The densities of mixed glass former 0.35 Na2O + 0.65 [xB2O3 + (1 − x)P2O5] glasses related to the atomic fractions and volumes of short range structures

► Mixed Glass Former Effect of 0.35Na2O + 0.65[xB2O3 + (1 − x)P2O5]. ► Density shows a positive non-linear and non-additive trend. ► The volumes of short range order structures vary with x.