Molecular dynamics simulation of fluid sodium

Hasheminasab, Fatemeh; Mehdipour, Nargess

doi:10.1016/j.fluid.2016.07.008

Cited by 8 publications

(3 citation statements)

References 22 publications

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“…As experimental data for the barrier height of the LJ(12–6) fluid at T ≈ 0.8 T m and p = 0.7 are unavailable, we checked our calculated barrier height (11.9ε) against the experimentally reported value for crystallization of supercooled metals at the same supercooling (∼60 k B T ) . 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 .…”

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 . The EAM potential is composed of a pairwise additive contribution plus an effective electron density-dependent embedding contribution.…”

Section: Theorymentioning

confidence: 99%

“…Even, inconsistencies between predictions of various potential models are reported. 22,23 It is known, however, that a class of potentials based on embedded atom models (EAM) are successful in predicting physical properties of liquid metals. 24 The EAM potential is composed of a pairwise additive contribution plus an effective electron density-dependent embedding contribution.…”

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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