Thank you very much for very accurate advices. * **Alexander Vozny wrote: also hope you have 2 pseudoH per As*
Do you think that I should also optimize the position of Hydroden atoms or I shoudn't care about it? * Secondly, what surface reconstruction do you use?* I don't use any reconstruction, I just optimize atoms on the surface. Optimazed surface is for me equal to reconstructed surface, am I right? Is it possible to get reconstcruced surface after optimization or it depends of the recontruction - I mean if reconstruction is far away from starting geometry is it possible not to get proper results. *600Ry is way too much! This is the main reason of your slow calculation. 300Ry should be enough.* But I checked that for bulk calculation, cell containing 64 GaAs atoms, Meshcutoff= 500 Ry is efficient to get accurate calculations. Cheers, Magdalena, 2010/7/23 Alexander Vozny <[email protected]> > I would add: > > 1. H should be 0.75 if you passivate As (and 1.25 if you passivate Ga) > otherwise you lack several electrons and this will contribute to surface > states. > (I also hope you have 2 pseudoH per As) > > 2. Secondly, what surface reconstruction do you use? > Most likely you will have a lot of surface states (maybe even a metallic > surface) because of Mn (and depending on surface reconstruction), so that > your results would be very sensitive to the k-point sampling (despite it is > a huge unit cell, you may need a 25A k-grid cutoff rather than 12A that you > use) and thus a very slow SCF convergence. > So yes, using a 1300K electronic temperature was a right choice. > > 3. 10 lattice constants in z-direction is way too much (which means > (10-3.25)*5.76A=39A of vacuum) - this is not a problem for strictly > localized orbitals, but for the grid it is still a considerable effort. > ~15A of vacuum should be typically enough, especially if you turn on the > SlabDipoleCorrection > > 4. 600Ry is way too much! This is the main reason of your slow calculation. > 300Ry should be enough. > If you really want a better grid try using GridCellSampling (even the > shortest example from the manual would work fine) > > Alex. >
