Structural determination of phosphosilicate glass based on first-principles molecular dynamics calculation

We report static and dynamic first-principles calculations determining the structure and electronic properties of phosphosilicate glass (PSG). A stable structure of PSG with composition of (SiO2)(x)(P2O5)(y) was calculated by simulated annealing based on Car-Parrinello molecular dynamics (CPMD) with a real-space density functional theory (RSDFT) code. As a result, phosphorus (P) atoms in PSG were four-fold coordinated with oxygen (O) atoms and one of the four PO bonds was dangling toward the interstitial region (an -O3PO configuration). We also compared the structures having a different number of O atoms to discuss the stable configuration of PSG in the realistic situation of phosphoryl chloride (POCl3) annealing. We found that -O3PO is most stable for O-2-rich conditions, whereas three-coordinate P (an -O3P configuration) becomes stable in O-2-poor conditions. The candidates of the states which create levels inside the bandgap of PSG were also calculated. (C) 2018 The Japan Society of Applied Physics