SQS of a ternary BCC equiatomic alloy

Alloy Theoretic Automated Toolkit (ATAT)
1

I am trying to generate SQS of a BCC ternary equiatomic alloy having 48 atoms.
rndstr.in file:

5.74544213        0.00100609        0.00000000
1.91609593        5.41651942        0.00000000
0.00000000        0.00000000       28.14784776
1 0 0
0 1 0
0 0 1
0.00000000        0.00000000        0.00000000 Nb=0.3333,Ta=0.3333,Ti=0.3334
0.25000000        0.25000000        0.08333334 Nb=0.3333,Ta=0.3333,Ti=0.3334
0.50000000        0.00000000        0.00000000 Nb=0.3333,Ta=0.3333,Ti=0.3334
0.75000000        0.25000000        0.08333334 Nb=0.3333,Ta=0.3333,Ti=0.3334
1.00000000        0.50000000        0.00000000 Nb=0.3333,Ta=0.3333,Ti=0.3334
0.25000000        0.75000000        0.08333334 Nb=0.3333,Ta=0.3333,Ti=0.3334
0.50000000        0.50000000        0.00000000 Nb=0.3333,Ta=0.3333,Ti=0.3334
0.75000000        0.75000000        0.08333334 Nb=0.3333,Ta=0.3333,Ti=0.3334
0.00000000        0.00000000        0.16666668 Nb=0.3333,Ta=0.3333,Ti=0.3334
0.25000000        0.25000000        0.25000002 Nb=0.3333,Ta=0.3333,Ti=0.3334
0.50000000        0.00000000        0.16666668 Nb=0.3333,Ta=0.3333,Ti=0.3334
0.75000000        0.25000000        0.25000002 Nb=0.3333,Ta=0.3333,Ti=0.3334
1.00000000        0.50000000        0.16666668 Nb=0.3333,Ta=0.3333,Ti=0.3334
0.25000000        0.75000000        0.25000002 Nb=0.3333,Ta=0.3333,Ti=0.3334
0.50000000        0.50000000        0.16666668 Nb=0.3333,Ta=0.3333,Ti=0.3334
0.75000000        0.75000000        0.25000002 Nb=0.3333,Ta=0.3333,Ti=0.3334
0.00000000        0.00000000        0.33333336 Nb=0.3333,Ta=0.3333,Ti=0.3334
0.25000000        0.25000000        0.41666670 Nb=0.3333,Ta=0.3333,Ti=0.3334
0.50000000        0.00000000        0.33333336 Nb=0.3333,Ta=0.3333,Ti=0.3334
0.75000000        0.25000000        0.41666670 Nb=0.3333,Ta=0.3333,Ti=0.3334
1.00000000        0.50000000        0.33333336 Nb=0.3333,Ta=0.3333,Ti=0.3334
0.25000000        0.75000000        0.41666670 Nb=0.3333,Ta=0.3333,Ti=0.3334
0.50000000        0.50000000        0.33333336 Nb=0.3333,Ta=0.3333,Ti=0.3334
0.75000000        0.75000000        0.41666670 Nb=0.3333,Ta=0.3333,Ti=0.3334
0.00000000        0.00000000        0.50000004 Nb=0.3333,Ta=0.3333,Ti=0.3334
0.25000000        0.25000000        0.58333338 Nb=0.3333,Ta=0.3333,Ti=0.3334
0.50000000        0.00000000        0.50000004 Nb=0.3333,Ta=0.3333,Ti=0.3334
0.75000000        0.25000000        0.58333338 Nb=0.3333,Ta=0.3333,Ti=0.3334
1.00000000        0.50000000        0.50000004 Nb=0.3333,Ta=0.3333,Ti=0.3334
0.25000000        0.75000000        0.58333338 Nb=0.3333,Ta=0.3333,Ti=0.3334
0.50000000        0.50000000        0.50000004 Nb=0.3333,Ta=0.3333,Ti=0.3334
0.75000000        0.75000000        0.58333338 Nb=0.3333,Ta=0.3333,Ti=0.3334
0.00000000        0.00000000        0.66666672 Nb=0.3333,Ta=0.3333,Ti=0.3334
0.25000000        0.25000000        0.75000006 Nb=0.3333,Ta=0.3333,Ti=0.3334
0.50000000        0.00000000        0.66666672 Nb=0.3333,Ta=0.3333,Ti=0.3334
0.75000000        0.25000000        0.75000006 Nb=0.3333,Ta=0.3333,Ti=0.3334
1.00000000        0.50000000        0.66666672 Nb=0.3333,Ta=0.3333,Ti=0.3334
0.25000000        0.75000000        0.75000006 Nb=0.3333,Ta=0.3333,Ti=0.3334
0.50000000        0.50000000        0.66666672 Nb=0.3333,Ta=0.3333,Ti=0.3334
0.75000000        0.75000000        0.75000006 Nb=0.3333,Ta=0.3333,Ti=0.3334
0.00000000        0.00000000        0.83333340 Nb=0.3333,Ta=0.3333,Ti=0.3334
0.25000000        0.25000000        0.91666674 Nb=0.3333,Ta=0.3333,Ti=0.3334
0.50000000        0.00000000        0.83333340 Nb=0.3333,Ta=0.3333,Ti=0.3334
0.75000000        0.25000000        0.91666674 Nb=0.3333,Ta=0.3333,Ti=0.3334
1.00000000        0.50000000        0.83333340 Nb=0.3333,Ta=0.3333,Ti=0.3334
0.25000000        0.75000000        0.91666674 Nb=0.3333,Ta=0.3333,Ti=0.3334
0.50000000        0.50000000        0.83333340 Nb=0.3333,Ta=0.3333,Ti=0.3334
0.75000000        0.75000000        0.91666674 Nb=0.3333,Ta=0.3333,Ti=0.3334

sqscell.out file:

1

1 0 0
0 1 0
0 0 1^C

mcsqs -2=2.88 gives:
Generating clusters…
Warning: unit cell is not primitive.
2 2.87255 192
2 2.87255 384
2 2.87255 192

mcsqs -rc gives "Impossible to match point correlations due to incompatible supercell size".
My smallest sub-lattice has 192 atoms/sites; which is a multiple of 3. Therefore, I tried with 192 atom rndstr.in file; but again I got the same message.

Update:
I tried rndstr.in file with 192 (48x2x2)/384 (48x2x2x2)/768 (48x4x4) atoms as well. But, the same message is coming up.

Could you please explain if I am doing something wrong here?

Thank you.
Sufyan

2

Thank you, Professor Walle!
There was a significant speedup after using cellcvrt on rndstr.in file.

3

For efficiency and simplicity, the rndstr.in should only contain a unit cell.
In your case, you can find the unit cell with

cp rndstr.in rndstr.in.org
cellcvrt.exe -s -cc -abc < rndstr.in.org > rndstr.in

(drop the -cc if you want coordinate system of the unit cell rather than the conventional cubic one)
Then you can edit sqscell.out to read:

1

3 0 0
0 3 0
0 0 3

(or some other cell)

The problem with your input file is that there are not enough "333" in the concentration. Use:

3.317398 3.317398 3.316311 90.000000 90.000000 90.005018
-0.500000 0.500000 0.500000
0.500000 -0.500000 0.500000
0.500000 0.500000 -0.500000
0.500000 0.500000 0.500000 Nb=0.33333,Ta=0.33333,Ti=0.33333

(you might also want to clean up the cell parameters so that it’s exactly cubic)

Then you can run
mcsqs -2=2.88

mcsqs -rc

This has worked for me.

4

Thanks so much Professor Walle!
This helped alot!