I am currently exploring the ORCA simulation and I am trying to figure out how to freeze the Ti5O10 cluster but I don't know how to do it. Can someone help how to freeze the clusters for geometry optimization in ORCA?
The answer to your question can be easily found in the ORCA documentation, see sections 8.3.6 "Constrained Optimizations" and 8.3.7 "Constrained Optimizations for Molecular Clusters (Fragment Optimization)" (pp. 171-176)