Neutron diffraction determination of the partial structure factors of molten CuCl

Abstract

Abstract A new neutron scattering determination of the partial structure factors of liquid CuCl is given, which emphasizes the necessity of an internal consistency check of the various coherent and absorption scattering cross-sections of the isotopically substituted samples. The amplitudes of the S ++ and S −- partials are about 30% more intense than in previous work, and their first peaks are in phase; however these two partials remain remarkably asymmetric. The ratio of the main peak positions of the S NN and S NN partials (Bhatia and Thorton) gives k q/k N = 0·58 which is very different from the alkali halide series. No shoulder is detected on the high-K side of the k N peak. An estimate of the radius ratio gives a value of 0·36 which is high. The number of nearest neighbours is small, 3±0·7, in agreement with Abramo's predictions. The analysis of the small-angle data confirms the size effect and the small partial molar volume of the positive ion, it also requires a value of the high-frequency dielectric constant higher than in the solid state. Interpretations of the structure require some weak ionic trends as well ∊s a local order consistent with the small size of the copper ion and the small number of nearest neighbours.