Structure of molten MCl3 systems from a polarizable ion simulation model

Computer simulations of a range of molten salts of stoichiometry MX3 using a polarizable, formal charge ionic interaction model are described. The sys tems studied - LaCl3, TbCl3, and YCl3 - span a range of cation sizes and th e interaction model is a "generic" one, in the sense that the cation size i s the only parameter in the interaction potential which distinguishes one s ystem from another. The liquid structures predicted from the simulations ar e compared with recently obtained neutron diffraction data. Excellent agree ment is found, except that the first coordination shell seems to be too tig htly bound in the computer simulations. The cation in LaCl3 is found to be 7-8 fold coordinate, and the coordination number drops to 6 for the smalles t cation considered (Y3+), so that the coordination number in these systems does not change substantially on melting, in contrast to earlier reports. The polarization effects promote a significant degree of edge-sharing betwe en these coordination polyhedra relative to predictions of a simple ionic p air potential. Associated with these changes is a shift to smaller scatteri ng vectors of the prepeak in the structure factor and an increase in the fl uidity. (C) 1999 American Institute of Physics. [S0021-9606(99)51629-2].