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Articles 1 - 9 of 9
Full-Text Articles in Physical Sciences and Mathematics
A Patching Model For Surface Tension Of Spherical Droplet And Tolman Length. Ii, T.V. Bykov, Xiao Cheng Zeng
A Patching Model For Surface Tension Of Spherical Droplet And Tolman Length. Ii, T.V. Bykov, Xiao Cheng Zeng
Xiao Cheng Zeng Publications
In the framework of density functional theory (DFT), two patching models for the density profile of spherical liquid droplet are developed. The patching is based on analytical expressions of the asymptote of the density profiles. The first model leads to analytic expressions of the Tolman length and the effective rigidity constant, from which the temperature dependence of the Tolman length and effective rigidity constant can be determined. The second model is developed particularly for small spherical droplets, from which the dependence of chemical potential and the surface tension of the droplet on the radius are obtained. The results are compared …
Confined Water In Hydrophobic Nanopores: Dynamics Of Freezing Into Bilayer Ice, Jan Slovak, Kenichiro Koga, Hideki Tanaka, Xiao Cheng Zeng
Confined Water In Hydrophobic Nanopores: Dynamics Of Freezing Into Bilayer Ice, Jan Slovak, Kenichiro Koga, Hideki Tanaka, Xiao Cheng Zeng
Xiao Cheng Zeng Publications
Molecular dynamics simulations for a thin film of water confined to a slit nanopore are performed in order to investigate the dynamic process of crystallization of the system. The system upon freezing creates a bilayer ice crystal composed of two layers of hexagonal rings. We perform one simulation at T=257 K during which the system remains a supercooled liquid state, and another one at T=253 K during which the system freezes. Many patterns of molecular arrangement are found upon freezing, and an account is given of the origin of multiple peaks in the distributions of binding energy and …
Imaging Point Defects In A Liquid Environment: A Model Afm Study, Kenichiro Koga, Xiao Cheng Zeng
Imaging Point Defects In A Liquid Environment: A Model Afm Study, Kenichiro Koga, Xiao Cheng Zeng
Xiao Cheng Zeng Publications
Effects of the liquid on atomic force microscopy (AFM) imaging are examined for a model system consisting of a hexagonal flake of seven Lennard-Jones (LJ) atoms as a multiatom tip, a monolayer of LJ crystal containing a single point defect as a substrate, and three-site model water as the liquid. A previous simulation [Koutsos et al., Europhys. Lett. 26, 103 (1994)] has shown that the true atomic resolution of a point defect cannot be achieved in vacuum by use of the multiatom tip. Here we examine the feasibility of such atomic resolution when both the tip and substrate are immersed …
A Patching Model For Surface Tension And The Tolman Length, T.V. Bykov, Xiao Cheng Zeng
A Patching Model For Surface Tension And The Tolman Length, T.V. Bykov, Xiao Cheng Zeng
Xiao Cheng Zeng Publications
In the framework of density functional theory (DFT), a patching model for the density profile of the liquid–vapor interface is developed. The patching is based on analytical expressions of the asymptote of the density profiles. Derived from the model the surface tension of planar liquid–vapor interface as well as the Tolman length can be computed from analytic expressions. Two prototype systems are considered; the Yukawa and the Lennard-Jones. As a result, the temperature dependence of the surface tension as well as the Tolman length are obtained. The results are compared with numerical DFT calculations.
