共查询到19条相似文献,搜索用时 69 毫秒
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不同边界条件下一维双原子链的晶格振动 总被引:10,自引:2,他引:8
在自由边界条件和驻波边界条件下,讨论分析了一维双原子链晶格振动的振动模和色散关系,并与周期性边界条件下的结果进行了比较;明确了在不同边界条件下讨论实际原子链晶格振动的振动模和色散关系,其结果是相同的。 相似文献
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讨论晶格的光频支格波对晶格热容的贡献,得到了这部分的热容的表达式。在低温极限情况下,光频支格波对晶格热容的贡献很小,可以忽略,只有频率较低的声频支格波对晶格热容有重要贡献;在高温情况下,复式 和中光频支格波对晶格热容有重要贡献,高温情况下的结果与杜隆-珀蒂定律给出的经典数值一致,该定律在高温时与实际实验符合得很好。 相似文献
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应用改进分析型嵌入原子法模型和晶格动力学理论,计算了金属钽和钨以及B2型钽钨有序合金的原子力常数和动力学矩阵,模拟了金属钽和钨沿[ζ00]、[ζζ0]和[ζζζ]三个对称方向以及B2型钽钨有序合金沿[ζζ0]、[11ζ]、[ζζζ]和[ζ00]四个对称方向的声子色散曲线,并分析了B2型钽钨有序合金的振动特性.结果表明:金属钽和钨的声子色散曲线的模拟结果和实验值符合较好,特别在低频附近二者几乎一致;B2型钽钨有序合金中既有声频振动支又有光频振动支,光频支的振动频率均大于声频支的振动频率,且光频带和声频带之间由宽度约为0.82THz的空带隔开;在[ζζ0]对称方向上有六个独立振动模,在[11ζ]、[ζζζ]和[ζ00]对称方向上六个振动模均兼并为四个独立振动模,且各振动支的振动方向不尽相同. 相似文献
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一维晶格振动声子谱的全量子理论和"不变量本征算符"方法 总被引:1,自引:1,他引:0
建立一维晶格振动声子谱的全量子理论,其哈密顿量是自动包含了Born-von-Karmann边界条件的环链量子哈密顿量,然后用不变本征算符方法简捷地求出其声子谱. 相似文献
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ZrO2晶格振动的相关分析和ZY系统的拉曼光谱 总被引:4,自引:1,他引:3
谷晋骐 《光谱学与光谱分析》1995,15(6):45-49
采用Fateley相关方法,详细讨论了ZrO2四方相、单斜相和立方相晶格振动的对称性分类及其光谱活性。根据拉曼光谱判定了ZY系统的相结构。 相似文献
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合成双射流激励器工作噪声远低于合成射流激励器工作噪声, 但其噪声特性仍然限制了其应用于笔记本电脑、空调、冰箱等室内电子设备散热. 为降低合成双射流激励器整体噪声, 采用数值模拟的手段探究合成双射流激励器在不同边界条件下的振动噪声特性, 为合成双射流激励器降噪设计提供指导. 结果表明: 压电振子与壳体的振动共同影响着激励器振动噪声声压级大小; 夹持条件对振动噪声影响很大, 压电振子处于夹支条件时, 激励器的振动噪声声压级比压电振子处于简支时的激励器最大声压级低10 dB. 相似文献
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MOCVD生长的GaN和GaN:Mg薄膜的拉曼散射 总被引:2,自引:1,他引:1
通过显微拉曼散射对用金属有机化学气相沉积(MOCVD)法在Al2O3衬底上生长的六方相CaN和掺Mg的P型GaN薄膜进行了研究。在两个样品的拉曼散射谱中同时观察到位于640,660cm^-1附近的两个峰。640cm^-1的峰归因于布里渊区边界(L点)最高声学声子的二倍频,而660cm^-1的峰为布里渊区边界的光学声子支或缺陷诱导的局域振动模。掺Mg的GaN在该处的峰型变宽是Mg诱导的缺陷引起的加宽或Mg的局域模与上述两峰叠加的结果。在掺Mg的样品中还观察到276,376cm^-1几个局域模并给予了解释。同时掺Mg的GaN中出现了应力弛豫的现象,掺Mg引起的失配位错和电子-声子相互作用都有可能对E2模的频率产生影响。 相似文献
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The separation of electronic and nuclear variables is considered for a molecule in an intense electromagnetic field with frequency ω close to some electronic transition frequency. In this case the electron potential curves are essentially modified and a new branch of the vibrational spectrum can appear which has no counterpart in the original spectrum. 相似文献
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Magnetic particles freely moving in a fluid may organize themselves into dense phases, bulk clusters, or linear chains. The dynamics of particles forming a chain is analyzed theoretically taking into account the magnetic dipole interaction as well as the Van der Waals molecular interaction. The vibrational spectrum has two branches (the magnetic branch associated with the rotation of the magnetic moment of a particle and the elastic branch associated with the displacement of particles). In the case of particles with constant mass density and magnetic moment, which is interesting for applications, these two modes are in fact independent; i.e., the effects of mode hybridization are weak. However, these effects can be manifested for hollow particles. From analysis of the vibrational spectrum, the criterion for the chain stability to a transition to a denser phase is established. 相似文献
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The Rayleigh–Schrödinger perturbation theory of high orders and the algebraic Padé–Hermite approximants are used to determine the singular points of a vibrational energy function of the formaldehyde molecule dependent on a complex perturbation parameter as on the argument. It is shown that the Fermi, Darling–Dennison, and other higher-order vibrational resonances are related to Katz’s points—common branch points on the complex plane of the energy of two vibrational states. Analysis of Katz’s points that connect different vibrational states allows one to reveal essential resonance perturbations, to introduce an additional classification for them, and to determine the polyad structure of an energy spectrum. 相似文献
