Wyckoff site in TlTe To finish this work, we want to make a comment regarding a recent paper in which the bond in a PCM, such as cubic rocksalt GeTe, has been compared to the bond in polyiodides . While there are similarities between GeTe and polyiodide bonding, the interpretation provided in Ref. cannot cover the range of possibilities encountered in polyiodides . In Scheme 1 we have already reasoned that the type of bonding in linear polyiodides depends on the length of the chain. Now in order to refute the reasoning in Ref. we also show in Scheme 2 that the type of bonding in polyiodides also depends on the geometry of the chain. In Scheme 2 we just show three types of infinite polyiodide molecules, the infinite linear chain of iodine atoms (I∞), the infinite zigzag or angular chain of iodine atoms that is bent at every atom (I∞(1 � )), and the infinite zigzag or angular chain of iodine atoms that is bent every two atoms (I∞(2 � )). A full discussion of the explanation of the different units in polyiodides is out of the scope of the present paper and will be published elsewhere.