Citation: Saskia Stegmaier; Sung-Jin Kim; Alexander Henze; Thomas F. F\"assler (2013). Tetrahedral Framework Structures: Polymorphic Phase Transition with Reorientation of Hexagonal Helical Channels in the Zintl Compound Na~2~ZnSn~5~ and its Relation to Na~5~Zn~2+x~Sn~10-x~. Journal of the American Chemical Society, 135, pp. 10654-10663.