[Wien] band structure dependence on symmetry and complex calculation

[venkatesh chandragiri]

Dear wein2k users,

I have calculated the band structure of the Fe2VAl lattice (fm3m, 225) for
the two cases.

*case one* : using the space group (225) defined structure with three atoms.

*case two* : by seeing the structure of Fe2VAl in xcrysden, i have
generated the case.struct file with 16 atomic unit cell (8-Fe, 4-V, 4-Al)
with a 16 number of co-ordinates such that the structure looks same as in *case
one*. But, in this structure file, i have used space group as a primitive
(1).

Using the Powder cell software, i also checked the XRD of the structures
from the both cases and similar diffraction pattern were found. I run the
volume optimization and min positions before running the spin polarized SCF
calculation. However, In the First case (space group structure), we run the
calculation without complex (no inversion). But, in the second case
(primitive), we did the calculations with keeping complex ON.

Now, i done the spaghetti plots for these two structures. For the space
group case, we have observed indirect band picture between gamma and X
k-points (X point will always followed by gamma). This nature is already
reported in the literature also. But, for the second case with primitive
structure, i have found the direct band like picture in which both band are
touching at the gamma point.

In preparing the case.klist and case.klist_band, i have used similar
k-point co-ordinates for the both cases.

Why the bands above the Fermi level would not shift to x point in the
primitive case. Is there any effect of removing the symmetry on the band
structure even though we did calculations on the similar structure...?

or else in the first case, calculations did with complex OFF while in the
second case with complex ON. Is this difference will change the band
structure nature...?

I could not attach the obtained figures, because i sent same mail with
figures in few days before but it is not published in wien2k mailing list
due to limitations in the mail content size.

thanks in advance and waiting for your replies.

regards,

Ch. Venkatesh,
C/o. Prof. V. Srinivas & Dr. S. K. Srivastava
Department of Physics & Meteorology,
IIT Kharagpur.
ph: +91-3222-283848 (Lab)
      +919445909693
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