Molecular Dynamics Simulation of Homogeneous Nucleation and Growth of Supercooled Al Liquid

NANO ◽  
2021 ◽  
Author(s):  
Tao Zhou ◽  
Zhengping Bao
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulation ◽  
Nucleation Rate ◽  
First Passage Time ◽  
Spherical Shape ◽  
Passage Time ◽  
Dynamics Simulation ◽  
Spontaneous Nucleation ◽  
Different Shapes ◽  
The Mean

Molecular dynamics simulation is used to study the spontaneous nucleation and solidification of Al liquid. According to the mean first-passage time (MFPT), the critical crystal nucleus size at 31.6% undercooling is 152 atoms, the nucleation rate is [Formula: see text][Formula: see text]m[Formula: see text][Formula: see text]s[Formula: see text]. The nucleation rate obtained by the survival probability (SP) is [Formula: see text][Formula: see text]m[Formula: see text][Formula: see text]s[Formula: see text], which is very consistent with the result obtained by MFPT. Using Johnson–Mehl–Avrami (JMA) law to analyze the growth of the two extreme conditions in the experiment, the system with the smallest average atomic volume (Run38) grows faster than the system with the largest volume (Run73). In terms of microstructure, Run38 is a lamellar (LAM) structure, and Run73 is a complex polycrystalline structure accompanied by five-fold twinning (FFT). The shapes of clusters in a given range (5–10,000 atoms) during solidification in 100 experiments were counted. The results show that no clusters are perfectly spherical, but ellipsoids are of different shapes, and the larger the ellipsoid size, the closer to a spherical shape.

Molecular Dynamics Based Analysis of Nucleation and Surface Energy of Droplets in Supersaturated Vapors of Methane and Ethane

2009 ◽  
Vol 131 (4) ◽  
Author(s):  
Jadran Vrabec ◽  
Martin Horsch ◽  
Hans Hasse
Keyword(s):  
Molecular Dynamics ◽  
Surface Energy ◽  
Droplet Size ◽  
Nucleation Rate ◽  
Homogeneous Nucleation ◽  
First Passage Time ◽  
Nucleation Theory ◽  
Dynamics Simulation ◽  
Classical Nucleation Theory ◽  
Critical Droplet

Homogeneous nucleation processes are characterized by the nucleation rate and the critical droplet size. Molecular dynamics simulation is applied for studying homogeneous nucleation during condensation of supersaturated vapors of methane and ethane. The results are compared with the classical nucleation theory (CNT) and the Laaksonen–Ford–Kulmala (LFK) model that introduces the size dependence of the specific surface energy. It is shown for the nucleation rate that the Yasuoka–Matsumoto method and the mean first passage time method lead to considerably differing results. Even more significant deviations are found between two other approaches to the critical droplet size, based on the maximum of the Gibbs free energy of droplet formation (Yasuoka–Matsumoto) and the supersaturation dependence of the nucleation rate (nucleation theorem). CNT is found to agree reasonably well with the simulation results, whereas LFK leads to large deviations at high temperatures.

Molecular Dynamics Simulation of Bubble Nucleation in Superheated Liquid

2010 ◽  
Author(s):  
Chao Liu ◽  
Xiaobo Wu ◽  
Hualing Zhang
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulation ◽  
Nucleation Rate ◽  
Homogeneous Nucleation ◽  
Argon Atom ◽  
Bubble Nucleation ◽  
Nucleation Theory ◽  
Dynamics Simulation ◽  
Superheated Liquid ◽  
Classic Nucleation Theory

The bubble homogeneous nucleation in superheated liquid argon is studied by molecular dynamics simulation in NVT ensemble. L-J potential is adopted for the interaction of argon atom. The simulated particle numbers of argon atom is 10976. The non-dimensional size of simulated box is 27.8×27.8×27.8. The initial non-dimensional temperature and density are 0.4 and 0.51 separately. The results show that the bubble homogeneous nucleation is divided into the waiting process, the appearing process of numerous small bubble nucleuses and the aggregation process of small bubble nucleuses. By fitting simulated data, we find that the bubble nucleation rate is eight orders of magnitudes bigger than the result of classic nucleation theory. The bubble nucleation rate increases along with the increasing of density and superheated temperature, which agrees well with one of classic nucleation theory.

