Covalency-Dependent Vibrational Dynamics in Two-Dimensional Titanium Carbides

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• 作者：Tao Hu ; Minmin Hu ; Zhaojin Li ; Hui Zhang ; Chao Zhang ; Jiemin Wang ; Xiaohui Wang
• 刊名：Journal of Physical Chemistry A
• 出版年：2015
• 出版时间：December 31, 2015
• 年：2015
• 卷：119
• 期：52
• 页码：12977-12984
• 全文大小：481K
• ISSN：1520-5215

文摘

Structure and vibrational dynamics of T-terminated titanium carbide monosheets Ti₂CT₂ (T = O, F, OH) are studied by means of first-principles calculations to understand their inherent relation. Terminations modulate the crystal structures through the redistribution of valence electron density among the atoms in the monosheets, particularly Ti atoms. Phonon partial density of states analysis shows a clear feature of collaborative vibration, which reflects the covalent nature of bonds in the monosheets. Two metrics of covalency and cophonicity proposed very recently are adopted to quantitatively correlate the vibrational properties with the electrostructural characteristics of the system. A remarkable positive correlation between the covalency and vibrational dynamics specified as Raman shifts and IR wavenumbers is found. The bond-specific covalency metrics depend on not only the identity of terminations but also the thickness of the two-dimensional titanium carbides. For example, in the case of Ti₃C₂T₂ with increased thickness, red shift in Raman shifts and IR wavenumbers occurs as a result of the decrease in covalency.