ab-initio study of electronic, optical, dynamic and thermoelectric properties of cusbx2 (x=s, se) compounds

In this work we investigate the electronic, optical, dynamic and thermoelectric properties of ternary copper-based chalcogenides cusbx2 (x= s, se) compounds. calculations are based on density functional theory and the semi-classical boltzmann theory. computations have been carried out by using quantum-espresso (pwscf) package and ab-initio pseudo-potential technique. to estimate the exchangecorrelation functional various approximations were used, which among them gga approximation led to better results. density of state calculations indicates that cusbse2 and cusbs2 compounds are semiconductors with a band gap of about 0.81 ev and 0.62 ev respectively. a lack of negative frequencies in the phonon dispersion curves of these compounds shows the stability of the compounds. the static refractive indices of cusbse2 compound are 4.38, 3.66 and 3.30 calculated within gga, gga+u and ggambj+u approximations respectively and plasmon frequencies obtained from the peak of the loss function is occurred at energies around 16ev.a trend of electrical conductivity behavior against temperature verify the semiconducting nature of the compounds which is in good agreement with electrical results.