Gas-Phase Reaction Pathways from SiH4 to Si2H6, Si2H4 and Si2H2: A Theoretical Study

Initial gas-phase reactions for a system containing silane (SiH4) and hydrogen (H2) were investigated using ab initio calculations at the MP2/6-311++g** level. Twenty-four minimum and 19 transition states were located on the potential energy surface of the neutral species containing one or two silicon atoms. The bonding nature of each species was elucidated by topological analyses of electron density using Bader's AIM theory. The reaction pathways were classified into three parts: Part (I) shows elimination of the first H2 and formation of disilane (Si2H6). Part (II) shows elimination of the second H2 and formation of five disilene (Si2H4) isomers. Part (III) shows elimination of the third H2 and formation of four disilyne (Si2H2) isomers. More energy is required to obtain species with less hydrogen content, and such species are more likely to be stabilized by a hydrogen bridged bond (Si−H−Si). Calculated IR spectra, dipole moments, and rotational constants were provided for comparison with the experiments.