Optical properties of graphite

Optical constants of graphite for ordinary and extraordinary waves are modeled with a modified Lorentz-Drude model with frequency-dependent damping. The model enables the shape of the spectral line to vary over a range of broadening functions with similar kernels and different wings, the broadening type being its adjustable parameter. The model parameters are determined by the acceptance-probability-controlled simulated annealing algorithm. Good agreement with the experimental data is obtained in the entire investigated spectral range (0.12-40 eV for ordinary wave and 2.1-40 eV for extraordinary wave). The significant discrepancies between the experimental data obtained by the reflectance measurements and the electron-energy-loss spectroscopy data are analyzed in details. Inconsistency in terms of unsatisfied Kramers-Kronig relations is discovered in the index of refraction data derived from reflectance measurements, and a method for correcting the data is proposed. (C) 1999 American Institute of Physics. [S0021-8979(99)02010-1].