[CP2K:1700] Re: GPW: strange behavior of cations

Lukasz Cwiklik cwi... at gmail.com
Sun Jan 25 10:56:57 CET 2009


Dear Ilya,
I had the same problems with sodium atom/cation in water (almost 2
years ago with an old version of cp2k). At that time I was discussing
it with Fawzi and it seems that the problem was in too small cutoff
value (as far as I understand it is simple - the small sodium cation
needs a finer grid). I had to go up to 400 Ry to get rid of unphysical
'shaking' of sodium. And yes - it made my simulations terribly long
:-(
If you find any other reason/solution of these problems with sodium,
please, let me or the group know.
Best,
Lukasz

-- 
Lukasz Cwiklik
http://cwiklik.wordpress.com



On Fri, Jan 16, 2009 at 5:55 PM, ilya <ily... at gmail.com> wrote:
>
> Thank you for the reply.
>
> A couple of additional questions:
> Could you give me a hint what kind of properties should i look at?
> (electronic density?)
> If the situation is not good, then the solution will be to change the
> electronic structure method?
> If i get rid of Na... does the simulation of charged system (periodic/
> isolated) makes any sense?
>
>
> Thanks again.
>
> Ilya.
>
> On Jan 16, 6:16 pm, Teodoro Laino <teodor... at gmail.com> wrote:
>> I had a quick look, of course not on your full system ( do you really
>> believe people look in a 330 atom system ? )
>> So I cut it retaining Na + OH + 3 H2O (overall neutral).
>>
>> First of all you should have a look if really you get Na+  and OH-. This
>> system can be not trivial at all, and the way
>> the SCF converges for such a small system, honestly suggests some
>> troubles in the electronic configuration.
>>
>> Having said that.. the Na is moving.. of course not like H, but that's a
>> matter of masses. Using a massive thermostat may help you a bit in
>> equilibrating the system faster.
>> I would also check the cutoff, the preconditioner (for speeding-up
>> convergence) and more important that out of this simulation you are
>> getting exactly what you want in terms of electronic structure.
>> Seeing the Na moving faster of course does not mean that your numbers
>> make sense.
>> So.. go back to a single energy calculation and check the properties of
>> your NaOH+few water molecules. That's the most important thing to do
>> before worrying about the velocity of Sodium.
>>
>> cheers,
>> Teo
>>
>> ilya wrote:
>> > I've uploaded asn.zip with input and a fragment of trajectory.
>>
>> > On Jan 16, 12:44 pm, Teodoro Laino <teodor... at gmail.com> wrote:
>>
>> >>> Any ideas?
>>
>> >> again and again.. input file?
>>
>> >>> Thanks a lot.
>>
>> >>> Ilya.
> >
>



-- 
Lukasz Cwiklik
http://cwiklik.wordpress.com



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