Least-squares refinement with the minimum number of parameters for structures containing rigid-body groups of atoms

A least-squares method for refinement of structures containing groups of atoms which may be treated as rigid bodies is described. The mtmber of parameters to be refined is reduced to the minimum possible. Each group is determined by 6 positional parameters and 1 isotropic or 6 anisotropic thermal parameters. The properties of convergence are discussed, and examples of refinements allow comparison with the normal least-squares method.