Hydrogen Bonding And Cooperative Effects In Mixed Dimers And Trimers Of Methanol And Trifluoromethanol: An Ab Initio Study, Ruben D. Parra, Xiao Cheng Zeng
Hydrogen Bonding And Cooperative Effects In Mixed Dimers And Trimers Of Methanol And Trifluoromethanol: An Ab Initio Study, Ruben D. Parra, Xiao Cheng Zeng
Xiao Cheng Zeng Publications
Ab initio calculations are used to provide information on the mixed dimers and cyclic trimers of the methanol-trifluoromethanol system. In order to better understand the systems, the monomers and their corresponding dimers and trimers are also investigated. Molecular structures and harmonic frequencies are obtained at the B3LYP/6-311++G(d,p) level. Interaction energies are calculated with the MP2 and B3LYP methods using the 6-311++G(d,p), 6-311++G(2d,2p), and 6-311++G(3d,2p) basis sets for the dimers and heterodimers. The 6-311++G(d,p) basis set was used to calculate the …
Molecular Dynamics Study Of A Phase-Separating Fluid Mixture Under Shear Flow, Ryoichi Yamamoto, Xiao Cheng Zeng
Molecular Dynamics Study Of A Phase-Separating Fluid Mixture Under Shear Flow, Ryoichi Yamamoto, Xiao Cheng Zeng
Xiao Cheng Zeng Publications
Molecular dynamics simulation is carried out to study domain structures and rheological properties of a two-dimensional phase-separating binary fluid mixture under shear flow. In the early stage of the phase separation, anisotropic composition fluctuations appear immediately after the quench. As the domain grows, the anisotropy in the composition fluctuations increases. The quenched system eventually reaches a dynamical steady state, in which anisotropic domain structures are preserved. In the steady state, the shortest characteristic length scale R⊥ of domains decreases with increasing shear rate γ̇ as R⊥∼γ̇-1/3. Stringlike domain structures are observed in the strong shear regime, …
Formation Free Energy Of Clusters In Vapor-Liquid Nucleation: A Monte Carlo Simulation Study, K.J. Oh, Xiao Cheng Zeng
Formation Free Energy Of Clusters In Vapor-Liquid Nucleation: A Monte Carlo Simulation Study, K.J. Oh, Xiao Cheng Zeng
Xiao Cheng Zeng Publications
The formation free energy of clusters in a supersaturated vapor is obtained by a constrained Monte Carlo technique. A key feature of this approach is to set an upper limit to the size of cluster. This maximum cluster size serves essentially as an extra thermodynamic variable that constrains the system. As a result, clusters larger than the critical cluster of nucleation in the supersaturated vapor can no longer grow beyond the limiting size. Like changing the overall density of the system, changing the maximum cluster size also results in a different supersaturation and thereby a different formation free energy. However, …
Thermodynamic Expansion Of Nucleation Free-Energy Barrier And Size Of Critical Nucleus Near The Vapor-Liquid Coexistence, Kenichiro Koga, Xiao Cheng Zeng
Thermodynamic Expansion Of Nucleation Free-Energy Barrier And Size Of Critical Nucleus Near The Vapor-Liquid Coexistence, Kenichiro Koga, Xiao Cheng Zeng
Xiao Cheng Zeng Publications
Nucleation free-energy barrier height and size of the critical nucleus are expanded in powers of the chemical potential difference between the supersaturated vapor (or expanded liquid) in the metastable state and the saturated vapor-liquid system in the stable equilibrium state at the same temperature. The coefficients in the expansions are expressed in terms of the thermodynamic properties at the stable equilibrium state. Comparisons with the results obtained from the density-functional calculation for nucleation of the Lennard–Jones fluid show that systematic improvement in predicting properties of the critical nucleus, either liquid droplet or vapor cavity, is achieved by adding the higher …
Effect Of Uniform Electric Field On Homogeneous Vapor–Liquid Nucleation And Phase Equilibria. Ii. Extended Simple Point Charge Model Water, G.T. Gao, K.J. Oh, Xiao Cheng Zeng
Effect Of Uniform Electric Field On Homogeneous Vapor–Liquid Nucleation And Phase Equilibria. Ii. Extended Simple Point Charge Model Water, G.T. Gao, K.J. Oh, Xiao Cheng Zeng
Xiao Cheng Zeng Publications
The effects of a uniform electric field on homogeneous vapor–liquid nucleation of the extended simple point charge (SPC/E) model water have been simulated. A grand canonical Monte Carlo simulation approach [I. Kusaka et al., J. Chem. Phys. 108, 3416 (1998)], which directly gives the equilibrium distribution of physical clusters, is employed to calculate the formation free energy of the SPC/E water cluster. The results show that the formation free energy is lowered in a uniform field if the chemical potential of the supersaturated vapor is fixed; in this case, the field enhances the rate of nucleation. However, if the vapor …