[gmx-users] Proper Dih. multiplicity

[David]

On Mon, 2005-08-15 at 12:34 -0300, Alberto Malvezzi wrote:
> Hello
> I'm having the same problem described bellow, which is the error message  
> 
> Fatal error: [ file "topology_A.itp", line 8909 ]:
>              Proper Dih. multiplicity can not be perturbed 6.000000!=3.000000

just add the parameters twice.


> 
> I have read the answer given earlier, and I seem to understand in which file I should define this B topology.
> Any help would be appreciated.
> Thanks
> Alberto
> 
> >/ 
> Hi all.
> />/ I'm trying to simulate a sugar molecule and I have some problems whith proper
> />/ dihedrals (ffgmx) when I try to run grompp.
> />/ I need to define dihedral angles with different multiplicity for the same
> />/ group of atoms. (I don't want to do FEP)
> />/ 
> />/     1     3     6     9     1       0.0         5.858             3
> />/     1     3     6     7     1       0.0         0.418             2
> />/ 
> />/ The program displays an error message:
> />/ 
> />/ Fatal error: [ file "./hial.itp", line 205 ]:
> />/              Proper Dih. multiplicity can not be perturbed 3.000000!=2.000000
> /
> This is caused by a dihedral type definition in the forcefield where
> a multiplicity is specified. In your topology you specify a different
> multiplicity, which is OK, except that Gromacs also *always* assigns
> a 'B' topology (which is used for FEP), even if you don't use FEP.
> The parameters for the 'B' topology come from the dihedral type
> definition and not from your topoligy definition. So the solution is
> to explicityly define the 'B' topology so it will be identical to
> the 'A', like:
> 
>    1     3     6     7     1       0.0      0.418     2     0.0     
> 0.418     2
-- 
David.
________________________________________________________________________
David van der Spoel, PhD, Assoc. Prof., Molecular Biophysics group,
Dept. of Cell and Molecular Biology, Uppsala University.
Husargatan 3, Box 596,          75124 Uppsala, Sweden
phone:  46 18 471 4205          fax: 46 18 511 755
spoel at xray.bmc.uu.se    spoel at gromacs.org   http://xray.bmc.uu.se/~spoel
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