| Abstract
| - Electronic structures of the silicide carbides Tm2Fe2Si2C, Th2Re2Si2C, and ThFe2SiC and the carbide Ho2Cr2C3were calculated, using the extended Hückel tight binding method, to probe the d-electron counts of their transitionmetal atoms M (Cr, Fe, Re) the bonding of their linear M−C−M (M = Cr, Fe, Re) units. The nature of the shortinterlayer X···X (X = C, Si) bonds in Tm2Fe2Si2C, Th2Re2Si2C, and Ho2Cr2C3 was also examined. Our studyshows that the M−C bonds of the M−C−M units exist as double bonds. There is significant bonding in theinterlayer Si···Si contacts of the silicide carbides R2M2Si2C (M = Fe, Re). The transition-metal atoms exist asd10 ions in Tm2Fe2Si2C and Th2Re2Si2C. The d-electron count is slightly lower than d10 in ThFe2SiC and closeto d5 in Ho2Cr2C3.
- Electronic structures of the layered compounds Tm2Fe2Si2C, Th2Re2Si2C, ThFe2SiC, and Ho2Cr2C3 were calculated and analyzed. The M−C bonds of their linear M−C−M units (M = Cr, Fe, Re) exist as double bonds. The d-electron count is close to d10 in Tm2Fe2Si2C and Th2Re2Si2C, slightly lower than d10 in ThFe2SiC, and close to d5 in Ho2Cr2C3. There is significant bonding in the interlayer Si···Si contacts of the silicide carbides R2M2Si2C (M = Fe, Re).
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