Semiconductor-Metal Transition inTi2O3

We present a free-energy description of a smooth semiconductor-metal transition based on a two-band model and including electron-electron Coulomb energy and lattice-displacement energy. The assumption that the lattice-displacement energy plays a weak, secondary role appears to be needed to obtain good qualitative agreement with a number of experimental observations in ${\mathrm{Ti}}_2$ ${\mathrm{O}}_3$.