Computational studies of self-trapped excitons in silica

A brief review of electronic structure calculations of the properties of self-trapped excitons (STEs) in silica is presented. The focus has been on crystalline systems because amorphous systems, such as fused silica, pose a significant technical challenge. The tremendous growth in speed of computer processors and available memory has led to a new generation of ab initio computer codes capable of carrying out extensive calculations. The capabilities of these codes have also grown with regards to the sophistication of both basis sets, for wave function based methods, and pseudopotentials, for density functional methods. In particular, these codes have made calculations of excited states more accessible. Calculations of varying degrees of sophistication are presented including preliminary studies of STEs at surfaces and in amorphous structures. Previous ab initio calculations have been repeated with larger basis sets and more accurate calculation methods. The new results agree nicely with experimental results, thus further legitimizing the original predictions. Recent results also predict the presence of multiple STEs that may have low energy connective paths between them.