Structure and properties of Cs containing borosilicate glasses studied by molecular dynamics simulations

Borosilicate glass is a very suitable matrix for immobilisation of nuclear waste. The major fission product in this waste is 137Cs. In the paper molecular dynamics simulations were used to study the influence of the gradual substitution of Na+ by Cs+. The caesium influence on the glass network Si and Al environment was relatively small. The biggest changes were observed in the case of B first neighbourhood. The boron coordination number and B-O bond length were linearly decreasing. In the studied glasses both sodium and caesium were mainly charge compensators of [AlO4] and [BO4] tetrahedra. The glass modifier structure was investigated using Voronoi analysis. There was observed aggregation and clustering of modifiers which was amplified by caesium substitution.