Hi Fabrício,
At this time, I cannot recommend using a four-site water model with
RISM. The extra site in these models causes problems for RISM and,
given the effects of orientational averaging in the RISM method, it
isn't clear that there is any benefit. Though MDL files are provided
for these models as part of the AmberTools distribution, they should be
considered experimental at best.
For convergence issues in general, there are a couple of other
approaches you can try. These use the ability to start a new
calculation from the restart file of a previous solution. Use
'ksave=-1' to automatically produce a restart file when a solution has
converged.
- start at a high temperature and slowly decrease it.
- turn off charges and slowly increase them.
- start at a low density and slowly increase it.
- If you are trying to use a higher order closure, start with KH and
then use increasing values of n for the PSE-n closure.
Hope this helps,
Tyler
On 06/06/2012 01:33 PM, Fabrício Bracht wrote:
> Sorry to resend. I am just correcting one information. I only had
> convergence problems with TIP4P and TIP4P/Ew models. TIP3P works fine.
>
> Below is the corrected message. Thank you
>
> I've been trying to follow the steps described by the A14 tutorial,
> but instead of using SPC water I am trying with TIP4p/Ew. I am using
> basically the same parameters given as example by the ambertools12
> manual, but once I got convergence problems, I tried using smaller
> MDIIS_DEL values (0.2 and 0.1). I have also tried using TIP4P water
> Last thing I tried was to remove entirely the presence of
> Na+ and Cl- ions. None of the calculations converged within the 10000
> step limit. SPC calculations run just fine. Which of these would be
> the recommended water model for ff12SB force field?
> I was hoping someone could help me here.
> Thank you
> Fabrício Bracht
>
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Received on Wed Jun 06 2012 - 12:30:04 PDT
