[QE-users] [SPAM] CONVERSION OF CELL_PARAMETERS (Angstrom) to alat(Bohr) or celldm & cell2ibrav.x

SK ksandinah at st.ug.edu.gh
Sat Aug 20 01:47:10 CEST 2022


Hello All,
I am a bit new to QE and DFT and need some assistance.
I know for unit cell coordinates, we either use:
1. ibrav=0 and then specify cell_parameters OR
2. ibrav>0 and then specify either celldm(1-6) or COSAB etc.
My input file currently has ibrav=0 and cell_paramters specified. At the 
start of vc-relax output, a celldm is generated but I believe it is 
unrelaxed.
After relaxation, I wish to proceed with scf, nscf, bands calculations 
using ibrav>0 (as recommended) and specify celldm in subsequent input 
files.
My problem is after relaxation, final relaxed coordinates in output file 
are presented in cell_parameters (angstrom) and not celldm as I wish to 
use in subsequent input files. So I am not sure which relaxed 
coordinates to transport to new scf.in file.
Also about using cell2ibrav.x to convert my "cell_parameters (angstrom)" 
to "ibrav and appropriate celldm"; I am a little unsure what to input 
when it gets to this stage:
Enter alat (or 'x' to skip if axis are in bohr): Because I now seek alat 
and my cell_parameters where in Angstrom.
Kindly assist me clarify how to go about both methods.

Kenneth Sandinah
MPhil Physics Student
University of Ghana


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