概念. Born-Oppenheimer (BO) 近似 实际系统在 BO- 势能面上的进动.

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北大新材料论坛（深圳， 2012 ）

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  1. 北大新材料论坛（深圳，2012） 新能源材料性质的全量子模拟 李新征1, 陈基1, Chris Pickard2, Richard Needs3, AngelosMichaelides2 1 School of Physics, Peking University, China 2 University College London, U. K. 3 University of Cambridge, U. K.

  2. 理解材料性质时的关键概念 • Born-Oppenheimer (BO) 近似 • 实际系统在BO-势能面上的进动 最为通行的方法：ab-initio MD 核量子效应 材料性质的全量子模拟，ab-initio path-integral molecular dynamics (PIMD)

  3. Outline • 方法的简介 • 一个实际的应用例子 • 核量子效应对金属与水界面结构的影响 • 这个方法解决的另两个在凝聚态物理中的 • 基本问题，以及在新能源材料中可能的应用

  4. 背后的物理: 路径积分 • Quantum mechanics: probability, propagator 第一部分: 方法 Schrodinger: b • Path-integral: a

  5. 第一部分: 方法 • 热力学计算中的价值: 密度矩阵 • Path-integral enters: Density matrix of a classical polymer of N beads (images) Density matrix of a quantum system

  6. 第一部分: 方法 • Path-integral enters: Density function of a polymer of N beads (images) Density function of a quantum system

  7. Bulk ice under high pressure • Water-metal interface is an important issue at the core of several fields • Corrosion • Electrochemistry • Catalysis 第二部分: 金属与水的界面 • Excess proton in liquid water - + - < 2.5 Ǻ [2] Tuckerman, Marx, Klein, and Parrinello, Science, 275, 817 (1997) [3] Benoit, Marx, Parrinello, Nature, 392, 258(1998) [1]Michaelides, andHu, JACS, 123, 4235 (2001)

  8. 第二部分: 金属与水的界面

  9. 第二部分: 金属与水的界面 • Structural properties of the overlayer at 160 K

  10. Correlate O-H and O-O 第二部分: 金属与水的界面

  11. Focus on the proton transfer 第二部分: 金属与水的界面 • Adiabatic proton transfer: general importance in water-metal interfaces • X.Z Li etal. Phys. Rev. Lett. 104, 066102 (2010)

  12. 3D Quantum Control of Hydrogen Bonds Mass Temperature Ideal model systems to systematically control tunneling (electrochemistry, biology, protonics) Lattice

  13. 第三部分:1)核量子效应对氢键强弱的影响 • X.Z Li etal. Proc. Natl. Acad. Sci. USA 108, 6369 (2011)

  14. 第三部分:2)氢在高压的低温液相 • Ji Chen, etal. submitted.

  15. 问题三:3)在新能源材料中的应用？ 表面态？

  16. 谢谢! …… 各位大家！ • 夏建白院士 • Prof. M. Scheffler • Prof. A. Michaelides • Prof. C. Pickard • Prof. R. Needs • 陈基同学

  17. Structural properties of the overlayer at 160 K 问题一: 金属与水的界面

  18. Impact of quantum nuclear effects on H-bond strength? Liquids: water structure is weakened, and liquid HF is strengthened Clusters: (HF)n when n > 4, strengthened, otherwise, weakened; (H2O)n always weakened In 1950s, Ubbelohde effect (replace H with D) in H-bonded crystals. Biggest question: is there a unified picture? 问题二: 核量子效应对氢键强弱的影响

  19. 问题二: 核量子效应对氢键强弱的影响

  20. Why? 问题二: 核量子效应对氢键强弱的影响 • (HF)2 • (HF)4 • (HF)5

  21. Quantitative 问题二: 核量子效应对氢键强弱的影响 • detail: X.Z Li etal. Proc. Natl. Acad. Sci. USA 108, 6369 (2011)

  22. Rule of Thumb 问题二: 核量子效应对氢键强弱的影响 • Flexible monomer with anharmonic potential must be used if one want to use force-field method in PIMD simulations

  23. Molecular solid 问题三: 氢的相图 Alkali metal: atomic solid Wigner and Huntington (1935): Under high pressure, will H2 become bcc solid?

  24. PNAS 100, 3051 (2003) Atomic liquid Molecular liquid 问题三: 氢的相图 1000 K PRL 100, 155701 (2008) Nature 431, 669 (2004) Temperature 500 K Molecular solid Phase I (hcp) Phase III transparent opaque Phase II 100 GPa 200 GPa 300 GPa Pressure 1) Phase I: free rotating molecular hcp phase 4) I/II isotope dependent, II/III not. 2) Phase II, III: molecular feature kept 5) Turns opaque at 300 GPa, completely dark at 320 GPa. 3) Phase boundary: spectrum changes

  25. Why do people know so little? • Experimentally, hard to probe, hydrogen has a very small scattering cross section for electrons and X-ray 问题三: 氢的相图 • Theoretically: 1) Electronic structure accurate 2) Configuration space explored 3) Quantum nature of hydrogen addressed accurately 4) Optical property properly described Pickard and Needs, 2007

  26. Theoretically: 1) Electronic structure accurate: PBE + DF-vdW 问题三: 氢的相图 2) Configuration space explored: AIRSS 3) Quantum nature of hydrogen : ab initio PIMD addressed accurately 4) Optical property properly described: GW, hybrid functional, IR, X-ray diffraction, and Raman

  27. 问题三: 氢的相图 not hcp hcp based molecular phase

  28. 问题三: 氢的相图

  29. Static PIMD 问题三: 氢的相图 Pbcn Pbcn transparent Opaque C2/c C2/c

  30. 问题三: 氢的相图

  31. 进行中的工作 • 现有程序基础上: • Proton transport along 1D water chain • Higher pressure hydrogen phase (>5Mbar) • Soft Phonon • ThermalConductivity …. • 新的程序:FHI-aims • 实时进动: CMD, RPMD

  32. Name a few reasons: • Different melting, boiling point of H2O and D2O • D2O is toxic if you keep drinking it • Phase transition between ice VII and VIII • Phase diagram of hydrogen under pressure …….

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