[Wien] change of lattice parameters while alloying

[pieper]

Accept the suggested structure. I always restart with initailization the 
new structure from nn.

If you replace one of the atoms occupying a position with multiplicity 
.gt. 1 (with more than one position line in struct) you break the 
symmetries inducing that multiplicity. You may well wind up with a 
larger primitive unit cell volume. That will change the basis vectors 
a,b,c.

Note that depending on what you want to compare in your series of 
calculations it probably is a good idea to do all calculations in the 
same space group - even if you are left with very low symmetry. Do this 
by giving all Cr in the pristine cell you want to substitute a differnet 
index (Cr1, Cr2 ...).

And remember that you do not calculate an (random) alloy, you calculate 
a periodic structure. Watch out for superstructure effects, perhaps by 
checking larger supercells with the same Br-concentration but different 
configuration.

Martin Pieper


Am 09.05.2017 01:55, schrieb Dr. K. C. Bhamu:
> Dear Wien2k Users
> 
> I am alloying a quaternery compound: replacing Cr with Br one by one.
> What I see is, the pristine compound is cubic with 225 SG. When I
> replace Cl by Br one by one then lattice parameters deviates from
> cubic to different structure.
> like a=b, c or a,b,c. SG also changes.
> During initialisation I accepted the new structure suggested by the
> w2web. Should I accept the suggested structure?
> As per my understanding from previous posts from mailing list we
> should accept the suggested structure which is with lower symmetry.
> 
> Is the change of lattice parameters is normal behaviour of material or
> I am doing any mistake?
> 
> Sincerely
> 
> Bhamu
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---
Dr. Martin Pieper
Karl-Franzens University
Institute of Physics
Universitätsplatz 5
A-8010 Graz
Austria
Tel.: +43-(0)316-380-8564