[gmx-developers] multiplicity check on proper dihedral

[Erik Lindahl]

Hi,

The actual released version does allow multiplicity=0, if all other  
parameters are also zero (as a marker of a non-interaction).

However, at least to me a line like

>    25   24    23    22     1  0.000      -2.8425   0

Indicates an error - why is there a potential coefficient, but  
multiplicity 0?

If you don't want the interaction, either comment it out or set the  
potential coefficient to 0.0 too!

Cheers,

Erik

On Oct 19, 2008, at 11:10 PM, Tim Sirk wrote:

> Hello,
>
> I've been using 3.3.3, and after updating to 4.0 RC4 I found that  
> grompp doesn't
> accept a proper dihedral with a multiplicity of zero. grompp returns  
> this error:
>
> Value of 'multiplicity' in Proper Dih. is 0, which is smaller than  
> the minimum
> of 1
>
> I understand that mult=0 probably isn't expected, but it is part of  
> a forcefield
> (see below) that I've used with 3.3.3 and I'd like to continue using  
> it. Might a
> warning be sufficient, instead of a fatal error? Any input on a  
> workaround would
> be appreciated.
>
> ; CH1-CH1-CH2-CH2  =>  C22-C23-C24=C25
>    25   24    23    22     1  0.000       7.47     1
>    25   24    23    22     1  0.000       3.9      2
>    25   24    23    22     1  180.000     1.1      3
>    25   24    23    22     1  0.000      -2.8425   0
> ; CH1-CH1-CH2-CH2  =>  C24=C25-C26-C27
>    27   26    25    24     1  0.000       7.47     1
>    27   26    25    24     1  0.000       3.9      2
>    27   26    25    24     1  180.000     1.1      3
>    27   26    25    24     1  0.000      -2.8425   0
>
>
> Thanks.
>
> Tim Sirk
> 12C Randolph Hall
> Graduate Research Assistant
> Mechanical Engineering Dept
> Virginia Tech
>
>
>
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------------
Erik Lindahl   <lindahl at cbr.su.se>  Backup: <erik.lindahl at gmail.com>
Associate Professor, Computational Structural Biology
Center for Biomembrane Research, Dept. Biochemistry & Biophysics
Stockholm University, SE-106 91 Stockholm, Sweden
Tel: +46(0)8164675  Mobile: +46(0)703844534  Fax: mail a PDF instead