[CP2K-user] [CP2K:14060] Force calculation in CELL_OPT vs MD

Krack Matthias (PSI) matthi... at psi.ch
Thu Oct 15 15:45:38 UTC 2020

Hi Martin

The probability of getting any feedback on this forum would increase, if you would provide the input files and the timings in the output files of the CELL_OPT and MD runs.



From: cp... at googlegroups.com <cp... at googlegroups.com> On Behalf Of mar... at gmail.com
Sent: Donnerstag, 15. Oktober 2020 14:52
To: cp2k <cp... at googlegroups.com>
Subject: [CP2K:14060] Force calculation in CELL_OPT vs MD


This may well just be a gap in my knowledge regarding how forces are calculated in CP2K for geometry optimisations vs molecular dynamics. In such a case, I would still appreciate any insight as well.

In short, for the same system with virtually the same SCF and other settings, force calculations during MD take over 4 times as long as the same step during CELL_OPT. I don't understand why this is happening and would appreciate any insight or solution.

Details: I have started by optimising the geometry of this system (relatively tight convergence criteria, no issues) prior to running any MD. My issue comes during the MD, where each step takes significantly longer (average of ~30 seconds per opt. step vs ~90 seconds per md step) than i would expect based on the corresponding CELL_OPT timings. Most of this seems to be taken up by force calculations (timings in the output file suggest ~20 seconds for the SCF process and finding the electron density and ~60-70 seconds for the force calculation, position update etc.). Previously, similar MD calcs on a cluster model of this system (but containing more atoms in a larger unit cell) required 35-45 s per time step. This is despite using the same numbers of cores, same basis sets, same cutoffs, and same settings where relevant.

Background: I am working on a certain porous material (unit cell 15x15x20) with regards to catalytic processes which can take place inside the pores. CP2K 6.1 or 7.1 (issue persists with both), 600/50 Ry cutoff and rel cutoff, PBE-d3 functional with DZVP-MOLOPT basis sets, BFGS optimiser for CELL_OPT,  GTH pseudopotentials. CSVR thermostat with 0.5 fs time step and 1 fs time constant.

Best regards,
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