Yoshida Laboratory Yuya Yamada （山田裕也）

1. Theoretical prediction of structures and properties of lithium under high pressure (高圧下におけるリチウムの構造と物性の理論的予測) Yoshida Laboratory Yuya Yamada（山田裕也）

2. Contents • Introduction • Motivation • Research method first-principles calculation（第一原理計算） • Successful example • Elemental substance under high pressure • My study –lithium • Summary

3. Introduction Definition example Where F is force, A area. http://www.flickr.com/photos/arejay/168460585/ Pressure Diamond Anvil Cell: 1011Pa 1000 times Elephant with high-heeled shoes : 108 Pa

4. Characteristic phases of elemental substances at high pressures Introduction Different from other elemental substances Complex Diversity 2 period elemental substances ・structures ・metal insulator ・formation of molecules ・molecular dissociation

5. Motivation • High pressure-> phase transition • Searching about elemental substances -> Basic knowledge of phase transition

6. Research method Study’s flow First-principles calculation ・Atomic number ・Atomic position Design Calculating by computer Get properties

7. Research method Solid State Physics • Classical Mechanics • Quantum Mechanics operator Schrödinger equation Newton's equation of motion

8. Research method Advantage of Computational physics including first-principles calculation • We can predict properties of materials instead of experiment.（at a low cost, No danger） • Properties under almost unrealizable conditions can be predicted.

9. Successful example Example of prediction being ahead • Ca-V structure is predicted theoretically. • Experimental results are useful ,but structure cannot be determined by only them. Takahiro Ishikawa Phys.Rev. B 77, 020101

10. Elemental substance under high pressure Phase diagram of oxygen S. Serra et al.,1998 εphase monoclinic orthorhombic monoclinic α- phase（Akahama et al.,2001) S. Serra et al.,1998 Fujihisa et al.,2006

11. My study –lithium Phase diagramof Li Unknown Predicted only theoretically. Expected to be Aba2etc. hR1 cI16 bcc fcc Not confirmed by Exp 80 ０ 40 GPa Confirmed by Exp. M.Hanflad et al. Nature 2000 Takahiro Matsuoka & Katsuya Shimizu Nature 2009

12. My study –lithium Band structure of Li (C2) ７４－９１GPa [eV] structure Brillouin Zone I used the parameters in the following paper. Yansun Yao et al. PRL 102, 115503 (2009)

13. My study –lithium Band structure of Li (C2) [eV] ７４－９１GPa Band gap 0.2450[eV] Semiconducting！ (indirect transition type)

14. My study –lithium Band Structure of Li(Aba2) [eV] Above９１GPa structure Brillouin Zone

15. My study –lithium Band structure of Li(Aba2) Above９１GPa [eV] semiconducting！ (almost direct transition type ） Band gap 0.5737[eV]

16. Summary • Li is semiconducting when it is under high pressure. • Structure of oxygen under high pressure is characteristic. • First-principles calculation is an useful method.

17. Thank you for your attention!!