Effect of substitutional Cu atoms on the electronic and optical properties of KCl: A DFT approach

The electronic and optical properties of KCl and Cu doped KCl (KCl:Cu) were calculated within full potential augmented plane wave method based on Density Functional Theory (DFT), as implemented in WIEN2k software. Calculations were carried out using two energy functional approximations, the exchange-correlation functional of Perdew, Burke and Ernzerhof (PBE96) to optimize the KCl lattice parameter, and the modified Becke-Johnson (mBJ) exchange potential in combination with the local density approximation (LDA) for correlation, to obtain the band structure. The energy bands reveal the insulating properties of KCl with a direct band gap of 8.6 eV, and the semiconductor nature of KCl:Cu with a direct band gap of 3.4 eV. From the analysis of the total and partial density of states, it is apparent that the KCl and KCl:Cu states at the Fermi level arise from Cl p states and Cu d states, respectively. Also, the optical properties reported here (dielectric function and absorption spectra) show that Cu atoms are responsible of electronic excitations occurring from Cu d valence bands to conduction bands of Cu, Cl and K with p character.