On the structure of Ce-containing silicophosphate glasses: a core–shell molecular dynamics investigation

Abstract

Classical molecular dynamics simulations have been used to investigate the local and medium range structure of Ce-containing silicophosphate glasses widely used in optical and photonic devices because of their enhanced UV absorption and radiation damage resistance properties. New Ce³⁺–O and Ce⁴⁺–O parameters for a force-field based on the core–shell model were developed by fitting on the crystalline structures of Ce-containing crystal phases, and used to get insights into the structure of five silicophosphate glasses with increasing Ce₂O₃ and P₂O₅ content. An excellent agreement between experimental and computational data was found for the local environment around cerium ions and network former cations. The Ce³⁺–O bond lengths are generally longer than Ce⁴⁺–O, which shows higher coordination numbers. Both P and Si are four-fold coordinated; their allocation in the network is not uniform: the increasing Ce content leads to the formation of silica-rich domains and phosphate-rich domains, which entrap Ce cations increasing their solubility in the glass. We found that both the Qⁿ distributions of phosphorous and Ce clustering depend on the Ce/P ratio in the glass. In particular, Ce clustering begins for Ce/P ratios between 0.17 and 0.29 in the glass series investigated.