Cubic ZnS under pressure: optical-absorption edge, phase transition, and calculated equation of state.

Ves S., Schwarz U., Christensen N.E., Syassen K., Cardona M.

The authors have measured the effect of pressure on the energy of the direct-optical-absorption edge (E0 gap, Gamma 15nu to Gamma 1c) of cubic ZnS, covering the full stability range (0-15 GPa) of the tetrahedral phase. The E0 gap exhibits a sublinear increase under pressure, with the corresponding (linear) gap deformation potential being -5.0(2) eV. X-ray diffraction shows the high-pressure phase of ZnS to have the NaCl-type structure for pressures up to at least 27 GPa. In contrast to earlier reports, this phase is not metallic but shows a broad optical-absorption edge with onset near 2 eV, which is characteristic of an indirect-gap material. Experimental results for the equation of state and band-gap deformation potential are compared with ab initio calculations based on local-density theory and the relativistic linear-muffin-tin-orbital method.

Physical Review B, 42 9113-18, 1990.

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