I looked into the DFTB+ tutorial and noticed that in DFTB+ Electronic Evaluation.xml there is a parameter called "UpperLimit" with energy unit. Wondering what is this parameter, is this the upper energy bound of a region in which the DFTB+ band structure is matched to that of DFT ? If so what is a good rationale to know what value to set it at? The tutorial mentions 4, so I guess sth higher than Fermi energy, but not far off in the conduction band...