共查询到18条相似文献,搜索用时 140 毫秒
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基于位错理论,利用分子动力学方法建立了〈100〉{010},〈100〉{011},1/2〈111〉{011}和1/2〈111〉{112}刃型位错的芯结构,并计算了这四种刃型位错的形成能、位错芯能量和芯半径.计算结果表明:〈100〉{010}和〈100〉{011}刃型位错的形成能比1/2〈111〉{011}和1/2〈111〉{112}刃型位错的要高,这表明〈100〉刃型位错比1/2〈111〉刃型位错更难形成.而〈100〉{010}和〈100〉{011}刃型位错的芯半径比1/2〈111〉{011}和1/2〈111〉{112}刃型位错的小,这说明在1/2〈111〉刃型位错中位于奇异区的原子数多于〈100〉刃型位错,而这些原子要比完整晶体中的原子具有更大的活性.可见,1/2〈111〉刃型位错比〈100〉刃型位错更易运动,且〈100〉刃型位错在bcc Fe中难以形成.
关键词:
bcc Fe
刃型位错
分子动力学模拟 相似文献
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锗酸铋(Bi4Ge3O12)作为一种新型的有发展前景的单晶闪烁材料,使得对这种材料的各种性质的研究很能引起人们的兴趣。本工作的目的是想通过核磁共振这一方法对锗酸铋样品的研究,得到有关其微观结构方面有用的信息。尝试性实验的结果说明锗酸铋中铋核具有非常强的四极相互作用,在7.0T的磁场下,铋核的核磁共振谱成为一个无法测量的宽谱。本文利用了零场这个实验条件,成功地避开了强四极耦合引起的在磁场下的谱线变宽的困难,在Bncker-MSL300脉冲FT核磁共振谱仪上首次精确地测定了国产锗酸铋单晶粉末样品中209Bi核的四极耦合常数:高温下e2qθ/h=1474.18MHz。我们还在288K到150K的温度范围内测量了四极耦合常数的温度效应。发现在这个温度区域2qθ/h的值在1509.59MHz至1474.00MHz之间有规律的变化。极强的四极相互作用和明显的温度效应可能暗示着某种有待进一步研究的现象的存在。D.Brinkmann和A.B.Dension在一九七二年为研究电光晶体(electro-optic crystal)的性质,用单晶核磁共振的方法得到e2qθ/h的值为488±1MHz的结果[1],与本实验得到的值相差很大。这种差別的原因也有待进一步研究。 相似文献
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利用锗酸铋(BGO)晶体的弹光双折射与电光双折射可以相互补偿的特性,设计并研究了一种新型光学应力传感器。折射率椭球分析结果表明,在垂直于BGO晶体的(111)晶面方向上同时施加应力和电场,晶体的弹光双折射能够被电光双折射所补偿,因而可以实现应力的闭环光学测量。光学传感单元主要包括两个棱镜偏振器和一块平行四边形的BGO晶体,该晶体自身能够通过对光波的两次全反射产生0.5π的光学相位偏置,因而不需要附加四分之一波片。实验测量了30kPa以内的压缩应力,被测压缩应力与补偿电压之间具有较好的线性关系,且每1kPa压缩应力所需要的补偿电压约为4.26V。 相似文献
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本文计算了铌酸锶钡(SBN)晶体中沿光轴的位错双折射像的反衬,计算中考虑了光弹系数的各向异性,结果表明与各向同性计算相比刃位错双折射像中的花瓣有伸长的趋势,螺位错无反衬,并与实验结果作了比较。 相似文献
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本文叙述了锗酸铋晶体的生长。采用二波耦合光路测试BGO晶体的衍射效率和增益系数,研究BGO晶体的二波耦合中光波的位相变化。 相似文献
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A.G. Apostolidis S. Mallick D. Rouède J.P. Herriau J.P. Huignard 《Optics Communications》1985,56(2):73-78
Due to the co-existence of optical activity and linear birefringence in a Bi12SiO20 crystal, a phase gratting induced in this medium has many interesting and unusual properties. We study the ellipticity and orientation of the directly transmitted and diffracted beams as a function of the read-beam vector orientation. In image processing experiments the signal to noise ratio can be increased significantly by appropriately choosing the read-beam orientation such that the strong direct beam is linearly polarized and can be eliminated with the help of a polarizer. 相似文献
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铌酸锂晶体材料具有较高的电光系数和稳定的物理、化学性质,广泛应用在各种电场传感器中。但是,铌酸锂晶体折射率对温度较为敏感,在使用最大电光效应方向时,由于自然双折射的存在,晶体工作点随温度漂移,一方面导致传感器无法稳定工作,另一方面也影响了传感器的灵敏度和动态范围。为了消除这一影响,探头中将使用长度相等、主轴正交的两块铌酸锂晶体,一块作为传感晶体,一块作为补偿晶体。由于补偿晶体的存在,传感器的自然双折射得到很大程度的抑制,温度稳定性也得到了改善。经实验对比,补偿之后的传感器工作状态稳定性比未补偿的传感器得到大幅提升。 相似文献
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Tianxing Lin Jinhai Si Tao Chen Xiaoli Wang Kazuyuki Hirao 《Optics Communications》2007,275(1):230-233
The ultrafast nonlinear optical properties of Bi2O3-B2O3-SiO2 oxide glass were investigated using a femtosecond optical Kerr shutter (OKS) at wavelength of 800 nm. The nonlinear response time of this Bi2O3-doped glass was measured to be <90 fs. The nonlinear refractive-index n2 was estimated to be 1.6 × 10−14 cm2/W. Measurements for the dependence of Kerr signals on the polarization angle between the pump and probe beams showed that the Kerr signals induced by 30-fs pulse laser arose mainly from the photoinduced birefringence effect. 相似文献
