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金属银熔体快冷过程的计算机模拟 总被引:2,自引:0,他引:2
利用分子动力学模拟技术研究了由周期性边界条件控制的500个银(Ag)原子构成的金属Ag熔体快速冷凝过程.冷却速率为8×1013K/s.模拟在FS(Finnis-Sinclair)相互作用势的基础上,通过双体分布函数、键对分析技术、键取向序等多种方法,对液银快速冷凝过程的微观结构转变特性作了分析,给出了连续快速冷凝过程中液银原子间依靠相互作用力形成的独特的微观结构图像.并考察了冷却过程中体系能量和元胞体积随温度的变化.模拟结果表明在快速冷凝过程中液Ag没有形成bcc结构的倾向. 相似文献
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采用嵌入原子法对深过冷条件下Ni2TiAl合金的焓和密度进行了分子动力学模拟,模拟获得了比热和密度在1200K至2000K范围内的温度依赖关系. 结果表明过冷条件下Ni2TiAl合金的比热、密度和温度之间存在着线性关系,它们都随着温度的降低而降低. 比热的大小与依据Neumann-Kopp法则估算的结果相近,同时模拟过程中的尺度效应经验证可以忽略.
关键词:
2TiAl合金')" href="#">Ni2TiAl合金
比热
密度
分子动力学模拟 相似文献
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采用分子动力学的模拟方法计算了水在依次降温,中间充分弛豫的降温过程以及同时对直接降温到某个温度,未足够弛豫的过程的径向分布函数(radial distribution function,RDF)曲线。在依次冷却方式下,选取了5种压力以研究压力对玻璃化温度和径向分布函数的影响;在每个温度段选取了5种冷速以研究依次冷却方式下不同温度段的冷速对径向分布函数的影响。同时对两种降温方式的结果进行了比较。结果表明:降温均匀,静止的水体系玻璃化温度可以大大提高,同时冷速对其玻璃化温度影响不大;压力对玻璃化温度影响不大;证实影响玻璃化温度的主要因素是传热;不同冷速对体系的RDF有影响,但缩小温差并采取中间温度充分驰豫的方式可减小这种差异。 相似文献
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石墨的化学腐蚀实验是在LAS-2000二次离子质谱仪的分析室中进行的,用高能氘离子束或与电子束联合辐照石墨,石墨温度从300-1000KW可调。辐照下释放的产物用四极质谱探头进行了质谱分析,得到了1.3μA、3keV氘束轰击下DSMF-800石墨释放氘甲烷的温度特性,在780K处有一释放高峰。 相似文献
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利用计算机模拟了在周期性边界条件下由500个银原子构成的液态Ag模型系统以8×1013K/s的速率快速凝固的全过程.模拟在FS相互作用势的基础上,通过双体分布函数、键对分析技术等多种方法,对液Ag快冷凝固过程的微观结构转变特性作了分析,给出了连续快速冷凝过程中液Ag原子间依靠相互作用力形成的独特的微观结构图像.模拟结果表明在快速冷却过程中液Ag没有形成bcc结构的倾向. 相似文献
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夏继宏 《原子与分子物理学报》2015,32(6)
本文利用分子动力学模拟方法, 研究了钯团簇在不同冷却条件下形成晶体及非晶的过程. 利用平均原子体积、双体分布函数、键对分析和键序参数方法研究了微观局域结构随温度的变化关系. 研究发现:在50 K/ps冷却过程中,液态Pd923团簇在1000 K发生玻璃化转变,在100 K下形成非晶结构; 而在0.1 K/ps冷却过程中,液态Pd923团簇发生结晶,并最终形成六角密排(hcp)晶体结构。 相似文献
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Many of water's peculiar physical properties are still not well understood, and one of the most important unresolved questions is its glass transition related dynamics. The consensus has been to accept a glass transition temperature (T(g)) around 136 K, but this value has been questioned and reassigned to about 165 K. We find evidence that the dielectric relaxation process of confined water that has been associated with the long accepted T(g) of water (130-140 K) must be a local process which is not related to the actual glass transition. Rather, our data indicate a glass transition at 160-165 K for bulk water and about 175 K for confined water (depending on the confining system). 相似文献
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We report a computer simulation study of the glass transition for water using the extended simple point charge potential. To mimic the difference between standard and hyperquenched glass, we generate glassy configurations with different cooling rates, and we calculate the temperature dependence of the specific heat on heating. The absence of crystallization phenomena allows us, for properly annealed samples, to detect in the specific heat the simultaneous presence of a weak prepeak ("shadow transition") and an intense glass transition peak at higher temperature. Our results support the view-point that the glass transition temperature is higher than the conventionally accepted value 136 K. We also compare our simulation results with the Tool-Narayanaswamy-Moynihan phenomenological model. 相似文献
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D. Starešinić A. Kiš K. Biljaković B. Emerling J. W. Brill J. Souletie H. Berger F. Lévy 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,29(1):71-77
Specific heats of the charge-density-wave compounds o-TaS3 and (TaSe4)2I have been measured over the wide temperature interval 10 K-300 K. Both systems exhibit strong non-Debye behavior. Very weak
and broad anomalies are observed at the Peierls transition temperatures. For o-TaS3, the change in the curvature of the specific heat occurs at temperature of 40 K where glass transition has been deduced from
dielectric measurements, and an extended scaling analysis suggests that the glass transition is associated with a dynamical
cross over in length scales. We briefly discuss the characteristics and physical origins of the anomalies at both the Peierls
and glass transitions.
