共查询到17条相似文献,搜索用时 62 毫秒
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基于力常数模型计算了一系列扶手椅型、锯齿型和手性单壁BC3纳米管的声子色散关系.描述了单壁BC3纳米管结构的表征方式,比较详细地给出了其结构、对称性和晶格动力学分析.基于数值计算结果,讨论了拉曼活性模和红外活性振动模的频率与管径的关系.由分析结果做出推断,BC3纳米管的拉曼光谱和红外光谱比单壁碳纳米管更为复杂. 相似文献
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介绍了平面波算法计算声子晶体带结构的分析过程,计算了二维双组分液相体系声子晶体的带结构.结果表明,四氯化碳/水银体系比水银/四氯化碳体系更容易产生带隙.随分散相填充分数f的增加,四氯化碳/水银体系声子晶体带隙宽度ΔΩ先增加,后减小,当f=0229时,有最大值ΔΩ=0549;水银/四氯化碳体系的带隙宽度一直增大,当f=0554时,有最大值ΔΩ=0515;f一定时,改变分散相单元的几何尺寸和点阵常数,带隙宽度ΔΩ保持不变.
关键词:
声子晶体
声子带隙
平面波算法
带结构 相似文献
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用一种非简谐晶格动力学方法, 使用相互作用势作为惟一的输入参数, 准确地计算了固体氩的各个声子的频率和弛豫时间. 并将这些结果进一步和玻尔兹曼输运方程相结合, 预测了固体氩从10 K 到80 K 区间的热导率, 并得到了与实验值非常符合的结果. 分析了运用非简谐晶格动力学方法进行数值计算过程中的各个相关的计算参数, 包括布里渊区中倒格子矢量的选取, δ 函数的展宽的选择等对热导率和声子弛豫时间预测结果的影响. 通过对各个声子模式对热导率贡献的分析, 发现随着温度升高, 高频声子对于热导率的贡献率也逐渐变大, 结果和理论预测完全一致.
关键词:
热导率
固体氩
非简谐晶格动力学
声子 相似文献
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利用密度泛函理论的平面波赝势方法研究了IrTi合金的晶格动力学行为. 声子谱计算表明四方(L10)结构动力学不稳定,通过冷冻不稳定声子模式, 发现IrTi会发生从四方(L10)到正交的结构相变.进一步分析软模对应的原子振动, 得到了具有正交对称性,空间群为Cmmm,相对于四方(L10)相能量更低、更稳定的结构. 这种正交新相(Cmmm)弹性稳定和动力学稳定,而且其结构参数与实验上观察到的低温结构有限的晶格参数相符合,表明IrTi合金的低温相是正交结构(Cmmm). 从理论上肯定了IrTi合金立方到四方再到正交的相变机制, 解决了实验上关于相变机制和低温相结构形式的争议. 相似文献
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Summary The phonon dispersion frequencies for Cu3Au, Cu3Zn and Ni3Fe alloys have been calculated using the model potential approach. The contribution of a short-range three-body interaction
to the dynamical matrix has also been included in the present study. The theoretically computed phonon dispersion curves of
these alloys are found to be in good agreement with the experimental data. 相似文献
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从动势能转换与守恒原理出发,在微正则(NVE)系综下,采用COMPASS力场对石墨烯纳米带及其应变传感器的谐振特性进行了分子动力学模拟.研究发现,非线性响应主导了石墨烯纳米带的动态行为,而其超高的基波频率则与长度和边界条件密切相关;单轴拉伸应变对石墨烯纳米带基波频率的影响显著且强烈依赖于边界条件,四边固支型应变石墨烯纳米带具有更高的频移,其灵敏度可高达7800 Hz/nanostrain,远大于相同长度碳纳米管应变传感器的灵敏度;石墨烯纳米带及其应变传感器的谐振特性均与手性无关.本文所得结果表明,由于超低
关键词:
石墨烯纳米带
分子动力学
应变
基波频率 相似文献
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石墨烯由于其独特的晶体结构展现出了特殊的电学特性,其导带与价带相交于第一布里渊区的六个顶点处,形成带隙为零的半金属材料,具有优异的电子传输特性的同时也限制了其在电子学器件中的使用.因而科研人员尝试各种方法来打开其带隙并调控其能带特性,主要有利用缺陷、应力、掺杂、表面吸附、结构调控等手段.其中石墨烯纳米带由于量子边界效应和限制效应,存在带隙.本综述主要介绍了制备各类石墨烯纳米带的方法,并通过精确调控其细微结构,从而对其进行精确的能带调控,改变其电学特性,为其在电子学器件中的应用提供一些可行的方向. 相似文献
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The electronic and transport properties of monolayer and AB-stacked bilayer zigzag graphene nanoribbons subject to the influences of a magnetic field are investigated theoretically. We demonstrate that the magnetic confinement and the size effect affect the electronic properties competitively. In the limit of a strong magnetic field, the magnetic length is much smaller than the ribbon width, and the bulk electrons are confined solely by the magnetic potential. Their properties are independent of the width, and the Landau levels appear. On the other hand, the size effect dominates in the case of narrow ribbons. In addition, the dispersion relations rely sensitively on the interlayer interactions. Such interactions will modify the subband curvature, create additional band-edge