立方晶系两套晶列,晶面指数的转换

晶列和昌面的指数与坐标系的选择有关.以布喇菲晶胞基矢为坐标系时,晶面密勒指数记为(hkl)[1],立方晶系的晶列指数记为[hkl];以初基原胞基矢为坐标系时,晶面指数记为(h1h2h3),而晶列指数记为[l1l2l3][2].坐标系不同,同一晶面族的晶面指数和密勒指数一股都不相同.晶列的情况也是如此.本文仅就体心立方和面心立方点阵的两套指数的转换关系加以讨论. 体心立方和面心立方的晶胞基矢a,b,c与初基原胞基矢a1,a2和a3的习惯选取方法如图1所示.山图1不难求出两套丛矢间的转换关系. 对于体心立方点阵, 对于面心立方点阵, 倒格基矢的转换也有类似的结果,…     

非晶Ni-P合金晶化过程中生成的六角亚稳相(Ⅱ) 孪晶生长关系

非晶Ni-P合金晶化过程中生成的六角亚稳相晶体有四种不同取向,用选区电子衍射证明它们之间存在孪晶生长关系。四种晶体共有一个面心立方亚点阵,孪晶关系可用绕此立方亚点阵的<100>轴旋转90℃得出。     

非晶Ni-P合金晶化过程中生成的六角亚稳相(Ⅱ)——孪晶生长关系

非晶Ni-P合金晶化过程中生成的六角亚稳相晶体有四种不同取向,用选区电子衍射证明它们之间存在孪晶生长关系。四种晶体共有一个面心立方亚点阵,孪晶关系可用绕此立方亚点阵的<100>轴旋转90o得出。 关键词：     

消光与原胞的选取

本文以面心立方结构的简单晶格为例，证明了对于一个给定的晶体，分别从固体物理学原胞基矢和结晶学原胞基矢出发定义的两个倒格子一般是不同的．进而证明了，在结晶学原胞基关系统中，既满足衍射方程又满足消光条件的方向，在固体物理学原胞基矢系统中看来，就不满足衍射方程．因而在该方向上也不出现衍射束．     

晶格中用不同的原胞表示的倒格子

对于同一个空间点阵，选取不同的固体物理学原胞，得到的倒易空间点阵是唯一的．从结晶学原胞基矢出发定义的倒易空间点阵，与从固体物理学原胞基矢出发定义的倒易空间点阵一般不一致．在二种方法中，倒格子与正格子间的关系一般相同．     

有简单取向关系的两晶体间电子衍射图相重的规律

有简单取向关系的两个晶体在倒易空间中有部分倒易点相重。仅由相重倒易点构成的倒易面所对应的电子衍射图必定被基体的衍射斑点所覆盖。给出判定第二相相重电子衍射图晶带轴指数的方法,用此方法考察了立方晶体与孪晶、六角密堆相和ω相等衍射图相重的情况。 关键词：     

名词浅释

知识与进展晶体对称轴和对称面 晶体是由按一定对称性排列成点阵的原子所组成.如果一个晶体结构对某个轴(或面)而言,按一定对称操作(如旋转或反射),便能使该晶体结构自身完全重合,则此轴为晶体的对称轴,相应的面为对称面.低密勒指数面、低标次轴 给出在一个晶面上的三个不共线的原子的坐标,就决定了该晶面的位置和取向,通常用密勒指数指明面的取向,因而把晶面记为(h,k,l),密勒指数低的面,也就是h,k,l值小的面,如立方晶体表面为(100),(010),(001),(100),(010)和(001),属于低密勒指数面。 晶体旋转对称轴可以分为一重、二重、三重、四重和六重…     

液晶近晶C相双轴特性的统计理论

采用格胞模型,定义了分子取向序参量、双轴序参量、质心位置序参量以及取向与质心位置耦合序参量.由自由能极小求得指向矢倾斜角与双轴序参量间的关系.对典型Sc相液晶物质TBBA,TBSA和NOBA的双轴序参量随温度的变化以及取向序参量和倾斜角对双轴序参量的影响作了数值计算,并与实验结果进行比较.表明这种双轴特性主要产生于Sc相的指向矢倾斜结构和分子取向的有序性. 关键词：     

正交曲线坐标系中单位基矢的导数

由不同正交曲线坐标系的单位基矢之间的变换矩阵,推导出正交曲线坐标系的单位基矢对本身坐标的求导和对时间的求导规律.并且以球坐标系与柱坐标系的单位基矢的本身空间坐标求导为例进行了讨论.     

以石墨烯为例分析二维六角晶格结构及振动模式

石墨烯因其独特的六角晶格结构,使其具有优异的力、热、光、电等特性,成为目前应用研究最广泛的新型材料之一.本文从固体物理学的教学角度出发,以单层石墨烯的晶格结构为例,采用图像的形式描述了二维六角晶格的正格子原胞和基矢、倒格子原胞和基矢、q空间和第一布里渊区,并推导了二维六角晶格的振动模式.     

