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The structural, mechanical, electronic, and optical properties of orthorhombic Bi2S3 and Bi2Se3 compounds have been investigated by means of first principles calculations. The calculated lattice parameters and internal coordinates are in very good agreement with the experimental findings. The elastic constants are obtained, then the secondary results such as bulk modulus, shear modulus, Young’s modulus, Poisson’s ratio, anisotropy factor, and Debye temperature of polycrystalline aggregates are derived, and the relevant mechanical properties are also discussed. Furthermore, the band structures and optical properties such as real and imaginary parts of dielectric functions, energy-loss function, the effective number of valance electrons, and the effective optical dielectric constant have been computed. We also calculated some nonlinearities for Bi2S3 and Bi2Se3 (tensors of elasto-optical coefficients) under pressure. Figure
Energy spectra of dielectric function and energy-loss function (L) along the x- and z-axes for Bi2S3 相似文献
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自学·质疑·精讲·练习”课堂教学方法,简易可行,便于推广,适宜不同年级、不同教学内容,便于穿插演示实验、讲解法等其他教学方法,使学生的主体作用、教师的主导作用得以充分发挥,有利于增强学生的集体主义精神,有利于培养学生的自学能力,提高分析问题、解决问题... 相似文献
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《现代生物医学进展》2012,12(27):5401-5404
《科学-转化医学》:按摩或可加速受损肌肉康复按摩疗法近年来被越来越多的人所接受。一项新研究也显示,按摩疗法可通过与大多数镇痛药相同的生物学机制来减轻肌肉疼痛,可能有助于受损肌肉 相似文献
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Ana A. Rodríguez-Sanz J. Carrazana-García Enrique M. Cabaleiro-Lago Jesús Rodríguez-Otero 《Journal of molecular modeling》2013,19(5):1985-1994
A computational study has been performed for studying the characteristics of the interaction of phenol with ammonium and methylammonium cations. The effect of the presence of water molecules has also been considered by microhydrating the clusters with up to three water molecules. Clusters of phenol with ammonium and methylammonium cations present similar characteristics, though ammonium complexes have been found to be more stable than the methylammonium ones. The first water molecule included in the complexes interacts with a N-H group of ammoniun cations and simultaneously with the hydroxyl oxygen atom of phenol (or the aromatic ring). This first water molecule is more tightly bound in the complex, so the stability gain as more water molecules are included drops significantly by 2-3 kcal?mol?1 with respect to the first one. As more water molecules are included, the differences between favorable coordination sites (the cation, the hydroxyl group or a previous water molecule) decrease. As a consequence, several of the most stable complexes located including three water molecules already exhibit hydrogen bonds between the hydroxyl group and one water molecule. The results indicate that a cyclic pattern formed by a series of hydrogen bonds: π···H-N-H···O-H···O-?, is characteristic of the most stable minima, being kept as more water molecules are included in the system. Therefore, this pattern can be expected to be crucial in ammonium cations···phenol interaction if exposed to the solvent to any degree. 相似文献
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《中国生物化学与分子生物学报》2005,21(5):590-590
《中国生物化学与分子生物学报》自2006年1月起改为月刊为缩短出版周期,提高期刊学术水平和刊印质量,经《中国生物化学与分子生物学报》编委会讨论决定,上报中国生物化学与分子生物学会同意,获得中国科协和北京市新闻出版局批准,本刊自2006年1月起改为月刊,每月20日出版.每期96 相似文献
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近年来,世界各地气候波动的幅度和频率都有所增大,出现了所谓“气候异常”。气候变迁问题涉及的面很广,这里仅从第四纪气候变迁与动植物进化、人类发展的关系方面,谈谈我们对这个问题的一些看法。地球上不断变化着的气候毛主席在《矛盾论》中指出:“整个地球及地球各部分的地理和气候也是变化着的”。地球上的地质、地理、气候和生物等等,都不是一成不变的,它们都有着自己发生、发展的过程。自从地球在大约50亿年前生成以来,大规模的气候变迁有过好几次,达到象大冰期那样寒冷的时期至少有3次。距今6亿年以前的震旦纪冰期,我国大约发生在距今7一7.5亿年左右(有人 相似文献
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