Valence bands of AgCl and AgBr: uv photoemission and theory

Abstract

AgCl and AgBr have been investigated by photoemission for photon energies $h\nu =16.8, 21.2, ,26.9, 40.8, \mathrm{and} 1486.6$ eV. By exploiting the strong dependence on $h\nu$ of the photoionization cross sections for the atomic orbitals composing the valence bands, we have been able to deduce approximate partial $p$ and $d$ densities of valence states for these compounds. The most conspicuous feature of the photoelectron distribution curves is a sharp peak near the center of the valence band, which our partial density of states shows to be mostly $d$-like. The $p$ density of states exibits two main peaks centered at 2- and 5-eV binding energy and a gap at the energy of the sharp $d$ peak. From the $p$ and $d$ densities of states we conclude that, except for the sharp $d$-like peak and the associated $p$ gap, the $p$ and $d$ functions are nearly equally and uniformly mixed throughout the valence band. The results are compared with partial densities of states calculated with a simplified tight-binding scheme and the band structure is discussed in detail.