Sorry , I meant that the dynamics fails when the M solute molecule and 15
Li ions are both treated with semi-empirical PM6, whereas the water at MM
level .
Any ideas would be more than welcome. Thanks.
Cheers
Manuele
Il 25 gen 2019 17:03, "emanuele falbo" <falbo.emanuele.gmail.com> ha
scritto:
> Dear users,
>
> I am running QM/MM dynamics on compounds (metal oxides, mainly the metal
> atoms are M= Mo or W) solvated in water.
>
> The solute molecule, let's say, is M^(n-) where n=3,10,27, so it can be a
> highly charged system. Thus, counter ions needed to be added to neutralize
> the total system. I do add Li+ ions with addions2 (atomic charges of solute
> molecule is taken from Mulliken analysis, PBE optimization).
>
> I do run the QM/MM dynamics at PM6/MM level of theory, because the PM6 is
> the only built-in semi-empirical method working for these compounds in
> AMBER.
>
> When I run the dynamics for the system Li3M (all treated at PM6 level) it
> works fine, and even if I get the following error, the dynamics continues
> and at some point it seems running fine.
>
> "
> QMMM: WARNING!
> QMMM: Unable to achieve self consistency to the tolerances specified
> QMMM: No convergence in SCF after 1500 steps.
> QMMM: Job will continue with unconverged SCF. Warning energies
> QMMM: and forces for this step will not be accurate.
> QMMM: E = -0.3570E+07 DeltaE = 0.1048E-06 DeltaP = 0.5871E-09
> QMMM: Smallest DeltaE = 0.1048E-06 DeltaP = 0.5871E-09 Step = 1500
> "
>
> However, when it comes to run, for example, the Li15M-where only the
> M^(15-) is modelled at PM6 level and the remainder, included 15Li+, is
> treated at MM-it gives the above error, and fails.
>
> Of course, this makes me think that there is a problem with highly charged
> systems, however, I am not sure how to get it work.
> Therefore, I wonder if you have any idea about how to sort this issue out ?
>
> Best Wishes,
> Manuele
>
>
>
>
> --
>
> *Emanuele Falbo*
> PhD student
> Penfold group
> School of Natural and Environmental Sciences
> Bedson Building, Newcastle University
> Newcastle upon Tyne, NE1 7RU
> w: http://tompenfoldresearch.weebly.com/
>
>
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Received on Fri Jan 25 2019 - 13:00:02 PST
