HYDROGEN ATOMS LOCALIZATION FROM COMPARISON OF DIFFRACTION AND PMR SPECTROSCOPY DATA. Valery Kavun, S.G.Kozlova¹ and S.P.Gabuda¹. Institute of Chemistry, 690020, Vladivostok, Russia; ¹Institute of Inorganic Chemistry, 630090 Novosibirsk, Russia

Neutron diffraction study of zeolite single crystals revealed the unusual shortening of intramolecular H-H distances for adsorbed H₂O molecules. The shortest ones are 1.42Å in edingtonite, 0.76Å in yugovaralite, 0.84Å in heulandite. All these data do not consist with well established intramolecular water parameters both for gas phase (1.515Å) and for condensed phase (ice I - 1.54Å, water in gypsum - 1.56Å, water in narrow-pored zeolite natrolite - 1.56A and so on). According to Busing and Levy (Acta Cryst. 17,142,1964), above distortion of bond lengths data indicates that thermal motion, or orientational disordering of water molecules takes place. This mechanism is supported by neutron diffraction study of the crystal structure of zeolite laumontite, where was established the "highest degree of disorder of the water molecules" among zeolites well characterized by neutron diffraction. But still there is no generally accepted ways how to account this effect and to correct the distorted bond length data deduced from diffraction measurements.

We propose an approach which is based on the use of the proton magnetic resonance (PMR) data. The correct interproton distances and amplitudes of both thermal motion or disordering parameters can be calculated from comparison of two independent data sets: (1) diffraction ones, (2) PMR spectroscopy. As illustration of fitness of proposed method we regarded the hydrogen atoms localization in potassium hexafluorostannatemonohydrate and in hemimorphite singlecrystals, using own PMR and X-ray diffraction data for K₂SnF₆.H₂O, and own PMR and previous neutron diffraction data on hemimorphite.