[QE-users] on VCA for use in d3q calculation

[Lorenzo Paulatto]

Hello Kenneth,
a very important factor in the thermal conductivity of such a compound would be the mass disorder of the B and C phase. This effect is not included in the simple calculation that you are doing.
The simple possible way to tackle this problem, and one that is actually implemented in the d3q codes, is to consider B and C as if they where two different isotopes.

In the input.TK file you set
isotopic_disorder = .true.

and then after the namelist you specify the "isotopes" by hand:
ISOTOPES
A natural
B isotopes 2
mass_of_B (1-x)
mass_of_C x

For example, let's say your material is GaAs_(0.9)Sb_(0.1)
ISOTOPES
Ga natural
As isotopes 2
74.922 0.9
121.76 0.1
Masses are in Dalton units (mass of C^12 = 12)

--
Lorenzo Paulatto - Paris
On Mar 8 2022, at 5:49 pm, kenneth senados <kenneth.senados at ustp.edu.ph> wrote:
> Dear qe and d3q experts,
>
> I have a clarification with the d3q for thermal conductivity.
>
> Supposed I have a system i.e., A2B1-xCx where A,B and C are atoms of a material and I did a VCA for this atom for x=0.2.
>
> I then do a pw.x, then a ph.x then a d3q.x calculation to get the thermal k. Is it correct that the calculated k is for the A2B0.8C0.2?
>
> What about if I include the isotope scattering? Do I specify also below
>
> B isotopes 2
> Mass(B) 0.8
> Mass(C) 0.2
>
> or is the input above not necessary?
>
> Thanks,
>
> Ken
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