[Pw_forum] need help on calculation...

Nguyen Doan Sau ndzsau at yahoo.co.uk
Fri Feb 3 05:03:09 CET 2012

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.
Thanks,Sau NguyenDepartment of ChemistryUniversity of Houston 

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