[CP2K-user] [CP2K:13145] CELL Optimization - Energy not decreasing

[Jan Elsner]

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 
> <javascript:> 
> Winterthurerstrasse 190 
> CH-8057 Zürich, Switzerland 
> --------------------------------------------------------------- 
>
> -----c... at googlegroups.com <javascript:> wrote: ----- 
> To: "cp2k" <c... at googlegroups.com <javascript:>> 
> From: "Jan Elsner" 
> Sent by: c... at googlegroups.com <javascript:> 
> 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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