scholarly journals Rheological Behavior of Polymer Nanocomposites Filled with Spherical Nanoparticles: Insights from Molecular Dynamics Simulation

2021 ◽  
Author(s):  
Haoxiang Li ◽  
Haoyu WU ◽  
Wenfeng Zhang ◽  
Xiuying Zhao ◽  
Yangyang Gao ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulation ◽  
Polymer Nanocomposites ◽  
Shear Viscosity ◽  
Rheological Behavior ◽  
Molecular Level ◽  
Dynamics Simulation ◽  
Mean Square ◽  
Shear Rates ◽  
The Mean

<div><div>It is very urgent to understand the rheological behavior of polymer nanocomposites (PNCs) on the molecular level, which is very important for their processing and application. Thus, here the reverse nonequilibrium molecular dynamics simulation isemployed to explore it by tuning the nanoparticle (NP) concentration, the polymer-NPinteraction and the NP size. The shear viscosity (η~-m) exhibits a power law with theshear rate where m varies from 0.42 to 0.53 at high shear rates. By adopting the Carreau-Yasuda model, the obtained zero-shear viscosity gradually rises with increasing the NPconcentration, polymer-NP interaction or reducing the NP size. This is attributed to thestrong adsorption of chains by NPs and the formed network, which leads to the retarded dynamics. In addition, both the first and second normal stress differences also show power laws on the shear rates. The chains are gradually extended as the increase of shear rates, which is characterized by the mean-square end-to-end distance and the mean square radius of gyration. Especially, the evolution process of the NP network and the polymer- NP network is analyzed to deeply understand the shear thinning behavior. The number ofthe direct contact structure of NPs increases while the number of polymer-NP bridgedstructure is reduced. This is further proved by the increase of the formation probability of the NP network and the decrease of the polymer-NP interaction energy. Finally, the chain dynamics is found to be enhanced due to the shear flow. In summary, this work provides a further understanding on the mechanism of the shear thinning of PNCs on the molecular level. <br></div></div>

scholarly journals Rheological Behavior of Polymer Nanocomposites Filled with Spherical Nanoparticles: Insights from Molecular Dynamics Simulation

2021 ◽  
Author(s):  
Haoxiang Li ◽  
Haoyu WU ◽  
Wenfeng Zhang ◽  
Xiuying Zhao ◽  
Yangyang Gao ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulation ◽  
Polymer Nanocomposites ◽  
Shear Viscosity ◽  
Rheological Behavior ◽  
Molecular Level ◽  
Dynamics Simulation ◽  
Mean Square ◽  
Shear Rates ◽  
The Mean

<div><div>It is very urgent to understand the rheological behavior of polymer nanocomposites (PNCs) on the molecular level, which is very important for their processing and application. Thus, here the reverse nonequilibrium molecular dynamics simulation isemployed to explore it by tuning the nanoparticle (NP) concentration, the polymer-NPinteraction and the NP size. The shear viscosity (η~-m) exhibits a power law with theshear rate where m varies from 0.42 to 0.53 at high shear rates. By adopting the Carreau-Yasuda model, the obtained zero-shear viscosity gradually rises with increasing the NPconcentration, polymer-NP interaction or reducing the NP size. This is attributed to thestrong adsorption of chains by NPs and the formed network, which leads to the retarded dynamics. In addition, both the first and second normal stress differences also show power laws on the shear rates. The chains are gradually extended as the increase of shear rates, which is characterized by the mean-square end-to-end distance and the mean square radius of gyration. Especially, the evolution process of the NP network and the polymer- NP network is analyzed to deeply understand the shear thinning behavior. The number ofthe direct contact structure of NPs increases while the number of polymer-NP bridgedstructure is reduced. This is further proved by the increase of the formation probability of the NP network and the decrease of the polymer-NP interaction energy. Finally, the chain dynamics is found to be enhanced due to the shear flow. In summary, this work provides a further understanding on the mechanism of the shear thinning of PNCs on the molecular level. <br></div></div>

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