Ti小团簇$_n$ C $_x$的结构、稳定性和光吸收谱：第一性原理研究
Structure, stability and optical absorption spectra of small Ti$_n$C$_x$ clusters: a first-principles approach
摘要：
碳化钛分子团被认为是在富碳的渐近巨支星（AGB）的星周包层（CSE）中形成的，但迄今为止，它们的探测仍然难以捉摸。为了便于在AGB和后AGB环境中对这些星系团进行天体物理识别，对小的Ti $_n$ C $_x$（n = 1-4，x = 1 -4）和一些选定的较大星系团Ti $_3$ C $_8$，Ti $_4$ C $_8$，Ti $_6$ C $_{13}$，Ti $_7$ C $_{13}$，Ti $_8$ C $_{12}$，计算了Ti $_9$ C $_{15}$和Ti $_{13}$ C $_{22}$。密度泛函的形式主义，在电子交换和相关的B3 LYP近似，被用来找到最低的能量结构。除了含有单个Ti原子的团簇外，其余的团簇均为三维结构。它们是由通常被碳二聚体包围的Ti碎片形成的。Ti $_n$ C $_x$的光谱，计算的含时密度泛函理论，使用修正的CAM-B3 LYP功能，显示在可见光和近红外区域的吸收功能，这可能有助于在空间中识别这些集群。此外，大多数星团都有相当大的电偶极矩，使得射电天文学观测可以探测到它们。
英文摘要：
Titanium-carbide molecular clusters are thought to form in the circumstellar envelopes (CSEs) of carbon-rich Asymptotic Giant Branch stars (AGBs) but, to date, their detection has remained elusive. To facilitate the astrophysical identification of those clusters in AGBs and post-AGBs environments, the molecular structures and optical absorption spectra of small Ti$_n$C$_x$ clusters, with n = 1-4 and x = 1-4, and some selected larger clusters, Ti$_3$C$_8$, Ti$_4$C$_8$, Ti$_6$C$_{13}$, Ti$_7$C$_{13}$, Ti$_8$C$_{12}$, Ti$_9$C$_{15}$, and Ti$_{13}$C$_{22}$, have been calculated. The density functional formalism, within the B3LYP approximation for electronic exchange and correlation, was used to find the lowest energy structures. Except the clusters having a single Ti atom, the rest exhibit three-dimensional structures. Those are formed by a Ti fragment surrounded in general by carbon dimers. The optical spectra of Ti$_n$C$_x$, computed by time-dependent density functional theory, using the corrected CAM-B3LYP functional, show absorption features in the visible and near infrared regions which may help in the identification of these clusters in space. In addition, most of the clusters have sizable electric dipole moments, allowing their detection by radioastronomical observations.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
