Table 1. Force-Field Parameter Values for Interactions between Sulfate/Carboxylate Oxygen Atoms and Ca2+/Na+ in the c36_jul20 and c36_jul17 Versions of the CHARMM C36 Additive Force Field.
| i | j | c36_jul20 parameters | c36_jul17 parameters | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| atom | atom type | charge q | atom | atom type | charge q | εij (kcal/mol) | rmin,ij (Å) | literature reference | εij (kcal/mol) | rmin,ij (Å) | literature reference |
| sulfate terminal oxygen | OC2DP | –0.650 | Ca2+ | CAL | +2 | 0.12 | 3.256 | (35) | 0.12a | 3.067a | (36) |
| carboxylate oxygen | OC2D2 | –0.760 | Ca2+ | CAL | +2 | 0.12 | 3.232 | (37) | 0.12a | 3.067a | (36) |
| sulfate terminal oxygen | OC2DP | –0.650 | Na+ | SOD | +1 | 0.07502 | 3.16 | (38) | 0.07502 | 3.16 | (38) |
| carboxylate oxygen | OC2D2 | –0.760 | Na+ | SOD | +1 | 0.07502 | 3.23 | (38) | 0.07502 | 3.23 | (38) |
a
No NBFIX entry for this pair. Value
shown is computed using default atom-wise LJ parameters εi and rmin,i and CHARMM force field combining rules, 
and 
.