[CP2K-user] [CP2K:18118] Non-physical pressure behavior for non-local vdW functionals

[Jürg Hutter]

Hi

difficult to say what goes wrong here. No atomic coordinates for further testing available.
But I would suggest to make the following test:
Debug the stress tensor using finite differences and avoid
STRESS_TENSOR DIAGONAL_ANALYTICAL
use
STRESS_TENSOR ANALYTICAL

Use the DEBUG run_type:

RUN_TYPE    DEBUG

with

&DEBUG
   DEBUG_FORCES .FALSE.
   DEBUG_STRESS_TENSOR .TRUE.
   DEBUG_DIPOLE .FALSE.
   DEBUG_POLARIZABILITY .FALSE.
   DE 0.001
   STOP_ON_MISMATCH .FALSE.
   EPS_NO_ERROR_CHECK 5.e-5
&END

regards
JH

________________________________________
From: cp2k at googlegroups.com <cp2k at googlegroups.com> on behalf of Luke Gibson <ldgibson819 at gmail.com>
Sent: Monday, November 28, 2022 4:19 PM
To: cp2k
Subject: [CP2K:18105] Non-physical pressure behavior for non-local vdW functionals

Dear developers and users,

We are looking at the equilibrium density for an AlCl3 molten salt melt by measuring pressure values over 10 ps in NVT at a variety of volumes. We are comparing the pressures for a variety of functionals with various vdW corrections: PBE-D3, optB86b-vdW, optB88-vdW, SCAN-D3, and SCAN-RVV10. The data are shown in the attached plot with the mean pressure (± 1 standard deviation) for each volume (the plot for PBE-D3-smooth can be ignored).

It seems optB86b-vdW, optB88-vdW, and SCAN-RVV10 are reporting unexpected behavior in the stress tensors. Both optB86b and optB88 seem to be the most "wrong" with negative pressures across the board and an unusual increase in the pressure as the system's volume is expanded (all systems have the same number of particles). SCAN-RVV10 at least follows a believable trend and isn't too far off, so it may just not be appropriate for this system.

We are wondering if the stress tensor calculation is properly implemented for these non-local vdW functionals, since both PBE-D3 and SCAN-D3 are producing believable trends.

For reference, I have included the input files for the 3 problematic functionals I mentioned for the volumes corresponding to V_exp in the attached plots. The versions used for each of those runs are listed below:

  *   optB86b-vdW: CP2K-8.2
  *   optB88-vdW: CP2K-6.1
  *   SCAN-RVV10: CP2K-2022.2

Any help or insight is appreciated!

Thank you,

Luke Gibson

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