MMAPS applied in supercell lattice, not only unitcell

Alloy Theoretic Automated Toolkit (ATAT)
1

Dear Axel,
The mmaps code was used to calculate the energy of SQS in alloy. The input file is unit cell and these obtained results are for the unit cell. I want to directly filtrate, calculate the supercell and get the stable supercell. For example, also my reseach work, the supercell (23Ni,16Co,9Fe)-(15Al,Fe)-4C-12Vac, similar to (Ni3Al)16-4C-12Vac, where C and Vac being in octahedral interstitial sites. would be calculated the different energy,causing by the elements occupied in sites at room temperature for the multicomponent alloy. It is similar to the M-NM-:'-carbides in low density steels. So how to select the stable situation being the lowest energy state?

Looking forward to your answer!

Thank you.

2

I’m sorry, the question is not clear.

3

Dear Axel,
I am sorry about my quetion.Now,I will directly explain my workM-cM-^@M-^B
I prepared an alloy using direct solidification, and a large number of ordered nano-precipitates were formed. The chemical formula of precipitates was (23Ni,16Co,9Fe)-(15Al,Fe)-4C-12Vac, similar to (Ni3Al)16-4C-12Vac, where C and Vac being in octahedral interstitial sites. I want to prove by calculation that the ordered nano-precipitates is more stable than the disordered FCC structure with the same composition. However, due to the different occupatied sites of the elements, they will always have different energies. If I want to prove that the energy of the ordered nano-precipitates is lower than that of the disordered FCC phase, I need to screen the ordered nano-precipitates and the disordered phase with the lowest energy,respectively. Then compare the energies of the two. In other words, when the energy of the ordered nano-precipitates is lower than the disordered FCC phase with the same type and number of atoms, the ordered nano-precipitates is more stable than the disordered FCC phase.
So,How to screen the lowest energy structures by ATAT code? and mmaps or mcsqs and mmaps?What is the lattice geometry input files for mmaps and mcsqs on lat.in and rndstr.in, respectively? These is similar to the SQS reference https://doi.org/10.1016/j.intermet.2016.08.002,referred to screening the structure because of the different occupatied sites of the elements.
Thanks you!

4

There is one too many lines defining the cell :

0.5 0 0.5
0 0.5 0.5
0.5 0.5 0
0.5 0.5 0.5
5

I have changed the line defining the cell as to follow , but the next command line ([root@localhost test1]#)did not present. It shows that the calculation is not completed. The situation is absolutely different from the case before.

0.5 0 0.5
0 0.5 0.5
0.5 0.5 0

Showing:
[root@localhost test1]# …/corrdump -l=rndstr.in -ro -noe -nop -clus -2=8 -3=3.2 -4=3.2

#no [root@localhost test1]# present#

Why?
And How does the format of the input file define the lattice structure of the M-NM-: phase, similar to perovskite structure(ABO3)?

6

The error "#no [root@localhost test1]# present#" comes from your shell, not from ATAT, please ask your local sys admin.

7

How does the format of the input file define the lattice structure of the M-NM-: phase, similar to perovskite structure(ABO3)?

8

Read the output of

maps -h

I cannot understand your questions.

9

What determine the relative stability of two phase is their free energy, not just their energy. If you don’t account for configurational entropy (at least) you may incorrectly find a stabilization of the ordered (or partially ordered) phases relative to a a disordered fcc solid solution when the fcc phase is actually stable. At the simplest level you can add x ln(x) terms to the energies of each phase to account for this (taking into account that the precipitate has multiple sublattices).

If the precipitate is partially disordered, you should not be looking for the lowest energy configuration. Rather, you should be using a sqs.

10 
 I think you are absolutely right.  Thank you for your guidance!
 But more things, my prepared alloy contains two phases(M-NM-:'/M-NM-3),which are coherentM-cM-^@M-^BAnd their components are differentM-cM-^@M-^BThat  the above disordered FCC phase is the fictional,aim at showing that this component(Al15Co16Fe10Ni23C4) tend to form ordered phases((23Ni,16Co,9Fe)-(15Al,Fe)-4C-12Vac)) . When I calculated this component using [i]mcsqs[/i], an error occurred. I suspect there is something wrong with [i]rndstr.out[/i]. Could you please help me to see what is wrong with [i]rndstr.out[/i]?

rndstr.out:
7.26 7.26 7.26 90 90 90
0.5 0 0.5
0 0.5 0.5
0.5 0.5 0
0.5 0.5 0.5
0.00000 0.00000 0.00000 Al=0.937500,Fe=0.062500
0.50000 0.00000 0.50000 Ni=0.47916666667,Co=0.33333333333,Fe=0.1875
0.00000 0.50000 0.50000 Ni=0.47916666667,Co=0.33333333333,Fe=0.1875
0.50000 0.50000 0.00000 Ni=0.47916666667,Co=0.33333333333,Fe=0.1875
0.50000 0.50000 0.50000 C=0.250000, Vac=0.750000

Command line and error:
[root@localhost test1]# …/corrdump -l=rndstr.in -ro -noe -nop -clus -2=8 -3=3.2 -4=3.2
[root@localhost test1]# …/mcsqs -n=80
terminate called after throwing an instance of ‘std::bad_alloc’
what(): std::bad_alloc
Aborted (core dumped)