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DFT evolutionary search for Mg 2 Si under pressure Yu.V. Luniakov Institute of Automation and Control Processes, Vladivostok, Russia Department of Surface.

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Presentation on theme: "DFT evolutionary search for Mg 2 Si under pressure Yu.V. Luniakov Institute of Automation and Control Processes, Vladivostok, Russia Department of Surface."— Presentation transcript:

1 DFT evolutionary search for Mg 2 Si under pressure Yu.V. Luniakov Institute of Automation and Control Processes, Vladivostok, Russia Department of Surface Physics

2 Оbjectives To search for new structures near transition pressures To study how Universal Structure Predictor for Evolutionary Xtallography can reproduce the known structure

3 Оbjectives To study how Universal Structure Predictor for Evolutionary Xtallography can reproduce the known structure To search for new structures near transition pressures

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6 A.R. Oganov. Modern Methods of Crystal Structure Prediction. (Wiley- VCH., 2010) ISBN: 978-3-527-40939-6.

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11 Methodology A.R. Oganov Modern Methods of Crystal Structure Prediction. (Wiley-VCH., 2010) ISBN: 978-3-527-40939-6.

12 Object of investigation

13 Thermoelectric conversion effective material Abundant and environmental friendly material

14 225, Fm3m62, Pnma 194, P6 3 /mmc Si Mg P=7.5 GPa P=21.3 GPa

15 VASP code, Kresse, G. and Furhmüller, J. (2007). Institut für Materialphysik. Universität Wien, Austria http://cms.mpi.univie.ac.at/vasp/ Conjugate gradient type of ionic relaxation Generalized Gradient Approximation of Perdew Burke Enzerof form 1 for the exchange and correlation functional 1 J.P. Perdew, K. Burke, M. Ernzerhof (1996). Phys. Rev. Lett. 77: 3865. projector-augmented wave pseudopotentials (PAW) Kresse, G. and Joubert, D. (1999). Phys. Rev. B 59: 1758- 1775 Details of total energy calculations: Computational details: E cut = 350-500 eV Unit cell consists of 4 Si and 8 Mg atoms k-point meshes resolution: 2  0.01 Å -1 – 2  0.02 Å -1 ~ 200 4 Si 8 Mg Random initial distributions

16 VASP code, Kresse, G. and Furhmüller, J. (2007). Institut für Materialphysik. Universität Wien, Austria http://cms.mpi.univie.ac.at/vasp/ Conjugate gradient type of ionic relaxation Generalized Gradient Approximation of Perdew Burke Enzerof form 1 for the exchange and correlation functional 1 J.P. Perdew, K. Burke, M. Ernzerhof (1996). Phys. Rev. Lett. 77: 3865. projector-augmented wave pseudopotentials (PAW) Kresse, G. and Joubert, D. (1999). Phys. Rev. B 59: 1758- 1775 Details of total energy calculations: Computational details: E cut = 350-500 eV Unit cell consists of 4 Si and 8 Mg atoms k-point meshes resolution: 2  0.01 Å -1 – 2  0.02 Å -1 ~ 200 Si Mg Random initial distributions

17 VASP code, Kresse, G. and Furhmüller, J. (2007). Institut für Materialphysik. Universität Wien, Austria http://cms.mpi.univie.ac.at/vasp/ Conjugate gradient type of ionic relaxation Generalized Gradient Approximation of Perdew Burke Enzerof form 1 for the exchange and correlation functional 1 J.P. Perdew, K. Burke, M. Ernzerhof (1996). Phys. Rev. Lett. 77: 3865. projector-augmented wave pseudopotentials (PAW) Kresse, G. and Joubert, D. (1999). Phys. Rev. B 59: 1758- 1775 Details of total energy calculations: Computational details: E cut = 350-500 eV Unit cell consists of 4 Si and 8 Mg atoms k-point meshes resolution: 2  0.01 Å -1 – 2  0.02 Å -1 ~ 200 Si Mg Random initial distributions

