First-principles Study of Oxygen Octahedron Torsion and Its Effect on the Dielectric Properties of CaCu3Ti4O12
This study employed the first-principles ultra-soft pseudopotential plane-wave method based on density functional theory(DFT)to twist TiO6 octahedron by adjusting the position of oxygen atoms.The bonding situation,band structure,atomic state density,and optical frequency dielectric function of CaCu3Ti4O12(CCTO)before and after oxygen octahedron torsion were compared.It was found that the change in the direction of Ti—O—Ti bond rotation had almost no effect on the charges,bond lengths,or populations of each atom,but the change in torsional angle played a crucial role.With an increase in the Ti—O—Ti bond angle,the amount of charge of Cu,the length of the Cu—O bond,population decreased,and the dielectric constant significantly increased,indicating that the rigid constraint of the Cu—O bond contributed to the increase in the optical dielectric constant of CCTO.This study reveals the influence of TiO6 octahedron torsion on the macroscopic dielectric properties of CCTO,providing new insights for optimizing the dielectric properties of CCTO based on adjusting the microstructure.
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