Journal Article IR and Raman spectra 7782-42-5 C interstitial defects in bulk silicon DFT simulation Graphite Jahn‐Teller effect K(Sc, Ti, Fe, Co)F ab initio calculation combining optimizer and dynamical matrix electronic structure ferromagnetic and anti‐ferromagnetic groups and subgroups negative wavenumbers orbital ordering patterns silicon spin states stationary points and real minima substitutional carbon defect the SCANMODE option unit cell size