Generating topology for a periodic lattice

GROMACS version: 2021.4
GROMACS modification: Yes/No
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I want to generate the topology for a silica slab. For that I have mentioned the corresponding atom types and their bond distances in the .n2t file and ran the x2top command (as pdb2gmx will not work for a periodic system). Now this command will generate a primitive topology wherein the bonded and non-bonded parameters are obtained in a trivial manner. In order to circumvent the problem, can I add the corresponding parameters in the ffbonded.itp and ffnonbonded.itp and then run the x2top command? Will that take the values for the force constants and the LJ parameters from these files? or will it still return the trivial values for these force constants?