Chapter 2 – Quantum Chemistry in Functional Inorganic Materials



  • Taku Onishi E-mail the corresponding author E-mail the corresponding author



  • Department of Chemistry for Materials, Graduate School of Engineering, Mie University, Tsu, Mie, Japan

  • The Center of Ultimate Technology on Nano-Electronics, Mie University, Tsu, Mie, Japan

  • The Centre for Theoretical and Computational Chemistry (CTCC), Department of Chemistry, University of Oslo, Postbox 1033, Blindern, Oslo, Norway





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1. Introduction


2. Theoretical Background


3. Magnetism


4. Onishi Chemical Bonding Rule


5. Lithium Ion Conduction


6. Oxide Ion Conduction


7. Proton Conduction


8. Bandgap Change


9. Conclusion


Acknowledgments


References






Abstract


The functional inorganic materials such as magnetic material, photocatalyst, and ion conductor have been widely developed for the practical use of the energy production system. In order to clarify their functionalities, we performed hybrid-density functional theory (DFT) calculations, based on the molecular orbital method. Onishi chemical bonding rule was established to judge the chemical bonding character in their molecular orbitals. This chapter reviews our studies on clarifying the mechanism of functionalities for the functional inorganic materials.




Keywords



  • Hybrid DFT;

  • Molecular orbital;

  • Magnetism;

  • Cooperative Jahn–Teller effect;

  • Onishi chemical bonding rule;

  • Onishi ionics model;

  • Lithium ion conduction;

  • Oxide ion conduction;

  • Proton conduction;

  • Bandgap change




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Figure 2.1. The energy production system by the use of photocatalyst, fuel cell, and lithium ion battery. Solar and waste heat are utilized as energy resource.



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Figure 2.2. The eight-nuclear KMn8F12 model for KMnF3 perovskite.



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Figure 2.3. The shapes and occupation numbers of the selected singly occupied natural orbitals (SONOs) for LS state of KMn8F12 model (UBHHLYP method).



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Figure 2.4. The schematic pictures of the two types of the superexchange (SE) interactions (a) between manganese's 3dx2y2 orbitals via fluorine's 2p orbital and (b) between manganese's 3dx2y2 orbitals via fluorine's 2p orbital.



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Figure 2.5. The crystal structure of K2CuF4 perovskite.



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Figure 2.6. The two types of the normal vibration modes of the octahedral fluorine around copper: (a) Q2 mode and (b) Q3 mode.



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Figure 2.7. The cluster models for K2CuF4 perovskite: (a) Cu4F4F12 and (b) Cu4F4F20 models.



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Figure 2.8. The potential energy curve for Cu4F4F12 model, changing the amplitude of the Jahn–Teller crystal distortion in Q2 mode (q) (UB2LYP method).



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Figure 2.9. The potential energy curve for Cu4F4F16 model, changing the amplitude of the Jahn–Teller crystal distortion in Q2 mode (q) (UB2LYP method).



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Figure 2.10. The shapes and occupation numbers of the singly occupied natural orbital (SONO + 1) for (a) Cu4F4F12 and (b) Cu4F4F16 models, at q = 0.0, 0.15, and 0.5 Å (UB2LYP method).



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Figure 2.11. (a) BaTi8O12 model for BaTiO3 perovskite and (b) PbTi8O12 model for BaTiO3 perovskite.



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Figure 2.12. The orbital energy diagram in BaTi8O12 model (BHHLYP method).



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Figure 2.13. The shapes of the selected molecular orbitals (MOs) in BaTi8O12 model (BHHLYP method).



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Figure 2.14. The orbital energy diagram in PbTi8O12 model (BHHLYP method).



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Figure 2.15. The shapes of the selected molecular orbitals (MOs) in PbTi8O12 model (BHHLYP method).



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Figure 2.16. The schematic picture of lithium ion migration through A-site vacancy.



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Figure 2.17. Onishi ionics model I: lithium ion for AMX3-type perovskite (LiM8X12 model). Lithium ion is displaced along x-axis.



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Figure 2.18. The obtained potential energy curve for La2/3 − xLi3xTiO3 perovskite (LLT), displacing lithium ion along x-axis. d is the lithium ion conduction distance along x-axis (BHHLYP method).



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Figure 2.19. The obtained potential energy curve for LaTiO3 perovskite, displacing lithium ion along x-axis. d is the lithium ion conduction distance along x-axis (BHHLYP method).



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Figure 2.20. The electron density map for Ti4O4 bottleneck: (a) La2/3 − xLi3xTiO3 perovskite (LLT) and (b) LaTiO3 perovskite (BHHLYP method).



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Figure 2.21. The selected molecular orbitals (MOs) for La2/3 − xLi3xTiO3 perovskite (LLT): (a) d = 0.0 Å and (b) d = 1.935 Å (bottleneck) (BHHLYP method).



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Figure 2.22. The selected molecular orbitals (MOs) for LaTiO3 perovskite: (a) d = 0.0 Å and (b) d = 1.979 Å (bottleneck) (BHHLYP method).



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Figure 2.23. The obtained potential energy curve for KxBa(1 − x)/2MnF3 perovskite, displacing lithium ion along x-axis. d is the lithium ion conduction distance along x-axis (BHHLYP method).



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Figure 2.24. Onishi ionics models I for the oxygen-doped KxBa(1 − x)/2MnF3 perovskite: (a) LiMn8F11O1 model, (b) LiMn8F10O2 (I) model, (c) LiMn8F10O2 (II) model. Lithium ion is displaced along x-axis.



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Figure 2.25. The obtained potential energy curves for LiMn8F11O1 model, displacing lithium ion along x-axis. d is the lithium ion conduction distance along x-axis (BHHLYP method).



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Figure 2.26. The obtained potential energy curves for LiMn8F10O2 (I) model, displacing lithium ion along x-axis. d is the lithium ion conduction distance along x-axis (BHHLYP method).



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Figure 2.27. The obtained potential energy curves for LiMn8F10O2 (II) model, displacing lithium ion along x-axis. d is the lithium ion conduction distance along x-axis (BHHLYP method).



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Figure 2.28. The two kinds of the oxide ion conduction paths on AlO2 layer in AMO3-type perovskite. The arrows show the oxide ion paths. In (a) and (b) paths, oxide ion migrates parallel and diagonally to Alsingle bondOsingle bondAl bond, respectively.



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Figure 2.29. Onishi ionics model II: oxide ion for AMO3-type perovskite (A2M4O3 model). Oxide ion is displaced along the diagonal line ((b) path).



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Figure 2.30. Onishi ionics models II for LaAlO3 perovskite: (a) Al4O3 model, (b) La2Al4O3 model, (c) LaSrAl4O3 model, and (d) Sr2Al4O3 model.



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Figure 2.31. The obtained potential energy curves for Al4O3 model, displacing oxide ion along the diagonal line. d is the oxide ion conduction distance along the diagonal line (BHHLYP method).



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