Rigid-unit phonon modes and structural phase transitions in framework silicates Hammonds, Kenton D. ; Dove, Martin T. ; Giddy, Andrew P. ; Heine, Volker ; Winkler, Bjoern Abstract Publication: American Mineralogist Pub Date: October 1996 DOI: 10.2138/am-1996-9-1003 Bibcode: 1996AmMin..81.1057H