Structure of the Wigner crystal

A model of the Wigner crystal with two localized electrons per cell is developed. The ground state energy of this model is evaluated. The Coulomb interaction within a cell is treated exactly for a certain range of electron concentrations. The calculation demonstrates that at very low electron concentrations the crystal contains a single localized electron per cell. As the concentration is increased the crystal comes to contain two, three or more electrons per cell. At high electron concentrations the entire crystal can be treated as a single cell.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 6, pp 47–51, June, 1988.     

相场晶体法模拟过冷熔体中的晶体生长

利用相场晶体(phase-field crystal)模型,采用有限差分法,模拟了过冷熔体中晶体生长过程,研究了不同相区、不同过冷度对晶体生长过程的影响.结果表明,在共存区中,随着演化的进行,晶体生长被抑制,液-晶边界层逐渐变厚;在单相区中,随着过冷度的增大,晶态区面积显著增加,液-晶边界层逐渐变薄.晶体生长速度和过冷度成近似线性的关系. 关键词： 相场晶体 自由能函数 过冷熔体 晶体生长     

Misfit disclinations at crystal/crystal and crystal/glass interfaces

Theoretical concepts have been developed for a new type of misfit defects, misfit disclinations, at crystal/crystal and crystal/glass interfaces. It is shown, in particular, that the formation of misfit disclinations is an efficient physical micromechanism of misfit stress relaxation at crystal/crystal interfaces. A model describing misfit disclinations at crystal/glass interfaces has been constructed. The energy characteristics of phase boundaries with misfit disclination ensembles are estimated. Fiz. Tverd. Tela (St. Petersburg) 41, 1637–1643 (September 1999)     

Vibrational spectroscopy of the seselin crystal

Seselin, C₁₄H₁₂O₃, is a coumarin which crystallizes in a monoclinic structure P2₁/b(C_2h⁵) with four molecules per unit cell. In a Fourier‐transform Raman spectroscopic study performed at room temperature, several normal modes were observed. Vibrational wavenumber and wave vector calculations using density functional theory were compared with experiment, which allowed the assignment of a number of normal modes of the crystal. Temperature‐dependent Raman spectra were recorded between 10 and 300 K. No anomalies were observed in the phonon spectra, indicating that the monoclinic structure remains stable. Copyright © 2007 John Wiley & Sons, Ltd.     

On the stability of crystal growth

We investigate properties of solid-on-solid models for crystal growth, involving general microscopic rates of capture of atoms by the crystal surface and of escape of atoms. The rates in this Markov process influence the stability of the growing surface. We prove, for various different ranges of the rate parameters, stability (i.e., ergodicity) and instability (i.e., nullity) of the growth process. Symmetry properties of the process, such as reversibility, dynamic reversibility, and reflection invariance, are proved or disproved under various conditions. We give a measure of surface smoothness that distinguishes between stable and unstable growth.     

Quasi-pyroelectricity in the TGS crystal

It has been shown that a side electrode perpendicular to the measurement ones can significantly enhance the transverse electric current in TGS. Such a current, measured in a zero external electric field, resembles the classic longitudinal one. However, the amplitude of the transverse current oscillation, observed while cooling and heating the sample, rises much more slowly with the time of the transverse electric field preliminary application. Such exposure to the transverse field is required prior to the measurements for the transverse current to be observed, in a similar way to a longitudinal field that is applied in order to achieve a single domain state before longitudinal pyroelectric current measurements. A huge difference in the time of reaction to the electric fields preliminarily applied in order to achieve the maximum amplitude of the current oscillations in both cases is the evidence that the transverse current cannot be considered to be originated just for geometrical reasons.     

向列相液晶缺陷光子晶体透射光谱偏振敏感特性研究

研究了向列相液晶缺陷TiO2和SiO2交替的光学多层膜一维光子晶体透射谱偏振敏感特性。外电压下透射光谱测试和模拟结果显示,对于平行取向的向列相液晶,当自然光垂直入射时,禁带中两处出现e(TE模式)光和o光(TM模式)透射峰,具有偏振敏感性。随着电压增大,e光透射峰蓝移与o光透射峰合二为一,光谱可调谐范围分别为31和34nm;而对于取向混乱的向列相液晶,禁带中两处出现独立的透射峰,无偏振敏感性。随着电压增大峰位也蓝移,光谱可调谐范围分别为64和15nm。通过混乱取向液晶分子,可以使o光和e光有效折射率值相等,获得偏振不敏感特性。     

Measure of the closeness of crystal lattices

A numerical measure of the difference between crystal lattices is determined. The fruitfulness of the definition is demonstrated for a specific example concerning the prominence of an orientational correspondence between the body-centered crystal lattice [bcc(bct)] of α-martensite and the face-centered crystal lattice (fcc) of γ-austenite in cases where the latter is perfect and where it differs from a perfect lattice near a screw dislocation. Zh. Tekh. Fiz. 69, 60–64 (May 1999)     

非线性光学晶体YCOB的性能表征

采用显微硬度计、差热扫描仪等表征手段开展了非线性光学晶体YCOB的硬度及热学等相关性能的测量。结果表明YCOB晶体在(100)、(010)及(001)三个方向上的硬度的各向异性较小,有利于YCOB晶体的后期加工。其在330K时的比热容为0.74J·g-1·K-1,经过计算,其在主轴化方向上的热导率分别为1.74,2.16及3.08W·m-1·K-1,具有比较适中的热导率。