排序方式: 共有15条查询结果,搜索用时 14 毫秒
1.
2.
3.
4.
Molecular dynamics computer simulation based on the Born-Mayer-Huggins potential function has been carried out to study the effects of duster size and temperature on the nucleation rate of sodium chloride dusters in the temperature range of 580 K to 630 K. Clusters with 256 and 500 NaCl molecules have been studied and the results have been compared with those obtained from 108 molecule dusters. The melting point (MP) of the clusters were observed to increase with the size of the clusters and can be well described by a linear equation MP =1107(37)-1229(23)N^-1/3(N is the number of molecules in the duster).The nucleation rate was found to decrease with increasing the duster size or temperature. Various nucleation theories have been used to interpret the nucleation rates obtained from this molecular dynamics simulation. It is possible to use a constant diffuse interface thickness to interpret the nucleation rate from the diffuse interface theory in the temperature range of this study. However, the interfacinl free energy estimated from classical nucleation theory and diffuse interface theory increases too fast with increasing the temperature while that from Gran-Gunton theory does not change with changing temperatures.The sizes of critical nuclei estimated from all the theories are smaller than those estimated from our simulations. 相似文献
5.
Molecular dynamics computer simulation has been carded out to study the structure and physical properties of iron nanoparticles with 331 to 2133 Fe atoms or with diameter from 2.3 to 4.3 nm. The core of liquid nanodroplets has the similar structure of the bulk molten iron liquid that has an average coordination number around 10.5 and the packing density around 0.45, although the closest Fe-Fe distance is slightly longer in the bulk liquid. Most of the iron nanoparticles formed from the cooling of molten nanodroplets have the same body center cubic crystal structure as it was observed in the bulk under the normal temperature and pressure. Lattice contraction was observed for iron nanoparticles. An amorphous solid and an HCP like solid were obtained accidentally during the quenching runs on Fe331 nanoparticles. The physical properties of iron nanoparticles such as molar volume, density, thermal expansion coefficient, melting point, heat of fusion, heat capacity and diffusion coefficient were estimated based on the results obtained from this simulation. The dependence of physical properties on the nanoparticle sizes was addressed. 相似文献
6.
Molecular dynamics (MD) computer simulations have been carried out to study the structures, properties and crystal nucleation of nanoparticles with 453 Cu atoms. Structure information was analyzed from the MD simulations, while properties of nanoparticles of Cu453, such as melting point, freezing temperature, heat capacity and mo- lar volumes, have been estimated. The face center cubic (FCC) phase and icosahedron (Ih) phase were observed during the quenching process, and nucleation rates of crystallization to FCC crystal of Cu453 at temperatures of 650, 700, 750, and 800 K were analyzed. Both classical nucleation theory (CNT) and diffuse interface theory (DIT) were used to interpret our observed nucleation rates. The free energy and diffuse interface thickness between the liquid and the FCC crystal phases were estimated by the CNT and DIT respectively, and the results show that the DIT does not work properly to the system. 相似文献
7.
用气相电子衍射法和质谱法相联合,分析了二元混合超声气流的剖面和质量分布情况。证明质谱利于确定气流剖面和气流中粒子的质量分布,而电子衍射则可以给出气流剖面和气流中生成了何种固相的信息。 相似文献
8.
9.
10.
2,2,3-三甲基丁烷(C7H16)晶体的成核动力学 总被引:1,自引:0,他引:1
High temperature solid phase I of 2,2,3-trimethylbutane(C7H16)(TMB) was investigated by X-ray powder diffraction. The electron diffraction technique for observing the kinetics of phase transitions in the condensed matter has been applied to study the freezing of TMB clusters with diameter of~13nm. Cluster beams were generated from the supersonically expanded TMB vapor with mole fraction of 0.01 in neon carrier gas. The freezing evolution was monitored by electron diffraction in interval of 7-9 μs. Clusters with an average size of ~5,500 molecules were observed to freeze into the solid phase I at a nucleation rate of 3.5 × 1028 m-3•s- 1 at the freezing temperature of clusters, ~170K. The estimated growth rate of postcritical nuclei indicates that the observed nucleation in the present experiment corresponds to mononuclear freezing of the clusters into single crystals of solid phase I. 相似文献