Adding new parameters to charmm ff for sulfur-carbon bond

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GROMACS version: 2021.5

Outcome: I am trying to achieve: Adding S-C bond parameters to the charmmfeb2021 forcefield to simulate a ligand in the gas-phase.

Issue: Unable to simply add a ‘parameter’.itp file into the .top file to do this.

*Topology file is below: *
#include “charmm36-feb2021.ff/forcefield.itp”

; additional params for the molecule
#include “lig1.prm”

#include “charmm36-feb2021.ff/tip3p.itp”
#ifdef POSRES_WATER
; Position restraint for each water oxygen
[ position_restraints ]
; i funct fcx fcy fcz
1 1 1000 1000 1000
#endif

; Include topology for ions
#include “charmm36-feb2021.ff/ions.itp”

#include “sulf_param.itp”
#include “lig1.itp”

[ system ]
; Name
mol

[ molecules ]
; Compound #mols
LIG1 1

#include “sulf_param.itp” include parameters for the S-C bond in this format:

[ atoms ]
; nr type resnr res atom cgnr charge mass

[ bondtypes ]
; i j func b0 kb

The error which keeps coming up is
Last line read:
‘[ bondtypes ]’
Invalid order for directive bondtypes

Question: Any advice on how to fix this? Or even simply, how can I add parameters to a ff?

Thanks in advance