How to generate a solid solution to use in VASP calculations

Alloy Theoretic Automated Toolkit (ATAT)
1

Hello everyone,
I am completely new to this code. I would like to study properties of a solid solution of KAlSi3O8 with Na (K0.2Na0.8AlSi3O8) using the VASP code. However, I do not know how to come up with the initial structure for the solid solution. Can someone who has tried this help me with a brief tutorial how to use the ATAT code as intergration with VASP to achieve this. I would really appreciate.
The POSCAR file for the KAlSiO3 is as follows:
Al K O8 Si3
1.0
9.3243999481 0.0000000000 0.0000000000
0.0000000000 9.3243999481 0.0000000000
0.0000000000 0.0000000000 2.7227001190
O Al Si K
16 8 8 2
Direct
0.541000009 0.162000000 0.000000000
0.458999991 0.838000000 0.000000000
0.838000000 0.541000009 0.000000000
0.162000000 0.458999991 0.000000000
0.041000009 0.662000000 0.500000000
0.958999991 0.338000000 0.500000000
0.338000000 0.041000009 0.500000000
0.662000000 0.958999991 0.500000000
0.143000007 0.218999997 0.000000000
0.856999993 0.781000018 0.000000000
0.781000018 0.143000007 0.000000000
0.218999997 0.856999993 0.000000000
0.643000007 0.718999982 0.500000000
0.356999993 0.281000018 0.500000000
0.281000018 0.643000007 0.500000000
0.718999982 0.356999993 0.500000000
0.347999990 0.170000002 0.000000000
0.652000010 0.829999983 0.000000000
0.829999983 0.347999990 0.000000000
0.170000002 0.652000010 0.000000000
0.847999990 0.670000017 0.500000000
0.152000010 0.329999983 0.500000000
0.329999983 0.847999990 0.500000000
0.670000017 0.152000010 0.500000000
0.347999990 0.170000002 0.000000000
0.652000010 0.829999983 0.000000000
0.829999983 0.347999990 0.000000000
0.170000002 0.652000010 0.000000000
0.847999990 0.670000017 0.500000000
0.152000010 0.329999983 0.500000000
0.329999983 0.847999990 0.500000000
0.670000017 0.152000010 0.500000000
Thank You!

2

Follow this paper: Redirecting

You can just put Al, Si, and O after their coordinates. For K sites, use “K=0.2, Na=0.8”. See Table 1 and 2 in the paper.