Mapping ground-state properties of silicon carbide molecular clusters using quantum mechanical calculations: SimCn and SimCn- (m, n ⩽ 4)

Ground-state structures, energies and vibrations for stable neutral and anion SimCn isomers (m, n ⩽ 4) were modeled using DFT and MP2 methods. Carbon-rich cluster molecules tend to form linear carbon sub-molecules or separate C2 groups as part of larger 3-dimensional structures. All silicon-rich clusters are ground-state singlet states. Linear chain clusters containing an even number of atoms are ground-state triplets. In absence of large structural differences between neutral clusters and their anions the adiabatic electron affinity (AEA) and the vertical detachment energy (VDE) are approximately equal. For clusters having two or more isomers with energies close to global minimum, the anions adopt structures similar to one of the nearly degenerate isomers. The VDE is significantly larger than AEA for clusters having an even number of carbon atoms. This difference generally increases with increasing number of silicon atoms, due to differences in bonding between the neutral molecule and its anion. Mapping cluster stability shows that adding Si or C atoms increases the binding energy of the most stable isomers for all clusters with the exception of SiC3 and Si2C3, which are locally stable. A parameterized method is presented to quickly predict the stability of other SimCn cluster structures.