ABSTRACT
A quantitative understanding of EELS and ELNES requires a quantitative comparison of experimental results with those obtained by calculations. Therefore, first principles electronicstructure calculations were performed for bulk (single crystalline) materials as well as for crystal regions containing specific interfaces (homophase boundaries and heterophase boundaries). The calculations based on the local density functional theory have turned out to be very reliable. From the one-electron band structures in crystalline materials, inelastic energy-loss functions, which are essentially determined by site-and angular-momentumprojected density of states (PDOS), can be obtained and compared with measured spectra. This is illustrated in Fig. 1 by the ELNES of the carbon K-edge of diamond. The measured spectrum (a) is in good agreement with the calculated p-PDOS (1=1) (b), employing a Gaussian smearing of 2 eV to mimic instrumental and life-time broadening effects. The calculated p-PDOS (c) with a smearing of 0.5 eV illustrates the gain in information which will be obtainable with future generations of analytical TEMs. This will allow to access small changes in the ELNES at defects and interfaces, which can be interpreted quantitatively with calculated PDOS.
