[xcrysden] Why is the final coordinates of pwscf output shown in Xcrysden in unit of alat different from the values shown in the pwscf output?

[liyincumt at gmail.com]

Dear Xcrysden community,

I encountered a strange problem with Xcrysden. I was visualizing  the final structure after geometry optimization using Xcrysden. When the coordinates of atoms shown in Xcrysden in the unit of crystal, they are same with those in pw.x output. But after I switched the unit from crystal to alat, I found those values are a little different from what were written in pw.x output file. I first thought it may be caused by different calculation equations they used.  But when I was visualizing the initial structure, the coordinates show in the unit of alat in pw.x output is completely same as the those in Xcrysden.

I recognized a sentence at the end of pw.x output file before the scf calculation of the relaxed structure, "The G-vectors are recalculated for the final unit cell. Results may differ from those at the preceding step". I am not clear what these words mean here. Perhaps the parameters of unit cell is changed in the last scf calculation resulting the discrepancy between pw.x and Xcrysden? 

Thanks a lot for your kind help!

Best Regards,
Yin


Dr. Yin Li 
Department of Biophysics,Medical School, University of Pecs,
No.12 Szigeti Street, Pecs, H-7624, HUNGARY
Phone: +36-72-535271/36271
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