Parity alternation of linear ground-state hydrogenated cationic carbon clusters HC_nSi⁺ (n = 1-10)

Making use of molecular graphics software, we have designed numerous models of HC_nSi⁺ (n = 1-10), and by means of the B3LYP density functional method, performed geometry optimization and calculation on vibrational frequency. The ground-state isomers of HC_nSi⁺ (n = 1-10) are found to be linear with the Si and H atom located at the ends of the C_n chain. When n is even, the C_n chain is polyacetylene-like whereas when n is odd, the C_n chain displays a structure that fades into a cumulenic-like arrangement towards the Si end. According to the results of mass spectrometric investigation available in the literature, the intensities of even-n HC_nSi⁺ are more intense than those of odd-n HC_nSi⁺, implying that the former are more stable than the latter. We detect trends of odd/even alternation in electronic configuration, the highest vibrational frequency, ionization potential, incremental binding energy as well as in certain bond length and certain atomic charge of the linear ground-state structures of the HC_nSi⁺ (n = 1-10) clusters. The calculation results reveal that the even-n cationic clusters are more stable than the odd-n ones.