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991.
在密度泛函理论框架下的局域密度近似方法 (LDA)能够准确地给出广延态电子体系的基态电子结构 ,是研究复杂体系的电子结构的一种非常成功的方法。由于这种方法不含参数 ,被广泛地用于微观体系的研究。但是 ,在处理的体系中含有局域电子时 ,由于方法的局限 ,给出的结果与光电子谱等试验结果符合得并不好。LSDA U方法是在局域自旋密度近似的框架下 ,结合模型哈密顿方法 ,对局域电子采用哈伯德模型描述 ,用以改进局域密度近似计算的一种方法。本文利用局域密度近似下的离散变分团簇方法 (DVM )对于内嵌稀土原子的富勒烯Er2 @C82 、Tm @C82 的电子结构进行了第一性原理的计算。对于体系中所含的稀土原子存在强关联的 4f电子 ,在LDA方法计算的基础上 ,考虑 4f电子在位库仑作用 ,用LSDA U方法研究了上述体系 ,得到了可以和XPS和吸收谱相比较的结果。 相似文献
992.
993.
A new kind of quantum state is introduced, which can be generated by the superposition of high-order (N) photon addition to two-mode thermal state (SPA-TMTS). By using the P-representation of thermal state, the normal ordering form of SPA-TMTS is obtained. Based on this, some analytical expressions, such as the normalization coefficient, Q-function, Wigner function (WF) are presented. It is shown that the WF can possess negative value at some region. In addition, the nonlocality of the SPA-TMTS is discussed in terms of the CH and CHSH inequalities. It is found that for a given small $\bar{n}$ , the CH inequality is violated for some small N and the violation decrease with the increasing N; while the CHSH inequality is violated only for N=1. 相似文献
994.
995.
Guo-Qiang Qi Ya-Jun Xu Wei Yang Bang-Hu Xie Ming-Bo Yang 《Journal of Macromolecular Science: Physics》2013,52(9):1747-1760
Polypropylene (PP) blends based on isotactic polypropylene (iPP), propylene-ethylene block copolymer (bPP), and propylene–ethylene random copolymer (rPP) were prepared by melt blending and the effects of content of bPP and rPP on the shrinkage during solidification and storage and mechanical properties of the blends were studied. It was found that the addition of polypropylene copolymer could effectively reduce the processing shrinkage of iPP and the lowest shrinkage of the blends was achieved at a loading of 2 wt% bPP or rPP. The flexural modulus and tensile strength of the blends decreased a little while the impact strength and elongation at break were improved greatly compared with those of iPP. 相似文献
996.
Hui-Juan Huang Bang-Hu Xie Wei Yang Yue-Xin Shen Ming-Bo Yang 《Journal of Macromolecular Science: Physics》2013,52(2):231-241
The influence of polyolefin elastomer (POE) content on the fracture behavior of injection-molded polypropylene (PP)/POE blends was evaluated by means of the essential work of fracture (EWF) method. The results indicated that the EWF approach worked well for the PP/POE blends when POE content was 0~7.5 wt% of the blends. The specific essential work of fracture (w e) increased with increasing POE content, and the dominant factor that affected w e was the necking and subsequent fracture process. The specific nonessential work of fracture (βw p) slightly decreased with increasing POE content, while the specific plastic work (w p) showed an increasing trend with the decrease of the shape factor (β) of the specimen. Finally, it was shown that w e could be predicted reasonably well via the COD values. 相似文献
997.
Zhimin Xie Young‐Jin Yum Chul‐Kyoung Lee 《Journal of Macromolecular Science: Physics》2013,52(3):561-567
It has been known that the carbon black (CB) network is responsible for the electrical and mechanical behaviors of filled rubber. Due to the complexity involved in the filled rubber in relation to the conductive mechanism of the CB network, there has been little work concerned with simulation of the electrical behavior at large strains. Based upon an infinite circuit model, the electrical resistivity of CB filled rubber under elongation is simulated. For CB (N330) filled natural rubber with volume fraction of 27.5%, the simulated electrical resistivity increases with elongation at small stains, corresponding to the breakup of the agglomerates. The reduction in resistivity at larger strains corresponds to the decrease of the junction width, which results in a decrease of the contact resistance. Good agreement is found between the simulations and the experimental data available in the literature. The simulated results confirm the effects of the breakdown of the CB network and the alignment of CB aggregates under strain on the electrical resistivity. 相似文献
998.
We present a method for calibrating the position error of phase retrieval with transverse translation diversity in optical wavefront in situation where the position error sharply influences algorithm precision. This method involves testifying that the essence of the position error in phase retrieval is the translation in frequency domain and the minimum of iterative error against position error reaches when there is no position error. Then the least square method is used for fitting the relationship between the iterative error and the assumed position error in polynomial function. The computer simulations used to prove the validity of this method are described. The results indicated that this method can calibrate the position error to approximately 1/500 mm which nearly has no influence on the phase retrieval. 相似文献
999.
Spectral analyses of vinylneoxantho- and vinylisoneoxanthobilirubic acid methyl esters, with endo and exo-vinyl groups respectively, show that the exo-vinyl group causes (1) a greater bathochromic and hyperchromic shift of the long wavelength UV-vis absorption and (2) a smaller dimer association constant in CDCl3 than does the endo-vinyl in these pyrromethenones. 相似文献
1000.
By applying a femtosecond stimulating pulse, we theoretically study the stimulated processes of an exciton and a biexciton in a polymer within the framework of an extended Su–Schrieffer–Heeger tight-binding model. For an exciton, it is obtained that the stimulated emission and absorption between the intragap levels take place with the same probability, by which we will not get the light amplification. However, the light amplification can be realized by the stimulated emission between the intragap levels in a biexciton, which is found to have two different modes. Finally, effect of the stimulating energy and intensity on the stimulated processes is separately analyzed. These results might be of great importance for further improving the optical applications of polymers, especially for optimizing the polymer laser properties. 相似文献