  A colossal insulator-to-metal transition in high-spin pyrite phase of
$MnS_{2}$ has been experimentally observed \cite{colomns2}. There are two
possibilities behind this colossal insulator-to-metal transition: (1) migration
of $Mn$ electrons to unoccupied $S^{2-}_{2}$ antibonding states under pressure
which leads to conducting ligand states and hence metallic transition, and (2)
possibility of band crossing transition. We have analyzed this experimental
obervation theoretically using a toy statistical model and found that the
transition is due to the migration of electrons from the transition metal ions
to the ligand sites (i.e. the possibility (1)). The calculated resistivity
compares well with the experimental data within the fitting parameters of the
model.

Strongly Correlated Electrons