• Title/Summary/Keyword: Lennard-Jones fluid

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Calculation of the Free Energy from the Average of the Modified Effective cceptance Ratio for the Two-Center-Lennard-Jones Liquid

  • 홍성도
    • Bulletin of the Korean Chemical Society
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    • v.20 no.7
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    • pp.815-818
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    • 1999
  • The method of calculating the excess Helmholtz free energy from the averaged effective acceptance ratio for the Lennard-Jones fluid and the inverse twelve fluid has been slightly modified and applied to the two-center-Lennard-Jones liquid. The excess Helmholtz free energy is calculated directly from the average of the modified effective acceptance ratio through a single Metropolis Monte Carlo simulation. Therefore this method does not need any reference system. The results of the present method were satisfactory compared with those of the perturbation theories and the overlap ratio method.

One-fluid Conformal Solution Theory for Lennard-Jones Liquid Mixtures (Lennard-Jones 유체 혼합물의 열역학적 연구)

  • Kwon, Yong Jung
    • Journal of Industrial Technology
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    • v.9
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    • pp.119-125
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    • 1989
  • Lennard-Jones 유체 혹은 거의 구형에 가까운 분자들의 혼합물의 열역학적 성질을 예측하기 위한 용액이론이 유도되었다. 이 이론에는 에너지와 분자직경에 대한 두 개의 변수가 존재하며, 강구(hard sphere)를 중심으로 하여 동경함수(pair distribution function)를 확장시키는 교반이론(perturbation theory)에서 1/kT에 대한 일차와 이차계수의 관계로부터 얻어지는 혼합법칙을 이용하는 HSE이론과 달리 Orstein-Zernike결과와 일치되는 분자직경 변수를 먼저 구한 다음, 일차계수와 함께 얻어진 혼합법칙이 유도되었다. 이 방법으로 위 유체들의 혼합물에 적용시켰을 때, 원래의 HSE나 vdW-1의 방법보다 좋은 결과의 열역학적 성질을 예측할 수 있었다.

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Molecular-dynamic simulation on the equilibrium and dynamical properties of fluids in a nano-channel

  • Hoang, H.;Kang, S.;Suh, Y.K.
    • 한국전산유체공학회:학술대회논문집
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    • 2008.03a
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    • pp.208-214
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    • 2008
  • The equilibrium molecular-dynamic simulations have been performed to estimate the properties of the three kinds of fluids (the Lennard-Jones fluid, water and aqueous sodium-chloride solution) confined between two plates that are separated by 1.086 nm; included in the equilibrium properties are the density distribution and the static structure, and the diffusivity in the dynamic property. Three kinds of fluids considered in this study are. The water molecules are modeled by using the SPC/E model and the ions by the charged Lennard-Jones particle model. To treat the water molecules, we combined the quaternion coordinates with Euler angles. We also proposed a plausible algorithm to assign the initial position and direction of molecules. The influence of polarization of water molecules as well as the presence of ions in the solution on the properties will be addressed in this study. In addition, we performed the non-equilibrium molecular-dynamic simulation to compute the flow velocity for the case with the gravitational force acting on molecules.

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Molecular-dynamic simulation on the equilibrium and dynamical properties of fluids in a nano-channel

  • Hoang, H.;Kang, S.;Suh, Y.K.
    • 한국전산유체공학회:학술대회논문집
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    • 2008.10a
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    • pp.208-214
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    • 2008
  • The equilibrium molecular-dynamic simulations have been performed to estimate the properties of the three kinds of fluids (the Lennard-Jones fluid, water and aqueous sodium-chloride solution) confined between two plates that are separated by 1.086 nm; included in the equilibrium properties are the density distribution and the static structure, and the diffusivity in the dynamic property. Three kinds of fluids considered in this study are. The water molecules are modeled by using the SPC/E model and the ions by the charged Lennard-Jones particle model. To treat the water molecules, we combined the quaternion coordinates with Euler angles. We also proposed a plausible algorithm to assign the initial position and direction of molecules. The influence of polarization of water molecules as well as the presence of ions in the solution on the properties will be addressed in this study. In addition, we performed the non-equilibrium molecular-dynamic simulation to compute the flow velocity for the case with the gravitational force acting on molecules.

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MOLECULAR-DYNAMIC SIMULATION ON THE STATICAL AND DYNAMICAL PROPERTIES OF FLUIDS IN A NANO-CHANNEL

  • Hoang, Hai;Kang, Sang-Mo;Suh, Yong-Kweon
    • Journal of computational fluids engineering
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    • v.14 no.1
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    • pp.24-34
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    • 2009
  • The equilibrium molecular-dynamic simulations have been performed to estimate the properties of the three kinds of fluids confined between two plates that are separated by 1.086 nm; included in the statical properties are the density distribution and the static structure, and the autocorrelation velocity function in the dynamic property. Three kinds of fluids considered in this study are the Lennard-Jones fluid, water and aqueous sodium-chloride solution. The water molecules are modeled by using the SPC/E model and the ions by the charged Lennard-Jones particle model. To treat the water molecules, we combined the quaternion coordinates with Euler angles. We also proposed a plausible algorithm to assign the initial position and direction of molecules. The influence of polarization of water molecules as well as the presence of ions in the solution on the properties will be addressed in this study. In addition, we performed the non-equilibrium molecular-dynamic simulation to compute the flow velocity for the case with the gravitational force acting on molecules.

