Electronic structure of bulk- and Na-intercalatedTiS2determined from aGGA+Ustudy with the Hubbard terms obtainedab initio

Abstract

A theoretical study on the electronic structure of titanium sulfide compounds ${\text{TiS}}_{2}$ intercalated with Na is presented using generalized gradient approximation $(\text{GGA})+U$ calculations. Na-intercalated ${\text{TiS}}_{2}$ compounds are well-known materials in the field of battery systems. The atomic structure of available experimental ultraviolet photoemission spectroscopy (UPS) data is discussed and modeled on a ${\text{Na}}_{3}{\text{Ti}}_{12}{\text{S}}_{24}$ unit cell. The on-site effective correlation term $U$ is determined from first principles following a linear-response method for the $\text{Ti}\text{ }3d$ electrons of this compound and the corresponding host ${\text{TiS}}_{2}$. Valence electronic structures obtained from subsequent $\text{GGA}+U$ calculations are compared to experimental UPS available data and to standard GGA results for both compounds. The improvement achieved with the ab initio $\text{GGA}+U$ method and the agreement with the experimental spectra are discussed.