Dear avdw:
Recently I have done some calculations about the SQS. After relaxations, the SQS keeps the same, the RDF changes, Is the results valid if the SQS keep the same? Different relaxation may cause the RDF to change especially ion relaxation, is it valid to carry out the ion relaxation for a SQS calculation?
Thank you so much in advance
It is absolutely valid (and, in fact, this is one of the main advantages of SQS relative to other methods) to allow atom positions to relax.
However, if the coordination of the atoms changes drastically during relaxations, then your SQS is no longer representative of the original lattice you intended. For a solution to this, see https://dx.doi.org/10.1038/ncomms8559
But I wouldn’t worry about this more advanced method if checkrelax reports less than ~0.05 relaxation of the cell.