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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