Flexibility and distortion of the collapsible framework of NAT topology; the crystal structure of H (sub 3) O-natrolite

A single crystal of oxonium natrolite was prepared by calcination of ammonium-natrolite and has the same space group (C112 (sub 1) ); a 17.912, b 18.474, c 6.542 Aa, V 2164.8 Aa (super 3) , i.e. slightly larger than NH (sub 4) -natrolite (a 17.899, b 18.390, c 6.529 Aa, V 2149.1 Aa (super 3) ). The original single crystal of NH (sub 4) -natrolite retained its twinning during calcination (normal to [100] or [010]). Starting with Na-natrolite, the distortion of the framework increases in NH (sub 4) -natrolite and is even stronger in H (sub 3) O-natrolite. The hydrogen bonding to framework oxygen atoms from the oxonium ions leads to asymmetrical distortions of the tetrahedra with short Si-O distances (min. 1.580 Aa) and relatively long Al-O distances (max. 1.769 Aa). Hydrogen bonded oxygen atoms have, on average, smaller T-O-T angles (4.3 degrees ) than non-hydrogen bonded oxygen atoms of the framework.