Effective ionic charges and chemical bonding in GaSe and GaTe from chemical shifts of X-ray K absorption discontinuities

Chemical shifts in the X-ray K absorption edges of gallium and selenium in some of their binary compounds have been studied using a bent crystal X-ray spectrograph. The shifts are found to be governed by the effective charges on the absorbing ions, which have been calculated using Suchet's theory. For the compounds GaSe and GaTe, however, the effective ionic charges cannot be calculated for want of data on the divalent radius of gallium. The plot of the chemical shift, δE, against the theoretically calculated effective ionic charge, q, has been used to determine the charges on the ions in these two compounds. The effective charges, thus determined, provide information about the chemical bonding in the compounds.