OPTICAL-PROPERTIES OF GRAPHITE FROM FIRST-PRINCIPLES CALCULATIONS

We present theoretical results for the frequency-dependent dielectric response, both for the electric field parallel and perpendicular to th e c axis of graphite. The calculations are performed using a full-pote ntial linear muffin-tin orbital method. Our calculations show fair agr eement with experimental data and the different features observed are identified from interband transitions in various regions of the Brillo uin zone. The anisotropy of the dielectric function is discussed in de tail and shown to be due to the difference in the optical matrix eleme nts for the two different polarizations, which is a result of the anis otropic crystallographic and electronic properties of graphite.