【作者】 王丽；

【导师】 李有成； 刘英；

【作者基本信息】 河北师范大学 ， 凝聚态物理， 2009， 硕士

【摘要】 星际分子的研究和探索对于恒星演化晚期、银河系结构以及生命起源的研究有着重要的意义。目前,包括腈、乙炔衍生物、乙醛、甲醇、醚、酮、乙醇等复杂有机化合物在内的星际分子已被确认的有140余种；在来自太空的陨石中发现了糖及糖的衍生物；星际空间存在氨基乙酸(甘氨酸)证据也被提出。近年来,关于星云中有机分子的重要发现和讨论丰富了人们关于星际分子形成过程的知识,也使人们关于宇宙生命演化过程有了新的思考。寻找新的、复杂的有机星际分子成为天文工作者关注的热点。链状分子SiCn的发现诱发了人们对此类星际分子的兴趣。研究人员在IRC+10216的包层中发现了SiCn(n=1-4)的光谱特征,对于SiCn(n=3-8)的结构、同分异构体和光谱的理论预言也广泛地展开。本文基于密度泛函理论,采用GGA-BLYP交换关联函数和缀加极化函数的双数值原子基组DNP,对可能的星际分子SiC4H的同分异构体进行了广泛的搜索；并在DFT/B3LYP/6-311+G(d, p)级别上对SiC4H的同分异构体的结构、偶极矩、转动常数、振动频率、红外强度等进行了进一步计算,得到了如下的结果：1)得到了SiC4H的29种同分异构体,其中平面直链结构SiC4H-1-1最为稳定；2)平面直链结构SiC4H-1-1在红外波段的特征频谱(强度)为495(22)、547(69)、721(37)、3470(172),单位为cm-1(km/mol);3) SiC4H-2-1、SiC4H-3-1、SiC4H-3-3、SiC4H-6-2、SiC4H-6-4存在较高的偶极矩,易于被探测。它们在红外波段的特征频谱(强度)分别为：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).更多还原

【Abstract】 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).更多还原