Dear all:
I want to construct a structure of steel with 68% Fe, 18% Cr, and 14% Ni which conforms to fcc lattice. For this structure, how to specify the rndstr.in file? I have tried to use the following file
4.157788 0.000000 0.000000
0.000000 4.157788 0.000000
0.000000 0.000000 4.157788
0.000000 0.500000 0.500000
0.500000 0.000000 0.500000
0.500000 0.500000 0.000000
0.000000 0.000000 0.000000 Fe=0.68,Cr=0.18,Ni=0.14
but the command mcsqs -n=108 fails. So What is the correct method to create such structures? Thank you very much!
It would be useful to report the error message. But in this case I can guess that it was "Impossible to match point correlations due to incompatible supercell size."
The number of atoms (specified with -n) must be such that composition*n is an integer.
There are other constraints for multi-sublattice systems (which is not the case here).
Thank you! I have realized this fact.
Another question is about the lattice parameter. In this case, I have chosen 4.157788. Is there any rule for this value? I see many cases people use 1 instead. What is the difference?
The second question is that how many pairs should I included? I learnt that it is system dependent. However, how to know the criterion for a good SQS structure? For example, if I include 4 pairs and 2 triplets and I obtain "Objective_function= Perfect_match". If I include 4 pairs and 6 triples I will obtain a value such as "Objective_function= -5.838334". So how do I know which one is enough?