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Even though the electronic structure information is available in the low-loss EEL spectrum (see page4360), the interpretation is difficult because there is no direct relationship between the EELS and the density of states (DOS). Therefore, in contrast to ELNES, low-loss EELS has been much less widely used to measure and understand electronic structure.
Among the various codes available for DFT calculations, two codes are commercially available and can be used to model ELNES: i) Pseudopotential code CASTEP, which was developed in University of Cambridge [4 - 5] (www.accelrys.com/cerius2/castep.html) and ii) WIEN2k which was developed at the Vienna University of Technology [6 - 7] (www.wien2k.at.).
Low loss spectra are calculated with the OPTIC package while core loss spectra are calculated with the TELNES program. The WIEN2k code has recently been used for the calculation of electron energy loss spectra. [3] Moreover, in few cases, low-loss EEL spectra have still been calculated using density-functional theory (DFT) based on WIEN2k codes. [1, 2]
[1] V. J. Keast, Ab initio calculations of plasmons and interband transitions in the low-loss electron energy-loss spectrum, Journal of Electron Spectroscopy and Related Phenomena 143 (2005) 97–104.
[2] K. Schwarz, P. Blaha, G.K.H. Madsen, Comput. Phys. Commun. 147 (2002) 71.
[3] C. Hébert, Practical aspects of running the WIEN2k code for electron spectroscopy, Micron 38 (2007) 12–28.
[4] Payne, M.C., Teter, M.P., Allan, D.C., Arias, T.A., Joannopoulos, J.D., 1992. Iterative minimization techniques for ab initio total-energy calculations: molecular dynamics and conjugate gradients. Rev. Mod. Phys. 64 (4), 1045 - 1097.
[5] Pickard, C.J., Payne, M.C., 1997. Ab initio EELS: beyond the fingerprint. In: Electron Microscopy and Analysis Group Conference EMAG97. IOP Publishing Ltd, pp. 179–182.
[6] Blaha, P., Schwarz, K., Sorantin, P., 1990. Full-potential, linearized augmented plane wave programs for crystalline systems. Comput. Phys. Commun. 59, 399–415.
[7] Hébert-Souche, C., Louf, P.-H., Blaha, P., Nelhiebel, M., Luitz, J., Schattschneider, P., Schwarz, K., Jouffrey, B., 2000. The orientation dependent simulation of ELNES. Ultramicroscopy 83 (1–2), 9–16.
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