The effects of solid-fluid interactions on the vapor-liquid phase diagram,coexistence density,relative volatility and vaporization enthalpy have been investigated for confined binary systems of CO 2-CH 4,CO 2-N 2 and ...The effects of solid-fluid interactions on the vapor-liquid phase diagram,coexistence density,relative volatility and vaporization enthalpy have been investigated for confined binary systems of CO 2-CH 4,CO 2-N 2 and CH 4-N 2.The Gibbs ensemble Monte Carlo(GEMC) simulation results indicate that the confinement and the solid-fluid interaction have significant influences on the vapor-liquid equilibrium properties.The confinement and the strength of the solid-fluid interaction make the p-x i phase diagram move to higher pressure regions.They also make the two-phase region become narrower for each binary mixture.The strength of the solid-fluid interactions can cause increases in the coexistence liquid and vapor densities,and cause the decrease of the relative volatility and the vaporization enthalpy for the systems studied.As the pore width is decreased,the two-phase region of the binary mixture becomes narrower.展开更多
Gibbs Ensemble Monte Carlo(GEMC)is a molecular simulation method commonly used for simulating phase equilibrium.This method has been proposed since 1987 and applied in many fields,such as geology,planetary science,che...Gibbs Ensemble Monte Carlo(GEMC)is a molecular simulation method commonly used for simulating phase equilibrium.This method has been proposed since 1987 and applied in many fields,such as geology,planetary science,chemical engineering,material science,etc.GEMC method combines canonical(NVT),isobaricisothermal(NPT),and grand canonical(μVT)Monte Carlo techniques in a single simulation.The GEMC method was developed on the fundamental law of phase equilibrium that chemical potentials of each phase all equal.Two key factors affect the rationality and reliability of GEMC simulations:1.particles can be efficiently moved in/out from certain phase during simulation;2.samplings can represent the whole system well,in other words,samplings hold good ergodicity.In addition,various parallel methods have been developed to improve the simulation efficiency.In this review,an introduction to the theoretical fundamentals,improvements on particle movement and sampling protocols,acceleration techniques and some applications of the GEMC method will be presented.This is the first integrated review introducing the fundamentals,improvements and applications of the GEMC simulation method.展开更多
The nonlinear radiation responses of two different n-doped bulk semiconductors: indium antimonide(In Sb) and indium arsenide(In As) in an intense terahertz(THz) field are studied by using the method of ensemble Monte ...The nonlinear radiation responses of two different n-doped bulk semiconductors: indium antimonide(In Sb) and indium arsenide(In As) in an intense terahertz(THz) field are studied by using the method of ensemble Monte Carlo(EMC)at room temperature. The results show that the radiations of two materials generate about 2-THz periodic regular spectrum distributions under a high field of 100 k V/cm at 1-THz center frequency. The center frequencies are enhanced to about 7 THz in In Sb, and only 5 THz in In As, respectively. The electron valley occupancy and the percentage of new electrons excited by impact ionization are also calculated. We find that the band nonparabolicity and impact ionization promote the generation of nonlinear high frequency radiation, while intervalley scattering has the opposite effect. Moreover, the impact ionization dominates in In Sb, while impact ionization and intervalley scattering work together in In As. These characteristics have potential applications in up-convension of THz wave and THz nonlinear frequency multiplication field.展开更多
The linear and nonlinear characteristics of time-resolved photoluminescence （PL） of n-type bulk semiconductor GaAs modulated with terahertz （THz） pulse are studied by using an ensemble Monte Carlo （EMC） method. ...The linear and nonlinear characteristics of time-resolved photoluminescence （PL） of n-type bulk semiconductor GaAs modulated with terahertz （THz） pulse are studied by using an ensemble Monte Carlo （EMC） method. In this paper the center energy valley （Г valley） electron concentration changes with the pulse delay time, sampling time and the outfield are mainly discussed. The results show that the sampling time and the THz field should exceed certain thresholds to effectively excite photoluminescence quenching （PLQ）. Adopting a direct current （DC） field makes the sampling time threshold shortened and the linear range of THz field-modulation PL expanded. Moreover, controlling the sampling time and the outfield intensity can improve the linear quality： with forward time, the larger outfield is used; with backward time, the smaller outfield is used. This study can provide a theoretical basis of THz field linear modulation in a larger range for new light emitting devices.展开更多
