单壁碳纳米管晶格振动模及红外吸收光谱的研究

碳纳米管晶格动力学的研究可以提供碳纳米管结构和螺旋性等方面的相关信息。在室温下测量了单壁碳纳米管的红外吸收光谱,首次在透射法模式下观察到了其晶格振动模的红外吸收峰,通过与晶格动力学理论计算值对照,做出了振动模的初步归属。讨论了单壁碳纳米管高频振动模与管径的关系,并与高取向热解石墨振动模进行了对比。结果表明,红外吸收光谱包含有碳纳米管的许多信息,是研究其晶格动力学的有效方法。     

晶格旋转对称性的单转轴证明

传统的晶格旋转对称性的双转轴证明方法不满足旋转对称操作至少要保持一点不动的要求，本文提出了晶格旋转对称的单转轴证明方法，克服双转轴证明方法的缺点。     

利用晶体的对称性讨论三维晶格振动

在晶格动力学中，立方晶格的本征方程的能力学矩阵Ｄ（Ｋ）比较复杂，利用晶体的对称性将Ｄ（Ｋ）化简，由化简后Ｄ（Ｋ）的矩阵形式，能较为容易地解久期方程及确定偏振矢量。     

有限晶格动力学

近３０年来晶格动力学取得了很大的成功，它是近代固体理论用于解释各种物理效应和材料性质的重要基础．这一理论的发展同时也暴露了起源于６０，７０年前的它的基本方程和边界条件的某些弱点．注意修正这些缺点并吸取分子振动理论成功的经验，可以建立从零维到一维、二维和三维的统一的有限晶格动力学方法．新方法给出了声子的更深刻的物理图像，并有可能导致许多更重要的新结果，以解决当前科学技术进展中正面临着的困难．     

纳米晶体线的晶格动力学格林函数及晶格振动

通过求解差分方程,推导了纳米晶体线的晶格动力学格林函数,分析了其晶格振动,并推导了声子数表象中的原子位移及晶格振动哈密顿公式.研究结果表明,纳米晶体线的晶格振动能带分裂为一系列的子带,格波只能沿纳米晶体线的纵向传播,沿纳米晶体线的横截面只存在驻波.     

正方结构La_(2-x)M_xCuO_4的晶格动力学

本文采用刚性离子模型,利用远红外和啦曼光谱的实验结果,确定模型中的参量,研究了正方结构 La_(2-x)M_xCuO_4Γ点的晶格振动.预言 R.J.Birgeneau 等观测到的软模,在Γ点具有 E_g 对称性.并用一种有效的方法,计算了多晶材料的平均声速.     

一类动力学方程的Mei对称性

研究一类动力学方程的Mei对称性的定义和判据，由Mei对称性通过Noether对称性可找到Noether守恒量.由Mei对称性通过Lie对称性可找到Hojman守恒量.同时，也可找到一类新型守恒量.     

单壁碳纳米管中的金属-半导体转变与对称性

报道了最近作者对受压扶手椅形单壁碳纳米管中的金属-半导体转变机理的理论研究。这种转变在两种因素的共同作用下得以发生，即外加压力造成碳纳米管镜像对称破缺，以及被压碳纳米管两侧原子发生成键相互作用．作者还进一步揭示了发生这种转变的普遍机制：只要将单壁碳纳米管中两套原来等价的子晶格变得可以区分(对称性破缺)，在费米能附近就会产生能隙．     

单壁氮化硼纳米管的结构、对称性和晶格动力学

本文分析了氮化硼纳米管的结构对称性,并对其晶格振动模的对称性进行了分类。计算了单壁氮化硼纳米管的声子色散关系,给出了扶手椅管和锯齿管拉曼和红外活性模的频率随管径的变化规律。     

碳纳米管的拉曼散射研究

本文介绍碳纳米管研究的最近进展。简单描述碳纳米管的生长和形貌结构特性,着重分析不同方法生长的多层和单层碳纳米管的拉曼散射测量结果     

Assessment of Timoshenko Beam Models for Vibrational Behavior of Single-Walled Carbon Nanotubes Using Molecular Dynamics

In this paper, we study the flexural vibration behavior of single-walled carbon nanotubes (SWCNTs) for the assessment of Timoshenko beam models. Extensive molecular dynamics (MD) simulations based on second-generation reactive empirical bond-order (REBO) potential and Timoshenko beam modeling are performed to determine the vibration frequencies for SWCNTs with various length-to-diameter ratios, boundary conditions, chiral angles and initial strain. The effectiveness of the local and nonlocal Timoshenko beam models in the vibration analysis is assessed using the vibration frequencies of MD simulations as the benchmark. It is shown herein that the Timoshenko beam models with properly chosen parameters are applicable for the vibration analysis of SWCNTs. The simulation results show that the fundamental frequencies are independent of the chiral angles, but the chirality has an appreciable effect on higher vibration frequencies. The SWCNTs is very sensitive to the initial strain even if the strain is extremely small.     

