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用气相法生长出了毫米尺寸的具有规则晶面和金属光泽的高质量的纯C60单晶.X射线衍射分析表明,C60单晶在室温下具有面心立方(fcc)结构,晶格常数为α=1.4199(4)nm。用扫描电子显微镜和光学显微镜观察了C60单晶的形貌,除观察到fcc结构的晶体所特有的{111}和{200}两种稳定晶面以及非常容易形成的孪晶之外,还发现了在{111}面上的树枝状、垄状和生长丘以及在{200}面上的树枝状、游泳池状和生长丘的生长缺陷。对C60
关键词: 相似文献
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采用泡生法生长了掺铥钨酸镱钾(KTm0.1Yb0.9(WO4)2)激光晶体。利用X射线单晶衍射法和X射线粉末衍射法研究了KTm0.1Yb0.9(WO4)2晶体的物相与结构。采用X射线单晶衍射法并结合Diamond晶体结构绘图软件,获得了晶体内部结构模型图:该晶体是由WO6、TmO8/YbO8和KO12基团组成。W2O10二聚体通过WOW单氧桥相连,在平行于c轴方向上形成(W2O8)n多重带。ReO8和KO12多面体共顶相连,沿[101]和[110]方向形成了具有二维层结构的延长带。X射线粉末衍射分析表明:该晶体具有低温β相双钨酸盐结构,属于单斜晶系,空间群C2/c;计算了晶胞参数、晶粒尺寸和结晶度。测试了晶体的振动光谱,对各个峰值的红外和拉曼活性及分子振动情况进行了归属,进一步验证了晶体中WO6原子基团及单氧桥(WOW)和双氧桥(WOOW)的存在。 相似文献
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本文报道了从粒子背散射堵塞效应的实验中所发现的单晶Si的{111}晶面粒子堵塞坑的新现象。单晶Si的{111}晶面有两个面间距d(111)(a)和d(111)(b),而{110}晶面只有一个面间距d(110)。由此导致两者的堵塞坑是不同的,我们已从α粒子和质子的Si单晶堵塞效应的实验得到了证实。并由此估计了d(111)(a)和d(111)(b)以及d(110)的2ψ1/2角。据作者了解,到目前为止,国内外还没有人发现此现象。此现象的发现对复杂晶体的堵塞和沟道效应的研究开阔了前景。
关键词: 相似文献
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采用基于单电子晶体场机制的对角化能量矩阵方法, 计算了Gd3+在钼酸盐AMoO4 (A=Ca, Sr, Ba, Pb)晶体中的自旋哈密顿参量(g因子g//, g⊥和零场分裂b20, b40, b44, b60, b64). 矩阵中的晶体场参量采用重叠模型计算. 计算结果显示, 应用三个合理的可调参量[即重叠模型中的内禀参量A2 (R0), A4 (R0)和A6 (R0)], 计算的七个自旋哈密顿参量与实验结果符合甚好, 表明该方法可用于计算或解释Gd3+在晶体中的自旋哈密顿参量.
关键词:
AMoO4 (A=Ca,Sr,Ba,Pb):Gd3+晶体')" href="#">AMoO4 (A=Ca,Sr,Ba,Pb):Gd3+晶体
自旋哈密顿参量
晶体场理论
对角化能量矩阵 相似文献
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有研究表明, 非共格∑3晶界的行为在中低层错能面心立方金属晶界 特征分布演化中发挥着重要作用. 为了掌握不同界面匹配的非共格∑3晶界的特性, 本文利用分子动力学(MD)模拟方法首先研究了纯铜的[0 1 1]倾侧型 非共格∑3晶界在700–1100 K温度范围内和常压下的结构稳定性. MD模拟采用原子间相互作用长程经验多体势, 步长为5×10-15 s. 模拟结果表明: 所研究的五个非共格∑3晶界, 其结构稳定性存在很大差异, 其一般规律是, 与(1 1 1)/(1 1 1)共格孪晶界之间的夹角(Φ角)越小, 晶界匹配值越大, 则非共格∑3晶界越稳定; 反之亦然. Φ角最小的 (2 5 5)/(2 1 1)非共格∑3晶界较稳定, 在退火过程中几乎不发生变化. 随着Φ角的增大, 非共格∑3晶界不再稳定, 这类晶界会通过Miller指数较高一侧晶体每三层原子面合并为一层原子面 (或Miller指数较低一侧晶体每一层原子面分解为三层原子面)的机理 转变为亚稳的“台阶”状晶界, 台阶面部分地处于精确的能量极低 的{111}/{111}共格孪晶界上; 当提高温度退火时, 这种“台阶”状晶界最终会全部转变成稳定平直的{111}/{111}共格孪晶界.
