Inverse band gap versus polarization relation in ferroelectrics from first principles

New pathways to design functional ferroelectrics are desired for electro-optic and solar energy conversion devices. Previous work has focussed on searching ferroelectrics with small band gaps in the visible solar spectrum. In this work, we take an alternative route, and use first principles methods and the modern theory of polarization to perform a high-throughput search of ferroelectrics that display an inverse relation between electronic band gap and polarization, such that the band gap decreases as the polarization increases with an external parameter. To our knowledge, such material property has not been reported before, and we propose it as a new way to design small band gap ferroelectrics. We start by studying a list of 200 materials previously reported as a ferroelectrics database, and later generalize our search to identify new ferroelectrics with inverse band gap versus polarization relation within the Materials Project database. We have found 21 ferroelectrics with the proposed property among different families of ferroelectric materials and use hydrostatic strain as an external parameter to explore their band gap and polarization relation. This work is supported by ANID Fondecyt Regular 1220986.