[gmx-developers] Modify Gromacs version 5.1.4 to include a new 4-body interaction

[Hoa Trinh]

Dear Gromacs developers,
I am trying to hack Gromacs to include a new 4-body short-ranged potential
which Gromacs has not implemented yet. My strategy is to define the
potential as a new dihedral types. I will have 2 input parameters, so I
expected that I will do something very similar to what Gromacs does for
improper dihedral angle. Therefore by grepping for F_IDIHS and
eNR_IMPROPER, I think I need to modify the following files:
src/gromacs/listed-forces/bonded.h
src/gromacs/listed-forces/bonded.cpp
src/gromacs/gmxlib/ifunc.c
src/gromacs/gmxlib/nrnb.c
src/gromacs/legacyheaders/types/nrnb.h
src/gromacs/topology/idef.h
src/gromacs/gmxpreprocess/topdirs.c
src/gromacs/gmxpreprocess/convparm.c
src/gromacs/gmxpreprocess/toppush.c
src/gromacs/fileio/tpxio.c

However, when I run test, I get the following fatal error at grompp step:
"Incorrect number of parameters - found 2, expected 32621 or -26576307 for.
"

I think there is something wrong related to toppush.c but I am really
clueless. The file is too complicated for me to understand. In your
opinion, what is wrong with my modification? Besides the following file, is
there any other files which I need to modify also?

I am looking forward to hearing from you.
Thank you very much in advance.
Best regards,


*Lan Hoa*
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