[CP2K-user] Ehrenfest MD together with UKS and HFX (using ADMM) does not work

[Dan_M]

Dear community,

I am trying to perform an Ehrenfest MD run in a system that requires both 
spin-polarization and a hybrid functional in order to be described 
correctly (in case you are wondering, an ionized water dimer, i.e. 
H2O...H2O^+). For the HFX, I am of course using the ADMM method.

I have done many tests and it happens that all three methods together do 
not work. The code crashes with a segfault, and the last lines in the 
output file are these (no warning/error message, the initial T I set is 
actually 0):  

 ************************** Velocities initialization 
**************************
 Initial Temperature                                                      
0.00 K
 COM velocity:            0.000000000000      0.000000000000      
0.000000000000
 *******************************************************************************

Given the system size, I assume it is not an issue of memory or anything 
similar, 
Now the curious thing is: when trying to narrow down the problem, all the 
following combinations of methods DO work fine:

- RT_PROPAGATION (instead of Ehrenfest) with UKS and HFX is ok.
- EHRENFEST_DYN with UKS and no HFX is ok.
- EHRENFEST_DYN with RKS and HFX is ok.
- EHRENFEST_DYN with RKS and no HFX is of course ok.
- And as expected, regular MD with UKS and HFX is ok.

I have tested more thoroughly version 5.1, and also a bit version 6.1 (not 
that thoroughly, but in the few tests I did, the case EMD+UKS+HFX does not 
work either). I have done quite some calculations using all these different 
approaches separetely (EMD with RKS, regular MD with HFX/ADMM, etc), and I 
am quite confident that the code is well compiled and produces correct 
results. I did not yet try the trunk version since it seemed to me that 
there have been no new additions in the EMD routines w.r.t. versions 
5.1/6.1, so I assumed that whatever is the problem probably it is still 
present there.

Since the RTP+UKS+HFX is fine, and given that the code crashes at the stage 
of MD initialization, seems to me that there is something happening when 
trying to compute the forces. But it is quite puzzling that the forces for 
EMD+HFX+RKS are fine, EMD+UKS+regularGGA are fine, but together EMD+HFX+UKS 
then it crashes.

Now, before I post the input file/s: Can anyone that has a deep knowledge 
of this part of the code tell me whether there is something that has not 
yet been implemented, or should this in principle work? Has anybody 
successfully done such a calculation?

Thanks a lot,
Daniel
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