共查询到18条相似文献,搜索用时 171 毫秒
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耐蚀合金Au3 Cu高温冷却过程中能量及结构转变的分子动力学模拟 总被引:1,自引:0,他引:1
张长桥 《化学物理学报(中文版)》2001,14(6)
用分子动力学模拟方法对液态Au3Cu冷却过程进行了研究,考察了不同冷却速度下Au3Cu结构变化特点,原子间相互作用势采用F-S多体势,结构分析采用键取向序和对分析技术.计算结果表明,冷却速度对液态Au3Cu能量及结构转变有重要影响,给出了不同冷却速度下液态Au3Cu结构转变的微观信息. 相似文献
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金属Cu熔化结晶过程的分子动力学模拟 总被引:3,自引:0,他引:3
采用常温、常压分子动力学模拟技术,研究了在周期性边界条件下,由864个Cu原子构成的模型系统的熔化、结晶过程。原子间相互作用势采用EAM势。模拟结果表明:在连续升温过程中,金属Cu在1520 K熔化;以不同的冷速进行冷却,在较慢冷却条件下,液态Cu在1010 K结晶;当冷速较快时,液态Cu形成非晶态。分析了升降温过程中熔体偶分布函数、原子体积、能量、MSD随温度的变化特征。 相似文献
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运用分子动力学方法模拟了小尺寸金属团簇的熔化过程, 原子之间的作用采用嵌入原子法(EAM)模型, 计算了均方根键长涨落δ随温度的变化, 以及升温过程中团簇热容的变化. 包含55、56个原子的面心立方(FCC)结构Au团簇的熔化过程是基本相同的. 而同样结构和数目Cu团簇的熔化过程却呈现出不同的趋势. Cu55、Cu56在模拟过程中都出现了FCC结构到二十面体结构的转变. 但由于表面多出了一个原子, Cu56的热容曲线比Cu55多了一个峰, 体系出现了预熔化现象. 这表明小尺寸团簇的固液转变的过程与团簇的原子类型、几何结构和原子数目密切相关. 相似文献
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针对结晶型聚合物熔体冷却过程的结晶行为,建立了偶合宏观温度场与微观结晶形态的多尺度模型.该模型揭示了宏观温度的变化会引起晶核数、晶体生长速率的改变,从而影响微观结晶形态;而微观结晶释放的潜热也将导致宏观温度的改变.为了求解上述多尺度模型,提出了有限体积/像素法偶合的多尺度算法,即在粗网格上采用有限体积法对宏观温度场进行求解,而在细网格上采用像素法对微观结晶形态进行模拟.基于多尺度模型及多尺度算法,文中对二维聚合物熔体模壁等速降温的冷却问题进行了研究,考察了温度、相对结晶度的变化及结晶形态的演化,并比较了不同冷却速率、初始温度对温度、相对结晶度及结晶形态的影响.数值结果表明,冷却速率是影响结晶行为的关键.高冷却速率下,温度平台出现较早,持续较短;结晶过程对应的温度范围较广;且平均晶体直径较小.而初始温度只影响温度平台及结晶行为出现的早晚,与其持续时间几乎无关。 相似文献
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金属单原子物种的可控制备对于包括多相催化在内的各种表面化学过程非常重要。在本工作中,我们在Au(111)表面制备了由蜜勒胺分子形成的具有周期性孔道结构的自组装薄膜。这种有机分子薄膜所携载的官能团能与金属原子进行有效作用。通过在室温下暴露CO气体,在表面上成功制备出Au单原子。由于蜜勒胺分子中的杂环氮原子与Au原子作用较强,因此所形成的Au原子具有突出的稳定性,并且具有多种形式的空间分布构型,有望为一些结构敏感性的表面反应提供合适的催化位点。 相似文献
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采用F-S多体势对液态合金Al3Ni和Ni3Al在不同冷却速度下的微观结构及其转变机制进行了分子动力学模拟,得到了不同冷速下各温度的双体分布函数;采用HA键型指数法对其结构进行了分析,结果表明: Al3Ni在两种冷速下均以非晶的形式出现,只是慢冷时体系的有序度略有升高;而Ni3Al的结构及能量转变受冷速影响较大,快冷时形成非晶,而慢冷时出现明显结晶;同样冷速下Al含量较少的Ni3Al体系的有序度高,更易形成晶体,晶体的形成过程中有能量突变. 相似文献
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The initial structure of flame-annealed Au(100) surfaces has been studied in air and in 0.1 M H2SO4 by scanning tunnelling microscopy (STM). It is shown that before, during and after contact with the electrolyte, at potentials sufficiently negative to prevent specific adsorption of anions, the flame-annealed Au(100) surface is reconstructed into exactly the same “hex” form as a surface which has been prepared by annealing in ultrahigh vacuum (UHV). However, the quality of the reconstructed surface depends sensitively on the sample preparation and on the experimental conditions of the flame-annealing procedure. The influence of the cooling procedure after flame annealing on the initial surface structure of the Au(100) electrode is demonstrated and briefly discussed in the light of results published previously. 相似文献
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Hernandez NC Sanz JF Rodriguez JA 《Journal of the American Chemical Society》2006,128(49):15600-15601
Using first principles DF calculations we have studied the structural and catalytic properties of Au supported on TiOx-Mo(112) films. Our theoretical models are consistent with an initial (8 x 2) Mo(112)-Ti2O3 pattern which after Au deposition gives rise to ordered Au films that completely wet the surface. The oxidation of CO on model surfaces at coverage 1, 4/3, and 5/2 ML has been analyzed. The oxidation proceeds through a peroxo-like complex in which molecular oxygen is simultaneously bound to the CO and the surface. The energy barrier computed for a Au coverage of 4/3 ML is found significantly lower in agreement with the unusual high activity observed for this catalyst. The detailed analysis of the geometry and electronic structure provides a fundamental understanding of the reaction. 相似文献
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Molecular dynamics simulation of the crystallization behavior of liquid gold (Au) nanoparticles, with 1, 2, 3, 4, 5 and 6 nm
