[gmx-users] adding ETHANOL to CGennFF in gromacs has problem

[Golshan Hejazi]

Hello,

I am trying to add ethanol as a new residue to CGenFF force field in gromacs. Basically, I need to bring this information from charmm rtf file to the gromacs format. This is the information taken from rtf file of charmm.

RESI ETOH          0.00 ! C2H6O Ethanol, adm jr.
GROUP
ATOM C1   CG321    0.05 !  H21  H11 H12
ATOM O1   OG311   -0.65 !     \   \  /
ATOM HO1  HGP1     0.42 ! H22--C2--C1
ATOM H11  HGA2     0.09 !     /      \
ATOM H12  HGA2     0.09 !  H23        O1--HO1
GROUP
ATOM C2   CG331   -0.27
ATOM H21  HGA3     0.09
ATOM H22  HGA3     0.09
ATOM H23  HGA3     0.09
BOND C1  C2   C1  O1   C1  H11  C1  H12  O1  HO1
BOND C2  H21  C2  H22  C2  H23
DONO HO1 O1
ACCE O1
! for ic build
IC O1   C1   C2   H21   0.0000  0.0000 180.0000  0.0000  0.0000
IC C1   H21  *C2  H22   0.0000  0.0000 120.0000  0.0000  0.0000
IC C1   H21  *C2  H23   0.0000  0.0000 240.0000  0.0000  0.0000
IC O1   C2   *C1  H11   0.0000  0.0000 240.0000  0.0000  0.0000
IC O1   C2   *C1  H12   0.0000  0.0000 120.0000  0.0000  0.0000
IC C2   C1   O1   HO1   0.0000  0.0000 180.0000  0.0000  0.0000

I have added The ATOM and BOND information to the aminoacid.rtp file. 
I thought that the rest of the information are optional and pdb2gmx doesn't complain while generating the topology. But when I use the topology and gro file to do a minimization. The molecule bonds break apart and what I see is an exploded molecule.

So I thought probably the rest of the information are important too, for example: 
DONO HO1 O1
ACCE O1

But I dont know where to put them. 
Thanks
G.