The variation of the lowest direct absorption edge (e0) of ZnSe with hydrostatic pressure has been measured at room temperature with a diamond anvil cell for pressures up to the phase transition (13.5+or-0.2 GPa). The gap varies sublinearly with pressure. However, when the gap is plotted as a function of the relative change of the lattice constant (- Delta a/a0) it shows a slight supralinearity in contrast to most III-V tetrahedral semiconductors which retain a slight sublinearity even as a function of (- Delta a/a0). The experimental results are compared to theoretical calculations based (a) on the local density approximation combined with the self-consistent band calculations using the MTO method (LD-LMTO) and (b) on a local empirical pseudopotential. Both calculations predict a sublinear dependence of E0 as a function of (- Delta a/a0). The semiempirical Murnaghan's equation of state that was calculated with the LD-LMTO method, has also been tested by determining the lattice constant under pressure with an energy dispersive X-ray diffractometer.
 

Solid State Communications, 56 479-83, 1985.