Dih types error in ions adding steps in gromacs

etting the LD random seed to 2097101926
Generated 100032 of the 100128 non-bonded parameter combinations
Generating 1-4 interactions: fudge = 1
Generated 65937 of the 100128 1-4 parameter combinations

ERROR 1 [file unk.itp, line 600]:
No default Proper Dih. types

ERROR 2 [file unk.itp, line 614]:
No default Proper Dih. types

ERROR 3 [file unk.itp, line 634]:
No default Proper Dih. types

ERROR 4 [file unk.itp, line 644]:
No default Proper Dih. types

ERROR 5 [file unk.itp, line 652]:
No default Proper Dih. types

Excluding 3 bonded neighbours molecule type ‘Protein_chain_A’
Excluding 3 bonded neighbours molecule type ‘UNK’
Excluding 2 bonded neighbours molecule type ‘SOL’

NOTE 2 [file topol.top, line 72404]:
System has non-zero total charge: -3.000000
Total charge should normally be an integer. See
GROMACS - Gromacs
for discussion on how close it should be to an integer.

There were 2 notes


Program: gmx grompp, version 2020.1-Ubuntu-2020.1-1
Source file: src/gromacs/gmxpreprocess/grompp.cpp (line 1928)

Fatal error:
There were 5 errors in input file(s)

For more information and tips for troubleshooting, please check the GROMACS
website at Errors - Gromacs

How to solve this issues

Hi,
I guess the problem is that dihedral angles are defined directive [ dihedral ] in the itp file, but pdb2gmx can not find information on the corresponding potential function and parameters, neither in the topology file nor force field files.
\Alessandra

Thank You