NUC

The (sub) key Nuc determines for which nuclei the chemical shifts are computed. If this (sub) key is omitted from the NMR block, the calculations are carried out for all nuclei. Else you may use this options by simply typing Nuc in the NMR block (without any further data); this means: for no nuclei at all. Alternatively you may type the index of the atom(s) you want to see analyzed.
Default 'all' (i.e. as for omitting this sub key).