I want to simulate ethylene carbonate like the paper "Lithium-Ion Model Behavior in an Ethylene Carbonate Electrolyte Using Molecular Dynamics " did. as you see it referred to the paper “An ab Initio CFF93 All-Atom Force Field for Polycarbonates” for parameters. but the parameters is less than I need(for example c-h bond). or many other parameters are not in the paper (for example cross-terms that are few).
how can I resolve this problem .
Your problem would be resolved by doing your research more carefully.
It took me less than 20 minutes to look up the paper you refer to and find the statement “Most parameters for alkyl and phenyl groups were derived separately”, then find that paper and confirm that it contains the missing C-H parameters for bonds and the corresponding charge increments.
As for missing cross terms, if they include the atom types that the paper is parameterizing and are not listed, they would be zero.