[Wien] band structure dependence on symmetry and complex calculation

[Rocquefelte]

I have the feeling that your problem is related to the Bravais lattice 
which is F-centered and Primitive in the first and second cases.
It is not related to the way the calculation is done (complex or not). 
Indeed, when you are using the space group Foum-3m, WIEN2k is doing the 
calculation in the related primitive cell which is 4-times smaller than 
the F-centered one.
In constrast when you are doing the calculation with the initial 
structure but keeping the P1 symmetry, WIEN2k do the calculation for the 
full-cell. Thus in the reciprocal space the directions will be different 
and thus the path.

On the other hand, could you provide the 2 structures to check that you 
didn't forget atoms in the case of the P1 symmetry calculation.

Best Regards

Xavier



Le 6/28/2013 7:18 PM, venkatesh chandragiri a écrit :
>
> 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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