Despite having similar valence structures, the geometries of silicon compounds differ strongly from their carbon counterparts. For example, C2H2 is stable as a linear molecule whereas such linear conformation is a saddle point for Si2H2. In addition, multiple local minima can be located on the Si2H2 potential energy surface, including the dibridged (which is also the global minimum) and trans-bent isomers. In this study, a new energy decomposition analysis (EDA) scheme derived from a multiconfiguration self consistent field (MCSCF) wavefunction is used to explain the relative stabilities of the Si2H2 isomers compared to their C2H2 counterparts. A rigorous analysis of the intra-atomic and inter-atomic changes upon rearrangment from dibridged to trans-bent to linear is presented. The important role of the kinetic energy in establishing the covalent bonds and lowering the overall molecular energy is emphasized.

Quasi-atomic bonding analysis of Si2H2 and C2H2 isomers

ACS Fall 2021

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