[CP2K-user] [CP2K:13207] CELL Optimization - Energy not decreasing

[Jan Elsner]

Dear Thomas, 

I attach inputs and outputs with the modified settings. As before, using 
VWN gives consistent forces. Using PW92 gives inconsistent forces (as 
before) however now the forces for Atom 2 are fine, but way off for Atom 3. 
I'm not sure why this would be the case. 

Best, 

Jan



On Thursday, April 30, 2020 at 5:14:33 PM UTC+1, tkuehne wrote:
>
> 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 <ja... at gmail.com 
> <javascript:>>:
>
> 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 (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). 
>>> 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), 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
> td... at mail.upb.de <javascript:>
> +49/(0)5251/60-5726
>
>
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