关键词:
纯铜
∑3晶界')" href="#">非共格∑3晶界
分子动力学模拟 相似文献
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This paper numerically investigates the magnetoelastic
instability in the S = 1/2 {XXZ} rings containing finite spins N
with antiferromagnetic nearest-neighbour ({NN}) and next-nearest
neighbour ({NNN}) coupling. It finds that, as the {NN} anisotropy
Δ1 equals the {NNN} anisotropy \varDelta2, there
exists a critical {NNN} coupling strength J2c(≈0.5), at which the systems always locate in dimerized phase for
arbitrary large spring constant. As Δ1 \ne
Δ2, the values of J2^{\rm c} are dependent on N
and the difference of (Δ1-\varDelta2). 相似文献
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本文在5.1—5.6 GPa,1230—1600℃的压力、温度条件下,以FeNiMnCo作为触媒,进行单质硼添加宝石级金刚石单晶的生长研究.借助于有限元法,对触媒内的温度场进行模拟.研究得到了FeNiMnCo-C-B体系下,金刚石单晶生长的P-T相图.该体系下合成金刚石单晶的最低压力、温度条件分别为5.1 GPa,1230℃左右.研究发现,在单晶同一{111}扇区内部,硼元素呈内多外少的分布规律.有限元模拟结果给出,该分布规律是由在晶体生长过程中,{111}扇区的增长速度逐渐减小所致.{111}晶向的晶体生长实验结果表明,硼元素优先从{111}次扇区进入晶体.研究发现,这是该扇区增长速度相对较快,硼元素扩散逃离可用时间短导致的.另外,同磨料级掺硼金刚石单晶生长相比,对于温度梯度法生长掺硼宝石级金刚石单晶,由于晶体的增厚速度较慢,即使硼添加量相对较高,也可以实现表面无凹坑缺陷的优质金刚石单晶的生长. 相似文献
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S. Dinakaran Sunil Verma S. Jerome Das G. Bhagavannarayana S. Kar K. S. Bartwal 《Applied physics. B, Lasers and optics》2011,103(2):345-349
Single crystals of the semi-organic non-linear optical material zinc tris (thiourea) sulphate (ZTS) were grown by slow evaporation
solution growth technique. The crystals were characterized for crystalline perfection and optical homogeneity using high-resolution
X-ray diffraction (HRXRD) and optical interferometric techniques. The FWHM of 6 arc sec in HRXRD rocking curve shows the good
crystalline quality. Transmittance of ∼75% shows that the crystal is free from volume defects. Conoscopy was used to assess
the optical quality and investigate the optical indicatrix of the grown crystal. Birefringence values of the crystal along
the three principal crystallographic axes were measured using birefringence interferometry. Mach–Zehnder interferograms exhibit
good refractive-index homogeneity of the grown crystal. 相似文献
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Yuui Yokota Takayuki Yanagida Yutaka Fujimoto Martin Nikl Akira Yoshikawa 《Radiation measurements》2010,45(3-6):472-474
We have investigated luminescent properties of nondope, Ce and Pr doped NaCl [nondope NaCl, Ce:NaCl, Pr:NaCl] single crystals grown by a modified micro-pulling-down method with a removable chamber system. Nondope, Ce 1% and Pr 1% doped NaCl crystals with a single phase of NaCl structure were obtained and the crystals indicated general crystal quality by the X-ray rocking curve measurement. For the nondope NaCl and Pr:NaCl crystals, the transmittance spectra indicated almost more than 60% in the wavelength from 200 to 800 nm and an absorption of Ce3+ ion was observed in the transmittance spectrum of Ce:NaCl crystal. The emission spectrum originated from Ce3+ 5d–4f transition appeared around 300 nm in the photoluminescence spectrum and the decay time was 19.7 ns. 相似文献
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A. Ciszewski 《Surface science》1979,83(1):253-266
Growth of indium single crystals on tungsten field emission tips was carried out by deposition of indium from vapour in ultra high vacuum, using substrate temperatures in the range of 293–420 K. Two different tungsten tips were used as the substrate: a perfect W single crystal in one case and a bi-crystal with a distinct grain boundary in the other. No influence of the grain boundary on the epitaxial growth was found. Two orientation relationships were observed mostly: {111}In ∥ {110}W with 〈110〉In ∥ 〈111〉W and {111}In ∥ {100}W with 〈110〉In ∥ 〈110〉W. In the first case the growth was initiated by the indium nucleus created on the ledges of the {110}W plane. A field strength of 0.9 V/Å was found for the evaporation field of indium. The field strength of the desorption of In-W interfacial layer atoms was found to be 4.4–5.2 V/Å. A mechanism of the growth of indium crystals has been proposed. 相似文献
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The morphology and thermal stability of different sectors in solution‐ and melt‐grown crystals of star‐branched polyesters with poly(?