ECIs calculated by mmaps

Alloy Theoretic Automated Toolkit (ATAT)
1

Dear Axel,

I would like to ask a question about ECI calculated by mmaps.
I’m studying about cubic ABO3-y perovskite oxides, where B-sites are occupied by atom B1 and B2 and oxygen-sites occupied by O and Vac.

I confirmed that ‘clusters.out’ file includes the interactions between atoms from the same site (B1-B2 and O-Vac).
However, I don’t understand what interactions between atoms from the different sites are included. (B1-O, B1-Vac, B2-O or B2-Vac?)

Please help me to understand my question.
Thank you very much for your explanation.

Best regards,
Takuya

‘lat.in’
3.962 3.962 3.962 90 90 90
1.0000 0.0000 0.0000
0.0000 1.0000 0.0000
0.0000 0.0000 1.0000
0.0000 0.0000 0.0000 A
0.5000 0.5000 0.5000 B1,B2
0.0000 0.5000 0.5000 O,Vac
0.5000 0.0000 0.5000 O,Vac
0.5000 0.5000 0.0000 O,Vac

2

The ECI do not have the meaning of specific atom-atom interactions, but a linear combination of them.
In a binary, a pair ECI connecting (A,B) and (C,D) has the meaning ECI=(AD+BC-AC-BD)/4
where each letter pair is a "bond energy".
Just set A=O and B=Vac and C=B1 and D=B2 in your case.

3

Dear Axel,

I’m grateful for your speedy response.
I understood the definition of ECI.

I’d like to ask you a question one more.
I want to know only the interaction between B2-Vac for example, is there the method to check it?

Best regards,
Takuya

4

You can’t get an absolute energy - it’s always relative to what could otherwise be there.