hi, i have a question regarding association scheme variables Na, Nb, Nc:

from "rehner2020.json", water _2B, _3B and _4C, I understand that NA is the number of electron accepting sites (~H) and NB is the number of electron donating sites ( ~O: ), but what is the NC field (currently set to default zero)?

as I understand, all interactions are calculated from a single couple of parameters for each molecule (kappa_ab and epsilon_k_ab) and these sites numbers and its intrinsic characteristics.

thanks,

iuri.