The stability of three dopants has been examined for . The room temperature phase is metallic and hence a dense k-mesh is required for the calculations of pure and doped .
Solution energies of tetravalent dopants in metallic
Using k-point parallelism in VASP, Dr Grau-Crespo tested
(18 irreducible k-points) and
(75 irreducible k-points) meshes for pure . The latter calculation was performed over 360 processors in the HECToR Phase2b supercomputer, with a speedup factor of 13 compared to the standard version running on 24 processors (ideal scaling would correspond to a speedup factor of 15).
The calculations of the doped cell were performed on 168 processors, with KPAR=7 groups (of 3 k-points each) running in parallel, on 24 processors each. All geometries were optimised until the forces on the ions were all less than 0.01 eV/Å.
Asimina Maniopoulou 2011-07-09