Comparison to WIEN2k; symmetry and spin-orbit coupling

Posted on : May 25, 2017 (Thu) 14:46:30

by 池田敦俊

Dear AkaiKKR users,

I calculated the band structure of Sr3SnO with AkaiKKR and also WIEN2k.
(Crystalline structure of Sr3SnO: http://aflowlib.org/material.php?id=aflow:2a7df972faaf8aaa)
I think that there are two important differences between the results of the two programs.
(I'm not sure which result is closer to the experiments.)

1. At the Gamma point in the Brillouin zone, there should be some four-fold degeneracies protected by the crystalline symmetry.
WIEN2k produces those degeneracies, but AkaiKKR breaks some of them.
Is this because AkaiKKR takes into account only of the Bravais lattice but not of the space group?
Maybe there is a mistake in my input which breaks the symmetry.
The input is attached in the end of this post.

2. The band splitting due to the spin-orbit coupling of Sn seems very smaller in AkaiKKR than in WIEN2k.
Because of this, Sr3SnO by AkaiKKR is metallic while Sr3SnO by WIEN2k is a zero-gapped semiconductor.
Is there any way to tune the strength of the spin-orbit coupling?

If this text-based question is difficult to understand, I'm happy to send the graphs by e-mail or to visit you for discussion.

Sincerely,
Ikeda

This is my input:
c----------------------------Sr3SnO--------------------------
go SrVc3SnO/Sr3SnO
c------------------------------------------------------------
c brvtyp a c/a b/a alpha beta gamma
sc 9.7113 , , , , , ,
c------------------------------------------------------------
c edelt ewidth reltyp sdftyp magtyp record
0.001 2.1 srals pbe nmag 2nd
c------------------------------------------------------------
c outtyp bzqlty maxitr pmix
update 8 500 0.03
c------------------------------------------------------------
c ntyp
3
c------------------------------------------------------------
c type ncmp rmt field mxl anclr conc
Sr 1 1 0.0 2 38 100
Sn 1 1 0.0 3 50 100
O 1 1 0.0 2 8 100
c------------------------------------------------------------
c natm
5
c------------------------------------------------------------
c atmicx atmtyp
0 0 0 Sn
0 0.5 0.5 Sr
0.5 0 0.5 Sr
0.5 0.5 0 Sr
0.5 0.5 0.5 O
c------------------------------------------------------------
end

# Number of k-points used along symmetry line
350
# For sc, dispersion along G-X-M-G-R-X is calculated.
0 0 0
0.5 0 0
0.5 0.5 0
0 0 0
0.5 0.5 0.5
0.5 0 0