[CP2K:5393] Re: graphite in CP2K

[Matt W]

Hi Michele,

please try using the MOLOPT basis sets provided with CP2K 
($CP2K_root/tests/QS/BASIS_MOLOPT) that prehaps give a more suitable 
starting point for describing a "molecular" system like graphite than 
atomic optimization based ones.

Using a DZVP-MOLOPT-SR-GTH basis - I get SCF convergence in ~10 cycles and 
geometry converges in ~10 steps (with BFGS).

Matt

On Wednesday, May 28, 2014 5:19:30 PM UTC+1, Michele Ceriotti wrote:
>
> Hi Matthias, 
>    Thanks for the quick answer. I have already played with the obvious 
> parameters, point is it is impossible to converge the scf properly. 
> Everything looks like what you get when the geometry is crazy, and indeed 
> my student tried to enlarge the cell (by almost 10%!) and got  converged 
> scf and more reasonable forces. 
> However this is inconsistent with the literature and the results from 
> siesta.
> We have been trying to fiddle with the scf parameters for days, but get 
> consistently 100au forces on a geometry that should be very close to 
> optimum.
> Do you see something wrong with how we define the cell or the positions?
> Best
> Michele
> On 28 May 2014 17:47, "Matthias Krack" <matth... at psi.ch <javascript:>> 
> wrote:
>
>> Hi Michele,
>>
>> I would suggest to set EPS_DEFAULT in @QS section at least to 1.0E-12 or 
>> lower and for the ALPHA in &MIXING I would also use a smaller value like 
>> 0.2. Maybe this will help to converge your system properly.
>>
>> Matthias
>>
>> On Wednesday, May 28, 2014 4:20:44 PM UTC+2, Michele Ceriotti wrote:
>>>
>>> Dear CP2K community, 
>>>
>>>      I have been trying for a few days to set up calculations of 
>>> graphite as an exercise for a student but I am getting the weirdest 
>>> results.  I am sure in the it will end up being a silly mistake in the 
>>> input, but I can't get to see it so perhaps someone can help. 
>>>
>>> Despite using a fairly large FD smearing, the SCF cycle has a hard time 
>>> converging, and when the maximum number of steps is reached 
>>>
>>>     50 Broy./Diag. 0.50E+00    1.2     0.00014351      -819.2909959720 
>>> -2.28E-09
>>>   *** SCF run NOT converged ***
>>>
>>> and the calculation carries on with what it has got, diagnostics are 
>>> really strange. 
>>>
>>> For a start, eigenvalues show two weird very low-energy states
>>>  MO EIGENVALUES AND MO OCCUPATION NUMBERS
>>> # MO index          MO eigenvalue [a.u.]            MO occupation
>>>          1                    -21.523076                 2.000000
>>>          2                    -21.517160                 2.000000
>>>          3                     -1.383548                 2.000000
>>>          4                     -0.510418                 2.000000
>>>
>>> forces on the atoms are insane
>>>  ATOMIC FORCES in [a.u.]
>>>  # Atom   Kind   Element          X              Y              Z
>>>       1      1      C           4.68736611     4.63921800  -222.86999309
>>>       2      1      C          -1.57720920    -4.48651652   124.33822840
>>>       3      1      C          -5.01734639     3.10518104   176.16292919
>>>
>>> and so is the stress tensor
>>>  STRESS TENSOR [GPa]
>>>             X               Y               Z
>>>   X   -8233.84728056      8.05482610      0.90481573
>>>   Y       8.05482610  -9552.76932222     -0.49445437
>>>   Z       0.90481573     -0.49445437  -2526.59040628
>>>
>>> I was thinking of an error in the structure or the cell parameters, but 
>>> I checked it many times and everything seems in order. The same structure, 
>>> with same functional and similar parameters in SIESTA converges like a 
>>> stone, and gives no problem whatsoever. 
>>>  
>>> Can you spot something obvious that I am missing? I'd really like to use 
>>> CP2K for this exercise, but I can't seem to figure out what is going wrong. 
>>>
>>> Many thanks,
>>> Michele
>>>
>>>  -- 
>> You received this message because you are subscribed to a topic in the 
>> Google Groups "cp2k" group.
>> To unsubscribe from this topic, visit 
>> https://groups.google.com/d/topic/cp2k/koy91UtxlQw/unsubscribe.
>> To unsubscribe from this group and all its topics, send an email to 
>> cp2k+... at googlegroups.com <javascript:>.
>> To post to this group, send email to cp... at googlegroups.com <javascript:>
>> .
>> Visit this group at http://groups.google.com/group/cp2k.
>> For more options, visit https://groups.google.com/d/optout.
>>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.cp2k.org/archives/cp2k-user/attachments/20140528/aa47eef6/attachment.htm>