On Wed, 20 Jun 2007, MUHAMMAD Amin wrote: > 1- Exactly how much periods and crystal stuffing should be introduced > through supercells?
It depends on the strength of confinement, but basically until the localized (defect) modes have decayed so much that the boundaries are irrelevant. The decay is exponential, so you can just keep increasing the supercell size until the frequency stops changing to within your desired accuracy. > 1- If the lowest band is "folded" supercell-y times. How to calculate the > exact bands from these folded bands due to supercells. If you want the unfolded bands, it is easier to use a unit cell. The supercell is mainly only useful for computing the effect of defects. > 2- In the example (define K' (lattice->reciprocal (vector3 0.5 0 0))) ; > edge of Brillouin zone. > (set! k-points (interpolate 4 (list Gamma K'))) > calcuates the bandgaps only in the x- direction why not find the bandgaps > in the irreducable brillouin zone. That is the irreducible Brillouin zone. A line defect has only one direction of (discrete) translational symmetry, and hence it has only a one-dimensional Brillouin zone. > 3- Consider '90 degree rotated triangular lattice'. Can I use the same > basis vectors as 'original triangular lattice'. Sure. A 90-degree rotated lattice is the same lattice under a change of coordinates, so there's no point in even changing your input file at all. Steven _______________________________________________ mpb-discuss mailing list [email protected] http://ab-initio.mit.edu/cgi-bin/mailman/listinfo/mpb-discuss
