[CP2K:5393] Re: graphite in CP2K
Matt W
MattWa... at gmail.com
Wed May 28 17:23:21 UTC 2014
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
>>>
>>> --
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>
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