Molecular dynamics simulation of potassium along the liquid-vapor coexistence curve

Eslami, Hossein; Mozaffari, Farkhondeh; Moghadasi, Jalil

doi:10.1007/bf03246015

Cited by 8 publications

(8 citation statements)

References 26 publications

(65 reference statements)

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“…It is known that liquid metals do not obey a simple pair potential , like the LJ(12–6) potential employed here. However, adopting liquid potassium as a typical example, for which the temperature-dependent LJ(12–6) parameters are reported in the literature, the ε values range from 4.5 to 14.5 kJ mol –1 . These values are obtained on the basis of a comparison of the melting temperature in the zero-pressure limit ( T m = 337 K) and the critical temperature ( T C = 2280 K) with the melting temperature ( T m = 0.62) and critical temperature ( T C = 1.3) of the LJ(12–6) fluid, respectively.…”

Section: Resultsmentioning

confidence: 99%

A Local Order Parameter-Based Method for Simulation of Free Energy Barriers in Crystal Nucleation

Eslami

Khanjari

Müller‐Plathe

2017

J. Chem. Theory Comput.

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While global order parameters have been widely used as reaction coordinates in nucleation and crystallization studies, their use in nucleation studies is claimed to have a serious drawback. In this work, a local order parameter is introduced as a local reaction coordinate to drive the simulation from the liquid phase to the solid phase and vice versa. This local order parameter holds information regarding the order in the first- and second-shell neighbors of a particle and has different well-defined values for local crystallites and disordered neighborhoods but is insensitive to the type of the crystal structure. The order parameter is employed in metadynamics simulations to calculate the solid-liquid phase equilibria and free energy barrier to nucleation. Our results for repulsive soft spheres and the Lennard-Jones potential, LJ(12-6), reveal better-resolved solid and liquid basins compared with the case in which a global order parameter is used. It is also shown that the configuration space is sampled more efficiently in the present method, allowing a more accurate calculation of the free energy barrier and the solid-liquid interfacial free energy. Another feature of the present local order parameter-based method is that it is possible to apply the bias potential to regions of interest in the order parameter space, for example, on the largest nucleus in the case of nucleation studies. In the present scheme for metadynamics simulation of the nucleation in supercooled LJ(12-6) particles, unlike the cases in which global order parameters are employed, there is no need to have an estimate of the size of the critical nucleus and to refine the results with the results of umbrella sampling simulations. The barrier heights and the nucleation pathway obtained from this method agree very well with the results of former umbrella sampling simulations.

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Section: Resultsmentioning

confidence: 99%

A Local Order Parameter-Based Method for Simulation of Free Energy Barriers in Crystal Nucleation

Eslami

Khanjari

Müller‐Plathe

2017

J. Chem. Theory Comput.

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“…A severe limitation of the theoretical approaches for studying fluid metals is the lack of accurate pair potential energy functions describing their interatomic interactions. , In fact, no reliable theoretical method is available to derive an effective potential function that describes liquid alkali metals accurately. Even, inconsistencies between predictions of various potential models are reported. , It is known, however, that a class of potentials based on embedded atom models (EAM) are successful in predicting physical properties of liquid metals .…”

Section: Theorymentioning

confidence: 99%

Metal–Nonmetal Transition in Fluid Cesium: A Many-Body Dissipative Particle Dynamics Simulation Approach

Faramarzi

Mehdipour

2017

J. Chem. Eng. Data

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A many-body dissipative dynamics simulation approach is presented for inclusion of many-body interactions in fluid cesium. Employing this many-body potential, simulations are done, in the grand canonical ensemble, to calculate the vapor−liquid equilibria over a wide range of temperatures (from the melting temperature to the critical temperature). The calculated coexisting liquid and vapor densities and the vapor pressures are in close agreement with experiment. The metal-nonmetal transition is examined in terms of cluster formation in low density cesium with increasing pressure. Our analysis of cluster formation along the critical isotherm shows that at pressures noticeably higher than the critical pressure very large spherical clusters are formed in the simulation box. The cluster sizes decrease with decreasing pressure to the critical pressure. At the critical pressure, only small clusters are seen in the simulation box. The cluster structures also change noticeably as the metal−nonmetal transition approaches. In the metallic state, high-density, spherical clusters are formed. Decreasing the pressure to the critical pressure causes rearrangement in the structure of spherical clusters to ellipsoidal (lower density) clusters. In the nonmetallic region, the clusters are very diffuse (low density) and do not have a well-defined structure. Adopting the fraction of cesium atoms involved in clusters larger than a threshold size as the fraction contributing to electrical conductivity, our simulation results well predict a sudden decrease in the electrical conductivity in close agreement with experimental observations.

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“…On the basis of this concept, a number of effective density-dependent potentials have been suggested in the literature for alkali metals. 4,9,10 It is known that potentials based on embedded atom models (EAM), in which the potential energy of metal is composed of a pairwise additive contribution plus an embedding contribution, depending on the effective electron density, are successful in predicting physical properties of liquid metals. 11−13 In this respect, Monte Carlo and molecular dynamics simulations on liquid sodium are done using the EAM potentials.…”

Section: Introductionmentioning

confidence: 99%

“…This means that such a potential must be a function of the electron density, and hence, of the metal density. On the basis of this concept, a number of effective density-dependent potentials have been suggested in the literature for alkali metals. ,, …”

Section: Introductionmentioning

confidence: 99%

Many-Body Dissipative Particle Dynamics Simulation of Liquid–Vapor Coexisting Curve in Sodium

Atashafrooz

Mehdipour

2016

J. Chem. Eng. Data

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It is known that pair potentials are not adequate to correctly describe the structure and dynamics of liquid metals. In this work many-body interactions in fluid sodium are taken into account through the generic form of the forces acting between fluid particles in the context of the many-body dissipative particle dynamics (DPD) simulation. It is shown that this method accurately takes into account the role of many-body interactions in the improvement of the equation of state and structural properties of sodium. A comparison of our calculated coexisting liquid and vapor densities with experiment indicates that this model well predicts the vapor pressure and the densities over a broad range of temperatures. Also the calculated radial distribution functions are in very close agreement with experimental values. However, the calculated diffusion coefficient of sodium at low temperature deviates considerably from experiment. Although the soft-core “pair” potential in the original DPD method results in an equation of state exhibiting no fluid–fluid phase transition, the present “many-body” DPD approach successfully predicts the liquid–vapor coexistence curve of sodium. This occurs because, in the many-body DPD model, the force acting on a pair of atoms depends not only on their positions but also on the positions of all their other neighboring atoms. Also calculations are done using “pair” potentials and using the potential of mean force (in which the effect of many-body interactions are implicitly taken into account). It is shown that the results obtained using the many-body DPD approach are more accurate than those obtained employing both pair potentials and potential of mean force.

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Molecular dynamics simulation of potassium along the liquid-vapor coexistence curve

Cited by 8 publications

References 26 publications

A Local Order Parameter-Based Method for Simulation of Free Energy Barriers in Crystal Nucleation

A Local Order Parameter-Based Method for Simulation of Free Energy Barriers in Crystal Nucleation

Metal–Nonmetal Transition in Fluid Cesium: A Many-Body Dissipative Particle Dynamics Simulation Approach

Many-Body Dissipative Particle Dynamics Simulation of Liquid–Vapor Coexisting Curve in Sodium

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