Lattice-mediated bulk flexoelectricity from first principles

• Main Authors: Royo, Miquel, Stengel, Massimiliano
• Format: Journal Article
• Language: English
• Published: 20-12-2021
• Subjects: Physics - Materials Science; Physics - Mesoscale and Nanoscale Physics
• DOI: 10.48550/arxiv.2112.10721

We present the derivation and code implementation of a first-principles
methodology to calculate the lattice-mediated contributions to the bulk
flexoelectric tensor. The approach is based on our recent analytical
long-wavelength extension of density-functional perturbation theory [Royo and
Stengel, Phys. Rev. X 9, 021050 (2019)], and avoids the cumbersome numerical
derivatives with respect to the wave vector that were adopted in previous
implementations. To substantiate our results, we revisit and numerically
validate the sum rules that relate flexoelectricity and uniform elasticity by
generalizing them to regimes where finite forces and stresses are present. We
also revisit the definition of the elastic tensor under stress, especially in
regards to the existing linear-response implementation. We demonstrate the
performance of our method by applying it to representative cubic crystals and
to the tetragonal low-temperature polymorph of SrTiO$_3$, obtaining excellent
agreement with the available literature data.