排序方式: 共有53条查询结果,搜索用时 15 毫秒
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甲醇在Au(111)表面吸附的密度泛函研究 总被引:2,自引:0,他引:2
采用基于第一性原理的密度泛函理论和周期平板模型相结合的方法,对CH3OH分子在Au(111)表面top, fcc, hcp和bridge位的吸附模型进行了构型优化、能量计算以及Mulliken布居分析,结果表明top位是较有利的吸附位. 吸附的CH3OH解离产生甲氧基CH3O和H, 对它们在Au(111)面的吸附进行的计算表明, bridge和fcc位分别是二者的最佳吸附位. 对过渡态的计算给出了CH3OH在Au表面解离吸附的可能机理: 首先发生 O-H 键的断裂,继而生成甲氧基中间体. 相似文献
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A PREDICTIVE APPROACH TO THE IN-PLANE MECHANICAL PROPERTIES OF STITCHED COMPOSITE LAMINATES 总被引:1,自引:0,他引:1
Zhang Junqian Wei Yuqing 《Acta Mechanica Solida Sinica》2007,20(2):130-140
This contribution attempts to model the alteration of the in-plane elastic properties in laminates caused by stitching,and to predict the in-plane effective tensile strength of the stitched composite laminates.The distortion of in-plane fibers is considered to be the main cause that affects the in-plane mechanical properties.A fiber distortion model is proposed to characterize the fiber misalignment and the fiber content concentration due to stitching.The undistorted region,the fiber distortion region,the resin-rich pocket and the through-thickness reinforcement section are taken into account.The fiber misalignment and inhomogeneous fiber content due to stitching have been formulated by introducing two parameters,the distortion width and maximum misalignment.It has been found that the ply stress concentration in stitched laminates is influenced by the two concurrent factors,the stitch hole and inhomogeneous fiber content.The stitch hole brings about the stress concentration whereas the higher fiber content at the local region induced by stitching restrains the local deformation of the composite.The model is used to predict the tensile strength of the [0/45/0/-45/90/45/0/-45]_(2s) T300/QY9512 composite laminate stitched by Kevlar 29 yarn with different stitching configurations,showing an acceptable agreement with experimental data. 相似文献
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Liming Wu Yongfan Zhang Jianming Hu Lixin Zhou Junqian Li 《Journal of Molecular Structure》1999,460(1-3):27-35
Using the ab initio method, the vibrational and electronic spectra of binuclear molybdenum clusters which contain Mo2OnS4−n(n=0–4) core were investigated. The main absorption bands in the IR spectra of these clusters are assigned and compared with each other, especially for the case of the trans isomers. The electronic spectra were studied by performing the CIS calculations. The ground state and the first excited state of the clusters were discussed by using the natural bond orbital method. It is shown that the band corresponding to the longest wavelength can be assigned to three kinds of transition types. Two transitions, σ(Mo–Mo)→π*(Mo–Xt)(X=S,O) and σ(Mo–Mo)→σ*(Mo–Mo), can be seen in most cases. 相似文献
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采用量子化学中的密度泛函理论(DFT),在B3LYP/6-311 G(3df,2p)水平上全优化得到了单卤代二硫烷HSSX(X-H,F,Cl,Br)链型和分叉型两种异构体的平衡结构。计算结果表明.在热力学上,所有链型的HSSX为稳定构型.其能量分别较分叉型构型低109.8、60.2、74.8和73.1kJ/mol。同时,采用统计热力学方法,研究了两种平衡结构之间相互转化的化学热力学性质,发现异构化反应的平衡常数很小。 相似文献
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不同晶向金属纳米线拉伸力学性能分子动力学研究 总被引:2,自引:0,他引:2
在经典等温分子动力学框架下,采用位移加载方式,准静态条件下数值模拟常温条件下金属纳米线的单向拉伸,研究了面心立方晶格(FCC)单晶金属纳米线的弹塑性力学性能。研究发现 <100>,<110>,<111>三个不同晶向纳米线拉伸时呈现不同的拉伸变形力学性能。其中<111>晶向拉伸有最高的屈服强度,<110>晶向屈服屈服最小,特别的是<100>晶向拉伸时屈服应变最大。由于不同的晶向对应纳米线的不同表面,三个晶向的纳米线拉伸呈现不同的应力应变关系曲线,变形过程中的局部结构具有不同的演化方式。分析了纳米单晶铜线的三个晶向拉伸表现不同的等效弹性刚度和屈服强度,讨论了相关的局部位错结构演化过程和与位错发射分解剪应力相关的纳米线塑性变形机理。 相似文献
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采用DFT/B3LYP方法研究了化合物Mo(CO)~n^+(n=1~6)的基态可能构型,对于各n值,基态可能构型(电子态)依次为:直线型(^6∑^+),直线型(^6∑~g^+),C~2~υ(^2A~2)或D~3~h(^6A~1),D~4~H(^4A~1~g),C~2~ν(^2B~2)或C~4~ν'(^2B~1),D~3~d(^2A~1~g)。计算结果表明,对于n≥3时,碎片离子的构型与体系自旋多重度关系敏感。进一步计算了Mo-CO键的逐级解离能,计算值与实验结果能较好吻合,并从Mo原子4d和5s轨道杂化角度来解释该键解离能随n值的非单调变化。 相似文献
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