Atomic-level insights into niobium-modified borophosphate glasses

This paper reports the use of molecular dynamics simulations to obtain structural information on sodium borophosphate glasses containing niobium. The results were compared with high-energy X-ray diffraction, neutron diffraction, Raman and IR spectroscopy, X-ray absorption measurements and NMR data to investigate the effects of niobium incorporation on the structure and properties of these glasses. The simulation results show good agreement with the experimental data. As expected, both boron (B) and phosphorus (P) act as tetrahedral network formers. The number of Nb-Nb linkages increases with increasing niobium content, initially leading to corner-sharing and then forming interconnected NbO6 units. At low niobium content, Nb adopts an off-center position within the octahedral site, and the distortion of the NbO6 units increases as niobium content rises. Additionally, as the niobium concentration increases, more phosphorus atoms form bonds with other network formers.