The DFT/CIS method has been implemented in the Q-Chem program and is available starting from v. 6.2. we focus on K-edge excitation spectra in the present work, in order to evaluate the accuracy and efficacy of DFT/ CIS for x-ray spectroscopy. These spectra are less complicated to simulate as compared to L-or M-edge spectra because relativistic and spin-orbit coupling effects are small, and because there is little interaction with valence occupied orbitals so that the CVS approximation is accurate and robust. For some second-row elements and 3d transition metals, we add an atomic relativistic correction to the TD-DFT and DFT/CIS excitation energies. Following Besley and co-workers, these scalar shifts are computed as the difference in relativistic (Douglass-Kroll-Hess) and non-relativistic (Hartree-Fock) energy levels for 1s orbitals of the isolated atoms, computed using the cc-pVQZ-DK basis set. These calculations only were performed using NWChem.