Computational investigation of functional perovskites




Li, Xinyu, Ph. D.

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Functional perovskites have been investigated extensively for many years. Thousands of new perovskites are synthesized and studied every year. Many functional perovskites have been widely employed in industry. Density functional theory (DFT) calculations have been used to obtain a better understanding of functional perovskites, especially their electronic and structural properties. During my graduate study, I investigated perovskite’s properties on ionic transport, magnetic ordering, ferroelectricity, physical property and phase transition using DFT calculations. In the first case, I simulated the ionic transport process in several Ruddlesden- Popper (RP) phases. Climbing image nudged elastic band (CI-NEB) calculation was used to get accurate oxygen interstitial migration barrier. I established a linkage between interstitial migration barrier and perovskite’s octahedral rotation with symmetry mode approach. Two factors, including A-site atom radius and epitaxial strain, were used to reduce interstitial migration barrier in my simulation. My study on ionic transport in RP phases provides guidance on the design of fast ionic transport in perovskite oxides.

In the second case, DFT calculation was employed to investigate a double perovskite’s magnetic and electronic properties. A new ferroelectric mechanism in perovskite, associated with the displacement of coplanar Mn²⁺, was discovered experimentally. My DFT calculation explained the origin of coplanar displacement from an orbital point of view. In addition, DFT simulations were used in the design of ferroelectricity enhancement perovskite. In the last case, I simulated structural behaviors under pressure of several double perovskites. The results show that these double perovskites can be divided into two groups based on their octahedral rotations under pressure. The origin of their distinct volume reduction mechanisms was studied through DFT simulations. The difference between the two mechanisms and their influence on bulk modulus were discussed based on my computational results.


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