Electronic Structure and Properties of Silicon-Doped Boron Clusters B_nSi withn= 15–24 and Their Anions

Abstract

We investigated the structures and properties of medium size silicon-doped boron clusters in both neutral and anionic states B n Si 0/− with n = 15−24. While geometries were optimized using DFT with both TPSSh and PBE functionals, energies were determined using the coupled-cluster theory (U)CCSD(T) with the 6-311+G(d) basis set, with a calibration using the 6-311+G(3df) basis set. Average binding energies, second-order energy differences, dissociation energies, and electron detachment energies were predicted by using the (U)CCSD(T) + ZPE energies for the entire series. The growth of the B n Si series considered does not follow a regular pattern, but a few trends can be established as follows: (i) most of the lowest-energy isomers of B n Si 0/− clusters arise from a replacement of a B atom of the B n+1 species by an Si atom or an addition of one Si atom into the neutral, anionic, or dianionic B n species; (ii) the predominance of the planar structures for B n Si 0/− clusters can be interpreted as a result of an effect of either the pure boron clusters or the Si dopant or also an effect of the negative charge; and (iii) the Si dopant prefers to be placed at an outer place of the B n framework in order to exchange for, or to connect to, the peripheral B atoms in forming a low coordination number. The B 19 Si − anion whose planar motif, MOs shapes, electron distribution, and magnetic ring current are similar to those of the pure anions, B 18 2− , B 19 − , and B 20 2− , can be considered as a disk aromatic species involving 12 valence π-electrons. The MOs and electron distribution of the pseudotubes B 20 Si, B 22 Si, and B 24 Si can be interpreted by the hollow cylinder model. The first stable pseudotubular shape was found for the size B 24 Si whose thermodynamic stability is enhanced by both σ and π aromatic characters.

Exploring the structure and electronic properties of germanium doped boron clusters using density functional theory based global optimization method

“…The second isomer exhibits a bowl-like structure and resembles the third low lying isomer of B 17 Si. 81 The third lowest energy structure is a three-dimensional structure and is 0.19 eV higher in energy than the ground state structure. All the three lowest energy structure of Ge 2 B 17 are highly unsymmetrical and possess a three-dimensional geometry.…”

“…The ground state of GeB 15 is a quasi-planar structure where the Ge atom caps on a pentagonal hole and resembles the second low lying isomer of B 15 Si. 81 The second isomer presents a folded bowl shape with the Ge atom bonded to two peripheral boron atoms on the convex side and is 0.90 eV above the ground state isomer of B 14 Si − . The third isomer is 1.36 eV above the ground state and resembles a distorted double ring in which Ge atom is connected to the peripheral boron atoms.…”

“…For Ge 2 B 19 , GeB 20 and Ge 2 B 20 all the three lowest energy structures are three-dimensional in shape. Interestingly, the third lowest energy structure of GeB 20 resembles the third lying isomer of B 20 Si, 81 whereas the ground state structure of Ge 2 B 20 is a semi-cage structure. From the above discussion, it is seen that the single and double Ge atom doped boron clusters exhibit diverse structures including planar or quasi-planar, bowl shaped or semi-cage structures in comparison to pristine boron clusters.…”

“…Mai et al 52 in an attempt to discern the growth pattern of B n Si clusters ( n = 8–14) using theoretical calculations found that the B n Si 0/− clusters are formed by substitution of a B-atom by a Si-atom with silicon favouring an external position with respect to the boron framework. Ribbon-like structures with enhanced thermal stability were proposed for B 10 Si 2 2− and B 12 Si 2 2− by Duong et al 80 Furthermore, Nguyen and co-workers 81 reported fascinating disc-like aromatic and pseudo tubular structures while investigating the structure and electronic properties of medium sized neutral and anionic B n Si 0/− ( n = 14–25) clusters. Apart from these few studies, not many investigations have been carried out to explore the effect of semi-metals on the structure and electronic properties of boron clusters.…”

Structural Evolution and Electronic Properties of Two Sulfur Atom-Doped Boron Clusters

“…Single metal atom-doped boron clusters BiB n – ( n = 6–8), MnB n – ( n = 6, 16), and ReB n – ( n = 3–4, 6, 8–9), CoB 16 – and two or three metal atom-doped boron clusters (M 2 B 6 (M = Mg, Ca, Sr), La 2 B 10 – , La 2 B 11 – , La 3 B 18 – , and Sc 3 B 20 ) have various unique structures. − ,, Single Pr atom-doped PrB 4 – can adjust the Pr atom to a very low oxidation state (OS) and single Pr atom-doped PrB n ( n = 7–16) have various unique structures; two metal atom-doped boron clusters Be 2 B 24 + have a four-ring tubular structure . However, nonmetallic atom-doped boron clusters have been less studied, − such as single O atom doping can adjust the quasi-planar pure boron cluster (B 12 ) to a low-symmetry (C 1 ) B 12 O cluster and different numbers of F atom doping can adjust the quasi-planar pure boron cluster (B 12 ) to various unique structures . In addition, there are some related studies on boron oxide clusters and boron sulfide clusters, such as the B 6 (BO) 7 – cluster with a face-capping μ 3 -BO, planar B 3 S 2 H 3 and B 3 S 2 H 3 clusters with a five-membered B 3 S 2 ring, B 6 S 6 , B 6 S 6 – , and B 6 S 6 2– clusters with a planar dicyclic structure, and BS –/0 clusters with a B–S triple bond .…”