First-principles calculations of the dielectric properties of perovskite-type materials |
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| Affiliation: | 1. Department of Physics, University of Lahore, 53700, Lahore, Pakistan;2. Department of Chemistry, College of Sciences, King Khalid University, P.O. Box, 9004, Abha, Saudi Arabia;3. Department of Physics, Riphah International University, Faisalabad campus, Pakistan;4. Institute of Physics, The Islamia University Bahawalpur, 63100, Pakistan;5. Department of Physics, Deanship of Educational Services, Qassim University, Buraydah, 51452, Saudi Arabia;6. Department of Chemistry, College of Science, Princess Nourah bint Abdulrahman University, P.O. Box 84428, Riyadh, 11671, Saudi Arabia;1. Division of Physical Science, Faculty of Science and Technology, Huachiew Chalermprakiet University, Samutprakarn 10540, Thailand;2. Extreme Condition Physics Research Laboratory and Center of Excellence in Physics of Energy Materials (CE: PEM), Department of Physics, Faculty of Science, Chulalongkorn University, Bangkok 10330, Thailand;3. Department of Chemistry, Center of Excellence in Materials Science and Technology and Materials Science Research Centre, Faculty of Science, Chiang Mai University, Chiang Mai 50200, Thailand;4. Condensed Matter Theory Group, Department of Physics and Astronomy, Uppsala University, Box 516, SE-751 20, Uppsala, Sweden;5. Department of Physics, Indian Institute of Technology Ropar, Rupnagar 140001, Punjab, India |
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| Abstract: | We compare first-principles (FP) calculations of the ionic effective charges, phonon frequencies, and static dielectric permittivities κs of several perovskite-type materials. Transition metal ions have anomalously large effective charges, though in the double perovskite CaAl1/2Nb1/2O3 (CAN), the effective charge of Nb is significantly lower than in the simple perovskite KNbO3, showing different Nb–O bonding chemistry. Tolerance factors, cation chemistry, and structural phase transitions all affect the nature of the softest phonons in perovskites. For the solid solution (CaAl1/2Nb1/2O3)1−x–(CaTiO3)x (CAN–CT), κs is modeled via a cluster expansion, with the parameters determined from FP. In pure CAN, κs is found to increase when cation disorder increases, in agreement with experimental results on analogous systems. The dielectric constant of CAN-CT increases nonlinearly with x, in agreement with experiment. |
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