The candidate circumstellar molecule SiC4H: Prediction of structure and infrared spectrum

The candidate circumstellar molecule SiC4H was investigated using density functional theory at the B3LYP/6-311 + G(d, p) level. For the first three low-lying isomers, more accurate energies were obtained using single point energy calculations at the MP2/6-311 + G(2df, 2p) and CCSD (T)/6-311 + G(2df, 2p) levels. The results predict that the linear SiCCCCH isomer has the greatest stability. In addition, at the MP2/6-311 + G(2df, 2p) level of approximation, the rotational constant for the most stable isomer was predicted to be 1.40316 GHZ. The predicted structures and spectroscopic properties for the relevant isomers are expected to be useful for the identification of SiC4H and even larger SiCnH species in the laboratory and the interstellar medium.