Band-Gap Engineering and Unusual Behavior of Electronic Properties during Anion Substitution of Sulfur in LaFSe
Dejan Zagorac, Constantin Buyer, Jelena Zagorac, Tamara Škundrić, J. Christian Schön, Thomas Schleid
Abstract
LaFSe and LaFS materials have shown great potential for various optoelectronic applications, such as photovoltaics, light-emitting diodes, and photodetectors. Mixed LaFSe/LaFS compounds have been synthesized through high-temperature experiments. The introduction of sulfur into LaFSe causes distortion in the crystal lattice, leading to changes in the unit cell. A new algorithm is presented that keeps the symmetries of the mixed LaFSe/LaFS phases, and it is combined with ab initio structure optimization in order to efficiently generate and compute models for solid solution-type compounds. There is good agreement between experimental and theoretical data, and additional predicted structures under extreme conditions in various lanthanoid fluoride selenides/sulfides have been introduced. The substitution of selenium for sulfur within the LaFSe lattice can result in some unusual electronic properties, including changes in the size of the band gap, the character of the gap, and the electronic structure of the material.