[CP2K-user] DFT ALMO-AIMD

[Phillip Seeber]

Dear all,
i would like to perform a MD simulation of a large dinuclear ruthenium 
complex. Im am interested in a ligand exchange process (Cl- <=> H2O) and 
would like to do a metadynamics simulation to obtain the free energy 
surface for the ligand exchange. As the system including water molecules in 
a cubic box of (35 Angstrom)^3 with ca 3100 atoms is quite large and a 
normal DFT calculation on our cluster takes about 3 hours per MD step, i 
was looking into linear scaling methods. Doing curvy steps with DFT (based 
on this tutorial <https://www.cp2k.org/exercises:2015_pitt:ls>), the time 
drops to 1.5 hours but this is still to long. 

I was also trying ALMO-SCF and tried to adapt some of the settings found 
here <https://pc2.uni-paderborn.de/fileadmin/pc2/cp2k_workshop/almo.pdf>. 
Unfortunately i am running into trouble in the first SCF cycle already, as 
the "hotelling inversion did not converge". Is there something i could 
tweak to get it running? Furthermore the informations about ALMO-AIMD seem 
a little bit spare to me, so i guess i am on thin ice, especially as the 
original paper recommends Langevin MD. According to the tutorial slides i 
was trying to use ALMO-SCF without early stopping and a larger cutoff 
radius to be able to use normal NPT_I ensemble, but i am not sure if i did 
it correctly?

As an alternative i was also trying XTB and XTB with curvy steps but i 
assume the energies will not be that good.

I am grateful for any suggestion and insight. :)

Best wishes and thanks in advance
Phillip
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