jry20 at cam.ac.uk
Sat Sep 20 15:03:03 CEST 2008
On Fri, 19 Sep 2008, fatemeh.mirjani wrote:
> if the spread becomes negative what does it mean?
> I found some mistakes in my code so I edited it . but I haven't succeed to get correct WFs yet.
> the flactuations in the bandstructure decreased but it is still wrong !
> the spread becomes negative:
> Final State
> WF centre and spread 1 ( -1.171555, 0.170504, -0.083959 ) -380.61012680
> WF centre and spread 2 ( 1.200799, -1.606712, -0.120351 ) -20.08399486
> WF centre and spread 3 ( 0.126184, 0.772680, 2.072708 ) -384.87801891
> WF centre and spread 4 ( 0.879826, 1.219855, -0.570418 ) -26.25860467
> Sum of centres and spreads ( 1.035253, 0.556326, 1.297980 ) -811.83074525
> Spreads (Bohr^2) Omega I = -1298.918567808
> ================ Omega D = 213.863027239
> Omega OD = 273.224795323
> Final Spread (Bohr^2) Omega Total = -811.830745246
> I know the omega & omega I & D should be positive. In this calculation
> only omega I is negative (Also the amoun of other omega aren't
> reasonable). With regard to the fact that omega I is invarient does it
> mean the projection is wrong?
For an isolated group of bands Omega_I is determined only from the data
contained in the *.mmn file - so you can ignore the projections and focus
on getting the Mmn matrix computed correctly.
A simpler test case, which I've found useful in the past, is to consider
just the lower valence band of GaAs. This gives an s-like WF centred on
the As atom (see Table III of MV for representative values of the spread)
Dr Jonathan Yates | Theory of Condensed Matter Group
Corpus Christi College | Cavendish Laboratory
Cambridge, CB2 1RH, UK | Cambridge, CB3 OHE, UK
email jry20 at cam.ac.uk | Tel +44 (0)1223 337461
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