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“Quasi-phase matching” is first introduced to the optical activity (OA) effect and a wave coupling theory for the quasi-phase-matched
(QPM) OA effect in periodically poled “gyroelectric” crystals is developed. The OA effect is observed clearly even though
the propagating direction of light deviates far from the optical axis in the QPM crystal with both optical activity and natural
birefringence. The QPM OA effect provides a special way to determine the gyration coefficients that cannot be observed by
the normal OA effect, and it provides a principle for building optical filters without external field. 相似文献
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Effects of Annealing on Microstructure and Optical Properties of TiO2 Sculptured Thin Films 下载免费PDF全文
The evolution of microstructure and optical properties of TiO2 sculptured thin films under thermal annealing is reported. XRD, field emission SEM, UV-Vis-NIR spectra are employed to characterize the microstructural and optical properties. It is found that the optimum annealing temperature for linear birefringence is 500℃. The maximum of transmission difference for linear birefringence is up to 18%, which is more than twice of that in as-deposited thin films. In addition, the sample annealed at 500℃ has a minimum of column angle about 12℃. The competitive process between the microstructural and optical properties is discussed in detail. Post-annealing is a useful method to improve the linear birefringence in sculptured thin films for practical applications. 相似文献
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Swapna S. Nair Francis Xavier P.A. Joy S.D. Kulkarni M.R. Anantharaman 《Journal of magnetism and magnetic materials》2008
Ferrofluids belonging to the series NixFe1−xFe2O4 were synthesised by two different procedures—one by standard co-precipitation techniques, the other by co-precipitation for synthesis of particles and dispersion aided by high-energy ball milling with a view to understand the effect of strain and size anisotropy on the magneto-optical properties of ferrofluids. The birefringence measurements were carried out using a standard ellipsometer. The birefringence signal obtained for chemically synthesised samples was satisfactorily fitted to the standard second Langevin function. The ball-milled ferrofluids showed a deviation and their birefringence was enhanced by an order. This large enhancement in the birefringence value cannot be attributed to the increase in grain size of the samples, considering that the grain sizes of sample synthesised by both modes are comparable; instead, it can be attributed to the lattice strain-induced shape anisotropy(oblation) arising from the high-energy ball-milling process. Thus magnetic-optical (MO) signals can be tuned by ball-milling process, which can find potential applications. 相似文献
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