[Pw_forum] Problem with visualization of pw.x output using XCrysden

Tone Kokalj tone.kokalj at ijs.si
Tue Nov 17 14:35:51 CET 2015

On Tue, 2015-11-17 at 14:19 +0100, liyincumt at gmail.com wrote:
> Dear QE community,
> I encountered a strange problem with visualization of pw.x output 
> using 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.
There can be two reasons: if they are marginally different the reason
may be due to, say, round-off errors.

But if they differ considerably the reason is different: in xcrysden
the "alat" always refers to the length of the first Bravais lattice
vector, whereas in pw.x the "alat" is the size of celldm(1) (or A).
Hence, if you set the celldm(1) (or A) to a value different then the
size of the first Bravais lattice vector in the input, then xcrysden's
alat and pw.x alat coordinates will be different.

What is the case in your situation I cannot say, unless you provide the
pertinent output file.

Regards, Tone

Anton Kokalj
J. Stefan Institute, Jamova 39, 1000 Ljubljana, Slovenia 
(tel: +386-1-477-3523 // fax:+386-1-477-3822)

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See:  http://www.gnu.org/philosophy/no-word-attachments.html

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