[Pw_forum] calculating the cell parameters in crystals

[O. Baris Malcioglu]

Dear Elie,

In case you are interested in isolated systems, not crystals, and if you are
trying to visually choose a cell that has the minimum volume with adequate
vacuum, apart from XCRYSDEN + playing with pwscf input solution you can also
use the free (but not open source) editor  DSVIEWER by Accelrys.

http://accelrys.com/products/discovery-studio/visualization-download.php

I use it to draw initial structures, to play with the periodic cell, and
align coordinates with respect to the cell. The program does not have any
means to export PWSCF input. I export the structure in XYZ format, which is
a text file that can be directly used in PWSCF in "angstrom" coordinate mode
when first two lines are removed, and I edit the cell dimensions using the
values I depicted by hand.

By the way, I would be glad if someone can point me an open source
alternative which has extensive editing/monitoring capabilites for isolated
systems like this one, and stable at the same time.

Best,
Baris



2010/3/10 mohnish pandey <mohnish.iitk at gmail.com>

> Dear Elie,
>                I you have to give the celldm's initially. You can get the
> experimental value from literatures and use that as initial value. Then you
> can do "vc-relax" calculation to get equilibrium values of cell parameters
> computationally. Of course it will be different from experimental value. GGA
> calculation overestimates the value while LDA calculation underestimates the
> lattice parameter.
> Regards,
> MOHNISH
>
> On Wed, Mar 10, 2010 at 1:20 AM, Elie Moujaes <elie.moujaes at hotmail.co.uk>wrote:
>
>>  Is there a way (maybe a free software or program) to get celldim (i)
>> (i=1,...6) before giving it as an input in the calculations?
>>
>>
>> Regards
>>
>> Elie Moujaes
>> University of Nottingham
>> NG7 2RD
>> UK
>>
>>
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>
>
> --
> Mohnish Pandey
> Y6927262,4th Year dual degree student,
> Department of Chemical Engineering,
> IIT KANPUR
> 09235721300
>
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