[CP2K-user] [CP2K:16988] Re: IR spectm for NaCl under PBC

Victor Volkov volkovskr at gmail.com
Mon May 16 11:33:21 UTC 2022
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Dear Dr. Hutter:
good afternoon.
thank you very much for the kind reply and the instructions.
I will study.
Best regards,
Victor


On Mon, May 16, 2022 at 1:56 PM Jürg Hutter <hutter at chem.uzh.ch> wrote:

> Hi
>
> just a few thoughts on geometry optimizations and frequency calculations
> using CP2K.
> It might help for the present discussion.
>
> In an ideal setting one expects that the energy of a molecule is constant
> for translations and rotations.
> For periodic systems, the energy should be constant for translations.
> In CP2K the XC energy is calculated using equidistant grids (the same for
> all PW codes) and this
> breaks translational invariants and rotational invariants for molecules.
> If you calculate the energy for a system while translating it rigidly you
> will observe a small periodic change
> of the energy with a frequency given by the grid spacing. This phenomenon
> is usually called 'ripples'.
> The size of the ripples depends on many parameters (cutoff,
> pseudopotential, smearing, etc).
> The GPW method in CP2K shows rather large ripples, which cause problems in
> tight geometry optimizations
> and frequency calculations. However, forces are consistent with the
> ripples, so there is no problem
> in MD.
> For geometry optimizations the optimizer gets "confused" by the ripples
> and starts to jump back and forth
> and might have problems to converge.
> In frequency calculations, you will observe non-zero translational and
> rotational modes. These modes
> can have positive or negative frequencies. In CP2K these modes are
> projected out from the Hessian
> assuming they don't couple to the internal molecular modes.
> If you want to reduce the ripples in CP2K you can explore some options:
> - use GAPW, it will reduce the size considerably
> - use smearing of density and gradients (this might have side effects, use
> with care!)
> - some functionals are worse than others (BLYP!)
>
> best regards
>
> Juerg Hutter
>
> ________________________________________
> From: 'Václav Havel' via cp2k <cp2k at googlegroups.com>
> Sent: Saturday, May 14, 2022 3:51 AM
> To: cp2k
> Subject: Re: [CP2K:16978] Re: IR spectm for NaCl under PBC
>
> Dear Viktor,
> I have the same question about imaginary frequencies.
> Have you tackled the problem of imaginary frequency ?  It seems that just
> increasing the optimization criteria  cannot  eliminate  all   imaginary
> frequencies .
>
> With best regards
> Vaclav
>
> 在2022年3月6日星期日 UTC+8 00:29:21<volk... at gmail.com> 写道：
> Dear Fabian:
> cannot say that evening is any good.
>
> Relatives are in leveled Starobelsk,
> and in Hadich, where the front is incoming.
>
> Science ...
>
> Here,
> are the results of calculations of the normal modes fro NaCl.at the Gamma
> point.
> Also, I attach the optimization files.
> It seems to me that after increasing the optimization criteria
>     MAX_DR    8.0E-07
>     RMS_DR    4.0E-07
>     MAX_FORCE 1.0E-07
>     RMS_FORCE 1.0E-08
>
> The results are curious.
> May be there are some mistakes I did?
>
> Again,
> I wish to ask if CP2K has an issue
> about the Fourier grid
> that may generate imaginary frequencies
> if the coords are not properly positioned?
>
> If you do not have energy/time/will,
> please,
> forgive and disregard the inquiry.
>
> With best regards,
> Victor
>
>
> On Friday, January 28, 2022 at 3:42:08 PM UTC+3 fabia... at gmail.com wrote:
> Dear Viktor,
>
> Several things:
>  - If you choose RUN_TYPE GEO_OPT then you should have MOTION&GEO_OPT and
> not MOTION&CELL_OPT and vice versa.
