EFFECTIVE PAIR POTENTIALS OF LIQUID CUBR ESTIMATED FROM THE ANOMALOUSX-RAY-SCATTERING DATA

We have proposed a method for calculating the effective pair potential s of molten salt from measured structural data in which a long-range C oulombic interaction is important [K. Omote and Y. Waseda: J. Phys. Se c. Jpn. 66 (1997)]. By applying this method, the effective pair potent ials of liquid CuBr have been successfully estimated from the experime ntal partial structure factors obtained by anomalous X-ray scattering. The resultant potentials show two characteristic features. One is rem arkable shielding for the Cu-Cu Coulomb repulsion in its nearest neigh bor region. This might be a possible origin for the absence of marked structure in the Cu-Cu correlation and the penetration of Cu ions into the first like-ion coordination shell. The other is the deviation fro m the Coulomb potential in the range of 0.4 similar to 0.9nm in the in teractions of Cu-Cu and Cu-Br pairs, suggesting a certain correlation to a pre-peak found in the Cu-Cu structure factor at about 10 nm(-1).