基于密度泛函理论研究受限水的太赫兹频谱和电子特性  

Study on Terahertz Spectrum and Electronic Properties of Confined Water Based on Density Functional Theory

作　　者：陈晨 孙庭钰 曹继华 朱智 CHEN Chen;SUN Ting-yu;CAO Ji-hua;ZHU Zhi(School of Optical-Electrical and Computer Engineering,University of Shanghai for Science and Technology,Shanghai 200093,China;The People's Hospital of China Three Gorges University,Yichang443000,China)

机构地区：[1]上海理工大学光电信息与计算机工程学院,上海200093 [2]三峡大学人民医院,湖北宜昌443000

出　　处：《真空电子技术》2022年第4期22-30,35,共10页Vacuum Electronics

摘　　要：利用密度泛函理论探究受限于纳米通道内的水分子结构、集体振动频率以及电子特性。研究表明受限于直径为0.677~1.086nm的纳米通道内的水分子,它们在太赫兹频段存在两种典型的振动模式,一种是平行于通道的轴向集体振动,另一种是受限水分子间的氢键拉伸振动。通过对比不同受限域下,受限水的这两种典型的振动模式所对应的特征频率,发现它们的数值变化存在一定的规律。对于受限水的轴向集体振动,随着通道的管径从0.677增大到0.815nm,它所对应的特征频率整体发生了红移,然而随着管径继续增大,该特征频率的变化发生了分化,即一部分发生了红移,另一部分发生了蓝移。对于受限水的氢键拉伸振动,随着管径从0.677增大到0.815nm,它所对应的特征频率整体发生了蓝移,然而随着管径继续增大,该特征频率的变化也发生了分化。其内在机理通过电子密度拓扑分析揭示为:水分子与通道或水分子间所形成H…π键和O…H键的键临界点电子密度ρ值的减小造成了键振动的红移,反之造成蓝移。鉴于细胞的动力学平衡,例如渗透压和体积变化,它们与受限水在水通道中的结构和动力学特性紧密相关,本研究将有助于在分子层次加深太赫兹波与受限水相互作用的理解,进而促进太赫兹技术在生物医学方面的应用。The structure,the collective vibrational frequencies and the electronic properties of water molecules confined in nanochannels are investigated using density functional theory.The result shows that the water molecules confined in nanochannels with diameters ranging from 0.677to 1.086nm have two typical motion modes in terahertz band,one is axial collective motion parallel to channels and the other is hydrogen bond stretching vibration between confined water molecules.By comparing the characteristic fre-quencies corresponding to the two vibration modes in different confinement domains,it is found that there is a certain pattern in the variation of their values.For the axial collective vibration,as the tube diameter increases from 0.677to 0.815nm,the corresponding eigenfrequency is red-shifted;as the tube diameter continues to increase,the change of the eigenfrequency diverges,i.e.,one part is red-shifted and the other part is blue-shifted.For the hydrogen bond stretching vibration,as the tube diameter increases from 0.677 to 0.815nm,the eigenfrequency corresponding to it shifts blue;as the tube diameter continues to in-crease,the change of the eigenfrequency also diverges.The intrinsic mechanism is revealed by electron density topology analysis:the decrease of the electron densityρvalue at the bond critical point of H…πbond and O…H bond formed between water molecule and channels or between water molecules causes the bond vibration red-shift,and vice versa causes blue-shift.In view of the dynamic equilibrium processes of cells,such as osmotic pressure and volume change,which are closely related to the structure and dynamic characteristics of confined water in nanochannels,this study will help to deepen the understanding of inter-action between terahertz wave and confined water at molecular level,and further promote the application of terahertz technology in biomedicine.

关 键 词：密度泛函理论 碳纳米管 受限水 氢键拉伸 蓝移 

分 类 号：O691[理学—化学]