[Wien] large deviation of atomic volume in BiNi compound

[pieper]

Since you ask for ideas and without really looking at the problem: 
Assuming that the experimental numbers are correct, is this a room 
temperature structure? The calculations are, of course, ground state 
zero Kelvin, so things might go south if there is a phase transition 
somewhere. Considering the elements you deal with maybe magnetic? What 
are the forces in your calculations?

Good luck,

Martin


---
Dr. Martin Pieper
Karl-Franzens University
Institute of Physics
Universitätsplatz 5
A-8010 Graz
Austria
Tel.: +43-(0)316-380-8564


Am 10.11.2015 10:21, schrieb Tomas Kana:
> Dear Wien2k users,
> 
> I came across a problem with equilibrium atomic volume of
> 
> the BiNi compound. The experimental lattice is hexagonal
> 
> with a = 4.079 Angstroem, c = 5.359 Angstroem
> 
> (P. Villars, Pearson's Handbook: Crystallographic Data for
> Intermetallic Phases)
> 
> However, the equilibrium volume turns out to be more
> 
> than 16 % higher than the experimental one.
> 
> I wonder since the equilibrium volume of
> 
> pure Bi and Bi3Ni comes out with much better agreement with
> 
> experiment (about 4 to 5 % deviation).
> I used GGA (no spin orbit coupling),
> 
> Rmt*Kmax = 8.8, lmax = 10, Gmax = 16, 5000 k-points in the
> 
> whole Brillouin zone. I enclosethe structure file in attachment.
> 
> I tried LDA that gives better agreement with experiment
> 
> (about 10 % deviation) but I think this is still too much. I have
> tried
> 
> to use gaussian smearing instead of the tetrahedron method,
> increase Rmt*Kmax to 11, increase k-points to 20 000 in the whole
> Brillouin zone but nothing helped.
> In the mailing list I found someone had similar problem with a more
> complicated structure containing bismuth, but that was not solved:
> http://www.mail-archive.com/wien%40zeus.theochem.tuwien.ac.at/msg10479.html
> Do you have any idea?
> Thank you in advance
> With best regards
> Tomas Kana
> Institute of Physics of Materials,
> Academy of Sciences of the Czech Republic
> Brno, Czech Republic
> 
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