Abstract
The MATCH procedure1 in Oxford University’s Crystals for Windows software2 has proven to be a useful tool to analyze pseudosymmetry within crystal structures. It will compare pairs of independent molecules, or parts within, to provide a detailed analysis of their pseudosymmetric relationship.3 Recently, MATCH has been used to study Z’=2 twins in space group P1. We have found when the transformation matrix determined by MATCH and the twin law are similar, this is an indication the crystal structure likely had been subject to a phase transition most often while being cooled by a cryostat. A number of examples will be presented.