Topology problem

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Here post your question Hello, Gromacs users! I am a beginner in MD simulation and have some troubles. I extracted pdb file from Gaussian DFT, and tried to generate topol file. But, the error comes always “LIG is not found in residual topology database”. How can I solve that problem? Any advice would be helpful. Thanks in advance!

https://manual.gromacs.org/current/user-guide/run-time-errors.html#residue-xxx-not-found-in-residue-topology-database