<html><head><meta http-equiv=Content-Type content="text/html; charset=utf-8"><META name="Author" content="Novell GroupWise WebAccess"></head><body style='font-family: Tahoma, sans-serif; font-size: 13px; '>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8"><meta name="Author" content="Novell GroupWise WebAccess"><meta http-equiv="Content-Type" content="text/html; charset=utf-8"><meta name="Author" content="Novell GroupWise WebAccess">Dear QE team,<br><br>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.<br><br>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'.<br><br>Regards,<br><br>Richard Charles Andrew<br><br/><div style='clear: both;'>Postgraduate Student<br>Physics Department<br>University of Pretoria<br>South Africa</div><br/></body></html>