in diameter, on cooling has been carried out based on the embedded-atom-method potential. With decreasing cooling time, the
final structure of the particle changes from amorphous to crystalline structure. We showed that the structure of the fully
crystallized particle is polycrystalline face-centered cubic (FCC). The FCC structure of the gold nanoparticle is proved energetically
the most stable form. And the final structure of nanoparticles is affected by cooling time and size of nanoparticles. We also
showed that the melting point of particles is affected by size of nanoparticles. 相似文献
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A. K. Gatin M. V. Grishin N. V. Dokhlikova N. N. Kolchenko B. R. Shub 《Doklady Physical Chemistry》2016,470(1):125-128
It has been demonstrated that hydrogen adsorption has an effect on the electronic structure of gold nanoparticles. The physicochemical properties of separate gold nanoparticles have been studied under an ultrahigh vacuum scanning tunneling microscope. The structure and electronic structure of gold–hydrogen clusters were modeled by the quantum-chemical density functional theory method. Hydrogen adsorption onto gold nanoparticles 4–5 nm is size at room temperature was experimentally revealed, and the lower limit of 1.7 eV for the Au–H bond energy was determined. The interaction of hydrogen with gold leads to a considerable rearrangement of the electronic subsystem of nanoparticles. The experimentally observed effects were supported by quantum-chemical calculations. The rearrangement mechanism is related to strong correlations in the electronic subsystem. 相似文献
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The adsorption of the two-dimensionally chiral naphtho[2,3-a]pyrene molecule has been studied on Au(111). Both structural and electronic properties of the naphtho[2,3-a]pyrene (NP)/Au(111) interface have been measured. Ultraviolet and X-ray photoelectron spectroscopy have been employed to measure the energies of the molecular orbitals of the NP film with respect to the gold Fermi level. A Schottky junction with a large interface dipole (0.99 eV) is formed between Au(111) and NP. Temperature-programmed desorption was used to determine that adsorbed NP has a binding energy of 102.2 kJ/mol. Chiral domains have been observed with scanning tunneling microscopy due to the spontaneous phase separation of the 2-D enantiomers. Two distinct structural polymorphs have been observed, one of which has homochiral paired molecular rows. Models of the 2D structure are proposed that are in excellent agreement with experimental measurements. 相似文献
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Wei Yunhe Zhang Changqiao Ma Xiaolong Zhang Guoyu Hou Qi Wang Hongchen Sun Yuansheng 《化学物理学报(中文版)》2004,17(4):443-448
During the hot-dip process of Cu on the surface of the steel,it involves the solidification from liquid to coating. The cooling rate has great influence on the microstructure and the performance. By means of constanttemperature,constant-pressure molecular dynamics simulation technique,the solidification process of the liquid model system made of 500 Cu particles has been studied with the period boundary condition. With the pairs analysis technology and the bond orientational order method,the difference of the structure and energy of the liquid Cu model system between different cooling velocities has been compared. The significant information of microcosmic structural transformation in the solidification process of liquid Cu system has been obtained. The calculation results show that the Finnis-Sinclair(FS)potential works very well in the solidification process of Cu. Cooling slowly the crystal copper layer can be obtained. Cooling quickly the amorphous copper layer can be obtained. 相似文献