Influence of The Local Environment on The Formation of Sulfur Vacancies in Calcium Lanthanum Sulfide

Sulfur loss during the processing of calcium lanthanum sulfide has been shown to negatively impact the optical properties of the material. In order to better understand the phenomenon, density functional theory is used to determine the structural stability and formation likelihood of sulfur vacancies across several stoichiometries within the calcium lanthanum sulfide system. It was found that the local atomic environment surrounding defect sites plays a significant role in their formation energies and this was strongly related to the redistribution of charge. Using this information, a functional relationship to predict the sites that are most likely to lose sulfur was developed. Simulated diffraction patterns were compared to experimental work in order to determine the atomic structure present after processing. With this knowledge, it may be possible to better predict the effects of different processing approaches to minimize sulfur loss and potentially speed the material development process.