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钙钛矿型CaSiO_3解压缩和重压缩过程的分子动力学模拟 总被引:3,自引:0,他引:3
用分子动力学模拟方法(MD)研究了300 K时钙钛矿型CaSiO_3,从高压到负压 的解压缩过程。MD模拟获得的P-V关系与实验数据相近,与已报道的MD模拟数据基 本一致,所得体积模量也在实验数据分布范围内。减压缩和重压缩的MD模拟数据与 实验结果相似。钙钛矿型CaSiO_3解压缩成非晶态时,存在两个结构破坏阶段:破 坏硅氧八面体和破坏钙氧二十面体。当钙氧二十面体被破坏后,重压缩不能得到钙 钛矿型结构。只要钙氧二十面体未被破坏,重压缩可恢复钙钛矿型结构。本研究得 到的结果尚未见相关报道。由MD模拟数据计算了CaSiO_3系统的红外光谱,分析这 些数据可知钙钛矿型CaSiO_3解压缩非晶化是一个二阶软模相变。研究表明钙钛矿 型CaSiO_3结构存在一个等容的亚稳极限,其解压缩非晶化是一个受动力学控制的 亚稳状态。 相似文献
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采用X射线衍射(XRD)和高分辨透射电镜(HRTEM)对Al-Fe-Ce非晶合金的局域结构进行了研究,分析了二十面体短程序对非晶合金的形成及热稳定性的影响.Al-Fe-Ce非晶合金中的二十面体短程序均匀弥散分布在非晶基体中.Al颗粒被二十面体化学短程序紧紧包围,二十面体化学短程序阻碍了Al颗粒的长大,面心立方铝(fcc-Al)的形核需要二十面体结构的分解及溶于其中的元素的扩散.二十面体结构单元的存在和均匀分布有利于增强非晶合金的玻璃形成能力和非晶相的热稳定性. 相似文献
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Ni3Al合金液态与非晶中的原子团簇 总被引:1,自引:0,他引:1
采用常温常压分子动力学模拟技术,模拟了液态Ni3Al中原子团簇在快速凝固条件下的演变过程,模型采用的是TB(tight binding)作用势.用偶分布函数、键对和多面体等结构参数来描述快速凝固条件下团簇种类和数量的变化,并将团簇结构可视化.在2 000 K下,液态Ni3Al中团簇数量较少,且都是由缺陷二十面体构成;在4×1013 K•s-1的冷速下,团簇的数量随温度的降低不断增加,且出现完整二十面体团簇,体系最终形成了由二十面体和缺陷二十面体团簇网络所组成的非晶结构. 相似文献
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LaBO3(B=Fe,Co)中氧的迁移与光催化反应活性 总被引:10,自引:0,他引:10
以柠檬酸法合成的钙钛矿型复合氧化物LaBO3(B=Fe,Co)为催化剂,对水溶性染料进行光催化降解,实验结果表明,其光催化活性与钙钛矿型结构中氧空位沿BO6八面体棱边以曲线而非直线的迁移机制有关.在光催化氧化过程中,光生电子首先被表面氧空位束缚,再与表面的吸附氧反应生成超氧基(O2-·)而加速对染料分子的降解.钙钛矿型复合氧化物中的氧空位是由氧的迁移产生的,它可以作为电子的陷阱而捕俘电子,并作为氧的吸附中心而提高催化剂表面的吸附氧量. 相似文献
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使用Tight-binding势函数, 对FCC-Ni升温熔化过程的结构变化进行了分子动力学模拟. 在定压条件下模拟得到的Ni的熔点在1850 K与1900 K之间. 计算得到了体系在各温度下的径向分布函数和配位数分布等静态结构信息以及动力学性质. 计算得出的液体Ni的扩散系数在1900 K时约为5.02×10−9 m2•s−1, 与实验数据相符. 对液态体系中FCC短程有序结构可能发生的畸变以及由此导致的H-A键型变化进行了分析, 结合配位体构型搜索和键对分析方法计算了各温度下不同短程有序结构的分布. 计算表明, Ni在熔化之后仍保留有部分晶态短程结构, 但发生了较大的畸变, 同时液态中有少量的缺陷二十面体结构存在. 而液体Ni中大多数的配位体的几何构型介于FCC与缺陷二十面体之间. 相似文献
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用分子动力学(MD)模拟方法设计了两个模拟时间为600ps的对比计算机模拟 实验,研究了R6态的胰岛素六聚体在水溶液中的稳定性以及苯酚和锌离子对结构稳 定性的影响。通过对MD模拟所得到的轨迹的分析发现,在维系胰岛素六聚体稳定性 的因素中,静电相互作用和氢键起着主要的作用。对于包含锌离子和苯酚的体系。 胰岛素六聚体的稳定性得到了增强;对不含锌离子和苯酚的关系,胰岛素六聚体的 稳定性明显减弱,在这种情况下,胰岛素六聚体还表现出解聚的倾向。这些模拟结 果与实验观测结果相吻合。 相似文献
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Uroš Grošelj Mojca Žorž Amalija Golobič Branko Stanovnik Jurij Svete 《Tetrahedron》2013,69(52):11092-11108
A new and simple synthesis of novel N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates, which exist in equilibrium with their 4-oxo tautomers, has been developed in two steps starting from N-protected α-amino acids. The key intermediates are enaminones, which can also be isolated, characterized, and used for the construction of other functionalized heterocycles, before they spontaneously decompose to pyrrole products. 4-Hydroxypyrroles are prone to partial aerial oxidation but can be efficiently alkylated or reduced to stable polysubstituted pyrrolidine derivatives. 相似文献
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The chemoselectivity in the intramolecular CH insertion of various diazosulfonamides has been experimentally studied. The results reveal that the aliphatic 1,4-, 1,5-, or 1,6-C(sp3)?H insertions of diazosulfonamides are not accessible, while the aromatic 1,5-C(sp2)?H insertion can be realized specifically by adjusting the diazo-adjacent group. In addition, the general chemoselectivities in the intramolecular CH insertions of diazosulfonyl compounds are summarized. Generally, diazosulfones undergo both aromatic 1,5-C(sp2)?H and aliphatic 1,5- and 1,6-C(sp3)?H insertions, while diazosulfonates undergo aliphatic 1,5- and 1,6-C(sp3)?H insertions. However, diazosulfonamides only undergo aromatic 1,5-C(sp2)?H insertion. 相似文献
