msi2lmp error information: Unable to find angle data for c2 c2 c=

Dear lammps users,
I used MS to build my model of natural rubber, and I used the forcefield of cvff ,but when I used msi2lmp to get data, it told me that msi2lmp error information: Unable to find angle data for c2 c2 c=, I have never met this problem,and it has troubled me for a few days, I can not find the answer.Have anyone met the same kinds of problems? Or could you give me some advices to solve it?
Best wishes,

Is “c=” a valid symbol for one of the Carbon atom types?
If not, I am guessing some file, like the one output by MS

is ill-formatted. I would search for that symbol in the MS output
file, which msi2lmp is trying to read and see if that line
looks funny. If that symbol is not in the force-field
file, then msi2lmp will complain.


“c=“ is indeed a valid atom type in CVFF; however, the forcefield does not have an explicit angle defined for c2 - c2 - c=. In the original implementations of CVFF there is a scheme of “equivalences” to allow for more general parameters. For angles, c= is equivalent only to itself, but c2 is equivalent to c. CVFF does not have angle terms defined for c - c - c= either, so in the original implementations would fall back on automatic parameters, which is yet another layer of (less accurate) more general parameters.

I am not familiar with msi2lmp, but presumably it does not fully implement the rich scheme of handling forcefields that is available in the commercial products.