STRUCTURE AND EFFECTIVE PAIR POTENTIALS OF MOLTEN CUBR ESTIMATED FROMTHE ANOMALOUS X-RAY-SCATTERING MEASUREMENTS

The anomalous x-ray scattering (AXS) measurements for molten CuBr have been made using the energies close to the Cu K(8.980 keV) and Br K(13 .470 keV) absorption edges for estimating three partial structural fun ctions, Cu-Cu, Br-Br and Cu-Br pairs by combining with the intensity d ata obtained at the energy of 17.0 keV, which is far from both edges. The data processing for obtaining three partials includes the help of the reverse Monte Carlo (RMC) simulation technique. The resultant stru cture factor of a(CuCu)(Q) for cation-cation pairs was found to be rat her structureless and the closest Cu-Cu distance in molten CuBr was si gnificantly smaller than that of a(BrBr)(Q) for anion-anion pairs, sug gesting the like-ion penetration into the first unlike-ion coordinatio n shell, similar to the molten CuCl case. The effective pair potential s of molten CuBr were also estimated from these experimental partial s tructural data by applying the modified hypernetted-chain (MHNC) equat ion coupled with a ''predictor-corrector method'' originally proposed by Reatto et al. in 1986 for a single component liquid system. It may be worth mentioning that the resultant pair potential for Cu-Cu pairs shows remarkable shielding for the Coulomb repulsion in its nearest ne ighbor region.