title: Singly and doubly lithium doped silicon clusters: geometrical and electronic structures and ionization energies.
abstract: The geometric structures of neutral and cationic Si(n)Li(m)(0/+) clusters with n = 2-11 and m = 1, 2 are investigated using combined experimental and computational methods. The adiabatic ionization energy and vertical ionization energy (VIE) of Si(n)Li(m) clusters are determined using quantum chemical methods (B3LYP/6-311+G(d), G3B3, and CCSD(T)/aug-cc-pVxZ with x = D,T), whereas experimental values are derived from threshold photoionization experiments in the 4.68-6.24 eV range. Among the investigated cluster sizes, only Si(6)Li(2), Si(7)Li, Si(10)Li, and Si(11)Li have ionization thresholds below 6.24 eV and could be measured accurately. The ionization threshold and VIE obtained from the experimental photoionization efficiency curves agree well with the computed values. The growth mechanism of the lithium doped silicon clusters follows some simple rules: (1) neutral singly doped Si(n)Li clusters favor the Li atom addition on an edge or a face of the structure of the corresponding Si(n)(-) anion, while the cationic Si(n)Li(+) binds with one Si atom of the bare Si(n) cluster or adds on one of its edges, and (2) for doubly doped Si(n)Li(2)(0/+) clusters, the neutrals have the shape of the Si(n+1) counterparts with an additional Li atom added on an edge or a face of it, while the cations have both Li atoms added on edges or faces of the Si(n)(-) clusters.
authors.affiliation: Department of Chemistry, Katholieke Universiteit Leuven, B-3001 Leuven, Belgium.
authors.forename: Nguyen Minh
authors.initials: NM
authors.lastname: Tam
authors.forename: Vu Thi
authors.initials: VT
authors.lastname: Ngan
authors.forename: Jorg
authors.initials: J
authors.lastname: de Haeck
authors.forename: Soumen
authors.initials: S
authors.lastname: Bhattacharyya
authors.forename: Hai Thuy
authors.initials: HT
authors.lastname: Le
authors.forename: Ewald
authors.initials: E
authors.lastname: Janssens
authors.forename: Peter
authors.initials: P
authors.lastname: Lievens
authors.forename: Minh Tho
authors.initials: MT
authors.lastname: Nguyen
mesh_terms: D004583:Electrons; D008094:Lithium / Q000737:chemistry*; D015394:Molecular Structure; D011789:Quantum Theory; D012825:Silicon / Q000737:chemistry*; D013499:Surface Properties
chemical_list: D008094:Lithium; D012825:Silicon