It has been proposed previously that the coherent detection of a terahertz（THz） pulse can be achieved based on the time-resolved luminescence quenching. In this paper, we investigate the frequency response range of ...It has been proposed previously that the coherent detection of a terahertz（THz） pulse can be achieved based on the time-resolved luminescence quenching. In this paper, we investigate the frequency response range of this novel detection technology by simulating the motion of carriers in gallium arsenide（GaAs） by the ensemble Monte Carlo method. At room temperature, for a direct-current（DC） voltage of 20 kV/cm applied to the semiconductor（GaAs） and sampling time o140 fs, the luminescence quenching phenomena induced by terahertz pulses with different center frequencies are studied The results show that the quenching efficiency is independent of the THz frequency when the frequency is in a range o0.1 THz–4 THz. However, when the frequency exceeds 4 THz, the efficiency decreases with the increase of frequency Therefore, the frequency response range is 0.1 THz–4 THz. Moreover, when the sampling time is changed to 100 fs the frequency response range is extended to be approximately 0.1 THz–5.6 THz. This study of the frequency-dependen characteristics of the luminescence response to the THz pulse can provide a theoretical basis for the exploration of THz detection technology.展开更多
The vapor-liquid equilibrium(VLE) properties for the binary and ternary mixtures of CH4,C2H4 and isoC4H10 are of great importance in the recovery of ethylene from mixture containing CH4 and C2H4 with iso-C4H10 as solv...The vapor-liquid equilibrium(VLE) properties for the binary and ternary mixtures of CH4,C2H4 and isoC4H10 are of great importance in the recovery of ethylene from mixture containing CH4 and C2H4 with iso-C4H10 as solvent.Hence,Gibbs ensemble Monte Carlo(GEMC) simulations were used to estimate vapor-liquid equilibrium for the binary and ternary mixtures of CH4,C2H4 and iso-C4H10 with the united atom potential NERD model.The selected simulation conditions are based on the experiment in the literature.The results of this work were shown to be in satisfactory agreement with available experimental data and predictions of Peng-Robinson equation of state.The structure of simulated liquid phase is also characterized by radial distribution function(RDF),which contributes to further understanding of the VLE curve of these systems.RDF is not sensitive to the pressure and temperature range.With the increase of pressure or the decrease of temperature,the molecules tend to gather together.展开更多
基金supported by National Natural Science Foundation of China (20876083,20736003)the Specialized Research Fund forthe Doctoral Program of Higher Education (20100002110024)Major State Basic Research Program of China (2009CB623404)
文摘The effects of solid-fluid interactions on the vapor-liquid phase diagram,coexistence density,relative volatility and vaporization enthalpy have been investigated for confined binary systems of CO 2-CH 4,CO 2-N 2 and CH 4-N 2.The Gibbs ensemble Monte Carlo(GEMC) simulation results indicate that the confinement and the solid-fluid interaction have significant influences on the vapor-liquid equilibrium properties.The confinement and the strength of the solid-fluid interaction make the p-x i phase diagram move to higher pressure regions.They also make the two-phase region become narrower for each binary mixture.The strength of the solid-fluid interactions can cause increases in the coexistence liquid and vapor densities,and cause the decrease of the relative volatility and the vaporization enthalpy for the systems studied.As the pore width is decreased,the two-phase region of the binary mixture becomes narrower.
基金supported by Chinese NSF projects(42130114)the strategic priority research program(B)of CAS(XD841000000)pre research Project on Civil Aerospace Technologies No.D020202 funded by Chinese National Space Administration(CNSA)。
文摘Gibbs Ensemble Monte Carlo(GEMC)is a molecular simulation method commonly used for simulating phase equilibrium.This method has been proposed since 1987 and applied in many fields,such as geology,planetary science,chemical engineering,material science,etc.GEMC method combines canonical(NVT),isobaricisothermal(NPT),and grand canonical(μVT)Monte Carlo techniques in a single simulation.The GEMC method was developed on the fundamental law of phase equilibrium that chemical potentials of each phase all equal.Two key factors affect the rationality and reliability of GEMC simulations:1.particles can be efficiently moved in/out from certain phase during simulation;2.samplings can represent the whole system well,in other words,samplings hold good ergodicity.In addition,various parallel methods have been developed to improve the simulation efficiency.In this review,an introduction to the theoretical fundamentals,improvements on particle movement and sampling protocols,acceleration techniques and some applications of the GEMC method will be presented.This is the first integrated review introducing the fundamentals,improvements and applications of the GEMC simulation method.
