[Pw_forum] need help on calculation...

Axel Kohlmeyer akohlmey at gmail.com
Fri Feb 3 14:37:11 CET 2012

On Thu, Feb 2, 2012 at 11:03 PM, Nguyen Doan Sau <ndzsau at yahoo.co.uk> wrote:
> Dear Q.E users,
> I am currently carrying a structural relaxation of the crystal structure of
> a new oxide compound. There are two new oxides: one I solved its crystal
> structure by single crystal X-ray diffraction data and the other is
> iso-structural to the first. As I have not been successful in obtaining the
> crystals of the later, I have to use the powder X-ray diffraction data for
> solving its crystal structure. I got its unit cell parameter by peak
> indexing, using the atomic coordinations of the crystal structure of the
> first as its initial atomic coordinations for refinement.
> Okay, I can do the refinement. It went well for the heavy metal atoms but
> not for light metal atoms like Li and anion like O (you may suggest using
> neutron diffraction for these light atoms. Actually, I talked to my boss
> about it but we are unable to have it done before next year. :) Therefore, I
> think of another solution: first, obtaining the atomic coordination of the
> heavy metal atoms by the refinement; second, structural relax of the lighter
> atom (Lithium, oxygen) to obtain their reasonable atomic coordination and
> bonds to the heavier atoms.
>  So far, everything have been going well except for that the relaxation is
> time-consuming as the relax involved 204 atoms in the unit cells of volume
> of 2750 Ang^3. I use a desktop equipped with  Xeon 2.66 GHz and 8 GB RAM.
> The time needed for an average iteration is 1 week. I guess it may take me
> more than 3 months to have it done properly or just nothing. :)
> Therefore, I would ask for a favor. Is there any way for me to submit my
> calculation to a strong computing facility. I would have it done in less
> than 2 weeks. I could not give my input here publicly but I can send input
> file personally to who kindly want to help.

computer time costs money and is always scarce.

as a member of the US research community, however,
you can apply for access to an NSF funded supercomputer
via XSEDE http://xsede.org/

to expedite the process, please have your adviser contact
your local XSEDE campus champion, who already has
some discretionary computer time for purposes of getting
researchers on XSEDE machines. check out:



> Thanks,
> Sau Nguyen
> Department of Chemistry
> University of Houston
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Dr. Axel Kohlmeyer
akohlmey at gmail.com  http://goo.gl/1wk0

College of Science and Technology
Temple University, Philadelphia PA, USA.

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