[Q-e-developers] Proposed code additions for 2D systems

[Richard Andrew]

Dear Layla Martin-Samos,

Thank you for cleaning up my code to meet the developers requirements.  I have checked the code and only noticed a small typo in my affiliation in the comments for the impose_deviatoric_strain2d and impose_deviatoric_stress2d subroutines in derviatoric.f90: it should be 'of' instead of 'if'.  As requested by Professor Gironcoli, I have attached an example directory (2D_example) with a small script to demonstrate the use of the new cell_dofree options.

Regards,

Richard Charles Andrew

Postgraduate Student
Physics Department
University of Pretoria
South Africa
>>> Layla Martin-Samos  09/06/12 2:42 PM >>>
Dear Andrew, your contribution has been included in the espresso repository. Could you please check that the results are consistent with your tests? I had to make small changes in order to fit the programming requirements for flib (no USE statements that involve calculation parameters. This is to avoid cross dependencies).

for downloading the repository follow the instruction at http://www.qe-forge.org/gf/project/q-e/scmsvn/?action=AccessInfo

cheers

Layla

2012/8/31 Richard Andrew <Richard.Andrew at up.ac.za>
Dear QE team,

You requested we send any code additions we may have.   I work in 2D systems and I noticed most DFT codes have no way for you to relax the 2D cell shape while keeping the area constant.  The cell_dofree='shape' option in QE relaxes all degrees of freedom for the cell shape at constant volume which for 2D systems means also changing the vacuum layer.  I have modified the cell_base.f90 module to include a cell_dofree='2Dshape' option which will relax the in-plane (xy plane) cell shape while keeping the area (therefore the vacuum layer) constant.  This also required a change in the deviatoric.f90 code in the flib.  Please find attached these modified files for your consideration.  All modifications are marked between '! RICHARD' comment lines.

I also included in cell_base.f90 a cell_dofree='2Dxy' option where the xy  plane is truly free as you had suggested in your code comment for cell_dofree='xy'.

Regards,

Richard Charles Andrew

Postgraduate Student
Physics Department
University of Pretoria
South Africa



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