18 VASP code, Kresse, G. and Furhmüller, J. (2007). Institut für Materialphysik. Universität Wien, Austria http://cms.mpi.univie.ac.at/vasp/ Conjugate gradient type of ionic relaxation Generalized Gradient Approximation of Perdew Burke Enzerof form 1 for the exchange and correlation functional 1 J.P. Perdew, K. Burke, M. Ernzerhof (1996). Phys. Rev. Lett. 77: 3865. projector-augmented wave pseudopotentials (PAW) Kresse, G. and Joubert, D. (1999). Phys. Rev. B 59: 1758- 1775 Details of total energy calculations: Computational details: E cut = 350-500 eV Unit cell consists of 4 Si and 8 Mg atoms k-point meshes resolution: 2  0.01 Å -1 – 2  0.02 Å -1 ~ 200 Si Mg Random initial distributions

19 VASP code, Kresse, G. and Furhmüller, J. (2007). Institut für Materialphysik. Universität Wien, Austria http://cms.mpi.univie.ac.at/vasp/ Conjugate gradient type of ionic relaxation Generalized Gradient Approximation of Perdew Burke Enzerof form 1 for the exchange and correlation functional 1 J.P. Perdew, K. Burke, M. Ernzerhof (1996). Phys. Rev. Lett. 77: 3865. projector-augmented wave pseudopotentials (PAW) Kresse, G. and Joubert, D. (1999). Phys. Rev. B 59: 1758- 1775 Details of total energy calculations: Computational details: E cut = 350-500 eV Unit cell consists of 4 Si and 8 Mg atoms k-point meshes resolution: 2  0.01 Å -1 – 2  0.02 Å -1 ~ 200 Si Mg Random initial distributions

20 Mg 2 Si crystal at ambient pressure conditions

21 Mg 2 Si crystal at P = 5 GPa

22 Mg 2 Si crystal at P = 10 GPa

23 Mg 2 Si crystal at P = 15 GPa

24 Mg 2 Si crystal at P = 20 GPa

25 Mg 2 Si crystal at P = 25 GPa

26 Theory Experiment 225, Fm3m62, Pnma 194, P6 3 /mmc 225, Fm3m 62, Pnma 63, Cmcm 194, P6 3 /mmc P=7.5 GPa P=21.3 GPa

27 Theory Experiment 225, Fm3m62, Pnma 194, P6 3 /mmc 225, Fm3m 62, Pnma 63, Cmcm 194, P6 3 /mmc P=7.5 GPa P=21.3 GPa ? ? ?

28 Enthalpies of various structures Mg 2 Si as a function of pressure

29 5.6 GPa 22.3 GPa

30 Enthalpies of various structures Mg 2 Si as a function of pressure 5.6 GPa 22.3 GPa 19.6 GPa24.1 GPA J.-H. Hao, Z.-G. Guo, Q.-H. Jin, Solid State Commun. 150, 2299 (2010). [Yu Ben-Hai and Chen Dong, Chin. Phys. B 20, 030508 (2011). 6.1 GPa Wien2k F. Kalarasse, B. Bennecer, J. Phys. Chem. Solids 69, 1775 (2008). 8.4 GPa Сaster F. Yu, J.X. Sun, W. Yang, R.G. Tian, G.F. Ji, Solid State Commun. 150, 620 (2010) 12.8 GPa Сaster J.-H. Hao, Z.-G. Guo, Q.-H. Jin, Solid State Commun. 150, 2299 (2010).

31 Enthalpies of various structures Mg 2 Si as a function of pressure 5.6 GPa 22.3 GPa 19.6 GPa24.1 GPA J.-H. Hao, Z.-G. Guo, Q.-H. Jin, Solid State Commun. 150, 2299 (2010). [Yu Ben-Hai and Chen Dong, Chin. Phys. B 20, 030508 (2011). 6.1 GPa Wien2k F. Kalarasse, B. Bennecer, J. Phys. Chem. Solids 69, 1775 (2008). 8.4 GPa Сaster F. Yu, J.X. Sun, W. Yang, R.G. Tian, G.F. Ji, Solid State Commun. 150, 620 (2010) 12.8 GPa Сaster J.-H. Hao, Z.-G. Guo, Q.-H. Jin, Solid State Commun. 150, 2299 (2010). P=7.5 GPa P=21.3 GPa

