Pressure induced metallization of fordite SnNb2O6 from first principles

From DFT based calculations establishing energy-volume equations of state, a proposition of high pressure candidate structures with reduced volumes, namely columbite and trirutile are proposed for fordite mineral SnNb2O6. The key effect is the destabilization of divalent tin in fordite towards tetravalent state upon compression. This is helped with smaller size tetravalent tin. The remarkable electronic structure change is the transformation from semi-conducting fordite to metallic high pressure forms thanks to the electron transfer from Sn to Nb and O as quantified from charge density analyses.