[CP2K:6108] Energy result of geometry optimization is not global minimum

[hut... at chem.uzh.ch]

Hi

If you increase the accuracy of the geometry optimization and
possibly the accuracy of the energy calculation (eps_default,
eps_scf, etc.) then the final energy should be the lowest.

That you are taking rather large steps even after 147 optimization
steps points to a very floppy system or a not enough converged
electronic system.

regards

Juerg
--------------------------------------------------------------
Juerg Hutter                         Phone : ++41 44 635 4491
Institut für Chemie C                FAX   : ++41 44 635 6838
Universität Zürich                   E-mail: hut... at chem.uzh.ch
Winterthurerstrasse 190
CH-8057 Zürich, Switzerland
---------------------------------------------------------------

-----cp... at googlegroups.com wrote: -----To: cp... at googlegroups.com
From: Atthar Luqman Ivansyah 
Sent by: cp... at googlegroups.com
Date: 02/14/2015 12:04PM
Subject: [CP2K:6108] Energy result of geometry optimization is not global minimum

Dear all,

I did a geometry optimization on a system using QUICKSTEP. After finished, i checked the output file and i found in this line : 

--------  Informations at step =   147 ------------
  Optimization Method        =                 BFGS
  Total Energy               =     -2928.4571378203
  Real energy change         =         0.0000194690
  Predicted change in energy =        -0.0000052606
  Scaling factor             =         0.8953959951
  Step size                  =         0.0020678657
  Trust radius               =         0.4724315332
  Decrease in energy         =                   NO
  Used time                  =              211.784

  Convergence check :
  Max. step size             =         0.0020678657
  Conv. limit for step size  =         0.0030000000
  Convergence in step size   =                  YES
  RMS step size              =         0.0005392482
  Conv. limit for RMS step   =         0.0015000000
  Convergence in RMS step    =                  YES
  Max. gradient              =         0.0003227289
  Conv. limit for gradients  =         0.0004500000
  Conv. in gradients         =                  YES
  RMS gradient               =         0.0000894336
  Conv. limit for RMS grad.  =         0.0003000000
  Conv. in RMS gradients     =                  YES

>From that line, even though :
Convergence in step size   =                  YES
Convergence in RMS step    =                  YES
Conv. in gradients         =                  YES
Conv. in RMS gradients     =                  YES

but,
Decrease in energy         =                   NO

My question is :
Does it mean that the energy is not global minimum? as far as i know, when we do some geometry optimization calculatioan, the final structure must have energy which is global minimum because it is the most stable structure.

Thank you very much for your answer and your attention. I am sorry for my silly question because i am newbie in cp2k.

highest regards,
atthar 





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