32 Experiment Theory 62, Pnma 63, Cmcm 194, P6 3 /mmc ? 225, Fm3m62, Pnma 194, P6 3 /mmc

33 Theory 62, Pnma 63, Cmcm 194, P6 3 /mmc

34 Theory 62, Pnma 63, Cmcm 194, P6 3 /mmc Side view

35 Theory 62, Pnma 63, Cmcm 194, P6 3 /mmc Side view Top view

36 Theory 62, Pnma 63, Cmcm 194, P6 3 /mmc Side view Top view

37 Theory Top view 63, Cmcm 194, P6 3 /mmc

38 Theory Top view 63, Cmcm 194, P6 3 /mmc

39 Theory Top view 63, Cmcm 194, P6 3 /mmc

40 Theory Mg1(1/3, 2/3, 1/4) Mg2 (0, 0, 0) Si (1/3, 2/3, 3/4) 63, Cmcm 194, P6 3 /mmc

41 Energy differences between and Pressure, GPa  SI, Å  Mg, Å  E, eV 16 -0.00020.0005-0.0004 17 -0.00020.0004-0.0005 18 -0.00010.0003-0.0004 19 -0.00010.0003-0.0005 20 0.00010.0002 21 0.00000.00030.0006 22 -0.00010.00040.0006 23 -0.00010.00040.0007 24 -0.00020.00040.0006 25 0.00000.00020.0007 26 -0.00010.00030.0012 27 0.00000.00020.0004 28 0.00020.00010.0005 194, P6 3 /mmc 63, Cmcm

42 Polymorphism of Mg 2 Sn at high temperatures and pressures T. I. Dyuzheva, S. S. Kabalkina, and L.F. Vereshchanig, Kristallografiya, 17, №4, р. 804. pseudohexagonal network of Ni atoms in the Ni 2 Si structure

43 Conclusion 1.DFT evolutionary search for global minima of Mg 2 Si silicide reproduces the experimental structures at pressure range 0–25 GPa 2.The P63/mmc structure is not the global minimum one. 3.A new possible high-pressure structure Cmcm was predicted, that is a little more stable than that.

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47 Enthalpies of various structures Mg 2 Si as a function of pressure

48 Symmetry Identification EA92 6.364 6.358 7.780 65.915 65.874 89.987 Sym.group: 225 1.0000 3.136808 5.462888 -0.902083 -3.133455 0.899467 -5.458945 -4.551043 6.310156 -0.046073 4 8 Direct 0.124559 0.874854 0.248101 0.374715 0.624543 0.748453 0.624602 0.374538 0.248229 0.875104 0.125194 0.748233 0.500588 0.250229 0.997983 0.000634 0.249708 0.998881 0.749828 0.499084 0.498024 0.749483 0.999420 0.498726 0.499018 0.749848 0.998337 0.998872 0.749998 0.998007 0.249379 0.500230 0.498178 0.249766 0.999779 0.498120 1.0 4.4209599495 0.0000000000 0.0000000000 0.0000000000 4.4209599495 0.0000000000 0.0000000000 0.0000000000 6.2600002289 Si Mg 1 2 Direct 0.500000000 0.500000000 0.500360012 0.500000000 0.000000000 0.250310004 0.000000000 0.500000000 0.250310004 Sym.group: 99

49 Lattice parameters of Fm3m, Pnma and P6 3 /mmc equilibrium structures Solid State Commun. 150, 2299 (2010)] 6.35 Å

50 Lattice parameters of Fm3m, Pnma and P6 3 /mmc equilibrium structures Solid State Commun. 150, 2299 (2010)] 6.35 Å 6.36

51 Lattice parameters of Fm3m, Pnma and P6 3 /mmc equilibrium structures Solid State Commun. 150, 2299 (2010)] 6.35 Å 4.1985.278

52 Lattice parameters of Fm3m, Pnma and P6 3 /mmc equilibrium structures Solid State Commun. 150, 2299 (2010)] 6.35 Å 6.5353.929 7.771

53 Lattice parameters of Fm3m, Pnma and P6 3 /mmc equilibrium structures Solid State Commun. 150, 2299 (2010)] 6.35 Å 6.5353.929 7.771

54 Lattice parameters of Fm3m, Pnma and P6 3 /mmc equilibrium structures Solid State Commun. 150, 2299 (2010)] 6.35 Å 9 %-12 % 14 %

55 Enthalpies of various structures Mg 2 Si as a function of pressure 1

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