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Intern: Shemekia Braddock, Chemistry, Jackson State University Mentor: Brent Melot Faculty Supervisor: Ram Seshadri Department: Materials

BOND LENGTH AND BOND DISTORTION OF FERROELECTRIC BATIO₃

BaTiO₃ is a ferroelectric oxide that exhibits a phase change from tetragonal to cubic at 130°C. In the tetragonal structure of BaTiO₃ the apical Ti-O bonds are longer than the equatorial bonds. In the cubic structure the titanium is centered octahedrally surrounded by six oxygen atoms, with all bond lengths being equal. Recent experiments have shown that as particle size get smaller bond distortion increases, i.e. one Ti-O apical bond increases while the other Ti-O apical bond decreases. Experiments also suggest that this distortion is because the size of the unit cell volume increases with smaller particle size, and the Ti atoms have more freedom to move off center. With the research presented, we determined if the cell volume is the primary contributing factor to bond distortion exhibited in smaller particle size. Density Functional Theory calculations were used to look at these factors using Quantum Espresso. A relaxation was done to test different cell volumes to get the short and long bond lengths for each value. The results show that the cell volume does cause the unit cell bond lengths to distort but the smaller particle size causes a greater distortion.

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