The Theoretical Prediction Of Isomers And Infrared Spectrum Of Interstellar Molecule SiC₄H

The study and exploration of Interstellar molecules has an important significance for the study of late stages of stellar evolution, the galaxy structure and the origin of life. At present, More than 140 species of interstellar molecules have been indentified including many complicated organic compounds:e.g nitriles, acetylene derivatives, acetaldehyde, methanol, ether, ketone and ethanol; Sugar and sugar derivatives have been found in meteorolite coming from outer space; The evidence of the existence of glycine in interstellar space has also been put forward. In recent years, The important discovery and discussion of nebula organic molecules not only enriched the knowledge of the formation of interstellar molecules, but also made people have a new thinking regarding the evolution of the universe life. Looking for new, complex interstellar organic molecules has become a hotspot for astronomical workers.The discovery of the chain molecular SiCn inspired people's interest in such interstellar molecules. Researchers found SiCn (n= 1-4) spectral characteristics at the IRC+10 216 envelope. The theoretical prediction of the structure, isomers and spectrum of SiCn (n = 3-8) was also widely unfolded.In this paper, our calculations are performed using all-electron density functional theory. The exchange and correlation are treated within the generalized gradient approximation (GGA) of Becke exchange functional and the Lee-Yang-Parr correlation funcional (BLYP). The double-numerical basis with polarized function(DNP) was taken. Possible isomers of interstellar molecules SiC4H were widely searched. The structure, dipole moment, rotational constants, vibrational frequencies, infrared intensity and so on of SiC4H isomers were further calculated, and the results were got as follows:(1) 29 kinds optimized structure of SiC4H isomers were got. With the lowest lying structure, linear SiC4H-1-1 possesses the largest kinetic stability;(2) The vibrational frequencies (infrared intensity) of linear SiC4H-1-1 are 495(22), 547(69),721(37),3470(172). unit:cm"'(km/mol);(3) SiC4H-2-1, SiC4H-3-1, SiC4H-3-3, SiC4H-6-2, SiC4H-6-4 have higher dipole moment so they should be detected more easily. The vibrational frequencies (infrared intensity) of them are separately:SiC4H-2-1:428(102),1031(23),1268(128),1548(306),1954(560);SiC4H-3-1:388(46),715(49),769(35),1013(20),1974(431);SiC4H-3-3:228(31),229(22),682(28),757(64),970(52),982(113),1963(768);SiC4H-6-2:349(25),597(75),702(41),761(32),790(55),1876(458),2098(104), 3450(68);SiC4H-6-4:238(27),447(74),598(127),1819(151),2073(88),2110(1193).