Optical properties of liquid silicon: the integral equation approach

A calculation of the optical conductivity and related optical properties of liquid silicon is presented. Starting from the results of a single superchain/effective medium approximation for the electronic properties, the frequency dependent conductivity is evaluated in terms of the Kubo-Greenwood formula. For a fast computation of the three and four centre terms therein the effective handling of the angular dependences of the Green's functions known from the sp³-fluid model is generalized to the current matrix elements. A good agreement of our results with experimental data for liquid silicon is found. At higher frequencies (>5 eV) and in the fitted Drude parameters, however, there are discrepancies due to the limitations of the sp³-model.