First, see Random Search (RS) for basic usage of CrySPY.
You can restrict the interatomic distance in structure generation. Here is an example of [structure] section in the input file to limit minimum interatomic distance for a A-B system.
[structure] natot = 8 atype = A B nat = 4 4 mindist_1 = 2.0 1.8 mindist_2 = 1.8 1.5
This means that minimum interatomic distances of A-A, A-B, and B-B are limited to 2.0, 1.8, and 1.5 Å, respectively. Structures with interatomic distances shorter than these values are automatically eliminated.
For ternary systems, you will need