GROMACS version: 2022.2
GROMACS modification: Yes/No
Here post your question
I am working on drug permeation on membranes. Generated the membrane using Charmm-Gui and the force field parameter for small molecule was generated using Cgenff. I have downloaded the ff parameter from Cgennff website: charmm36-jul2021.ff
My question is how to merge two force-field.
This is my topology field:
;;
;; Generated by CHARMM-GUI FF-Converter
;;
;; Correspondance:
;; jul316@lehigh.edu or wonpil@lehigh.edu
;;
;; The main GROMACS topology file
;;
; Include forcefield parameters
#include “toppar/forcefield.itp”
#include “toppar/POPG.itp”
#include “toppar//POPE.itp”
#include “toppar//POT.itp”
#include “toppar/CLA.itp”
#include “toppar//TIP3.itp”
#include “lig.prm”
#include “lig.itp”
[ system ]
; Name
Title
[ molecules ]
; Compound #mols
POPG 74
POPE 26
POT 80
CLA 6
TIP3 2503
LIG 1
While generating the .tpr file I got this error.
Fatal error:
Syntax error - File POPG.itp, line 11
Last line read:
‘[ moleculetype ]’
Invalid order for directive moleculetype
This is hoe POPG.itp looks like:
;;
;; Generated by CHARMM-GUI FF-Converter
;;
;; Correspondance:
;; jul316@lehigh.edu or wonpil@lehigh.edu
;;
;; GROMACS topology file for POPG
;;
[ moleculetype ]
; name nrexcl
POPG 3
;;
;; Generated by CHARMM-GUI FF-Converter
;;
;; Correspondance:
;; jul316@lehigh.edu or wonpil@lehigh.edu
;;
;; GROMACS topology file for POPG
;;
[ moleculetype ]
; name nrexcl
POPG 3
[ atoms ]
; nr type resnr residu atom cgnr charge mass
1 CTL2 1 POPG C13 1 0.050000 12.0110 ; qtot 0.050
2 HAL2 1 POPG H13A 2 0.090000 1.0080 ; qtot 0.140
3 HAL2 1 POPG H13B 3 0.090000 1.0080 ; qtot 0.230
4 OHL 1 POPG OC3 4 -0.650000 15.9994 ; qtot -0.420
and so on.
Is it due to inconsistency in the difference force field? Where should I include the lig.prm? Here I have included it on topol.top file along with other FF.
Thank you