[CP2K-user] [CP2K:18000] Forces and stress for DCD_aligned_Cell

[Krack Matthias (PSI)]

Hi Abhishek

The .cell, .stress, and .frc files provide the instantaneous cell parameters, stress tensors, and atomic forces for the unaligned cell along a trajectory, respectively. You can retrieve from the DCD_ALIGNED_CELL data the scaled coordinates for each trajectory frame and use these to reconstruct with the cell parameters from .cell file the original atomic coordinates of the unaligned cell which will then match your .frc and .stress file data. Try

  1.  r_scaled = h_aligned^(-1)*r_aligned
  2.  r_unaligned = h_unaligned*r_scaled

h_aligned can be constructed from the DCD data a, b, c, alpha, beta, gamma and
h_unaligned can be retrieved from the .cell file.

HTH

Matthias

From: cp2k at googlegroups.com <cp2k at googlegroups.com> on behalf of Abhishek Sharma <asharma.ms.in at gmail.com>
Date: Tuesday, 8 November 2022 at 14:27
To: cp2k <cp2k at googlegroups.com>
Subject: [CP2K:18000] Forces and stress for DCD_aligned_Cell
Hi All,

I am running ab-initio MD in NPT ensemble for a triclinic system using CP2K. I am printing trajectory in DCD_ALIGNED_CELL format and also printing the forces and stress (for further analysis) in the FORCE_EVAL section and printing CELL details in the MOTION section.

I guess the printed forces and stress are for non-aligned cell and I need to do some mathematical transformation (using cell vectors) to assign these forces and stress to the DCD_ALIGNED _CELL. If so, can you please tell me the easy way to do this transformation for the different components of the stress tensor?

Thanks and regards

Abhishek
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