基金supported by the National Natural Science Foundation of China(Grant Nos.11574105,61177095,61405063,and 61475054)the Natural Science Foundation of Hubei Province,China(Grant Nos.2012FFA074 and 2013BAA002)+1 种基金the Wuhan Municipal Applied Basic Research Project,China(Grant No.20140101010009)the Fundamental Research Funds for the Central Universities,China(Grant Nos.2013KXYQ004 and 2014ZZGH021)
文摘The nonlinear radiation responses of two different n-doped bulk semiconductors: indium antimonide(In Sb) and indium arsenide(In As) in an intense terahertz(THz) field are studied by using the method of ensemble Monte Carlo(EMC)at room temperature. The results show that the radiations of two materials generate about 2-THz periodic regular spectrum distributions under a high field of 100 k V/cm at 1-THz center frequency. The center frequencies are enhanced to about 7 THz in In Sb, and only 5 THz in In As, respectively. The electron valley occupancy and the percentage of new electrons excited by impact ionization are also calculated. We find that the band nonparabolicity and impact ionization promote the generation of nonlinear high frequency radiation, while intervalley scattering has the opposite effect. Moreover, the impact ionization dominates in In Sb, while impact ionization and intervalley scattering work together in In As. These characteristics have potential applications in up-convension of THz wave and THz nonlinear frequency multiplication field.
基金supported by the National Natural Science Foundation of China(Grant Nos.11574105,61475054,61405063,and 61177095)the Hubei Science and Technology Agency Project,China(Grant No.2015BCE052)the Fundamental Research Funds for the Central Universities,China(Grant No.2017KFYXJJ029)
文摘The linear and nonlinear characteristics of time-resolved photoluminescence （PL） of n-type bulk semiconductor GaAs modulated with terahertz （THz） pulse are studied by using an ensemble Monte Carlo （EMC） method. In this paper the center energy valley （Г valley） electron concentration changes with the pulse delay time, sampling time and the outfield are mainly discussed. The results show that the sampling time and the THz field should exceed certain thresholds to effectively excite photoluminescence quenching （PLQ）. Adopting a direct current （DC） field makes the sampling time threshold shortened and the linear range of THz field-modulation PL expanded. Moreover, controlling the sampling time and the outfield intensity can improve the linear quality： with forward time, the larger outfield is used; with backward time, the smaller outfield is used. This study can provide a theoretical basis of THz field linear modulation in a larger range for new light emitting devices.
基金supported by the Wuhan Applied Basic Research Project,China(Grant No.20140101010009)the National Natural Science Foundation of China(Grant Nos.61405063,61475054,11574105,and 61177095)+1 种基金the Hubei Science and Technology Agency Project,China(Grant No.2015BCE052)the Fundamental Research Funds for the Central Universities,China(Grant No.2017KFYXJJ029)
文摘It has been proposed previously that the coherent detection of a terahertz（THz） pulse can be achieved based on the time-resolved luminescence quenching. In this paper, we investigate the frequency response range of this novel detection technology by simulating the motion of carriers in gallium arsenide（GaAs） by the ensemble Monte Carlo method. At room temperature, for a direct-current（DC） voltage of 20 kV/cm applied to the semiconductor（GaAs） and sampling time o140 fs, the luminescence quenching phenomena induced by terahertz pulses with different center frequencies are studied The results show that the quenching efficiency is independent of the THz frequency when the frequency is in a range o0.1 THz–4 THz. However, when the frequency exceeds 4 THz, the efficiency decreases with the increase of frequency Therefore, the frequency response range is 0.1 THz–4 THz. Moreover, when the sampling time is changed to 100 fs the frequency response range is extended to be approximately 0.1 THz–5.6 THz. This study of the frequency-dependen characteristics of the luminescence response to the THz pulse can provide a theoretical basis for the exploration of THz detection technology.
基金Supported by the Program for Changjiang Scholars and Innovative Research Team in University of Ministry of Education of China(No.IRT0936)National Basic Research Program of China("973"Program,No.2009CB219905 and No.2009CB219907)
文摘The vapor-liquid equilibrium(VLE) properties for the binary and ternary mixtures of CH4,C2H4 and isoC4H10 are of great importance in the recovery of ethylene from mixture containing CH4 and C2H4 with iso-C4H10 as solvent.Hence,Gibbs ensemble Monte Carlo(GEMC) simulations were used to estimate vapor-liquid equilibrium for the binary and ternary mixtures of CH4,C2H4 and iso-C4H10 with the united atom potential NERD model.The selected simulation conditions are based on the experiment in the literature.The results of this work were shown to be in satisfactory agreement with available experimental data and predictions of Peng-Robinson equation of state.The structure of simulated liquid phase is also characterized by radial distribution function(RDF),which contributes to further understanding of the VLE curve of these systems.RDF is not sensitive to the pressure and temperature range.With the increase of pressure or the decrease of temperature,the molecules tend to gather together.