Comparison of Potentials for Polymeric Liquids (고분자액체에 대한 포텐셜의 비교)

  • Jeong, Hae Yeong
    • Journal of the Korean Chemical Society
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    • v.46 no.6
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    • pp.545-549
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    • 2002
  • Many theories for polymeric liquids are based on the concepts of cell, hole, free volume or lattice etc. In the theories, van der Waals potential, Lennard-Jones 6-12 potential and their modified potentials are commonly used.In this work, Mie(p, 6) potential was applied to the Continuous Lattice Fluid Theory (which extends the discrete lattices of Lattice Fluid Theory to classically continuous lattices) and Dee-Walsch's Cell Theory (which modifies Flory's Equa-tion of State Theory). Both of them are known to be successful theories for polymeric liquids. Thus, PVT values chang-ing with p (the exponent in the repulsion potential) were calculated and compared with experimental values. And, calculated values of Lattice Fluid Theory, Flory's Equation of State Theory and Cho-Sanchez Theory using pertubation method were also compared. Through the calculated results, van der Waals potential, Lennard-Jones 6-12 potential and Mie(p, 6) potential for polymeric liquids were compared with each other.

Estimation of diffusion coefficient at the interface between liquid and vapor phases using the equilibrium molecular dynamics simulation (분자 동역학 모사를 이용한 액상과 기상 계면에서의 확산계수의 예측)

  • Kim, Kyeong-Yun;Choi, Young-Ki;Kwon, Oh-Myoung;Park, Seung-Ho;Lee, Joon-Sik
    • Proceedings of the KSME Conference
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    • 2003.04a
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    • pp.1584-1589
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    • 2003
  • This work applies the equilibrium molecular dynamics simulation method to study a Lennard-Jones liquid thin film suspended in the vapor and calculates diffusion coefficients by Green-Kubo equation derived from Einstein relationship. As a preliminary test, the diffusion coefficients of the pure argon fluid are calculated by equilibrium molecular dynamics simulation. It is found that the diffusion coefficients increase with decreasing the density and increasing the temperature. When both argon liquid and vapor phases are present, the effects of the system temperature on the diffusion coefficient are investigated. It can be seen that the diffusion coefficient significantly increases with the temperature of the system.

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Estimation of Thermal Conductivity at Liquid and Vapor Interface by Molecular Dynamics Simulation (분자동역학을 이용한 액상과 기상계면에서의 열전도율 예측)

  • Koo, Jin-Oh;Choi, Young-Ki;Lee, Joon-Sik;Park, Seung-Ho
    • Proceedings of the KSME Conference
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    • 2004.04a
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    • pp.1558-1563
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    • 2004
  • This work applies the nonequilibrium molecular dynamics simulation method to study a Lennard-Jones liquid thin film suspended in the vapor and calculates the thermal conductivity by linear response function. As a preliminary test, the thermal conductivity of pure argon fluid are calculated by nonequilibrium molecular dynamics simulation. It is found that the thermal conductivity decrease with decreasing the density. When both argon liquid and vapor phase are present, the effects of the system temperature on the thermal conductivity are investigated. It can be seen that the thermal conductivity of liquid-vapor interface is constant with increasing the temperature

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A Simulational Study of a Simple Fluid Monolayer on a Smooth Solid Surface (연속고체 표면 위의 단순유체 홑층에 대한 시늉연구)

  • Han, Kyu-Kwang
    • The Journal of Natural Sciences
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    • v.10 no.1
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    • pp.1-7
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    • 1998
  • A Lennard-Jones fluid layer adsorbed on a smooth solid surface was studied at coverages $\theta$ ~ 0.8 to 1.8 on an isotherm by performing intensive grand canonical Monte Carlo simulations. The results clearly show a picture of two-step melting process which used to be observed in recent thermodynamic measurements of argon monolayer melting on graphite. The observed melting process consist of an abrupt density change followed by a gradual transition. Snapshots of monolayer configurations indicate that the creation and dissociation of a dislocation pair are involved in the melting mechanism. Taking the effect of system size into account, it is suggested that, while the abrupt density change may be not related to the theory of Kosterlitz, Thouless, Halperin, Nelson, and Young (KTHNY), the second gradual transition is probably a KTHNY-type melting transition.

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Transient Analysis of Pressure Behavior of Cryogenics in Closed Vessel (극저온 저장용기의 내부압력 거동에 대한 비정상해석)

  • 강권호;김길정;박영무
    • Journal of Energy Engineering
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    • v.5 no.1
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    • pp.19-27
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    • 1996
  • Self-pressurization of cylindrical container of cryogen is numerically analyzed. The container is axi-symmetric and heated from side wall with constant heat flux. Natural convection by external heat flux is studied numerically using finite difference method. Oxygen, nytrogen and hydrogen are working fluids in this paper. Liquid is considered incompressible fluid and vapor is assumed to behave as gas meeting with virial equation of gas. The Second virial coefficients of gas are obtained from Lennard-jones model. The important variables which have effects on self-pressurization are external heat flux, heat capacity of wall and initial ullage in container. The most important variable of them is external heat flux. The pressure rise calculated from the virial gas model is slightly different from that calculated using Ideal gas model for oxygen.

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