[gmx-users] Help with RB dihedrals implementation

[Mark Abraham]

Jones de Andrade wrote:
> Hi all.
> 
> I'm trying to implement a samll RB-potential for some molecules I'm 
> working with. I choosen to go following the files from opls-aa force 
> field included with gromacs. Unfortunatelly, I get this error:
> 
> "No default Proper Dih. types, using zeroes"
> 
> Which is quite strange, as the error latelly refers to the following lines:
> 
>  CT  CT  CT  F  3      0.65084     1.95253     0.00000    -2.60338     
> 0.00000     0.00000
>  F   CT  CT  F  3      5.02080     5.02080     0.00000     0.00000     
> 0.00000     0.00000
> 
> And, for a final point that makes my doubt, I don't see any difference 
> between this lines and this ones from ffoplsaabon.itp from gromacs 3.3.1 
> itself:
> 
>   CA     CT     CT     NC      3      5.77183  -2.67148   0.95814  
> -4.05848   0.00000   0.00000 ;
>   CA     CT     CT     NT      3      3.33465  -1.55226   2.82001  
> -4.60240    0.00000   0.00000
> 
> Could anyone give me some help on this issue, please?

I guess that you've mangled some format, either in your modifications to 
the .itp file or your .top file. Read the relevant parts of Chapter 5 
closely and compare with what you've done. We can't tell what the 
problem is from the information you've provided so far.

Mark