The astrochemically relevant molecules of type HC2H, C 2H2 and C2H (n = 2-4) have been investigated theoretically by means of both standard and explicitly correlated coupled cluster theory. Equilibrium structures and harmonic vibrational frequencies have been calculated for all nine species. Accurate values for the molar enthalpies of isomerization of the C2H2 species and for the molar enthalpies of the dissociative electron attachment reactions C2H 2 + e - C2H + H (both at 0 K) are predicted. Both quantities differ substantially from the results of previous hybrid density functional (B3LYP) calculations. The explicitly correlated CCSD(T)-F12a method in conjunction with Dunning's aug-cc-pVTZ basis is found to yield results in excellent agreement with standard CCSD(T) calculations with much larger basis sets.
All Science Journal Classification (ASJC) codes
- Physical and Theoretical Chemistry