>  - Set EPS_DEFAULT to 1e-12
>  - For CELL_OPT: you should have a &CELL_REF section with dimensions
> approx. 1.3-1.5 times larger (test this!) than &CELL
>  - You need MULTIPLE_UNIT_CELL in &CELL_REF too
>
> Cheers,
> Fabian
>
> On Friday, 28 January 2022 at 09:30:16 UTC+1 volk... at gmail.com wrote:
> Dear Fabian:
> good morning.
>
> According to your notice
> I redefined MAX_FORCE to be under
> &MOTION
>    &CELL_OPT
> However, the cp2k failed convergence - energy was just oscillating.
>
> After studying your replies to other members,
> I did two changes in the input.
>
> 1.
> While keeping the definitions in
> &MOTION
>    &CELL_OPT
> ....
> in GLOBAL
> I changed to
>  RUN_TYPE GEO_OPT
>
> The logic of the guess is that apparently &CELL_OPT can not lead.
> Then, may be,
> GEO should lead, while CELL should be set to follow.
>
> It is not clear, if under such setting STRESS TENSOR would have any
> meaning.
> Perhaps it has not role no more and becomes redundant.
>
> 2.
> Also, I introduced
> CELL_REF
>
> I attach the input.
> This is the job I am testing.
>
> Would you have a minute to comment, criticize - I be thankful.
>
> In any way,
> thank you for your time,
> and nice weekend
> :-)
> Best!
> Victor
>
>
>
> On Thu, Jan 27, 2022 at 2:30 PM fabia... at gmail.com <fabia... at gmail.com>
> wrote:
> cp2k works just fine and does everything you tell it to do. The issue is
> that you specified MAX_FORCE 1.0E-07  etc. for &GEO_OPT instead of
> &CELL_OPT...
>
> On Thursday, 27 January 2022 at 11:39:21 UTC+1 volk... at gmail.com wrote:
> Dear Fabian:
> Dear Dr. Hutter:
>
> is it possible that CP2K is present not to follow the input instructons?
>
> According to my instructions (pleas, see attached)
> in the MOTION section there are instructions
>     MAX_DR    8.0E-07
>     RMS_DR    4.0E-07
>     MAX_FORCE 1.0E-07
>     RMS_FORCE 1.0E-08
>
> but
> as Fabian has noticed:
>
> The output you attached shows for step 28:
>   Max. gradient              =         0.0002958006
>   Conv. limit for gradients  =         0.0004500000
>   Conv. in gradients         =                  YES
>
> So that output is for MAX_FORCE 4.5E-4 and not 1.0E-7. You should also
> decrease EPS_SCF (to 1e-7 or 1e-8) and probably EPS_DEFAULT.
>
> Is it possible that there is a bug
> that prevents a certain level of precision?
>
> Thank you.
> With best regards.
>
> Victor
>
>
>
>
> On Thu, Jan 27, 2022 at 12:00 PM fabia... at gmail.com <fabia... at gmail.com>
> wrote:
> Dear Viktor,
>
> The output you attached shows for step 28:
>   Max. gradient              =         0.0002958006
>   Conv. limit for gradients  =         0.0004500000
>   Conv. in gradients         =                  YES
>
> So that output is for MAX_FORCE 4.5E-4 and not 1.0E-7. You should also
> decrease EPS_SCF (to 1e-7 or 1e-8) and probably EPS_DEFAULT.
>
> Fabian
>
> On Wednesday, 26 January 2022 at 21:12:03 UTC+1 volk... at gmail.com wrote:
> Dear Fabian:
> please forgive me
>
> If I set
>     OPTIMIZER BFGS
>
>     MAX_DR    8.0E-06
>     RMS_DR    4.0E-06
>     MAX_FORCE 1.0E-06
>     RMS_FORCE 1.0E-07
> then the forces are
> ATOMIC FORCES in [a.u.]
