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synht木虫 (正式写手)
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Despite the increasing volume of researches on SiNWs, to the best of our knowledge, only limited information is currently available (theoretical or experimental) on their electromechanical properties [11]. In the absence of definitive experimental data, first-principles calculations can provide robust predictions of the mechanical properties of the silicon nanowires. In this Letter, we investigate energetic, relative stability, and mechanical properties of the hydrogen- passivated SiNWs with various diameters and growth directions using first-principles methods. To compare the physical properties and to understand the possible reason for a preferential growth direction, nanowires grown along the [100], [110], [111], and [112] crystallographic orientations have been studied. The starting configurations of the nanowires were cut from a bulk silicon crystal and were bounded by the low-index lateral surfaces. Fig. 1 shows the representative cross-sections of the SiNWs with different growth directions. The geometry of the first plot in Fig. 1 is bounded by four (110) planes in all lateral directions and is oriented along [100] direction. The geometry of the second SiNWs (Fig. 1) is the same as those of the larger diameter nanowires inferred from experiments [7]. It is oriented along [110] direction and has a hexagonal crosssection with four (111) and two (10 0) lateral surfaces.The third one (Fig. 1) is oriented along [11 1] direction and all of its lateral directions are bounded by (110) planes. Finally, the geometry of the last one (Fig. 1) is similar to the thinnest SiNWs observed experimentally [7]. It is oriented along [112] direction and bounded by two (110) and two (111) surfaces in the lateral directions. In all the SiNWs considered, the dangling bonds on the surface are fully terminated with H atoms so that each Si atom lying on the nanowire surface is tetrahedrally coordinated. Each wire was placed in a tetragonal supercell so that the nanowire was infinitely extended along axial direction and each nanowire is separated far enough from its periodic images in the lateral directions (at least 10A ˚ ). The number of atoms in the unit cell and the mean diameter of the SiNWs growth in different directions are summarized in Table 1. The mean diameter d of a wire is derived from S ¼ pðd=2Þ2, S is the cross-section area of the wire (excluding the H atoms). Geometry optimizations were performed using density functional theory (DFT) implemented in the DMOL package [12]. All-electron treatment and double numerical basis including p-polarization function (DNP) [13] were chosen. The exchange–correlation interaction was treated within the generalized gradient approximation (GGA) with the functional parameterized by Perdew, Burke and Enzerhof (PBE) [13]. Self-consistent field calculations were done with a convergence criterion of 106 Hartree on the total energy. All the structures were fully optimized without any symmetry constraint with a convergence criterion of 0.002 Hartree/ A˚ for the forces and 0.005 A ˚ for the atomic displacements. The one-dimensional (1D) Brillouin zone along the wire axis was sampled by 10 k points. |
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thorny_rose
金虫 (小有名气)
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sltmac: 金币+1 2012-05-22 07:52:38
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sltmac: 金币+1 2012-05-22 07:52:38
爱与雨下: 金币+2 2012-05-24 19:09:18
synht: 金币+200, 翻译EPI+1, ★★★★★最佳答案, 这几天没上，回复晚了，不好意思~ 万分感谢呐！ 2012-05-31 23:57:47
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第一段： 【译】尽管有关硅纳米线的研究越来越多，但据我们所知，目前仅有少量资料（理论性或试验性）与其机电性能有关。在没有明确的实验数据的情况下，第一原理计算可以提供强大的硅纳米线的力学性能预测。本文我们使用第一原理方法研究活跃的、相对稳定的具有不同直径和生长方向的氢钝化硅纳米线的力学性能。为比较物理性质和理解优先选择生长方向的可能的原因，我们在【100】，【110】，【111】和【112】样式的器皿中栽培硅纳米线，研究晶体方位。（crystallographic orientations有好多意思，我根据上下文意思译做晶体方位） （注：从这里开始有些专业性比较强的词汇翻译时我把握不了，希望你能看的明白。） 纳米线的立体基阵原材料取自大块的硅晶体，以低指数侧表面为边界（专业的又来了，你自己理解吧，我深感无力）。图1显示了典型的不同生长方向的硅纳米线横断面。图1中第一个图形的几何结构由四个横向的（110）位面联接起来，并且沿着【100】方向确定方位。图1中的第二个图形的几何结构和从实验中推断的那些较大直径的纳米线相同，以【110】方向来确定方位，有一个六边形横切面，该横切面有4个【111】和两个（100）侧表面。第三个图形以【111】方向来确定方位，且它的所有横向方位均由【110】位面环绕。最后一个图形的几何结构与实验中观察到的最薄的硅纳米线相似，以【112】方向确定方位，且在横向方位由2个（110）和2个（111）表面环绕。 第二段： 【译】所有使用的硅纳米线，表面的悬空键尾端全是氢原子，因此每一个纳米线表面的硅原子都处于四配位状态。每条线都放置在一个四超级单体中，因此纳米线可以轴向无限延伸，且每个纳米线与它在横向方位的周期性图像相隔足够远（至少10埃）。表1概括了晶胞中的原子数量和硅纳米线的平均直径按不同方向发展。线的平均直径d由公式S=∏(d/2)2 得来，S代表线的横截面面积（氢原子除外）。 第三段： 【译】几何体的优化通过采用密度泛函理论Dmol软件包得以实现；采用全电子处理和双数值基组加极化函数；交换相关的交互作用采用由约翰.佩卓、菲利浦.乔治 伯克（P.G.Burke）和 Enzerhof提出的泛函量化参数的广义梯度近似（GGA）进行处理;使用总能量的10-6哈特里收敛性判据进行自洽场计算。 虽然是翻译完了，可实在是汗颜，专业性太强了。相信这篇研究你自己应该多少能看懂一些，所以这些翻译只能做为你看不懂有些句子时的一个参考。 |
2楼2012-05-22 02:01:43