[CP2K-user] [CP2K:13207] CELL Optimization - Energy not decreasing
Thomas Kühne
tku... at gmail.com
Thu Apr 30 16:14:22 UTC 2020
Dear Jan,
thanks for putting this to our attention, the deviation looks indeed on the upper end.
However, computing numerical derivatives is a bit tricky and has to be done with
maximum accuracy, since relative deviations of small values are reported.
So this may be an error, but can you please increase EPS_DEFAULT to 10E-16
and EPS_SCF to 10E-7 and try this also with DX to 5.0E-4?
Cheers,
Thomas
P.S. BTW, I did a similar test with the sole PADE XC functional, which is supposed
to mimic PW92 LDA many years ago and it passed the test ...
> Am 30.04.2020 um 17:30 schrieb Jan Elsner <janel... at gmail.com>:
>
> Dear all,
>
> I thought I should post an update on this.
>
> It seems that there is a problem with using PW92 as the local correlation part of XC functional. When I use VWN instead, the analytical and numerical forces are equal. I attach input and output files for DEBUG runs on a single H20 molecule using optPBE in combination with PW92 and VWN. In the case of PW92, there is a mismatch between analytical and numerical forces.
>
> I note that the same applies for the some of the other functionals listed here: https://github.com/cp2k/cp2k/tree/master/data/xc_section <https://github.com/cp2k/cp2k/tree/master/data/xc_section> (at least, I can confirm that optB88 and C09 also give a mismatch between numerical and analytical forces using the settings listed here).
>
> Best wishes,
>
> Jan
>
>
>
>
> On Friday, April 24, 2020 at 10:43:00 AM UTC+1, Jan Elsner wrote:
> Dear Juerg,
>
> Many thanks for the quick response! Unfortunately, decreasing EPS_SCF (all the way to 1.0E-10) does not solve the problem.
>
> I have done a DEBUG run which results in the following error (see end of attached file debug.out): 'Abort: A mismatch between the analytical and the numerical stress tensor has been detected. Check the implementation of the stress tensor'. I'm not entirely sure how I should proceed from here / what the problem is exactly - any insight would be very much appreciated.
>
> If it helps shed some light on the problem, I also attach a figure showing Total Energy, RMS Gradient and Cell Volume as a function of optimization step (plotted from the original cell.out file I sent). The optimiser seems to overshoot the minimum energy configuration.
>
> One other question which comes to mind is whether it's ok to use GTH-PBE or GTH-PADE pseudopotentials with optPBE-vdW?
>
> Best wishes,
>
> Jan
>
>
>
>
>
> On Monday, April 20, 2020 at 10:20:34 AM UTC+1, jgh wrote:
> Hi
>
> I don't know how well a setup as this is tested. However, from
> your output I would guess the problem could be related to your
> SCF convergence. With the methods you are using you have to set
> the convergence criteria much tighter in order to get converged
> energy and forces. I would suggest to use at least 1.E-8.
>
> The ultimate test would be to do a DEBUG run in order to verify
> forces and stress tensor for the setting of options.
>
> regards
>
> Juerg Hutter
> --------------------------------------------------------------
> Juerg Hutter Phone : ++41 44 635 4491
> Institut für Chemie C FAX : ++41 44 635 6838
> Universität Zürich E-mail: h... at chem.uzh.ch <>
> Winterthurerstrasse 190
> CH-8057 Zürich, Switzerland
> ---------------------------------------------------------------
>
> -----c... at googlegroups.com <> wrote: -----
> To: "cp2k" <c... at googlegroups.com <>>
> From: "Jan Elsner"
> Sent by: c... at googlegroups.com <>
> Date: 04/18/2020 08:33PM
> Subject: [CP2K:13145] CELL Optimization - Energy not decreasing
>
> Dear all,
>
> I am trying to run a Cell Optimisation on a periodic molecular crystal (beta-resorcinol: C6H6O2, 4 molecules in unit cell) using K-points and BFGS as optimiser. I am using the vdW-DF-optPBE functional (https://github.com/cp2k/cp2k/commit/74ef05b96a46523a0daf7da04e75804420b5cd5e <https://github.com/cp2k/cp2k/commit/74ef05b96a46523a0daf7da04e75804420b5cd5e>). After 83 optimisation steps, my system does converge to the required MOTION thresholds, however from step 7 onwards the total energy increases at every step i.e.:
>
> -------- Informations at step = 7 ------------
> Optimization Method = BFGS
> Total Energy = -280.1489665596
> Internal Pressure [bar] = -2667.4573178334
> Real energy change = 0.0001037473
> Predicted change in energy = -0.0001063956
> Scaling factor = 0.0000000000
> Step size = 0.0124910496
> Trust radius = 0.4724315332
> Decrease in energy = NO
> Used time = 60.978
>
> Convergence check :
> Max. step size = 0.0124910496
> Conv. limit for step size = 0.0010000000
> Convergence in step size = NO
> RMS step size = 0.0029192108
> Conv. limit for RMS step = 0.0010000000
> Convergence in RMS step = NO
> Max. gradient = 0.0034738629
> Conv. limit for gradients = 0.0001000000
> Conv. for gradients = NO
> RMS gradient = 0.0006857738
> Conv. limit for RMS grad. = 0.0001000000
> Conv. for gradients = NO
> Pressure Deviation [bar] = -2668.4705678334
> Pressure Tolerance [bar] = 200.0000000000
> Conv. for PRESSURE = NO
> ---------------------------------------------------
>
> The resulting cell-optimised structure is therefore not a minimum in energy. I've attached the input and output files. Some points which may (or may not) be relevant:
> I did not encounter this problem when using a different functional (PBE + D3 instead of optPBE-vdW as used here), but otherwise identical settings.
> I encountered the same issue (energy increasing at every step) using CUTOFF/REL_CUTOFF = 800/60
> I initially tried to converge CUTOFF and REL_CUTOFF as in the tutorial (
> https://www.cp2k.org/howto:converging_cutoff <https://www.cp2k.org/howto:converging_cutoff>), however my single point calculations did not converge quite as nicely as in the tutorial - instead oscillating with an amplitude of order ~ e-4 Ha (I've attached a figure showing this). This is why I use such large CUTOFF/REL_CUTOFF values. I note that this was also the case when I ran PBE + D3 calculations, however in the latter case my cell optimisation did work.
>
> Any input would be greatly appreciated.
>
> Best wishes,
>
> Jan
>
>
>
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>
>
> [attachment "cell.inp" removed by Jürg Hutter/at/UZH]
> [attachment "cell.out" removed by Jürg Hutter/at/UZH]
> [attachment "E_vs_cutoff.png" removed by Jürg Hutter/at/UZH]
> [attachment "subsys.include" removed by Jürg Hutter/at/UZH]
>
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> <pw92.inp><pw92.out><vwn.inp><vwn.out>
==============================
Thomas D. Kühne
Dynamics of Condensed Matter
Chair of Theoretical Chemistry
University of Paderborn
Warburger Str. 100
D-33098 Paderborn
Germany
tdku... at mail.upb.de
+49/(0)5251/60-5726
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