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

[Layla Martin-Samos]

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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