[QE-users] [SPAM] A problem about cell_dofree='ibrav'

[Tianhua Wang]

Dear Quantum ESPRESSO developers,
  I am doing the cell optimization for cassiterite (SnO2) using the variable cell shape molecular dynamics (i.e., cell_dynamics='damp-w') in QE 7.0. I had set ibrav=6 for the crystal of cassiterite, and wanted to constrain cell_dofree='ibrav+shape' during the optimization. However, I found the none-zero values of v1_y&z, v2_x&z, v3_x&y in the output file, e.g.,


CELL_PARAMETERS (alat=  8.95238858)
   0.999715701   0.000000089  -0.000000001
   0.000000089   0.999715701  -0.000000001
  -0.000000001  -0.000000001   0.672987836



which was not absolutely consistent with the initial ibrav choice (i.e., ibrav=6). Then I tested the performance of cell_dofree='ibrav', and found the same phenomenon. It seems that the cell_dofree command does not strictly constrain the initial ibrav choice. I also tested cell_dofree='xyz+shape' although I had guessed that it did not work.
  I am wondering if there is any way to strictly achieve cell_dofree='ibrav+shape' (which is equal to cell_dofree='xyz+shape' in this case) during the cell optimization. Perhaps another solution is to fix the angles during the cell optimization, but how to achieve? My input file is attached for reference.
  Thank you for your time and I am looking forward to your reply.
Sincerely,
Tianhua Wang




Tianhua Wang
State Key Laboratory for Mineral Deposits Research
School of Earth Sciences and Engineering
Nanjing University
163 Xianlin Avenue, Nanjing
Jiangsu 210023, China
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.quantum-espresso.org/pipermail/users/attachments/20220308/7aa1110a/attachment.html>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: SnO2.in
Type: application/octet-stream
Size: 945 bytes
Desc: not available
URL: <http://lists.quantum-espresso.org/pipermail/users/attachments/20220308/7aa1110a/attachment.obj>