(Li₆Si₅)_2–5: The Smallest Cluster‐Assembled Materials Based on Aromatic Si₅⁶⁻ Rings

Abstract

Extensive explorations of their potential energy surfaces, combined with high‐level quantum chemical computations, strikingly show that the lowest energy structures of the (Li6Si5)2–5 systems consist of 2–5 Si56− aromatic units, surrounded by Li+ counterions, respectively. These viable gas‐phase compounds are the pioneering reported cases of oligomers made by planar aromatic silicon rings. Based on the key evidence that these oligomers are energetically favored, and that their silicon rings aromaticity is thoroughly preserved, the Li6Si5 cluster is proposed as a potential assembly unit to build silicon‐lithium nanostructures, thus opening new paths to design Zintl compounds at the nanoscale level.

Li8Si8, Li10Si9, and Li12Si10: Assemblies of Lithium‐Silicon Aromatic Units

“…For Li 8 Si 8 stoichiometry, both the global minimum and its three closest isomers (at 2.9, 4.5, and 5.9 kcal.mol −1 ) consist of two tetrahedral Si 4 moieties. The global minimum of Li 10 Si 9 and the second isomer (at 0.87 kcal.mol −1 ) consist of one pentagonal Si 5 and one tetrahedral Si 4 moieties, whereas Li 12 Si 12 global minimum consists of two Si 5 pentagonal rings, in agreement with previous reports from Yañez et al [31] . In all these assemblies, the lithium atoms lie between and around the silicon fragments (Figure 1 and Figures S3–S5 in the Supporting Information).…”

“…The D 5h −Si 5 6− and T d ‐ Si 4 4− moieties are planar and spherical aromatic systems, [26] fulfilling the 4n+2 π‐electrons Hückel's and the 2(N+1) 2 Hirsh's electron‐counting rule, [27–30] respectively. Here, we report the theoretical prediction of the lowest energy structures of Li 8 Si 8 and Li 10 Si 9 for the first time, besides confirming the lowest energy structure of Li 12 Si 10 [31] . Remarkably, the first one consists of two T d −Si 4 4− units; the second of one Td −Si 4 4− and one D 5h −Si 5 6− units, and the third of two D 5h −Si 5 6− units, thus clearly showing a general growth pattern towards CAMs [1] .…”

Si5-pentagonal rings and Y-shaped Si4building blocks in Li32Si18system: similarities with the crystalline Zintl phase Li12Si7

“…Two methods were used to explore the PES, the AUTOMATON program 61 and the KICK method. 62,63 In AUTOMATON, a probabilistic automata method built an initial population of 5 N individuals ( N is the number of atoms in the cluster of interest). Then this population evolved, through different generations, employing genetic operations.…”

“…Thus, for example, our group recently demonstrated that the global minima T d -Li 4 Si 4 and C 2v -Li 6 Si 5 consisting of Zintl Si 4 4− (tetrahedron) and Si 5 6− (pentagon) anions maintain their silicon motifs, almost unchanged, in the Li 8 Si 8 , Li 10 Si 9 , and Li 12 Si 10 combinations. 51,52 Furthermore, Li 6 Si 5 can be stacked to form a nanowire within a carbon nanotube. 53 These findings suggest that these small clusters could work as assembly blocks for CAMs, which is particularly interesting because these structural patterns have been identified in Li–Si materials.…”

Li6E5Li6: Tetrel Sandwich Complexes with 10‐π‐Electrons

“…[11b,15] D 5h Si 5 6À has been recognized as a suitable building block for larger clusters like (Li 6 Si 5 ) 2-5 systems. [16] Numerous strategies have been proposed to stabilize aromatic hydrocarbons with ten π-electrons. [17] These strategies often involve starting with six π-electrons rings, like benzene, and introducing four additional electrons through doping.…”