Misleading evidence for covalent bonding from (EuX)-X-III and (AmX)-X-III density functional theory bond lengths

作者：Dolg Michael^*; Cao Xiaoyan; Ciupka Jan

来源：Journal of Electron Spectroscopy and Related Phenomena, 2014, 194: 8-13.

DOI：10.1016/j.elspec.2013.07.004

• Bond distances
• Density functional theory
• Cyanex 301

In complexes of trivalent Eu and Am standard unrestricted Kohn-Sham density functional calculations tend to yield shorter bond distances for the Am-X than for the Eu-X bonds, especially when X is a so called soft ligand. Since the ionic radius of Am-III is larger than the one of Eu-III the reversed order of the bond distances is sometimes explained by a higher covalency of the Am-X bond compared to the one of the Eu-X bond. A comparison of density functional with wavefunction-based correlated calculations for several model systems reveals, however, that the energetically low-lying and spatially compact 4f shell of Eu-III often is erroneously filled with significantly more than 6 electrons at the density functional theory level, thus yielding considerably too long bond distances. Particularly claims based on comparisons of structures optimized at the density functional level that the strong preference of the Cyanex 301 ligand for Am-III over Eu-III is due to an increased covalency in the Am-S bonds should be viewed with some reservation.

• 出版日期2014-6