Changes in the structural properties of Er3+ doped soda-lime silicate glasses were investigated as a function of Al2O3 content. A combined approach of experimental techniques and molecular dynamic simulations (MD) was used to evaluate the structural features directly correlated to the glass properties. The experimental results in term of density, thermal properties as well as microstructural and mineralogical data showed a significant variation when increasing the alumina content from 10 mol% to 15 mol%. These results were compared to the MD information and discussed: changes in erbium and aluminium local configuration, due to the glass structural evolution as a function of the alumina concentration, have been investigated. (c) 2006 Springer Science + Business Media, Inc.