Theoretical study of one-electron bonds in a series of high-spin lithium-beryllium-hydrogen clusters: 'Valence shell single-electron repulsion' rule and electron localization function analysis

摘要

A series of high-spin clusters containing Li, H, and Be in which the valence shell molecular orbitals (MOs) are occupied by a single electron has been characterized using ab initio and density functional theory (DFT) calculations. A first type (Li-5(2) n+1LiHn+ (n = 2-5), (Li2H6+)-Li-8) possesses only one electron pair in the lowest MO, with bond energies of similar to 3 kcal/mol. In a second type, all the MOs are singly occupied, which results in highly excited species that nevertheless constitute a marked minimum on their potential energy surface (PES). Thus, it is possible to design a larger panel of structures ((LiBe)-Li-8, Li-7(2), Li-8(2)-, (LiH+)-Li-4, (BeH2+)-Be-6, n+3LiHn+ (n = 3, 4), n+2LiHn2+ (n = 4-6), (Li2H2+)-Li-8, (Li2H42+)-Li-9, (Li3Be3)-Li-22 and (Li6H63+)-Li-22), single-electron equivalent to doublet "classical" molecules ranging from CO to C6H6. The geometrical structure is studied in relation to the valence shell single-electron repulsion (VSEPR) theory and the electron localization function (ELF) is analyzed, revealing a striking similarity with the corresponding structure having paired electrons. (C) 2006 Wiley Periodicals, Inc.