# Changing orientation of SQS structure generated from ATAT

I generated the following SQS cell using ATAT (the sructure is converted to POSCAR format)

POSCAR
3.5169
1.000000 -1.000000 0.000000
-2.000000 -1.500000 0.500000
-0.500000 0.000000 -3.500000
A  B
45   5
Cartesian
-2    -1.5    -0.5
-1.5    -2  -0.5
-1.5    -1.5    0
-1  -2  0
-1.5    -2  -1.5
-1.5    -1.5    -1
-1  -2  -1
-1  -1.5    -0.5
-1  -1  0
-0.5    -2  -0.5
-0.5    -1.5    0
-1.5    -2  -2.5
-1.5    -1.5    -2
-1.5    -1  -1.5
-1  -2  -2
-1  -1.5    -1.5
-1  -1  -1
-0.5    -1.5    -1
-0.5    -1  -0.5
0   -1.5    -0.5
0   -1  0
-1.5    -1.5    -3
-1  -1.5    -2.5
-1  -1  -2
-0.5    -1.5    -2
-0.5    -1  -1.5
-0.5    -0.5    -1
0   -1.5    -1.5
0   -1  -1
0   -0.5    -0.5
-1.5    -2.5    -3
0.5 -1  -0.5
-2  -2  -3
-1  -1  -3
-1  -0.5    -2.5
-0.5    -1.5    -3
-0.5    -1  -2.5
-0.5    -0.5    -2
0   -1  -2
0   -0.5    -1.5
0.5 -1  -1.5
-0.5    -0.5    -3
0   -1  -3
0   -0.5    -2.5
0.5 -1  -2.5
-2  -1.5    -1.5
-2  -1.5    -2.5
-0.5    -0.5    0
-1.5    -1  -2.5
-1  -2  -3


I wanted to create slabs such that:

a = [3-3 0]
b = [1 1 -2]
c= [1 1 1]


but whenever I try to transform the cell the structure ends up in an incorrect form.

I have tried transforming (in VESTA) using the inverse of the initial lattice matrix to get to a = [100] b=[0 1 0] and c = [0 0 1] but I end up changing the composition of the structure.

Do you know the correct way to create a slab from SQS files?

• +1 and welcome to our new community! Thank you for contributing your question here and we hope to see much more of you in the future !!! Please take a look at the edits I made! Oct 19, 2021 at 20:28
• Its better to rotate first and then do SQS!! Oct 20, 2021 at 6:17
• @nikeDattani Thanks a lot for the edit.
– Aman
Oct 20, 2021 at 14:54
• @pranavkumar Thanks a lot!
– Aman
Oct 20, 2021 at 14:54
• @pranavkumar It sounds like you now a bit about this subject, do you think you can write an answer? Dec 25, 2021 at 21:24

## 1 Answer

In general ,SQS changes shape of cell to find best quasi random structure, here you are trying for an orthogonal cell, but as output you are getting non-orthogonal cell. In order to get SQS structure with constrained cell, use following method

Run mcsqs -n xx. Stop the mcsqs process as soon as it generates the sqscell.out file. Trim the sqscell.out file, and leave only cell shapes which have equal lattice vector lengths. If many cells have equal lengths, only use those with the shortest lengths, because it means they are the closest to a cubic shape. Restart mcsqs -rc For example, if we want to build a 2-2-2 fcc supercell with 32 atoms, we can define the sqscell.out as:

1

2 0 0
0 2 0
0 0 2