Nonlocal effects in absorption edges: Energy-dependent pseudopotentials

The promotion of electrons between parallel single-particle bands in the neighborhood of zone boundaries is known to constitute a major source of those excitations largely responsible for the dominant structure observed in the optical conductivity σ(ω) of simple polyvalent metals. Departures from parallelism are shown to lead to distinct features in this structure (particularly at interband edges), and the origin and consequences of these departures are investigated particularly insofar as they bear on energy nonlocality in the effective one-electron pseudopotential.