EQUATIONS OF STATE AND OPTICAL-PROPERTIES OF THE HIGH-PRESSURE PHASE OF ZINC-SULFIDE

The static compression of the high pressure (B1) phase of zinc sulfide has been measured at room temperature using X-ray diffraction through a diamond anvil cell between 11 and 45 GPa. The volume, the bulk modulus, and its derivative of the B1 phase, extrapolated to zero pressure, are V02/V01 = 0.851 (+/- 0.021), K02 = 85.0 (+/- 3.8) GPa, and K'02 = 4 based on a third order Birch-Murnaghan finite strain analysis. Alternatively, a universal equation of state fit yields V02/V01 = 0.895, K02 = 47.5 (+/- 8.2) GPa, and K'02 = 6.2 (+/- 1.1). The large discrepancy between these two sets of zero pressure parameters highlights the difficulty in extrapolating properties from a high pressure equation of state. Thin samples of the high pressure phase of zinc sulfide were discovered to transmit light in the visible region. Optical absorption spectra were recorded from 15.9 to 36.2 GPa. With the increase of a few GPa in pressure past the phase transition at 15 GPa, the direct band gap narrows to approximately 2.1 eV. Further compression induces a slight, but poorly resolved, increase of direct gap energy with compression (almost-equal-to 10 meV/GPa).