Invalid order for directive atom type

User discussions
1

GROMACS version:2023.1
GROMACS modification: Yes/No

Hi.
I am almost new to using the Gromacs and sorry If this question is a boring one for you!
I have two separate itp files for two different molecules from the LigPargen server!
I used the insert-molecules command and mixed these two molecules together!
By using the gmx solvate I could get a solvated system (mix_solvated.gro).
Now when I want to add ions to this system I get this error:

Last line read:
‘[ atomtypes ]’
Invalid order for directive atomtype

I checked the two molecules itp files and the topol.top file and I think their orders are fine!
Would you please let me know what is the reason for this error?!

mix_solvated.gro :
1CHO H0J 20 2.094 2.269 2.168
1CHO H0K 21 2.054 2.072 2.352
…
2AcOH O03 25 1.938 1.122 3.416
2AcOH H04 26 2.165 0.945 3.577
…
3SOL OW 30 0.230 0.628 0.113
3SOL HW1 31 0.137 0.626 0.150

CHO.itp :

; GENERATED BY LigParGen Server
; Jorgensen Lab @ Yale University
;
[ atomtypes ]
opls_810 H810 1.0080 0.000 A 2.50000E-01 1.25520E-01
opls_802 C802 12.0110 0.000 A 3.50000E-01 2.76144E-01
…
[ moleculetype ]
; Name nrexcl
CHO 3

AcOH.itp:

[ atomtypes ]
opls_800 C800 12.0110 0.000 A 3.50000E-01 2.76144E-01
opls_802 O802 15.9990 0.000 A 2.96000E-01 8.78640E-01
…

[ moleculetype ]
; Name nrexcl
AcOH 3
[ atoms ]
; nr type resnr residue atom cgnr charge mass
1 opls_800 1 AcOH C00 1 -0.3389 12.0110

topol.top:

; Include forcefield parameters
#include “oplsaa.ff/forcefield.itp”

; Include ligand parameters
#include “CHO.itp”

; Include ligand parameters
#include “AcOH.itp”

; Include water topology
#include “oplsaa.ff/spce.itp”

; Include topology for ions
#include “oplsaa.ff/ions.itp”

[ system ]
; Name
ACH in water

[ molecules ]
; Compound #mols
CHO 1
AcOH 1
SOL 3140

3

All atomtypes (and all other interaction types) must be defined before the first moleculetype. See, https://manual.gromacs.org/current/user-guide/run-time-errors.html#invalid-order-for-directive-xxx.

You have atomtypes in your AcOH.itp file, after the moleculetype specification in CHO.itp

Make sure you set all forcefield parameters before starting to use them (i.e. by specifying moleculetype).