1 / 12

Takahiro Ishikawa,Hitose Nagara , Naoshi Suzuki,Taku Tsuchiya, and Jun Tsuchiya

High-pressure phase of calcium: Prediction of phase Ⅵ and upper-pressure phases from first principle. Phys.Rev.B 81,092104(2010). Takahiro Ishikawa,Hitose Nagara , Naoshi Suzuki,Taku Tsuchiya, and Jun Tsuchiya. Shimizu lab. ORII Daisuke. Contents. Introduction

sondra
Download Presentation

Takahiro Ishikawa,Hitose Nagara , Naoshi Suzuki,Taku Tsuchiya, and Jun Tsuchiya

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. High-pressure phase of calcium:Prediction of phase Ⅵ and upper-pressure phases from first principle Phys.Rev.B 81,092104(2010) Takahiro Ishikawa,HitoseNagara, NaoshiSuzuki,Taku Tsuchiya, and Jun Tsuchiya Shimizu lab. ORII Daisuke

  2. Contents • Introduction What’s “High-pressure phase”? ⇒An interesting property What’s “phase Ⅵ”? First principles calculations • Motivation • Research • Summary High-pressure phase of calcium:Prediction of phase Ⅵ and upper-pressure phases from first principle

  3. What’s “High-pressure phase”? Pressure The structure change!! =Structural phase transition (構造相転移) simple cubic Decreasing inter atomic distance by compression bcc Electronic states change! fcc

  4. An interesting propertypressure-induced superconductivity • Superconductivity(超伝導) ⇒electrical resistance= 0 ⇒Meissner effect B=0 cool @ extremely-low-temperature Phase transition!! Normalconductivity(常伝導) Superconductivity (超伝導) !! electrical cable linear motor car

  5. What’s “phase Ⅵ”? Ca-I Ca-II Ca-III Ca-IV Ca-V fcc bcc sc (simple cubic) ① ② ? • Structural phase transitions (構造相転移) of calcium [GPa] 20 32 113 139 • ②【Ca-Ⅴ structure】 • OrthorhombicCmca structure with zigzag atomic arrangement • ①【Ca-Ⅳ structure】 • TetragonalP41212structure with fourfold helical atomic arrangements • 　　　　⇒HighestTcin simple element! • Transition temperature Tc 25K @ 161GPa (Ca-Ⅴ?) Ca Matsuoka private communication

  6. First principles calculations Input data • Crystal structure • Type of atoms Output data Charge density Total energy Stress Inter atomic force etc… Determination of electronic states

  7. Motivation Background Investigating mechanism of high Tc superconductivity Predicting the structure of Cain which the highest Tc is observed

  8. Computational details structure fcc bcc sc (simple cubic) hcp Cmca Cmcm Pnma I41/amd P41212 I4/mcm(0,0,γ) Input data Making crystal structure (lattice vectors and atomic coordinates) Type of atoms ⇒structural optimization ⇒electronic states Comparing the enthalpies up to 200Gpa (enthalpy) The most stable structure @ 0K

  9. Comparing enthalpies (enthalpy) The lowest ΔH point ⇒Most stable structure figure 1 figure 2

  10. Experiment Ca-I Ca-II Ca-III Ca-IV Ca-V fcc bcc sc (simple cubic) P41212 Cmca Ca-IV Ca-VI? Ca-VII? Ca-I Ca-II Ca-Ⅲ Ca-V I4/mcm(00γ) P41212 Cmca Pnma Pnma I4/mcm(00γ) fcc bcc I41/amd [GPa] 20 32 113 139 Calculation in this paper [GPa] 109 117 135 3.5 32 74 Ca-VII? Ca-VIII? hcp I4/mcm(00γ) [GPa] 495

  11. Superconductivity • Theoretically ,Tc=25K was obtained around the phase boundary between Ca-Ⅵ and Ca-Ⅶ. Experimental result 158(GPa) (⇒Recently ,thestructure of Ca-Ⅵ was experimentally confirmed.) (Y.Nakamoto et al , Phys.Rev.B , 81, 140106(R) (2010).) Ca-Ⅵ J.Phys. Soc. Jpn. 75, 083703 (2006). 50 100 150 pressure(GPa)

  12. Summary • The structures of the phases Ca-Ⅵ and Ca-Ⅶ were predicted. • The highest TC of 25K in the Ca-Ⅵ or Ca-Ⅶ phase.

More Related