Calculational Aspects of the Assessment of Dielectric Response Function and Energy Loss in Materials: Applications To Ice and Polyacetylene

Abstract

Understanding the effects of low doses of ionizing radi ation on living systems requires detailed information on electron transport in biomaterials. This, in turn, can be obtained from the wave-vector- and frequency-depen dent dielectric response function of the system, ∈(q,ω), via the energy-loss function, Im[-1/∈( q,ω)]. We describe two different possible approaches to obtaining these functions, one based on the semiempirical tight-binding approximation, the other using Hedin's many-body treatment of quasiparticle states in solids. These methods are exemplified with calculations for cubic ice (as a model for cellular "structured" water) and trans- polyacetylene. The availability of supercomputers makes the application of these techniques feasible.