Theoretical studies on the bonding and thermodynamic properties of GenSim (m+n=5) clusters: The precursors of germanium/silicon nanomaterials

Abstract

Theoretical studies on the Ge n Si m clusters have been carried out using advanced ab initio approaches. The lowest energy isomers were determined for the clusters with compositions n+m=2-5. All possible isomers arising due to permutations of Ge and Si atoms were investigated. The L-shaped structure for the trimers, tetragonal with diagonal bond for tetramers, and a trigonal bipyramid for pentamers represent the energy optimized ground state geometries. The bonding analyses revealed that the trimers and tetramers are stabilized through multicenter pi bonding. In pentamers, this stabilizing factor is eliminated due to the further cluster growth. The ionization of clusters does not change their geometrical characteristics. The agreement of the calculated ionization and atomization energies with those obtained from the mass spectrometric studies (through estimated appearance potential) validated the reported structures of the clusters. The bonding properties of these species are discussed using their molecular orbital characteristics and analysis of natural bond orbital population data.

Enantiotropic Nematics From Cross‐Like 1,2,4,5‐Tetrakis(4′‐alkyl‐4‐ethynylbiphenyl)benzenes and Their Biaxiality Studies

“…On the contrary, in the SiSn 2 molecule our calculated Sn–Sn interatomic distance, 3.325 Å (CCSD(T)) or 3.420 Å (B3LYP), is definitely larger than that of the homonuclear molecules. It can also be noted that similar ground‐state structures have been very recently found in the computational study of the SiGe 2 and Si 2 Ge molecules both at the DFT B3LYP/6‐311+G(d) level11 and at the MP2/aug‐cc‐pVTZ and CCSD(T)/aug‐cc‐pVTZ levels 21. The spatial orientation of the three highest occupied molecular orbitals of the triatomic species as calculated at the CCSD(T)/cc‐pVTZ level are reported in the Supporting Information of this paper.…”

“…We observe a negligible lengthening, +0.018 Å, and a more pronounced shortening, −0.065 Å, of the bond lengths associated with the neutral‐to‐cation and to the neutral‐to‐anion electronic transitions, respectively. This can be interpreted as being due to the nonbonding character of the HOMO σ and bonding nature of the π orbital, as recently observed by Wielgus and co‐workers in the GeSi molecule 21…”

“…computed these clusters ( m =1–7; n =1, 2) at the B3LYP/6‐311G level. Finally, Wielgus et al 21. studied in the detail the structure and bonding in the Si m Ge n species with m + n =2–5 at the MP2 and CCSD(T) levels of theory, with augmented triple‐zeta basis sets making use of effective core potentials for germanium.…”

“…We present here an experimental and computational study of the SiSn gaseous molecular species that we succeeded in observing at high temperatures in the equilibrium vapor produced from SiSn mixtures. This contribution to the knowledge of the bonding properties of the elemental building blocks of the SiSn system is expected to prove useful in the atomic‐scale analysis of this system and in understanding the spontaneous processes that occur in the heterostructure hepitaxial growth14b and that can lead to the formation of self‐organized quantum structures such as those observed in other Group 14 systems 21. This investigation, experimentally performed with the combined Knudsen effusion mass spectrometric technique, resulted in the first determination of the bond energy of the simple diatomic SiSn as well as of several previously unreported triatomic (Si 2 Sn and SiSn 2 ) and tetratomic (Si 3 Sn, Si 2 Sn 2 , and SiSn 3 ) mixed molecules.…”

Investigation of New Intermetallic Bonds and Molecules by Knudsen Effusion Mass Spectrometry Integrated with ab Initio Calculations

“…Dissociation energy (kJ/mol) of intra-group 14 diatomics. Data from ref.s [24] (C 2 ), [25] (SiC), [26] (Pb 2 ), [27] (GeC), [11] (Si 2 , SiSn, Sn 2 ), [28] (GeSi), [29] (Ge 2 ), [30] (GeSn), [10] (SiPb,GePb), [9] (SnPb).…”