X-ray photoemission studies of the ternary intermetallic compounds Li2MGa and LiMGa2 (M = Rh, Pd, Ir, Pt)

X-ray photoelectron and x-ray excited Auger spectra were measured for the i ntermetallic compounds LiMGa2 and Li2MGa (M = Rh, Pd, Ir, Pt). The valence band spectra exhibit characteristic differences in the location of the M d- band between group 9 elements (Rh, Ir) and group 10 elements (Pd,Pt) on one side and between LiMGa2 and Li2MGa on the other. The experimentally observ ed differences are in excellent agreement with results from band structure calculations. The combination of binding energy shifts with Auger kinetic e nergy shifts allowed a separation of initial and final state contributions. Core hole screening is very efficient in accordance with the metallic char acter of the investigated phases. The magnitude of the screening correlates with the theoretically predicted composition of the density of states at t he Fermi level. Application of Wertheim's electrostatic model allowed to es timate the charge distribution for LiRhGa2 and Li2RhGa. The sign of the cha rges agrees with expectations that result from the Extended Zintl Concept. The results show, how dangerous it is to draw conclusions on the chemistry of such systems from photoemission data alone.