Density functional theory (DFT) calculations were performed using the Perdew-Burke-Ernzerhof (PBE) functional, within the generalized gradient approximation (GGA), as implemented in the package. The Linear Combination of Atomic Orbitals (LCAO) method, with norm-conserving pseudo-potentials, was applied . The density of state spectra for CS monomers and chains was calculated using multi-pole boundary conditions (single k-point).