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N-Heterocyclic carbene-palladacyclic complexes 3 were successfully achieved in a one-pot procedure under mild conditions. The structure of 3a was unambiguously confirmed by X-ray single crystal diffraction and it was an active catalyst in the Buchwald-Hartwig amination and α-arylation of ketones even at very low catalyst loadings (0.01?mol%). 相似文献
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Shashikant U. Dighe Surya K. Samanta Shivalinga Kolle Sanjay Batra 《Tetrahedron》2017,73(17):2455-2467
An efficient iodine-mediated oxidative Pictet-Spengler reaction in dimethyl sulphoxide (DMSO) using terminal alkynes as the 2-oxoaldehyde surrogate for the synthesis of aryl (9H-pyrido[3,4-b]indol-1-yl)methanones is described. The scope of the protocol includes the total synthesis of Fascaplysin, Eudistomins Y1 and Y2. The methodology is extended for preparing pyrrolo[1,2-a]-quinoxaline and indolo[1,5-a]quinoxaline derivatives. The utility of 1-aroyl-β-carbolines was demonstrated by performing palladium-catalyzed β-carboline directed ortho-C(sp2)-H functionalization of the phenyl ring with thiomethyl (SMe) group using DMSO as source and for accessing 4-aryl-canthin-6-ones. 相似文献
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In this Letter, we described a facile method for constructing fused bicyclic 1-arylpyrazol-5-one ring system. We employed various methylene-containing carboxylic acids as the substrates and proved that the pyrazolone ring closure requires activated methylene group in intermediate II. Accordingly, a series of structurally diversified, fused bicyclic 1-arylpyrazol-5-ones was prepared in moderate to high yields using the requisite substrates. 相似文献
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Synthesis of substituted pyrrolo[1,2-a]pyrazines and pyrazino[1,2-a]indoles from the Morita-Baylis-Hillman derivatives of acrylates via saponification followed by Curtius reaction is described. 相似文献
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用正丁胺作为碳源,采用射频辉光放电制备碳膜,选用激光染料R6G和聚乙二醇混合液作为蒸气源,采用单源热蒸发,在蒸发室与染料同时沉积得到混合膜,用拉曼光谱和红外光谱分析了碳膜的结构和键合方式,分析表明:碳膜中存在胺基团和氢原子.混合膜的荧光谱测量结果表明,认为正丁胺对染料荧光谱的影响是因为胺基和氢原子的存在. 相似文献
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Jona Mirnik Eva Pušavec Kirar Sebastijan Ričko Uroš Grošelj Amalija Golobič Franc Požgan Bogdan Štefane Jurij Svete 《Tetrahedron》2017,73(24):3329-3337
A series of 20 CuAIAC reactions between eight 4-acylamino substituted pyrazolidine-3-one-1-azomethine imines and four terminal ynones were performed using Cu0 as catalyst. The corresponding fluorescent cycloadducts were obtained in very high yields upon simple workup. Thus, Cu-metal turned out to be a better catalyst than CuI in terms of yield and ease of isolation. Availability of azomethine imines, mild reaction conditions, and simple workup enable a “click” access to libraries of densely substituted 2,3-dihydro-1H,5H-pyrazolo[1,2-a]pyrazol-1-ones. Reactivity of differently substituted dipoles was evaluated experimentally and by quantum chemical methods (DFT). 相似文献
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George E. Magoulas Thomas Garnelis Constantinos M. Athanassopoulos Dionissios Papaioannou George Mattheolabakis Konstantinos Avgoustakis Dimitra Hadjipavlou-Litina 《Tetrahedron》2012,68(35):7041-7049
(E)-4-(Fullerenopyrrolidin-1-yl)-3-methylbut-2-enoic acid and its corresponding succinimidyl ester, readily obtained through Prato-type modification of C60, were used for the selective N-acylation of polyamines. The thus obtained conjugates were evaluated for their antioxidative and anti-inflammatory activity and their cytotoxicity was determined. Members of this family of compounds showed interesting anti-lipid peroxidation, anti-lipoxygenase and anti-inflammatory activity and comparable cytocompatibility to spermidine. 相似文献