Publication date: Apr 11, 2025
We present an ab initio method to calculate the clamped Pockels tensor of ferroelectric materials from density-functional theory (DFT), the modern theory of polarization exploiting the electric-enthalpy functional, and automated first- and second-order finite-difference derivatives of the polarizations and the Hellmann-Feynman forces. Thanks to the functional-independent capabilities of our approach, we can determine the Pockels tensor of tetragonal barium titanate (BTO) beyond the local density approximation (LDA), with arbitrary exchange-correlation (XC) functionals, for example, PBEsol. The latter, together with RRKJ ultra-soft pseudo-potentials (PP) and a supercell exhibiting local titanium off-centering, enables us to stabilize the negative optical phonon modes encountered in tetragonal BTO when LDA and norm-conserving PP are combined. As a result, the correct value range of r51, the largest experimental Pockels coefficient of BTO, is recovered. We also reveal that r51 increases with decreasing titanium off-centering for this material. The lessons learned from the structural, dielectric, and vibrational investigations of BTO will be essential to design next-generation electro-optical modulators based on the Pockels effect.
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File name | Size | Description |
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pockels.aiida
MD5md5:69f82d2bd9e7e347a3b831f8040b270e
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63.3 MiB | AiiDA data for the pockels tensor of BaTiO3 |
BTO.hubbard.zip
MD5md5:61d95e30e1a01c126bb11b157aafe455
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2.0 KiB | Quantum Espresso input files to reproduce the U and V Hubbard parameters calculation for tetragonal BTO. This folder also contains the optimum U and V output values. |
README.md
MD5md5:fb5dfa89bb0bce5384e017a02500a5af
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3.1 KiB | Instructions |
2025.57 (version v1) [This version] | Apr 11, 2025 | DOI10.24435/materialscloud:9p-tz |