On Mon, 27 Nov 2006, paolo bettotti wrote:
I am trying to simulate a PC asymmetric slab. I've used the run-yeven/yodd run
function but if I ask the program to print mode parity, in order to recover the
quasi-TE/TM like modes, I've got the following error after the first k-point
calculation, while the program is trying to find out parity of the last band:
"Finished solving for bands 2 to 10 after 107 iterations.
yevenfreqs:, 1, 0, 0, 0, 0, 0, 0.110314, 0.120346, 0.223496, 0.239816, 0.339623,
0.357412, 0.458293, 0.476587, 0.53817
elapsed time for k point: 5 minutes, 52 seconds.
yevenzparity:, 1, -1.0, 0.817931093575246, -0.804035178956196, 0.416573429618825
, -0.280294019299509, -0.0453411909561938, 0.186153766371718, -0.213838267739919
, -0.112659261038628, -0.979660245893559
CHECK failure on line 512
of ../../../mpb-ctl/mpb.c: k vector is incompatible wi
th specified parity
solve_kpoint (0,0.0454545,0):"
Why is not possible to calculate that parity (and how to solve the
problem to find the quasi-TE/TM modes for an asymmetric slab)?
First, you can calculate any parity you want. What MPB is complaining
about is that you are telling it to run-yeven but your k-point breaks the
y=0 symmetry (really, the symmetry in the direction of the 2nd lattice
vector).
The deeper problem is that you can't really use run-yeven/run-yodd with a
non-orthogonal computational cell. Or at least, it won't really do what
you want. You should just do "(run)".
It only really makes sense to use the yeven/yodd if you want to do a
line-defect calculation. In that case, you could rearrange your
computational cell into a rectangular one by making your (super)cell
something like:
o o o o o o o o o o o
o o o o x o o o o o
o o o o o o o o o o o
where I've put an "x" to indicate where your defect(s) would go.
You don't want to use such a rectangular cell when you are computing
the band diagram of the slab with no defect, because there you want to
use the primitive cell to prevent band-folding. However, for the band
structure you need k-points in all directions so you are not going to
have any particular mirror symmetry anyway.
Steven
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