Bug? The conserved quantity is NOT conserved after flexible cell MD is restarted

[Matthias Krack]

Hi Rustam

in the first place I would suggest to use a compatible pair of basis set 
and potential for Mg. The Mg TZV2P-GTH basis set was generated for a Mg 
GTH-*-q10, but a GTH-BLYP-q2 is employed. Unfortunately, the GTH_BASIS_SET 
file provides only generic labels. I will fix that. Please, run the case 
with a valid combinations of potential and basis set and report if the 
error persists. Note, that the Mg q10 potential requires a very large 
cutoff and for the Mg q2 potential there is only a DZVP basis set available 
in the file BASIS_SET.

Best regards

Matthias

PS: The basis sets in GTH_BASIS_SETS are usually not well suited for 
(dense) solid state systems as they have been generated mainly for 
molecular systems.

On Saturday, 13 August 2016 07:56:39 UTC+2, Rustam wrote:
>
> Hi guys,
>
> As Amandine Chouanard mentioned in a recent post  
> <https://groups.google.com/forum/#!topic/cp2k/mwieBkpEjns>the conserved 
> quantity shows discontinuities when a flexible cell MD simulation is 
> restarted. I used her input file and found that restart works fine with NVT 
> and NPT_I simulations, but NOT with NPT_F (see attached figure). The 
> discontinuities in NVT_F the conserved quantity are larger if restarts are 
> less frequent (i.e. trajectory pieces are longer).
>
> It seems that the conserved quantities in NPT_I and NPT_F simulations are 
> computed by the same subroutine in motion/md_conserved_quantities.F:390. So 
> it seems that the restart file contains ALL data on the current state of 
> the barostat and thermostat to ensure a smooth restart.
>
> Is it possible that this has something to do with the CELL_REF setting? 
> Something along the lines that the grids before and after the restart are 
> different? I tried printing the GRID info but it seems to keep the number 
> of points constant...
>
> I will appreciate any suggestions/comments,
> Rustam
>
>
>
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