Density functional theory study of small alkali-metal cluster radicals

Abstract

Gradient corrected (PWP86) density functional theory has been applied to investigate the geometric and electronic structures of small neutral and charged Li, Na and K cluster radicals with up to four atoms. Comparing with other theoretical studies, we find a good agreement in the geometric structure for the cationic tetramers and for the trimeric form of lithium. For K₃ and Na₃, the linear forms are instead predicted as the energetically most stable structures, in contrast with previous theoretical data. For the ionization energies (E_i) and fragmentation energies, we note a constant overbinding of ca. 0.1 eV in the binding/fragmentation energies, and an error in E_i of ca. 0.35 eV. We also report calculated hyperfine coupling constants for all compounds studied. Comparisons with experimental electron spin resonance data, available for the trimers only, reveal a satisfactory agreement with the calculated triangular structures.