‐caprolactone) (PCL) arms, and of a reference linear PCL, have been studied by tapping‐mode atomic‐force microscopy (AFM). Real‐time monitoring of melt‐crystallization in thin films of star‐branched and linear PCL has been performed using hot‐stage AFM. A striated fold surface was observed in both solution‐ and melt‐grown crystals of both star‐branched and linear PCL. The presence of striations in the melt‐grown crystals proved that this structure was genuine and not due to the collapse of tent‐shaped crystals. The crystals of the star‐branched polymers had smoother fold surfaces, which can be explained by the presence of dendritic cores close to the fold surfaces. The single crystals of linear PCL grown from solution showed earlier melting in the {100} sectors than in the {110} sectors, whereas no such sectorial dependence of the melting was found in the solution‐grown crystals of the star‐branched polymers. The proximity of the dendritic cores to the fold surface yields at least one amorphous PCL repeating unit next to the dendritic core and more nonadjacent and less sharp chain folding than in linear PCL single crystals; this evidently erased the difference in thermal stability between the {110} and {100} sectors. Melt‐crystallization in thin polymer films at 53–55°C showed 4 times faster crystal growth along b than along a, and more irregular crystals with niches on the lateral faces in star‐branched PCL than in linear PCL. Crystal growth rate was strictly constant with time. Multilayer crystals with central screw dislocation (growing with or without reorientation of the b–axis) and twisting were observed in both classes of polymers. 相似文献
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J. Larsson A. Allen P.H. Bucksbaum R.W. Falcone A. Lindenberg G. Naylor T. Missalla D.A. Reis K. Scheidt A. Sjögren P. Sondhauss M. Wulff J.S. Wark 《Applied Physics A: Materials Science & Processing》2002,75(4):467-478
We have employed time-resolved X-ray diffraction with picosecond temporal resolution to measure the time-dependent rocking
curves of laser-irradiated asymmetrically cut single InSb crystals. Coherent acoustic phonons were excited in the crystals
by irradiation with 800-nm, 100-fs laser pulses at irradiances between 0.25 and 12 mJ/cm2. The induced time-dependent strain profiles (corresponding to the coherent phonons) were monitored by diffracting collimated,
monochromatic pulses of X-rays from the irradiated crystals. Recording of the diffracted radiation with a fast low-jitter
X-ray streak camera resulted in an overall temporal resolution of better than 2 ps. The strain associated with the coherent
phonons modifies the rocking curve of the crystal in a time-dependent manner, and the rocking curve is recorded by keeping
the angle of incidence of the X-rays upon the crystal fixed, but varying the energy of the incident X-rays around a central
energy of 8.453 keV (corresponding to the peak of the rocking curve of the unperturbed crystal). The observed time-dependent
diffraction from the irradiated crystals is in reasonable agreement with simulations over a wide range of energies from the
unperturbed rocking-curve peak.
Received: 22 March 2002 / Revised version: 25 March 2002 / Published online: 6 June 2002 相似文献
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The validity of the “bubble method” is discussed for the measurements of contact angles between a crystal and its own melt and for the observations of interface morphology. Experiments were done on KCl crystals pulled in various directions. Gold decoration technique was employed to observe the surface morphology. The measurement of the contact angle a is valid for the 〈100〉 axis of pulling but lacks accuracy for the other directions. The {100} interface shows two dimensional nucleation, curved growth fronts and no trace of a liquid layer. The {110}, {310}and {111} interfaces show steps and pyramids constituted by {100} facets, completely stripped of the melt, and “structureless” regions resulting from freely frozen liquid surface. 相似文献
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Ni thin films are prepared on GaAs(100) single-crystal substrates at room temperature by using an ultra-high vacuum radio-frequency magnetron sputtering system. The growth behavior and the crystallographic properties are studied by in-situ refection highenergy electron diffraction and pole-figure X-ray diffraction. In an early stage of film growth, a metastable bcc Ni(100) single-crystal film is formed on GaAs(100) substrate, where the bcc structure is stabilized through hetero-epitaxial growth. With increasing the film thickness, fcc crystals coexist with the bcc(100) crystal. High-resolution cross-sectional transmission electron microscopy shows that the film consists of a mixture of bcc and fcc crystals and that a large number of planar faults exist parallel to the fcc(111) close-packed plane. The results indicate that the bcc structure starts to transform into fcc structure through atomic displacement parallel to the bcc{110} close-packed planes. 相似文献
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The ns2-type metal elements (Pb and Sn) doped LiCaAlF6 single crystals were grown by a micro-pulling-down (μ-PD) method. Pb doped LiCaAlF6 [Pb:LiCAF] crystals showed high transparency and single phase of the LiCAF structure. However, we could not obtain Sn:LiCAF crystals due to the evaporation of SnF2 during the crystal growth. There was an absorption peak around 193 nm in the transmittance spectrum of Pb:LiCAF crystal. In the radioluminescence spectrum of the Pb:LiCAF crystal under X-ray irradiation, two emission peaks around 200 and 830 nm were observed. 相似文献