We present a combined theoretical and experimental investigation of the electron properties of calcium silicides (Ca2Si, CaSi, and CaSi2). The theoretical study is performed by a self-consistent calculation of the electron states, while the experimental analysis is based on synchrotron-radiation photoemission measurements. The overall agreement between the computed and measured spectra allows us to investigate the main features of the Ca-Si interaction in different compounds. We find that covalent character is present in the Ca-Si bond and that the strength of this interaction increases with Si concentration. Furthermore all the Ca s-p-d states are involved in this coupling with Si. In Ca2Si, the Si s states are found in a corelike configuration, while in the other compounds they are promoted to form an s-p valence band. The covalent interaction is not sufficient to interpret the results and some ionic character is present in the Ca-Si bond. Ca2Si is found to be a semimetal and many structures in the density of states can be correlated to well-defined interactions between the nonequivalent Ca-Si couples that are found in these complex compounds.

Chemical bond and electronic states in calcium silicides: theory and comparison with synchrotron radiation photoemission / BISI, Olmes; L., BRAICOVICH; C., CARBONE; I., LINDAU; A., IANDELLI; G. L., OLCESE; A., PALENZONA. - In: PHYSICAL REVIEW. B, CONDENSED MATTER. - ISSN 0163-1829. - STAMPA. - 40(1989), pp. 10194-10209.

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