Theoretical Study of Structures, Energetics and Reactivities of Linear Carbon Chains and Cyclic Carbon Rings

Description

Carbon plays an important role in the evolution of the interstellar medium since it provides mainly the free electrons in diffused interstellar clouds, and it contributes to the heating of interstellar gases. In last decade, major scientific advances have been made to observe and identify the unknown, ubiquitous, molecular and solid-state features of carbonaceous materials in astronomical spectra. Relevant experimental and theoretical studies stimulated by these astronomical observations have allow scientists to better understand various forms of cosmic carbon such as carbon chains, rings and clusters, polycyclic aromatic hydrocarbons, and carbonaceous solids. The carbon chains are suggested to play an important role in the formation of PAHs in interstellar medium. Among exclusively carbon atoms, chemical bonds can be formed through sp, sp2, and sp3 hybridizations. For finite linear carbon chains and cyclic carbon rings, two possible forms of structures are suggested: consecutive double-bond (cumulenic) or alternative single triple bond (polyynic). This proposal calls for comprehensive investigations to the structures, energetics and reactivities of linear carbon chains (HCnH, H2Cn and HCn) and cyclic carbon rings (Cn) by mean of couple-cluster theory and multi-reference  configuration interaction methods. Our work is to (i) study the trend of the structures and energetics (such as HOMO/LUMO gap, ionization energy) from short chain or small ring to longer chain or larger ring; (ii) examine the distinct pattern for even and odd nseries; (iii) correlate the capping effect and the even-odd parity effects with the structural and energetic properties; (iv) extrapolate the computed results to infinite chain length and ring size to give sight to the relevant properties at classical limit (v) investigate the formation mechanism and reaction energetics of PAHs and ladderanes from linear carbon chains. We study the physical and electronic factors governing the stability and energetic of carbon chains and rings and investigate the mechanisms for the synthesis of carbonaceous materials in the context of astrochemistry, atmospheric chemistry, andmaterial science.