Theoretical enthalpies of formation for small silicon hydrides

Halogenated silanes, radicals, and cations: Theoretical predictions on ionization energies, structures and potential energy surfaces of cations, proton affinities, and enthalpies of formation

“…However, CATCH and JANAF argued that Si(s) produced was in amorphous state of in crystalline state, and raised the values by 4.2 kJ/mol per silicon atom, leading to fairly large discrepancies to G3(CC) predictions. The corrected values for SiH 4 and Si 2 H 6 were adopted in photoionization study on SiH x [31] and in a large number of theoretical studies on the thermochemistry of silicon hydrides [98][99][100][101][102] where they were taken as reference for calibrating the theory and setting up the correction parameters. However, Feller and Dixon [59] [27]; e From G3 atomization energies [55]; f BAC-MP4 calculation, using 34.3 ± 2.1 kJ/mol for the enthalpy of formation of SiH4, for silicon hydrides and chlorinated compounds [48], and fluorinated compounds [47]; g Fluorinated silanes at MP4/6-31G(d,p) level using isodesmic reactions [49]; h MP4/6-31++G(2d,2p) with isodesmic reactions based on experimental SiHn and SiF4 [17]; i Chlorinated compounds at MP4/6-31+G(2df,p) level using isodesmic reactions [50]; j SiFx (x = 1-3), from the calculated CCSD(T)/CBS bond dissociation energies [54]; k SiClx (x = 1-3), from the calculated G2(MP2) bond dissociation energies [51]; l From heat of decomposition [96,97]; m Chemical equilibrium; n From threshold energies in reaction of Si + + SiF4 [40]; p From photoionization of SiHx [31]; q From collision-induced dissociation and charge transfer reactions [41]; r From chemical equilibrium study [28].…”

The acidity of polyhalogenated silanes and silyl radicals

“…Recently ab itzitio molecular orbital calculations were used to calculate heats of formation of SiH,, (29,(34)(35)(36), SiH,,F,,, (35, 37), and SiH,,CI,,, (38). When large basis sets are used, and correlation energy is calculated at the MP4 level it is possible to calculate AH:(298 K) to at least within 3 kcal/ mol (38).…”

Pressure-dependent rate coefficients of chemical reactions involving Si2H4 isomerization from QRRK calculations

“…A value of 7.3 kcal mol À1 has been first derived by Sakai et al [44] for E À2 , but most recent calculations have reached the conclusion that the reaction proceeds with no barrier [50], or even with a negative activation energy [49]. The most stable electronic state of both H 3 SiSiH and H 2 SiSiH 2 isomers is singlet [33,49,50], however, reaction (R À2 ) between triplet Si atoms and singlet SiH 4 molecules (ground states) produces silylsilylene with triplet multiplicity [36,[49][50][51]. Rate constants close to the gas kinetic upper limit have been measured for the reaction between Si( 3 P) and SiH 4 in the range 300-1300 K at moderate or low pressure [45][46][47][48][49], hence, the corresponding pathways should neither be collisional stabilization of H 3 SiSiH( 3 A 00 ) and H 2 SiSiH 2 ( 3 B) nor dissociation to H 2 SiSi( 3 A 2 ) + H 2 since the corresponding transition states are located above the reactants in energy (Fig.…”

“…A variety of isomers have also been listed in the Si-H chemical system and most of the corresponding heats of formation have been estimated by ab initio calculations [6,[32][33][34][35]. However, only few reactions involving isomerizations have been previously studied or included in the chemical schemes used for modeling silicon deposition from SiH 4 or Si 2 H 6 mixtures.…”