Table 2.

The maximal integrated electron number difference around each site for each atomic species

Atom type	Maximal charge increase	Maximal charge decrease
Hydrogen	0.016	−0.018
Carbon	0.022	−0.013
Nitrogen	0.012	−0.017
Oxygen	0.010	−0.014

Units are in electronic charge e. The integrated difference is defined as “number of electrons on site X at field = 0” − “number of electrons on site X with field = 3 V/nm.” The corresponding atoms are highlighted in Fig. 3 by enlarging their radii by a factor of 2 for the maximal decrease and a factor of 3 for the maximal increase.