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A theoretical model of vibrational dynamics is proposed for a glass, which comprises acoustic and soft-mode vibrational excitations interacting with each other and gives rise to a vibrational spectrum “broken” into two branches separated by a pseudogap. The latter appears to be associated with a Ioffe–Regel cross-over to strong inelastic scattering of the excitations. The upper branch contains acoustic-like high-frequency excitations, which are similar to those recently observed in inelastic X-ray scattering spectra of a series of glasses. The present model may resolve the recent controversy concerning the interpretation of the scattering spectra. 相似文献
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M. L. Strekalov 《Optics and Spectroscopy》2005,98(1):1-5
The pressure-induced transformation of the spectrum of the Q branch of the ν1 mode (1388 cm?1) of CO2 molecules is quantitatively interpreted. The contributions to the width of the spectrum from three relaxation mechanisms—vibrational dephasing, rotational relaxation, and the Doppler effect—are taken into account. From the fitting of the calculated and measured spectra of the Q branch, the effective cross section of the rotational energy relaxation is determined. 相似文献
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The change in the atomic vibrational frequency spectrum of an fcc crystal due to the presence of a grain boundary is obtained by lattice dynamics methods. The grain boundary is a 36.9° 〈100〉 symmetric tilt coincidence boundary. An orthorhombic computational cell of 58 atoms containing two such boundaries of opposite rotational sense is employed. The atomic interactions are simulated by a Morse potential developed by Cotterill and Doyama to fit aluminum. From the changes in frequency spectrum the excess thermodynamic functions of the grain boundary are calculated and compared with results from both experiment and the Einstein model. The general shift of frequencies toward lower values is probably due to the weaker binding of many atoms near the boundary, while there are some higher frequency states associated with a few more tightly bound atoms. 相似文献
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A well-defined band has been observed in the low temperature infrared spectrum of KI, KBr, NaI, and RbCl in the region corresponding to the sum of three optical branch phonos and no corresponding band in the two- and four-phonon regions. These results can be accounted for by deducing an odd-even quasiselection rule for crystals having a gap between the optical and acoustical branches of the vibrational spectrum. 相似文献
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The results of a nonempirical calculation of the static and dynamic properties of a Rb2KScF6 crystal with elpasolite structure in cubic, tetragonal, and monoclinic phases are presented. The calculation is performed
on the basis of a microscopic model of an ionic crystal that takes account of the deformability and polarizability of the
ions. The deformability parameters of the ions are determined from the condition that the total energy of the crystal is minimum.
The computational results for the equilibrium lattice parameters are in satisfactory agreement with experimental data. Unstable
vibrational modes are found in the vibrational spectrum of the lattice in the cubic and tetragonal phases. These modes occupy
the phase space throughout the entire Brillouin zone. The characteristic vectors of the most unstable mode at the center of
the Brillouin zone of the cubic phase are related to the displacements of the fluorine ions and correspond to rotation of
ScF6 octahedra. Condensation of this mode leads to a tetragonal distortion of the structure. In the tetragonal phase the most
unstable mode belongs to the boundary point of the Brillouin zone and condensation of this mode leads to monoclinic distortion
with doubling of the unit-cell volume. In the monoclinic phase unstable modes are absent in the vibrational spectrum of the
lattice.
Fiz. Tverd. Tela (St. Petersburg) 41, 1297–1305 (July 1999) 相似文献