[Pw_forum] Question about Cell Parameter

[Ari P Seitsonen]

Dear Paolo et co,

   Indeed that appears to be the problem (based on private mails with 
Leong), with the newest version of XCrysDen on Ubuntu 1.5.53; I just 
misunderstood Leong's initial mail, I thought the error appeared when 
visualising the _output_ file - there have been these issues already 
earlier, I have not tried if the newer versions of XCrysDen understands 
the syntax like "1/3" (instead of "0.333333333333") in the coordinate 
section, for example. "If in doubt, use the output, as that is the 
ultimate result anyway"?

     Greetings and thank you Paolo for the confirmation, :)

        apsi

-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-
   Ari Paavo Seitsonen / Ari.P.Seitsonen at iki.fi / http://www.iki.fi/~apsi/
   Ecole Normale Supérieure (ENS), Département de Chimie, Paris
   Mobile (F) : +33 789 37 24 25    (CH) : +41 79 71 90 935


On Sat, 27 Jun 2015, Paolo Giannozzi wrote:

> My hypothesis: option "angstrom" to CELL_PARAMETER is relatively recent.
> Older versions of xcrysden might not know about it
> 
> Paolo
> 
> On Sat, Jun 27, 2015 at 2:34 PM, Ari P Seitsonen <Ari.P.Seitsonen at iki.fi>
> wrote:
>
>       Dear Leong,
>
>         If I am not horribly wrong, indeed 15/20/35 Ångströms are
>       indeed used; the values in the output of pw.x are just always in
>       units of Bohr radii. Would this explain your observation?
>
>         Another option would be to define
>
>           ibrav = 8
>               a = 15
>               b = 20
>               c = 25
>
>       as the values of 'a', 'b' and 'c' are always in Ångströms. I
>       tried with QE 5.1.2 and no matter which input I used, indeed the
>       values are taken and used as Å. What do you mean with "all the
>       value that I defined...", where do you see Bohr in XCrysDen?
>
>         Hopefully this clarified something. :)
>
>           Greetings from Sunny Montrouge,
>
>              apsi
> 
> -=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*
>       =-
>         Ari Paavo Seitsonen / Ari.P.Seitsonen at iki.fi /
>       http://www.iki.fi/~apsi/
>         Ecole Normale Supérieure (ENS), Département de Chimie, Paris
>         Mobile (F) : +33 789 37 24 25    (CH) : +41 79 71 90 935
> 
>
>       On Sat, 27 Jun 2015, Leong Jun Xing wrote:
>
>             Dear all
>
>             I am currently dealing with molecule in relax
>             calculations. I choose ibrav =
>             0 and define the cell parameters by myself. Is that
>             impossible to define the
>             cell parameter in angstrom? I try to define my cell
>             parameter as below:
>             CELL_PARAMETERS angstrom
>               15.000   0.000   0.000
>                0.000  20.000   0.000
>                0.000   0.000  25.000
>             However, all the value that I defined is shown in
>             bohr in xcrysden. Wish to
>             receive your reply soon.
> 
>
>             Thank you
> 
>
>             Regards
>             Leong
> 
> 
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> 
> 
> --
> Paolo Giannozzi, Dept. Chemistry&Physics&Environment,
> Univ. Udine, via delle Scienze 208, 33100 Udine, Italy
> Phone +39-0432-558216, fax +39-0432-558222
> 
>