You must check the {0, 1/2, 1} . This one means that the pattern is family of reflections, which is related to the cation displacement but also with octahedral distortions. If your films are a0 a+a0 or a-a+a-(in Glazer Notation) you would expect the (0 1/2 1) or (1 1/2 0) for the permitted reflections and viceversa...