Structural Collapse or Expansion of the Hydro‐Sodalite Series Na₈[AlSiO₄]₆(OH)₂·<i>n</i>H₂O and Na₆[AlSiO₄]₆·<i>n</i>H₂O Upon Dehydratation

Abstract

Abstract The two end‐member series of hydro‐sodalites show different structural expansion characteristics during dehydratation at elevated temperatures (300–900 K). The anomalous expansion in cell volume which is observed for series Na 6 [AlSiO 4 ] 6 · n H 2 O upon loss of 0 &lt; n ≤ 8 H 2 O is correlated to the destruction of the significant hydrogen bonding system between non‐framework and framework oxygen atoms of the corresponding sodalite structures. The contraction of the unit cell of the basic sodalites Na 8 [AlSiO 4 ] 6 (OH) 2 · n H 2 O upon loss of 0 &lt; n ≤ 4 H 2 O, however, is well understood in terms of space filling of the non‐framework constituents and some special stereochemical features amongst sodium, oxygen and hydrogen atoms.