Study of the Fundamental Units of Novel Semiconductor Materials: Structures, Energetics, and Thermodynamics of the Ge–Sn and Si–Ge–Sn Molecular Systems

Abstract

The binary Ge(y)Sn(z) and ternary Si(x)Ge(y)Sn(z) molecular systems containing up to five atoms were investigated by means of density functional theory and coupled cluster calculations. The minimum energy structures were calculated and higher energy isomers are also proposed. The atomization energies of the ground state isomers were calculated by the CCSD(T) method with correlation consistent basis sets up to quadruple-ζ quality. The resulting values were extrapolated to the complete basis set limit and corrected by an approximate evaluation of the spin-orbit effect. Energetic properties such as binding, fragmentation and mixing energies, and HOMO-LUMO gap were analyzed as a function of the cluster size and composition. By using empirically adjusted atomization energies and DFT harmonic frequencies, the thermal functions were evaluated, and a thermodynamic database for the Si-Ge-Sn system was built, containing data for 55 gaseous species. On this basis, equilibrium calculations were performed in the temperature interval 1600-2200 K aimed at predicting the composition of the gas phase under various conditions. The results presented here can be of interest to improve the microscopic knowledge of Ge-Sn and Si-Ge-Sn materials, which are among the most promising candidates for advanced applications in the field of electronic and optoelectronic components, both as epitaxially grown layers and as nanocrystal quantum dots.

Mechanistic Investigations on E–N Bond-Breaking and Ring Expansion forN-Heterocyclic Carbene Analogues Containing the Group 14 Elements (E)

“…Furthermore, in the first step of eq ( Rea – E + SiH 2 Ph 2 → TS1 – E – Si → Int1 – E – Si ), one Si–H bond is broken, and two bonds are formed (E–Si and E–H). It was reported that the bond strengths for E–Si and E–H bonds decrease in the general order (kcal/mol) C–Si (82.7) > Si–Si (76.0) > Ge–Si (70.6) > Sn–Si (55.7) > Pb–Si (31.5) and C–H (92.2) > Si–H (86.0) > Ge–H (78.8) > Sn–H (69.2) > Pb–H (57.8), respectively. Again, these data are consistent with the trend in the first intermediate energy (Δ E Int1 ) for eq .…”

Preparation of Light and Moisture Stable Flexible and Rigid Asymmetrical Polystannanes

“…28 In later years, progress in studies employing a 3c-4emodel has been confirmed by development in computational studies and quantum physics. 33 The hypervalent bonding of molecules has also been investigated by von Schleyer et. al.…”