Electronic structure and thermochemical properties of silicon‐doped lithium clusters Li_nSi^0/+, n = 1–8: New insights on their stability

Abstract

A theoretical investigation on small silicon-doped lithium clusters Li(n)Si with n = 1-8, in both neutral and cationic states is performed using the high accuracy CCSD(T)/complete basis set (CBS) method. Location of the global minima is carried out using a stochastic search method and the growth pattern of the clusters emerges as follows: (i) the species Li(n)Si with n ≤ 6 are formed by directly binding one Li to a Si of the smaller cluster Li(n-1)Si, (ii) the structures tend to have an as high as possible symmetry and to maximize the coordination number of silicon. The first three-dimensional global minimum is found for Li(4)Si, and (iii) for Li(7)Si and Li(8)Si, the global minima are formed by capping Li atoms on triangular faces of Li(6)Si (O(h)). A maximum coordination number of silicon is found to be 6 for the global minima, and structures with higher coordination of silicon exist but are less stable. Heats of formation at 0 K (Δ(f)H(0)) and 298 K (Δ(f)H(298)), average binding energies (E(b)), adiabatic (AIE) and vertical (VIE) ionization energies, dissociation energies (D(e)), and second-order difference in total energy (Δ(2)E) of the clusters in both neutral and cationic states are calculated from the CCSD(T)/CBS energies and used to evaluate the relative stability of clusters. The species Li(4)Si, Li(6)Si, and Li(5)Si(+) are the more stable systems with large HOMO-LUMO gaps, E(b), and Δ(2)E. Their enhanced stability can be rationalized using a modified phenomenological shell model, which includes the effects of additional factors such as geometrical symmetry and coordination number of the dopant. The new model is subsequently applied with consistency to other impure clusters Li(n)X with X = B, Al, C, Si, Ge, and Sn.

Tuning Spin-States of Carbynes and Silylynes: A Long Jump with One Leg

“…For molecules containing elements K, Rb, I, Zn, and Cd, the Sapporo-TZP basis set is used. This methodology gives a 42.8 kcal/mol dissociation energy for the 4 Σ – state of SiLi, close to the recently reported value (43.3 kcal/mol) from a CCSD(T)/complete-basis-set calculation . All calculations are performed using the program package GAMESS-US , unless further specified.…”

“…This methodology gives a 42.8 kcal/mol dissociation energy for the 4 Σ − state of SiLi, close to the recently reported value (43.3 kcal/mol) from a CCSD(T)/complete-basis-set calculation. 95 All calculations are performed using the program package GAMESS-US 96,97 unless further specified. All orbital graphical presentations are prepared using MacMolPlt.…”

Theoretical investigation of geometry and stability of small lithium-iodide LinI (n= 2-6) clusters

“…However, the electronic structure and relative stability of Li 9 I do not show that this species is special, contrary to the case of Li 3 I and Li 4 I + . For group IVA‐doped lithium clusters Li n X, the enhanced stability is found for the species that possess: (a) a closed shell electronic configuration that satisfies the PSM, (b) a high‐symmetry geometry, and (c) the coordination number of impurity at least equal to the number of Li atoms. In the structures 2.n.1 , 3.n.1 , 4.n.1 , and 5.n.1 , the coordination number is two; in 6.n.1 to 9.n.1 the coordination number is three; there is no significant difference in bonding of the iodine atom to Li cage in the neutrals.…”

“…A subset of the clusters of interest is small alkali metal clusters, particularly lithium clusters, which are computationally accessible yet physically and chemically complex. Lithium ability to form clusters with various elements is well known; in particular, the structural and bonding properties of boron‐lithium clusters, aluminum doped lithium clusters, mixed silicon‐lithium clusters, Li n Ge, Li n O, and (Li 2 O) n clusters were investigated; furthermore, the properties of small lithium halide, Li n F n −1 clusters, mixed sodium‐lithium, hydrogenated lithium clusters, or small bimetallic Li n Cu m clusters were also examined; the interaction with carbon monoxide or with various functional groups was recently reported. The primary interest in studying heterogeneous lithium clusters was the characterization of changes in bonding, and consequently their properties, from small clusters to the limit of delocalized electrons in the bulk metal (where heteroatoms are treated as impurity).…”

Magnetic Superatoms in VLin (n = 1–13) Clusters: A First-Principles Prediction

“…In addition, a considerable amount of work has been carried out on lithium clusters doped with an impurity atom, which can lead to fundamental changes in geometries, energy properties, and the bonding nature of lithium clusters. For example, the heterogeneous XLi n clusters doped with group IA elements with X = Na and K, − group IIA elements including beryllium BeLi n and magnesium MgLi n , group IIIA elements such as BLi n − and AlLi n , − and group IVA with X = C, Si, Ge, and Sn − have extensively been studied by many groups. These studies focused on the investigations of s-block and p-block element doped small lithium clusters; however, there have been few studies on lithium clusters doped with transition elements.…”