Republished: Colossal density-driven resistance response in the negative charge transfer insulator <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>MnS</mml:mi><mml:mn>2</mml:mn></mml:msub></mml:math>

The Mn chalcogenides show a remarkable variation in structural and physical properties with density. In ${\mathrm{MnS}}_{\text{2}}$ we observe a pronounced difference with the effects of varying hydrostaticity with pressure inducing a structural transition at 300 K. Within the pyrite phase, a colossal electrical resistance drop of ${10}^{8}\phantom{\rule{0.16em}{0ex}}\mathrm{Ohms}$ is observed by 12 GPa of nonhydrostatic compression at 300 K. DFT simulations reveal the metallization to be unexpectedly driven by previously unoccupied ${\mathrm{S}}_{2}^{2\ensuremath{-}}\phantom{\rule{4pt}{0ex}}{\ensuremath{\sigma}}_{\text{3p}}^{*}$ antibonding states crossing the Fermi level. This is a seldom seen variant of the charge transfer insulator to metal transition for negative charge transfer insulators which have anions with an unsaturated valence. By 36 GPa of nonhydrostatic compression, the single presence of the low-spin insulating arsenopyrite ($P{2}_{1}/c$) phase is confirmed, and the bulk metallicity is broken with the system returning to an insulative electronic state.