Microsoft PowerPoint - IBIS2015-Nov-ITanaka-open.pptx

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2 To double the speed with which we discover, develop, and manufacture new materials. FY12 budget includes $100 million to launch the Materials Genome Initiative. 2

3 3

7 Ce の単一原子形成エネルギー ( 第一原理計算 )

8 ( 無機 ) 材料科学のキャストの例 : 結晶性物質 Periodic Table Al face centered cubic structure light metal tube NaCl rock salt structure table salt BaTiO 3 perovskite structure ferroelectrics

9 Enormous number of chemical combinations Periodic Table Number of chemical elements Number of chemical combinations (only for simple composition ratio) 1 ~100 2 ~100,000 3 ~10,000,000 4 ~1,000,000,000 9

10 Inorganic Crystal Structure Database (ICSD) World largest database for known inorganic crystals. 177,000 crystal structures 55,000 structures excluding duplicates. 9,100 structure prototypes (e.g. rock-salt, perovskite,...) Number of chemical elements Number of structure prototypes in ICSD , , ,300 10

11 First Principles Calculations Useful to fill the gap between enormous number of chemical combinations and experimental database. Electronic structure calculations entirely based on quantum theory without using empirical parameters. Total energy Force/Stress Electronic/Magnetic structures Physical properties 11

First Principles Calculations INPUT Space Group Unit Cell Parameters Atoms / Atomic Number and Coordinates Density Functional Theory Calculations 1 2 2 V ion ( r) ( r' ) dr' v r r' OUTPUT Total

12 First Principles Calculations INPUT Space Group Unit Cell Parameters Atoms / Atomic Number and Coordinates Density Functional Theory Calculations V ion ( r) ( r' ) dr' v r r' OUTPUT Total Energy Stress / Force Electronic Structures XC ( r) i ( r) Computational Cost 0 (CC0) i i ( r) structure optimization SrTiO 3 (cubic perovskite) Space Group 3 1 x Sr + 1 x Ti + 3 x O = 5 atoms/unit cell Computational Cost CC0 x 10 = CC1 12

1 week 1 year 2x2x2 supercell Single shot GGA Phonon frequency Lattice thermal conductivity Diffusivity by FPMD

13 Cost for First Principles Calculations CC0 1min Single shot GGA PC cluster CC1 Structure opt. 5 nodes x 20 cores =100 cores price ~ USD30k (JPY 4M) Computational Cost with 1 core CC2 CC3 CC4 CC5 1hour 1day 1 week 1 year 2x2x2 supercell Single shot GGA Phonon frequency Lattice thermal conductivity Diffusivity by FPMD simulation 1000 atoms cell Single shot GGA Computational Cost with 100 cores CC5 CC6 CC7 1min 1hour 1day 1 week 1 year 10 nodes 13

14 A set of DFT calculations during a lunch break cubic perovskite Number of compounds: 530 CC1 x 530 calculations by a 100 core PC cluster 14

15 ICSD 収録の構造データについて, 生成エネルギーやバンドギャップなどの第一原理計算結果 15

16 ICSD 収録の構造データについて, 生成エネルギーやバンドギャップなどの第一原理計算結果

Seko, Atsushi Togo, Hiroyuki Hayashi, Koji Tsuda, Laurent Chaput, and IT A.

17 Discovery of new low thermal conductivity materials First-Principles Anharmonic Lattice-Dynamics Calculations and Bayesian Optimization Atsuto Seko, Atsushi Togo, Hiroyuki Hayashi, Koji Tsuda, Laurent Chaput, and IT A. Seko, A. Togo, H. Hayashi, K. Tsuda, L. Chaput, and IT PRL 115, (2015) 17

18 Discovery of ultra-low thermal conductivity materials of 0.1W/m K level in ICSD database (55,000 crystals) diamond >2000 Thermal conductivity (W/m K) Thermal conductivity 18

