[gmx-users] Proper Dih. multiplicity

[Alberto Malvezzi]

Sorry, I got that wrong. The question is:
I DONT understand in which file I should define this B topology.
Alberto

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
>
> 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