Any transition from a semiconductor to a metallic state under the influence of a temperature or pressure change or both. Examples:
- Ti2O3: band-edge crossing in a semiconductor to semimetal transition.
- SmS: localized level crossing a band edge. In SmS hydrostatic pressure above the critical pressure P c ≈ 0.65 GPa broadens the Sm-5d band to make the band edge cross the Sm-4f6 level.
- A localized-itinerant transition.
- A switching transition.
PAC, 1994, 66, 577. 'Definitions of terms relating to phase transitions of the solid state (IUPAC Recommendations 1994)' on page 590 (https://doi.org/10.1351/pac199466030577)