Morphology and surface structure of cubic BaTiO3 using first-principles density functional theory

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First-priciples density functional theory (DFT) techniques are used to provide atomic-scale insight into the surface structures and crystal morphologies of cubic barium titanate, BaTiO3. Relaxed surface structures and energies are calculated for 3 low index planes and resulting equilibrium morphology based on Wulff's theorem with {001} and {011} faces were constructed. The calculated surface energies are strongly dependent on the coordination loss of TiO6 octahedra at the surface. The optimized structure at the low-energy surfaces shows that only atoms at 1st perovskite layer are displaced from ideal position, while no significant displacements are indicated. On the other hand, the Bader charge analysis shows that the ionicity of whole the cations in the slab (7 perovskite layers) is larger than that in the bulk. Therefore, change of electric property is expected at the surface region, which is not due to the surface reconstruction, but to the change of electronic structure.
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