RESUMEN
High-pressure single-crystal to 20â GPa and powder diffraction measurements to 50â GPa, show that the structure of Pb2SnO4 strongly distorts on compression with an elongation of one axis. A structural phase transition occurs between 10â GPa and 12â GPa, with a change of space group from Pbam to Pnam. The resistivity decreases by more than six orders of magnitude when pressure is increased from ambient conditions to 50â GPa. This insulator-to-semiconductor transition is accompanied by a reversible appearance change from transparent to opaque. Density functional theory-based calculations show that at ambient conditions the channels in the structure host the stereochemically-active Pb 6s2 lone electron pairs. On compression the lone electron pairs form bonds between Pb2+ ions. Also provided is an assignment of irreducible representations to the experimentally observed Raman bands.