A neutron diffraction study of the bonding of zeolitic water in scolecite at 20 K *

Abstract

Abstract A neutron diffraction study at 20 K of a single crystal of scolecite (CaAl2Si3O10 · 3H2O, a = 6.516(2), b = 18.948(3), c = 9.761(1) Å, β = 108.98(1)°; Cc, Z = 4,Dc = 2.28 g/cm3) utilized 2109 diffraction intensities from the Brookhaven National Laboratory High Flux Beam Reactor (λ = 1.0505(1) Å, R(F) = 0.016). There is no indication of substitutional disorder in the structure. The Ca atoms coordinate four framework oxygens and three water oxygens in a distorted pentagonal bipyramid. The hydrogen bonds to the framework oxygens vary in length [O … H: 1.746(1) – 2.119(1) Å] and linearity [O – H … O:130.9(1)° – 177.1(1)°]. The O – H distances in water fall in the range 0.979 – 0.993 Å, and the water angles H – O – H are 106.7(1)°, 107.3(2)° and 111.1(1)°. A neutron scattering length for Ca of 0.465(3) × 10−14 m is suggested.