>  # Atom   Kind   Element          X              Y              Z
>       1      1      Na          0.00000796     0.00000796     0.00000796
>       2      1      Na          0.00000796     0.00001127     0.00001127
>       3      1      Na          0.00001127     0.00000796     0.00001127
>       4      1      Na          0.00001127     0.00001127     0.00000796
>       5      2      Cl          0.00000052     0.00000052     0.00000052
>       6      2      Cl          0.00000052     0.00000052     0.00000052
>       7      2      Cl          0.00000052     0.00000052     0.00000052
>       8      2      Cl          0.00000052     0.00000052     0.00000052
>  SUM OF ATOMIC FORCES           0.00004056     0.00004056     0.00004056
>    0.00007026
>
> and the soectrum is terrible (please, see the attached xxx_F.out)
>
> Then I try to instruct more strict convregence by
>     OPTIMIZER BFGS
>     MAX_DR    8.0E-07
>     RMS_DR    4.0E-07
>     MAX_FORCE 1.0E-07
>     RMS_FORCE 1.0E-08
>
> but the forces deteriorate
> ATOMIC FORCES in [a.u.]
>  # Atom   Kind   Element          X              Y              Z
>       1      1      Na          0.00009945     0.00009945     0.00009945
>       2      1      Na          0.00025879    -0.00001513    -0.00001513
>       3      1      Na         -0.00001519     0.00025872    -0.00001518
>       4      1      Na         -0.00001513    -0.00001513     0.00025879
>       5      2      Cl          0.00031492     0.00004422     0.00004422
>       6      2      Cl          0.00024177     0.00024177     0.00024177
>       7      2      Cl          0.00004422     0.00004422     0.00031492
>       8      2      Cl          0.00004422     0.00031492     0.00004422
>  SUM OF ATOMIC FORCES           0.00097305     0.00097303     0.00097305
>    0.00168536
>
> I attach the optimization inp and out pair.
> I donot see what is wrong?
> May be GPW and BFGS are not for such optimizations?
> Thank you.
> Victor
>
>
>
> On Mon, Jan 24, 2022 at 4:22 PM fabia... at gmail.com <fabia... at gmail.com>
> wrote:
> Dear Victor,
>
> You need a much tighter convergence criterion for the optimization prior
> to the vibrational analysis. You increased MAX_FORCE to 5e-3 (guessing from
> the output), instead you have to decrease it to at least 1e-5, maybe even
> lower.
> CP2K prints the forces for the replica in the output. The forces under
> "Minimum Structure - Energy and Forces:" should be more or less 0 and
> considerably differ between the other images. Currently you are computing
> the vibrational analysis from almost pure noise.
>
> Cheers,
> Fabian
> On Sunday, 23 January 2022 at 19:58:05 UTC+1 volk... at gmail.com wrote:
> Dear colleagues:
> here is the normal mode analysis I could manage by now for NaCl under PBC.
>
> There is only one unit cell: previously, I reported that I could not
> configure CP2K to reproduce NaCl structure using multiple cells 2 2 2.
> There are strange distortions, which I did confirm to sustain under
> different CUTOFF values (1000 and 600), and regardless if dispersion is
> switched off or not.
>
> When a single cell under PBC, optimization leads to the “right” structure,
> when ESP 10^-12.
>
> However, the negative(imaginary) frequencies are many and they are very
> large.
> I may anticipate that the “miss performance” is enhanced due to the PBC.
>
> Eventhough the results are "devastating",
> :-)
> nonetheless, I find this might be very good, very helpful – I got an idea.
>
> Dear Dr. Hutter,
> is it possible that CP2K may have an “issue” about positioning a structure
> in respect to both, in respect to the FT grind and in respect to the PBC.
> Perhaps, there could be a relative mismatch phenomenon, which could
> stimulate artificial transition states with negative frequencies?
>
> May be, what I observe is that PBC on the unit cell helps to sense this
> better?
>
>
> Thank you for your time and for any comments.
>
> With best regards,
> Sincerely
> Victor
>
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