Received 5 April 2002 / Received in final form 28 June 2002 Published online 17 September 2002 相似文献
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采用分子动力学方法对液态金属Al在不同的初始状态下,以相同急冷速率凝固的过程进行模拟跟踪研究,发现:在玻璃转变温度Tg以上(即过冷液态)时,系统的微结构组态情况基本一致,相差甚微;但在Tg以下时,不同的初始液态微结构对其固态微结构有明显的影响;且在Tg处各种固态微结构之间的差别发生突发性的变化。这一结果对于深入理解液-固微结构之间的转变关系,具有一定的重要意义。 相似文献
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The heat capacity results for platinum from 80 to 1000 K, reported in our previous paper, have been analyzed. The contributions of bare electrons and harmonic phonons to the heat capacity have been evaluated from the available data on the band structure and the phonon spectrum of platinum. At low temperatures, the present estimates for the temperature dependence of the electron-phonon enhancement agree qualitatively with those derived from theoretical calculations found in the literature. The anharmonic heat capacity obtained is negative and linear with temperature in the vicinity of the Debye temperature (237 K), and becomes constant above 450 K. The enhancement in the heat capacity above 1000 K has been analyzed and found to be due mainly to the enlargement of the dilation term corresponding to the similar enhancement in the thermal expansion. 相似文献
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N. Geier M. Weiss M. Moske K. Samwer 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,13(1):37-40
The thermal expansion of non-crystalline Zr65Al7.5Cu17.5 Ni10 has been studied in the range of the glass transition and in the undercooled liquid using a dilatometric device. The measuring
technique used permits reliable experimental results up to 40 K above the glass transition temperature. The linear thermal
expansion coefficient obtained is almost constant in the glassy state with a value of . It discontinuously increases at the glass transition temperature yielding a value of in the undercooled liquid. The results are compared with specific heat measurements of the amorphous material in this temperature
range and are interpreted in the framework of a cluster model.
Received 5 March 1999 and received in final form 11 June 1999 相似文献
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S. Mukherjee H.D. YangA.K. Pal S. Majumdar 《Journal of magnetism and magnetic materials》2012,324(9):1690-1697
Magnetic nanocrystalline MnO particles have been synthesized in a silica glass matrix by the sol-gel method at calcination temperatures up to 1000 °C. EPR spectra of 0.1 mol% MnO doped silica gel and glasses studied in the temperature range 10-290 K show with the exception of those samples calcined at 900 and 1000 °C 6-line characteristic Mn(II) hyperfine (HF) lines. Additionally five spin-forbidden doublets have been observed at 100 K and below. Small spreads in spin Hamiltonian parameters (D and E) imply that the ligand field environments of Mn(II) ions embedded in the silica glass are nearly uniform. Monotonous decrease in HF linewidth in going from 120 °C gel to 800 °C calcined glass has been interpreted as the continuous decrease in population of isolated Mn2+ ions in silica glass matrix resulting in the decrease of magnetic dipolar interactions leading to the observed decrease in HF linewidth. XRD and TEM of sample calcined at 1000 °C shows the presence of nanocrystals of MnO having orthorhombic crystalline phase and sizes about 10 nm. The thermal behavior of magnetization (zero-field-cooled and field-cooled) and magnetic hysteresis of MnO nanocrystals in the 5-300 K temperature interval have demonstrated that the MnO nanocrystals display superparamagnetic-ferromagnetic transition at low temperatures. X-band EPR linewidth data plotted versus inverse of temperature (1/T) for samples calcined at 900 and 1000 °C (EPR recorded in the vicinity of 0.35 T applied field) depict similar transitions. 相似文献