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Noureddine Selmi

Hello, how we define the different zones (intergranular zone, bulk zone, zone between this two)

Please, I would like an answer to my question and sorry for this long letter:
Well, I construct a supercell of 60 atom of Zr contains two grains oriented with an angle theta, and formed symmetrical grain boundary.
To calculate the segregation energy of tin (Sn) in the grain boundary, please, if I’m true in what i will do:
1- I do the relaxation of the supercell of 60 atoms of Zr to search on new positions (x,y,z) of the equilibrium state.
2-I replace a Zr atom located in the grain boundary by the Sn atom, and I do the calculation of the energy after relaxation (E1).
3- I replace an atom of Zr in the site located far to grain boundary (in bulk) by another atom of Sn, and I calculate the energy after relaxation (E2).
4- The energy of segregation is the difference: Eseg = E1 - E2.
5- If Eseg < 0, segregation is favored, if Eseg > 0: segregation is disadvantaged.
There is another approach:
1- I define the different zones (intergranular, bulk, and the zone between these two zones),  but how?
By calculations of sites energies of all atoms, then we do a comparison between the energy of each atom site, i.e.  If there are atoms have very similar site energy (Delta << meV) we can say ZONE 1 , ZONE2, ZONE3.
Segregation energy is the difference between the site energy of the intergranular zone and site energy in the bulk zone, but the question is how I will define this different zones, i.e. how I calculate the site energies by the ABINIT (first principle ab initio) because ABINIT gives the total energy of the system not sites energies !!!? Thank you and Best regards.

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    Benjamin P Haley

    Your first approach seems reasonable.  You may want to average over several different bulk positions (step 3).  I don't know if the second approach can work, since, as you noted, ABINIT will give you the total system energy.  I don't know that ABINIT can calculate isolated site energies.

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