New exploration on phase transition and structure of PbS under high pressure and temperature.

In-situ time-of-flight neutron powder diffraction and electrical resistance measurements are performed to determine the behaviors of PbS under pressure and temperature up to 5 GPa and 773 K. The phase diagram in our experimental range is shown based on electrical resistance measurements. Both the two approaches indicate that only the starting cubic PbS phase remains stable when the temperature reaches above 573 K. The Rietveld refinements of the neutron diffraction patterns verify that the orthorhombic (ortho) PbS phase has a Cmcm space group. The fitting of experimental data with the Birch-Murnaghan equation of state at 300 K, yields the bulk modulus of the cubic phase as K0T = 60.0 ± 0.5 GPa with its pressure derivative K0′ fixed to 4.2. [ABSTRACT FROM AUTHOR]