[gmx-users] grompp error:Invalid order for directive defaults

[Dongsheng Zhang]

Dear GMX users,

I'd like to study the interaction between carbon nanotube and a polymer
chain. I have made cnt.itp for the nanotube and poly.itp. Both itp files
contains force field parameters (such as [ defaults ], [ atomtypes],
[ bondtypes ]), in this way, I don't need to include any force field in
my topology file (but it will include *.itp) and it is much easier to
modify the parameters. For use nanotube or polymer alone as my system, I
can use grompp to process .gro, .itp, .top to get .tpr file. If I use
nanotube and polymer together as my system, grompp give me the following
error message:

Invalid order for directive defaults, file ""poly.itp"", line 16 

line 16 is [ defaults ], so I am thinking maybe I can't have
[ defaults ] in each of two itp files. If I delete [ defaults ] in the
second itp file. It will complain [ atomtypes] in the second itp file.
It seems I can't put force field parameters in two itp files which will
be included in one topology file. Could anyone tell me if my guessing is
correct? If so, why does gromacs prevent it? 

Thank you in advance! If you need more information, I will be more than
happy to provide it.


Best wishes!


Dongsheng