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） Contents Motivation Research method first principle calculation（第一原理計算） Successful example Elements under high pressure My study –lithium Summary Pressure Definition example F P A Where F is force, A area. http://www.flickr.com/photos/arejay/168460585/ Diamond Anvil Cell: 1011Pa 1000 times Elephant with high-heeled shoes : 108 Pa Characteristic phases of elemental substances at high pressures 2 period elemental substances ・structures ・metal insulator ・formation of molecules ・molecular dissociation Motivation High pressure-> phase transition Searching about elemental substances -> Basic knowledge of phase transition Study’s flow First-principles calculation ・Atomic number ・Atomic position Get properties Design Calculating by computer Solid State Physics Classical Mechanics e F ma Newton's equation of motion Quantum Mechanics operator Hˆ E Schrödinger equation Advantage of Computational physics including first principle calculation We can predict properties of materials instead of experiment.（at a low price,No danger） Properties under almost unrealizable conditions can be predicted. 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 Phase diagram of oxygen S. Serra et al.,1998 monoclinic α- phase（Akahama et al.,2001) orthorhombic S. Serra et al.,1998 ε phase monoclinic Fujihisa et al.,2006 Phase diagram of Li Unknown Predicted only theoretically. Expected to be Aba2 etc. hR1 bcc cI16 fcc Not confirmed by Exp ０ 40 Confirmed by Exp. M.Hanflad et al. Nature 2000 Takahiro Matsuoka & Katsuya Shimizu Nature 2009 80 GPa Band structure of Li (C2) [eV] ７４－９１GPa structure Brillouin Zone I used the parameters in the following paper. Yansun Yao et al. PRL 102, 115503 (2009) Band structure of Li (C2) [eV] ７４－９１GPa Band gap 0.2450[eV] Semiconducting！ (indirect transition type) Band Structure of Li(Aba2) [eV] Above９１GPa structure Brillouin Zone Band structure of Li(Aba2) [eV] semiconducting！ (almost direct transition type ） Band gap 0.5737[eV] Above９１GPa 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 .
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