[gmx-users] Use dihedraltype 4 to allow several multiplicity terms

Baptiste Demoulin bat.demoulin at gmail.com
Thu Mar 7 23:24:12 CET 2013


Hello Steven,

I would suggest you to look if this angle is not defined somewhere else in
your file. Indeed, it seems that the program has another value for this.
The 2 and 6 at the end of the line are the multiplicity, so they don't need
to be changed. The relevant value is the one indicated in the 'func'
column. 9 should be ok, since it describes a function of several Fourier
term. I don't understand why grompp propose to chage this to 4...

Baptiste


2013/3/7 Steven Neumann <s.neumann08 at gmail.com>

> Dear Gmx Users,
>
> I used charmm server to get the parameters for my new molecule -
> alkane. i converted it into the gromacs topology.
> When I try grompp:
>
> WARNING 1 [file ffbonded.itp, line 7948]:
>   Overriding Proper Dih. parameters.
>   Use dihedraltype 4 to allow several multiplicity terms.
>
>   old: 0 0.159787 2 0 0.159787 2
>   new: CG331      CG321      CG321      CG331      9          0.00
>   0.1598288  2
>
>
> WARNING 2 [file ffbonded.itp, line 7949]:
>   Overriding Proper Dih. parameters.
>   Use dihedraltype 4 to allow several multiplicity terms.
>
>   old: 0 0.159829 2 0 0.159829 2
>   new: CG331      CG321      CG321      CG331      9          180.00
>   0.1330512  6
>
> My ffnonbonded.itp corresponding lines:
>
> [ dihedraltypes ]
> ; i     j       k       l       func    phi0    cp      mult
> CG331      CG321      CG321      CG331      9          0.00
> 0.1598288  2
> CG331      CG321      CG321      CG331      9          180.00
> 0.1330512  6
>
> Can you please explain me this? Shall use 4 instead of 2 or 6 at the
> end of these lines?
> I am using Gromacs 4.5.5
>
> Stevem
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