19 Background Thermal Conductivity (TC) κ = κ electonic + κ lattice Lattice Thermal Conductivity (LTC) Reliable experimental dataset is limited ( < 100 crystals). Reliable first principles calculations are very expensive. (CC5 class : 1 day/100 cores for 1 simple crystal.) Little knowledge to predict LTC deductively. (Chemistry-structure-LTC relationships are not clear.) Materials search has been made through modification of known compounds showing high/low LTC. 19

20 Thermoelectric materials Essential for utilizing otherwise waste heat. Power Low T Electric current Heat flux Electric current n-type p-type Electric current High T Figure of Merit Seebeck coefficient : electrical conductivity : thermal conductivity 20

21 Physical origin of thermal resistivity Phonon-phonon scattering (phonon anharmonicity) Harmonic phonons do not interact. q phonon q'' q' phonon 21

22 phonopy: open source for ab-initio phonon calcs Phonon dispersion Entropy C V Free Energy Atsushi TOGO Kyoto Univ. Free Energy Volume Thermal Expansion Number of citations Web of Science 2015 Oct Year 22

23 Lattice Thermal Conductivity First principles calculation vs. Experimental data CC5 class : 1 day by 100 cores for 1 simple crystal Reliable calculations whose accuracy are comparable to experiments! 23

24 Virtual Screening 24

25 CC5 class Correlations between LTC and predictors CC1 class CC3 class 25

26 Candidates of descriptors for LTC Model 1: Volume V and Density ρ Model 2: Model 1 + primitive elemental descriptors H Li Be B C N O F LiH LiF BeO BN

Toward discovery of new low LTC materials Kriging Interpolation method for which the interpolated values are modeled by a Gaussian process governed by

27 Toward discovery of new low LTC materials Kriging Interpolation method for which the interpolated values are modeled by a Gaussian process governed by prior covariances, originally from geo-statistics. point of next experiment concentration of mineral confidence intervals interpolation geographical location 27

28 Kriging using 101 ab-initio LTC data First prediction was made using N 0 (=5) LTC data and GPR. Use of 34 elemental descriptors on top of V and ρ is found to be effective to overcome an outlier problem. 28

29 Ranking of LTC for 54,779 compounds in ICSD library Z score logκ The higher Z-score, the lower predicted LTC! Virtual screening 29

30 Top 10 lowest LTC compounds among 54,779 Virtual screening of 54,779 compounds in MPD library ab initio LTC 30

31 Lattice Thermal Conductivity (LTC) Newly discovered!! 31

32 Thermoelectric materials Essential for utilizing otherwise waste heat. Power Low T Electric current Heat flux Electric current n-type p-type Electric current High T Figure of Merit Seebeck coefficient : electrical conductivity : thermal conductivity 32

33 Top 10 lowest LTC compounds among 54,779 Virtual screening of 54,779 compounds in MPD library ab initio LTC 33

34 Newly discovered candidates for thermoelectrics with low LTC of < 0.5 W/mK K) and narrow band gap of < 1 ev. A. Seko, A. Togo, H. Hayashi, K. Tsuda, L. Chaput, and IT PRL 115, (2015) 34

35 Fin

42 1 Fig. 2. Li 2 B 4 O 7 crystals with 3inches and 4inches in diameter. Fig. 4. Transmission curve of Li 2 B 4 O 7 crystal. Fig. 5. Refractive index

$42 1 Fig. 2. Li 2 B 4 O 7 crystals with 3inches and 4inches in diameter. Fig. 4. Transmission curve of Li 2 B 4 O 7 crystal. Fig. 5. Refractive index$ MEMOIRS OF SHONAN INSTITUTE OF TECHNOLOGY Vol. 42, No. 1, 2008 Li 2 B 4 O 7 (LBO) *, ** * ** ** Optical Scatterer and Crystal Growth Technology of LBO Single Crystal For Development with Optical Application