[gmx-users] [ implicit_genborn_params ] for Gromos54a7 FF

[Alex]

Hi David,
Thank you.

On Tue, Dec 4, 2018 at 4:24 PM David van der Spoel <spoel at xray.bmc.uu.se>
wrote:

> Den 2018-12-04 kl. 21:58, skrev Alex:
> > Dear all.
> > I wonder where the [ implicit_genborn_params ] section should come in the
> > below topol.top file for which the Gromos54a7 force fields are used?
> >
> > For the Amber and OPLS-FF I notice that all the [
> implicit_genborn_params ]
> > parameters are in a gbsa.itp file but that was not the case for
> Gromos54a7
> > and even it did not worked when I created a gbsa.itp for for gromos5a7.
> >
> Please note first that only the 4.5 and 4.6 branches of gromacs run
> generalized born efficiently and reliably (as far as I know).
>
I didn't know that, I use the 2018.2 version and at least the tpr file can
be produced ... .

>
> Second, if there is no predefined force field you should not make an
> ad-hoc one but use a well-defined one instead.


> Third, why bother with generalized born at all? There are so many papers
> showing that the predictive power is poor that it will be hard to defend
> any results based on it.

If non of Still, HCT and OBC, then what else you would suggest that has
been implemented in Gromacs and could be used easily in Gromacs?
I just wanted to see the diffusion and adsorption of some polymers to solid
surface. The process is so slow in explicit water and I just wanted to see
it the polymer come to the surface at all!  However I see too much force in
the slab with the current [ implicit_genborn_params ] parameter which I
have used for now.

BTW, meanwhile I found that the  [ implicit_genborn_params ] should come
immediatly after the [ atomtypes ] section in topol.top file.

Regards,
Alex

>
> > %-------------TOP-----------
> > #include "/u/alex/.local/gromos54a7.ff/forcefield.itp"
> > ;
> > #include "A.itp"
> > #include "B.itp"
> > #include "C.itp"
> > ;
> > [ system ]
> > A-B-C in implicit water
> >
> > [ molecules ]
> > A               1
> > B               29
> > C               14
> > B               29
> > C               14
> > %--------------------------
> >
> > Thank you
> >
> > Regards,
> > Alex
> >
>
>
> --
> David van der Spoel, Ph.D., Professor of Biology
> Head of Department, Cell & Molecular Biology, Uppsala University.
> Box 596, SE-75124 Uppsala, Sweden. Phone: +46184714205.
> http://www.icm.uu.se
> --
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