Diffractometry of closely superimposed twins and clusters: a method and a program for establishing UB matrices of single-crystal individuals

The diffractometer measurement of twinned and clustered crystals requires an accurate knowledge of Q_i = U_iB_i matrices of single-crystal individuals contained in the sample. A determination of the Q_i matrix is best done from several accurately centered orienting reflections diffracted by the ith single-crystal individual. The assignment of the orienting reflections to the individuals is easy for well resolved reciprocal lattices; for closely superimposed ones a method is presented which facilitates this assignment.