Ideal gas thermochemical properties of silicon containing inorganic, organic compounds, radicals, and ions

Abstract

The ideal gas thermochemical properties such as standard heat of formation, entropy, and heat capacities of 112 inorganic and 35 organic neutral compounds, radicals, and ions containing silicon were calculated using molecular properties obtained with the G3B3 (or G3//B3LYP) method. Among them were linear and cyclic silanes, silenes, hydrocarbonsilanes, fluorine, and oxygen containing compounds. Many of their molecular and thermodynamic properties were calculated for the first time and 16 of them had no CAS number. Additionally the thermochemical properties were presented in the NASA 7 term polynomial format for the temperature range of 200‐6000 K commonly used in chemical kinetic modeling and simulation programs. The polynomials are available in the Supporting Information supplement to this article free of charge.

High-Level Ab Initio Predictions of Thermochemical Properties of Organosilicon Species: Critical Evaluation of Experimental Data and a Reliable Benchmark Database for Extending Group Additivity Approaches

“…A comparison of computational data for Si x H y systems shows that our W1X-1 values for SiH 4 , Si 2 H 6 , and Si 3 H 8 (35.9, 81.1, and 120.4 kJ mol –1 , respectively) are identical, within the accuracy of the methods, to prior results of Feller and Dixon and Burcat and Goos after adjusting the latter values to the same temperature (298.15 K) and employing the same atomic reference values including spin–orbit corrections (adjusted values 33.0, 76.3, and 122.7 kJ mol –1 for SiH 4 , 27 Si 2 H 6 , 27 and Si 3 H 8 , 28 respectively). The G4 enthalpies of formation given by Janbazi et al 29 for Si 2 H 6 and Si 3 H 8 agree with the above values after similar adjustments (78.8 and 118.4 kJ mol –1 , respectively).…”

“…Interestingly, the same does not hold for the methylsilane series, for which the adjusted data from Janbazi et al 29 (−26.2, −87.3, −160.0, and −233.6 kJ mol –1 for SiH 3 Me, SiH 2 Me 2 , SiHMe 3 , and SiMe 4 , respectively) show a gradually increasing deviation from our W1X-1 values (−23.8, −85.9, −149.9, and −215.0 kJ mol –1 , respectively). For comparison, the adjusted G3 values of Burcat and Goos 28 for SiHMe 3 and SiMe 4 are −157.7 and −223.8 kJ mol –1 , respectively. Most surprising are, however, the CBS-QB3 values of Janbazi et al 29 that are, after adjustments, 69.2, 107.3, and −213.8 kJ mol –1 for Si 2 H 6 , Si 3 H 8 , and SiMe 4 , respectively, and differ from the values reported by us (74.2, 113.7, and −207.4 kJ mol –1 ), even though the computational method used is identical.…”

Optical Emission Imaging and Modeling Investigations of Microwave-Activated SiH4/H2 and SiH4/CH4/H2 Plasmas

“…48 We have probed various sets of k i values and found no substantial differences in the calculated concentrations of SiH x species (including Si( 1 D 2 ) atoms) or in their spatial distributions in the hot regions, with R i ≈ R -i . This is unsurprising: the SiH x concentrations in such equilibrium conditions are determined by thermochemistry, 70 the local T gas , and the [H]/[H 2 ] ratio. As a result, the SiH x species partition in favor of low (x ≤ 2) species, mostly Si( 3 P) atoms.…”

“…It is important to note that the rates of the forward and reverse H-shifting reactions in the SiHx family (reactions ( 1)-( 6) in Table 2) and in the SiC2Hy family (reactions ( 45)-( 46) in Table 3) are close to equilibrium, especially in the hot plasma region. Thus the relative population distributions within each family are largely determined by the thermochemical properties of the species, 73,95 the local Tgas and the…”

Gas Phase Synthesis of the Elusive Trisilacyclopropyl Radical (Si3H5) via Unimolecular Decomposition of Chemically Activated Doublet Trisilapropyl Radicals (Si3H7)

“…However, electronic structure calculations suggest that the Si 3 H 5 isomer trisilacyclopropyl ( VII ) and trisilaallyl ( VIII ) should be kinetically stable with VII predicted to be energetically favorable by 45 to 70 kJmol –1 (Scheme ). , Trisilacyclopropyl ( VII ) belongs to the C s point group and has a 2 A′ electronic ground state. Whereas the allyl radical ( III ) holds a C 2 v symmetric structure with all atoms within the plane of symmetry, the C 2 v symmetric trisilaallyl ( IX ) was predicted to have two imaginary frequencies.…”