[Wien] Concerns on the obtained values of momentum matrix elements

[Yong Woo Kim]

Dear Wien2k users,

Hello, I am running wien version 14.2 on linux compiled with gfortran.

Right now I am trying to calculate the momentum matrix elements of
Al2O3 sapphire.
I have managed to get some results but some part of the results worry
me that I may have done it wrong.
I am particularly interested in the matrix elements between the
highest valence and the lowest conduction band.

The following is part of the results that I have obtained along the
Gamma-A direction that I want to obtain the results for.

36	37	-0.475170000000000	2.31369000000000e-11	0.464830760000000
36	37	-0.475054000000000	2.33653000000000e-11	0.464900790000000
36	37	-0.474937000000000	2.35933000000000e-11	0.464971500000000
36	37	0.474819000000000	-2.38216000000000e-11	0.465042880000000
36	37	0.474699000000000	-2.40493000000000e-11	0.465114930000000
36	37	0.474579000000000	-2.42775000000000e-11	0.465187660000000
36	37	-0.474457000000000	2.45054000000000e-11	0.465261060000000
36	37	0.474334000000000	-2.47330000000000e-11	0.465335140000000
36	37	-0.474210000000000	2.49604000000000e-11	0.465409880000000
36	37	0.474085000000000	-2.51880000000000e-11	0.465485300000000
36	37	0.473959000000000	-2.54153000000000e-11	0.465561390000000
36	37	0.473832000000000	-2.56427000000000e-11	0.465638150000000
36	37	-0.473704000000000	2.58700000000000e-11	0.465715590000000
36	37	-7.66604000000000e-13	-8.84059000000000e-18	0.465756180000000
36	37	1.32939000000000e-11	-3.78270000000000e-19	0.465793770000000
36	37	-6.20312000000000e-13	-1.29951000000000e-17	0.465831680000000
36	37	-6.78245000000000e-12	-2.77438000000000e-17	0.465869910000000
36	37	1.13307000000000e-11	-2.48713000000000e-17	0.465908460000000
36	37	-2.17293000000000e-12	5.12272000000000e-17	0.465947330000000
36	37	7.86763000000000e-12	-1.91488000000000e-17	0.465986520000000

36 and 37 are the band index for my valence and conduction band. Each
row refers to a k point along the G-A path and I have 501 rows in
total.

I also eliminated the x,y components and leaved only the z component
plus the energy difference.

One minor concern is that the signs of the values change and this
doesn't seem to be right.

Another concern is that as can be seen from the real part of z above,
the value suddenly drops to less than 1e-10 order.

Although not shown here, at the same k point, the real part of the x
component showed the opposite behaviour,

increasing from less that 1e-10 to about 0.4. This abrupt change
doesn't seem to be right either.

The procedure went like this.

run_lapw

create case.klist_band

x lapw2 -fermi

x lapw1 -band

x optic

I have tried this for different k mesh by using x kgen and run_lapw
repeatedly from 1000 to 15000 and the results only had minor
differences.

Any help would be really appreciated.

Thank you very much in advance.

Yong Woo Kim
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