Milman, V., Refson, K., Clark, S., Pickard, C., Yates, J., Gao, S. -., …Segall, M. (2010). Electron and vibrational spectroscopies using DFT, plane waves and pseudopotentials: CASTEP implementation. Journal of molecular structure. Theochem, 954(1-3, SI), 22-35. https://doi.org/10.1016/j.theochem.2009.12.040