OPTICAL-PROPERTIES OF INCOMMENSURATELY MODULATED CALAVERITE, AUTE2

The optical reflection spectrum of incommensurately modulated calaveri te is presented. Using a Kramers-Kronig analysis the dielectric functi on is derived from the reflection spectrum. The results for the imagin ary part of the dielectric function are qualitatively discussed in ter ms of absorption by phonon, free electron and interband scattering. Th e phonon contribution clearly shows the influence of the incommensurab ility by the activity of phonons with k not-equal 0. The free electron scattering can be understood in terms of a simple Drude model. The in terband scattering is found at a lower frequency than predicted from e lectronic band structure calculations.