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 example Where F is force, A area. Elephant with high-heeled shoes : 10 8 Pa Diamond Anvil Cell: Pa Definition 1000 times

Characteristic phases of elemental substances at high pressures 2 period elemental substances ・ structures ・ metal   insulator ・ formation of molecules ・ molecular dissociation

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

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

Solid State Physics Classical Mechanics Quantum Mechanics Newton's equation of motion Schrödinger equation operator

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,

Phase diagram of oxygen S. Serra et al.,1998 α- phase （ Akahama et al.,2001) monoclinic orthorhombic ε phase Fujihisa et al.,2006 monoclinic S. Serra et al.,1998

Phase diagram of Li ０ GPa bcc fcc hR1 cI16 Confirmed by Exp. Not confirmed by Exp Unknown Predicted only theoretically. Expected to be Aba2 etc. M.Hanflad et al. Nature 2000 Takahiro Matsuoka & Katsuya Shimizu Nature 2009

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

Band structure of Li (C2) [eV] Semiconducting ！ (indirect transition type) Band gap [eV] ７４－９１ GPa

Band Structure of Li(Aba2) [eV] Brillouin Zone Above ９１ GPa structure

Band structure of Li(Aba2) [eV] Band gap [eV] semiconducting ！ (almost direct transition type ） Above ９１ GPa

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.