Low-temperature Gru¨ neisen gamma of II–VI semicoductor ZnS

The theoretical study of low-temperature lattice thermal expansion of the II–VI semiconductor ZnS is attempted. The generalized Gru¨ neisen gammas of the elastic waves propagating in different directions with respect to the [001] crystallographic axis of ZnS are calculated using the second- and third-order elastic constants. The values of mode Gru¨ neisen gammas cj are determined and found generally positive except from c2 at h = 25 to h = 65 . The low-temperature limit of the Gru¨ neisen gamma c is determined and compared with experimental values. Using this c; we calculated the Brugger gamma cBr and hence the lowtemperature volume lattice thermal expansion cL. It is expected that the volume expansion is positive down to absolute zero for ZnS.