[CP2K-user] Weird "convergence" of L-BFGS CELL_OPT

[Daniele Ongari]

Dear CP2K mailing list,

We experience a strange behavior of the L-BFGS optimization algorithm when 
dealing with cases where SCF convergence is problematic.

After 20 minimization steps the cp2k printed the following:


--------  Informations at step =    21 ------------
 Optimization Method        =                LBFGS
 Total Energy               =     -2345.6430825804
 Internal Pressure [bar]    =        23.9760390703
 Real energy change         =         0.0028283710
 Decrease in energy         =                   NO
 Used time                  =             5864.105

 Convergence check :
 Max. step size             =         0.0000000000
 Conv. limit for step size  =         0.0030000000
 Convergence in step size   =                  YES
 RMS step size              =         0.0000000000
 Conv. limit for RMS step   =         0.0015000000
 Convergence in RMS step    =                  YES
 Max. gradient              =         0.0082916384
 Conv. limit for gradients  =         0.0004500000
 Conv. for gradients        =                   NO
 RMS gradient               =         0.0009846623
 Conv. limit for RMS grad.  =         0.0003000000
 Conv. for gradients        =                   NO
 Pressure Deviation [bar]   =       -76.0239609297
 Pressure Tolerance [bar]   =       100.0000000000
 Conv. for  PRESSURE        =                  YES
---------------------------------------------------

--------------------------
OPTIMIZATION STEP:     22
--------------------------

***********************************************
* Specific L-BFGS convergence criteria
* WANTED_PROJ_GRADIENT and WANTED_REL_F_ERROR
* satisfied .... run CONVERGED!
***********************************************



The two things that look strange for us are:

1) Max. step size and RMS step size were 'artificially' set to 0.0000000000
2) Not all checks are showing convergence, while L-BFGS algorithm has 
decided to stop.


Therefore, we would like to know if this is an expected behavior of the 
L-BFGS algorithm and if yes, what is the reason behind working this way?

Please see input and output files attached.

With best regards,
Daniele and Sasha
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.cp2k.org/archives/cp2k-user/attachments/20190222/110bd2dc/attachment.htm>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: aiida.coords.xyz
Type: chemical/x-xyz
Size: 26446 bytes
Desc: not available
URL: <https://lists.cp2k.org/archives/cp2k-user/attachments/20190222/110bd2dc/attachment.xyz>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: aiida.inp
Type: chemical/x-gamess-input
Size: 4024 bytes
Desc: not available
URL: <https://lists.cp2k.org/archives/cp2k-user/attachments/20190222/110bd2dc/attachment.inp>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: aiida.out
Type: application/octet-stream
Size: 796100 bytes
Desc: not available
URL: <https://lists.cp2k.org/archives/cp2k-user/attachments/20190222/110bd2dc/attachment.obj>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: aiida-pos-1.xyz
Type: chemical/x-xyz
Size: 590238 bytes
Desc: not available
URL: <https://lists.cp2k.org/archives/cp2k-user/attachments/20190222/110bd2dc/attachment-0001.xyz>