EMC: PCFF force field misses the related parameters of pair {c_1 na}

I created a polymer by EMC. When I implemented the command ( build.emc) to generate the parameters of PCFF , I encountered a error that showd the parameters of pair {c_1 na} is missing (see Fig)

I encountered this similar problem before with {s=}. The pcff force field contained is not comprehensive, sometimes you have to modify the frc file. But also check your smiles code, you might not specify it in a correct way.

EMC uses a stricter implementation of PCFF than for instance Materials Studio does. This means, that EMC throws an error on missing increments. Materials Studio would set the bond increment contribution to the partial charge to zero without a warning. You can make EMC do the same by adding

field_increment ignore

to your ITEM OPTIONS paragraph in your .esh.

Thank you for your response and kind suggestions, and I will try it again.

Thank you for sharing your experience, and I will check my code.