NEUTRON DIFFRACTION DETERMINATION OF THE HYDROGEN POSITIONS IN NATROLITE

Neutron diffraction data obtained with single crystals of natrolite, Na 2 Al 2 Si 3 O 10 .2H 2 0, have been analyzed using Fourier difference synthesis arid least squares methods. The details of the aluminosilicate framework were found to be in agreement with the results of earlier X-ray diffraction studies. The oxygen atom of the water molecule is linked by bent hydrogen bonds to two oxygen atoms in the framework, making an O—O—O angle of 134°. Lying almost in the O—O—O plane, the hydrogen atoms are located at distances of 0.94 ± 0.03 and 0.98 ± 0.02 Å from the oxygen of the water molecule and make with it an H—O—H angle of 108°. Natrolite thus provides an excellent example of the ability of the water molecule to resist the influence of the environment in opening the H—O—H angle.