PULSED NEUTRON DIFFRACTION STUDY ON LITHIUM (I) HYDRATION IN SUPERCOOLED AQUEOUS CHLORIDE SOLUTIONS

Pulsed neutron diffraction measurements have been performed on aqueous LiCl solutions (mole ratio D2O:LiCl=5) in the supercooled state (258, 213, and 173 K) and at room temperature (295 K). An isotopic substitution method with respect to Li has been used to derive the Li+‐related radial distribution function. The neutron diffraction data at all the temperatures have shown the Li–O and Li–D distances to be 2.02±0.05 and 2.61±0.05 A, respectively, and the most likely orientation of the coordinated water molecules has been found to be such that the four atoms in a Li+–D2O unit is pyramidal. It has also been found that at temperatures from 295 K down to 213 K the Li+ hydration is represented mostly by the primary hydration shell of about four coordinated water molecules, whereas at 173 K, about 40 K above the glass transition temperature, the definite second hydration shell of Li+ is formed. The obtained structural characteristics of the supercooled solutions are discussed in connection with nucleation of ice...

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