Molecular Dynamics Study of Effects of Si-Doping Upon Structure and Mechanical Properties of Carbon Nanotube

In this paper, a Si-doped single-walled carbon nanotube (SWCNT) (7,7) and several perfect armchair SWCNTs are investigated using the classical molecular dynamics simulations method. The inter-atomic short-range interaction is represented by empirical Tersoff bond order potential. The computational results show that the axial Young's modulus of the perfect SWCNTs are in the range of 1.099 ± 0.005 TPa, which is in good agreement with the existing experimental results. From our simulation, the Si-doping decreases the Young's modulus of SWCNT, and with the increased strain levels, the effect of Si-doped layer in enhancing the local stress level increases. The Young's modulus of armchair SWCNTs are weakly affected by tube radius.     

多壁碳纳米管的拉曼散射

本文报导了用直流碳弧放电方法制备的多层碳纳米管的拉曼光谱。和ＨＯＰＧ相比,由于碳纳米管的量子尺寸效应和碳纳米管直径的分布,在纯化和未纯化的碳纳米管中均存在Ｅ２ｇ模的软化,其红移范围分布在２～１３ｃｍ １范围内。     

碳纳米管与有机小分子官能团相互作用的分子动力学研究

利用Material Studio软件先对不同半径的碳纳米管进行结构优化,再对优化后的纳米管进行分子动力学模拟。得到如下结论：经过优化后小半径纳米管结构基本不变,但是随着半径增大纳米管形变越来越明显。同时通过对多根管簇研究后发现也有相似动力学特性。在以上纳米管结构外面加上一定密度随机排列的对苯二甲酸二辛酯（DOTP）有机分子,发现DOTP有机分子与不同结构、不同半径的纳米管之间都存在相互作用,纳米管半径越大相互作用力也越大,同时DOTP分子在纳米管周围排列也逐渐从无序趋于有序。通过计算以上结构的径向分布函数（RDF）等热力学特性,定性和定量地验证了以上结果。     

Lattice Dynamics Study of Magnesium Chalcogenides

First-principles calculations,which are based on the plane-wave pseudopotential approach to density functional perturbation theory within the local density approximation,have been performed to investigate the structural,lattice dynamical and thermodynamic properties of zinc blende(B3) structure magnesium chalcogenides:MgS,MgSe and MgTe.The results of ground state parameters and phonon dispersion are compared and agree well with the experimental data available and other calculations.We obtain the change of Born effective charge and LO-TO splitting under hydrostatic pressure.Finally,by the calculations of phonon frequencies,some thermodynamic properties such as the entropy,heat capacity,internal energy,and free energy are also successfully obtained.     

Interaction of Carbon Nanotubes with Some Polymers

Microscopical, differential scanning colorimetry (DSC), and X-ray structural investigations of solution crystallized carbon nanotube (CNT) composites with linear polyethylene (LPE), isotactic polypropylene (iPP), polybutene-1 (PB-1), and nylon 6 (PA6) disclosed varying degrees of surface interaction and nucleation effect of CNT in these polymers and formation of oriented shish-kebab overgrowths on the CNT ropes in LPE and PA6. The character of the attraction and orientation forces at the CNT-polymer interface is discussed.     

碳纳米管场发射显示器的研究进展

碳纳米管因具有良好的电子发射特性而成为理想的场发射阴极材料,利用碳纳米管作阴极的场致发射平板显示器件的研究是目前显示技术领域的研究热点之一。报道了场发射显示器（FED）的结构及工作原理、阴极发射材料应具有的特点及碳纳米管在场发射领域中的应用情况。详细地论述了碳纳米管的场致发射特性,包括开启电场、发射电流密度、电流稳定性及发射点密度等,对国内外碳纳米管场发射显示器的发展现状及趋势作了回顾和展望,并对目前所面临的主要问题作了分析,同时提出了一些改进的思路。     

Lattice Dynamics at Zone-Center of Sulphide and Selenide Spinels

A rigid-ion model is used to calculate the force constants and effective dynamical charges of sulphide and selenide spinels. The Raman and infrared phonon modes of normal cubic sulphide spinels MCr2S4 （M = Mn, Co, Fe, Hg, Zn, and Cd） and selenide spinels MCr2Se4 （M = Hg, Zn, and Cd） are calculated at the first Brillouin zone-centre using above model, The significant outcome of the present work is （i） the interatomic interaction between Cr-S （Se） dominates over the Cr-S（Se） and S-S（Se-Se） type of interatomic interactions, （ii） the effective dynamical charges of the bivalent metal ions are nearly zero, and （iii） the selenide spinels are less ionic than the sulphide spinels and the ionicity decreases as MnCr2S4 〉 FeCr2S4 〉 CoCr2S4 〉 and CdOr2C4 〉 ZnCr2C4 〉 HgCr2C4 （C = S and Se）. The zone-center phonon frequencies, calculated using these parameters, are found to be in very good agreement with the observed results.