  Oxide glasses are made of a network of glass former polyhedra, and modifiers
which have a role in neutralizing the charge of the glass former polyhedra or
depolymerize the glass network. The effect of the modifier content on the
structure and properties of the glass are to some extent, well known. However,
the effect of the type of modifiers on the clustering and the tendency to form
a phase separation in the glass is not investigated in detail and still not
fully understood until now. Here, we use molecular dynamics to investigate the
effect of the modifier type on the structure and the clustering tendency of a
series of modified silicate glasses. Specifically, we show that the tendency of
modifier -- modifier cluster formation is linked to the modifier size and
modifier -- oxygen bond strength. The effect of different modifiers on the
short- and medium-range structure of the glass is also discussed. This allows
us to get an overview of the effect of cations nature on the properties of the
glass and opens a new window for further development and optimization of the
glass properties.
