CRITICAL-APPRAISAL OF THE SEMIEMPIRICAL WAVE-FUNCTIONS BY CALCULATINGESCA CHEMICAL-SHIFTS - INNER-SHELL BINDING-ENERGIES IN HALOGEN ATOMS

Semiempirical F(1s), Cl(2s), Cl(2P3/2), Br(3d5/2) and I(3d5/2) electro n spectroscopy for chemical analysis (ESCA) chemical shifts obtained b y using the SCC-MO, AM1 and PM3 methods are presented and compared wit h the experimental data. Agreement with experiment for fluorine and ch lorine inner-core binding energy shifts is good, being particularly sa tisfactory for Cl(2s) electrons. It is concluded that atomic charge di stributions in molecules involving highly electronegative fluorine and chlorine atoms are fairly well described by the examined semiempirica l approaches. However, Br(3d5/2) and 1(3d5/2) ESCA shifts are less suc cessfully reproduced by the semiempirical models. The origins of the c orresponding discrepancies are briefly discussed. The use of ESCA shif t in the parameterization of semiempirical methods is recommended.