states, change the subband spacing or the energy gap, and separate the partial flat bands. The band structures are symmetric or asymmetric about the Fermi energy for monolayer or bilayer nanoribbons, respectively. The chemical-potential-dependent electrical and thermal conductance exhibits a stepwise increase behaviour. The competition between the magnetic confinement and the size effect will also be reflected in the transport properties. The features of the conductance are found to be strongly dependent on the field strength, number of layers, interlayer interactions, and temperature. 相似文献
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Hui Wang Jinghan You Lin Wang Min Feng Yufang Wang 《Journal of Raman spectroscopy : JRS》2010,41(2):125-129
A double‐resonance process gives rise to the 2D band in the Raman spectra of monolayer and bilayer graphene. Based on the electronic and vibrational dispersion energies of graphene, the wavenumbers of the 2D band were calculated under different laser excitation energies (from 1.0 to 4.4 eV). Calculated results are in good agreement with experimental data and reproduce the experimental dispersion slope of the 2D band very well. The calculated wavenumbers of the 2D band do not show a linear dependence on the laser excitation energies. Moreover, it is explained that the lowest wavenumber peak of the 2D band of the bilayer graphene, which is composed of four components, has the largest slope with laser excitation energy. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
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We have used a tight-binding Hamiltonian of an ABA-stacked trilayer zigzag graphene nanoribbon with β-alignment edges to study the edge magnetizations. Our model includes the effect of the intralayer next-nearest-neighbor hopping, the interlayer hopping responsible for the trigonal warping and the interaction between electrons, which is considered by a single band Hubbard model in the mean field approximation. Firstly, in the neutral system we analyzed the two magnetic states in which both edge magnetizations reach their maximum value; the first one is characterized by an intralayer ferromagnetic coupling between the magnetizations at opposite edges, whereas in the second state that coupling is antiferromagnetic. The band structure, the location of the edge-state bands and the local density of states resolved in spin are calculated in order to understand the origins of the edge magnetizations. We have also introduced an electron doping so that the number of electrons in the ribbon unit cell is higher than in neutral case. As a consequence, we have obtained magnetization steps and charge accumulation at the edges of the sample, which are caused by the edge-state flat bands. 相似文献
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采用格林函数方法研究了堆叠石墨片对锯齿型石墨纳米带电子输运性质的影响,计算了两种不同堆叠方式下锯齿型石墨纳米带的电导.研究发现,由于堆叠石墨片与石墨纳米带的耦合作用,锯齿型石墨纳米带的电导谱出现了电导谷.在远离费米能处,两种堆叠方式下的电导谷位置相近甚至重合;而在费米能附近,两种堆叠方式下的电导谷存在差异.此外,讨论了堆叠石墨片的几何尺寸对锯齿型石墨纳米带电子输运的影响.结果显示,随石墨片几何尺寸的增大,锯齿型石墨纳米带在两种堆叠方式下远离费米能处的电导谷逐渐向费米能方向移动,同时其费米能附近的电导谷在两种堆叠方式下的差异随石墨片尺寸的增大变得更为明显.研究结果表明,堆叠石墨片能够有效地调制锯齿型石墨纳米带的电子输运性质. 相似文献