The electron momentum density distribution and phase transition in ZnS are reported in this paper. The calculations are performed on the basis of density functional theory (DFT) based on the linear combination of atomic orbitals (LCAO) method. To compare the theoretical Compton profile, the measurement on polycrystalline ZnS has been made using a Compton spectrometer employing 59.54？keV gamma rays. The spherically averaged theoretical Compton profile is in agreement with the measurement. On the basis of equal valence-electron-density Compton profiles, it is found that ZnS is less covalent as compared to ZnSe. The present study suggests zincblende (ZB) to rocksalt (RS) phase transition at 13.7？GPa. The calculated transition pressure is found in good agreement with the previous investigations. 1. Introduction Zinc sulfide (ZnS) is an important member of the II–VI group due to its wide range of technological applications [1–4]. ZnS is a wide band gap (3.6？eV) material used in the optoelectronic devices such as optical memories and visual displays. It has two different crystal structures (zincblende and wurtzite), both of which exhibit direct band gaps. It is believed that ZnS transforms from the zincblende (ZB) or wurtzite (WZ) structure to the rocksalt (RS) structure and then to the β-Sn phase. The electronic, optical, and structural properties of ZnS have been reported earlier by the number of research groups [5–36]. Liu and Chan [5] have performed density functional calculations within local density approximation (LDA) to explore the electronic properties of ZB ZnS with various impurities and defects. Khenata et al. [6] also have investigated the electronic properties of zinc monochalcogenides including ZnS using full-potential linear augmented plane-wave method plus local orbitals (FP-LAPW + lo) within LDA. Goswami et al. [7] have reported the electronic properties of low dimensional ZnS using density functional tight binding (DFTB) method in ZB and WZ modifications. Erbarut [8] have reported the electronic spectra of vacancies and their various charge states in cubic ZnS using Green’s function approach within the localized orbital method. Benmakhlouf et al. [9] have predicted the pressure dependency on the electronic structure of ZnS using pseudopotential scheme. They observed that ZnS was found to exhibit direct and indirect band gaps under pressure. The band structure of ZnS has been investigated by Jaffe et al. [10] using an all-electron Hartree-Fock (HF) method including correlation corrections and evaluated the role of Zn 3d-band states in the
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