Electron Affinities of Atomic Clusters

One of the major applications of the CURES-EC procedure has been in calculating the electron affinities of the carbon clusters C [46]. Carbon clusters are common species in nature, since they are a product of combustion and contribute to environmental problems. They have been observed in the interstellar medium. The fuller-enes represent one of the most recent discoveries of a new form of carbon. Carbon clusters have many forms—linear chains, cyclic compounds and the fullerenes— because carbon can form covalent bonds. The NIST tables give 54 electron affinities values for C 14 for Si 17 for Ge 45 for Sn and 55 for Pb . Only the structures for the carbon compounds from n = 3 to 30 are identified [12]. 

The density functional values for cyclic C2, C4, and Cg are significantly different from those of the CURES-EC. The PM3 values, not shown, give good agreement with the experimental values up to Ci0 but the deviations for C12 and C13 are about 0.5 eV. The use of modified electron correlation improves the agreement. The standard deviation between the CURES-EC and experimental values is 0.06 eV. Without the clear outliers for density functional values the standard deviation is 0.2 eV. The CURES-EC values cover a wider range of complexes and agree better with experiment. 

TABLE 8.4 Experimental, CURES-EC, and Density Functional Electron Affinities (in eV) of Carbon Clusters, n = 2 to 30 [45 51] 

Three groups of atomic AEa can be discerned those that are precisely and accurately measured to one meV those that have been precisely measured but have 

The experimental work functions of the metals are related to the Mulliken electronegativities by a constant displacement, P = —0.9, —0.5, 0, 0.2, and 0.5 eV, for the majority of the elements. The Pauling and Allen Rochow electronegativities have systematic variations similar to the Mulliken electronegativities for the main group of elements, but the values are different in magnitude for the d and f block elements. 

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