二氧化硅纳米结构径向呼吸振动的理论研究

Theoretical study on Raman radial breathing vibration of SiO2 nanostructures

  • 摘要: 运用密度泛函理论的B3LYP方法,在6-31G(d)基组水平上,计算了由Si2O2二元环组成的准一维SiO2纳米链及三元环(3MR)、四元环(4MR)、六元环(6MR)和八元环(8MR)组成的SiO2纳米管的Raman振动光谱。从Raman光谱发现纳米链和纳米管的径向呼吸振动频率随链或管长的增加而频率移动相反,即分别发生红移和蓝移,但随着链和管趋于无限长频率趋近稳定值;同时,随着直径的增大,振动频率减小。在小尺寸时,由于结构内部的应力影响使频率移动更明显,进一步对键长和键角分析说明,结构应力的作用使频率随尺寸变化发生移动。

     

    Abstract: Using the B3LYP method based on the density functional theory, a quasi-1D SiO2 nanochain formed by SiO2 2MR, and the Raman vibration spectra of a SiO2 nanotube composed of 3MR, 4MR, 6MR and 8MR were calculated at 6-31G(d) level. Through the analysis of Raman spectra, it is found that Raman radial breathing vibration frequency of the nanochain and nanotube moves to the opposite direction with the increase of their length, namely, the red shift and blue shift turn up. However, Raman frequencies trend to reach the different stable values with the approximation of the infinite frequency, and the vibration frequencies reduce with the diameter increase of the nanochain and nanotube. Due to the internal structure stress of nanomaterial, the frequency shift is more obvious for small size material. The further analysis of bond length and bond angle of all kinds of structures shows that the function of the structure stress causes the frequency drift according to the size of the nanomaterial.

     

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