The phase transition between a massive dense phase and a diluted superparamagnetic phase has been studied by means of a direct molecular dynamics simulation. The equilibrium structures of the ferrofluid aggregate nucl...The phase transition between a massive dense phase and a diluted superparamagnetic phase has been studied by means of a direct molecular dynamics simulation. The equilibrium structures of the ferrofluid aggregate nucleus are obtained for different values of a temperature and an external magnetic field magnitude. An approximate match of experiment and simulation has been shown for the ferrofluid phase diagram coordinates ＂field-temperature＂. The provided phase coexistence curve has an opposite trend comparing to some of known theoretical results. This contradiction has been discussed. For given experimental parameters, it has been concluded that the present results describe more precisely the transition from linear chains to a dense globes phase. The theoretical concepts which provide the opposite binodal curve dependency trend match other experimental conditions： a diluted ferrofluid, a high particle coating rate, a high temperature,and/or a less particles coupling constant value.展开更多
Particle exchange molecular dynamics (PEMD) simulation technique is proposed to study the gas-liquid phase diagram of fluids. In the simulations, the fluid parti-cles can be transferred between the two coupled boxes, ...Particle exchange molecular dynamics (PEMD) simulation technique is proposed to study the gas-liquid phase diagram of fluids. In the simulations, the fluid parti-cles can be transferred between the two coupled boxes, which possess constant total number of particles and volume. The particle transfer is controlled by the difference of chemical potential in the respective simulation box. After equilibrium the two boxes have the same pressure, temperature and chemical potential. The method is further used to study the gas-liquid phase diagram of Stockmayer fluid. Increasing the dipole strength will enhance the critical temperature. The predicted critical points are in agreement with those from Gibbs ensemble Monte Carlo simulations, while the small systematic difference is attributed to the system size effects and the thermostat methods.展开更多
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文摘The phase transition between a massive dense phase and a diluted superparamagnetic phase has been studied by means of a direct molecular dynamics simulation. The equilibrium structures of the ferrofluid aggregate nucleus are obtained for different values of a temperature and an external magnetic field magnitude. An approximate match of experiment and simulation has been shown for the ferrofluid phase diagram coordinates ＂field-temperature＂. The provided phase coexistence curve has an opposite trend comparing to some of known theoretical results. This contradiction has been discussed. For given experimental parameters, it has been concluded that the present results describe more precisely the transition from linear chains to a dense globes phase. The theoretical concepts which provide the opposite binodal curve dependency trend match other experimental conditions： a diluted ferrofluid, a high particle coating rate, a high temperature,and/or a less particles coupling constant value.
基金This work was supported by the National Natural Science Foundation of China(Grant Nos.20304015 and 20404005)for the GeneralMajor Programs(Grant No.20490220)subsidized by the Young Teacher Fund of Jilin University.
文摘Particle exchange molecular dynamics (PEMD) simulation technique is proposed to study the gas-liquid phase diagram of fluids. In the simulations, the fluid parti-cles can be transferred between the two coupled boxes, which possess constant total number of particles and volume. The particle transfer is controlled by the difference of chemical potential in the respective simulation box. After equilibrium the two boxes have the same pressure, temperature and chemical potential. The method is further used to study the gas-liquid phase diagram of Stockmayer fluid. Increasing the dipole strength will enhance the critical temperature. The predicted critical points are in agreement with those from Gibbs ensemble Monte Carlo simulations, while the small systematic difference is attributed to the system size effects and the thermostat methods.
基金This work was supported by the National Natural Science Foundation of China(No.22022504,No.22003022)of ChinaNatural Science Foundation of Guangdong,China(No.2021A1515010213,No.2021A1515110406)+2 种基金Guangdong“Pearl River”Talent Plan(No.2019QN01L353)Higher Education Innovation Strong School Project of Guangdong Province of China(No.2020KTSCX122)Guangdong Provincial Key Laboratory of Catalysis(No.2020B121201002).Most calculations are performed on the CHEM Highperformance Computing Cluster(CHEM-HPC)located at the Department of Chemistry,Southern University of Science and Technology(SUSTech).The computational resources are also supported by the Center for Computational Science and Engineering at SUSTech.
