Constant-force approach to discontinuous potentials

Orea, Pedro; Odriozola, Gerardo

doi:10.1063/1.4808038

Cited by 19 publications

(8 citation statements)

References 50 publications

(67 reference statements)

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“…The equations of motion are integrated with the velocity Verlet algorithm 53 employing a time step ∆t = 1×10 −5 τ to guarantee the numerical stability of the CFA. It is worth to point out that in difference with previous works 34,35 ,SecIV we do not use an external input table to compute any the interaction potential or the force between the fluid particles, instead such contributions are explicitly computed at each time step in order to avoid numerical inaccuracies. In all cases, we performed 1.1×10 9 integration steps, where 1×10 8 integration steps were carried out to reach thermal equilibrium and the subsequent time steps were used to compute the static and dynamic properties like the radial distribution function and the mean-squared displacement, respectively.…”

Section: Constant Force Approach and Computer Simulationmentioning

confidence: 99%

“…Recently, Orea and Odriozola have proposed the so-called constant force approach 34 , to deal with any non-continuous interaction potential. Padilla and Benavides have used this approach to compute the liquid-vapor phase diagram of the SW fluid only for a range interaction λ = 1.5 35 .…”

Section: Introductionmentioning

confidence: 99%

“…Thus, in this endeavor we used MD simulations to determine the time evolution of the SW fluid particles. The discontinuities of the pair potential are treated by means of the constant force approach (CFA), i.e., we remove the discontinuities of the pair potential by approaching them with linear functions, whose derivative is a constant value [34][35][36] . Details of the CFA and the SW parametrization are discussed further bellow.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Self-diffusion coefficient of the square-well fluid from molecular dynamics simulations within the constant force approach

Torres-Carbajal

Trejos

Nicasio-Collazo

2018

The Journal of Chemical Physics

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We present a systematic study of the self-diffusion coefficient for a fluid of particles interacting via the square-well pair potential by means of molecular dynamics simulations in the canonical (N, V, T ) ensemble. The discrete nature of the interaction potential is modeled through the constant force approximation and the self-diffusion coefficient is determined for several packing fractions at super critical thermodynamic states. The dependence of the self-diffusion coefficient with the potential range λ is analyzed in the range of 1.1 ≤ λ ≤ 1.5. The obtained molecular dynamics simulations results are in agreement with the self-diffusion coefficient predicted with the Enskog method. Additionally, we show that diffusion coefficient is very sensitive to the potential range, λ, at low densities leading to a density dependence of this coefficient not shared with other macroscopic properties such as the equation of state. The constant force approximation used in this work to model the discrete pair potentials has shown to be an excellent scheme to compute transport properties using standard computer simulations. Finally, the simulation results presented here are resourceful to improving theoretical approaches, such as the Enskog method.

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Section: Constant Force Approach and Computer Simulationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Self-diffusion coefficient of the square-well fluid from molecular dynamics simulations within the constant force approach

Torres-Carbajal

Trejos

Nicasio-Collazo

2018

The Journal of Chemical Physics

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“…To survey the issue related to the force between hardspheres, along years, different approaches have been proposed to establish a continuous and differentiable function that represents the HS interaction potential [19,[73][74][75][76]. Although many of those approaches have been thought and designed to numerically reproduce structural or thermodynamic properties of the HS fluid [75], some authors have determined dynamic properties like diffusion [77] or shear viscosity [78] as a function of volume fraction.…”

Section: Introductionmentioning

confidence: 99%

Pseudo hard-sphere viscosities from equilibrium Molecular Dynamics

Nicasio-Collazo

Ramı́rez-Medina

Torres-Carbajal

2023

J. Phys.: Condens. Matter

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Transport coefficients like shear, bulk and longitudinal viscosities are sensitive to the intermolecular interaction potential and finite size effects when are numerically determined. For the hard-sphere (HS) fluid, such transport properties are determined almost exclusively with computer simulations. However, their systematic determination and analysis throughout shear stress correlation functions and the Green-Kubo formalism can not be done due to discontinuous nature of the interaction potential. Here, we use the pseudo hard-sphere (PHS) potential to determine pressure correlation functions as a function of volume fraction in order to compute mentioned viscosities. Simulation results are compared to available event-driven molecular dynamics of the HS fluid and also used to propose empirical corrections for the Chapman-Enskog zero density limit of shear viscosity. Moreover, we show that PHS potential is a reliable representation of the HS fluid and can be used to compute transport coefficients. The molecular simulation results of the present work are valuable for further exploration of HS-type fluids or extend the approach to compute transport properties of hard-colloid suspensions.

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“…This is highly relevant when dealing with the diffusive dynamics of colloidallike particles. Almost all known discrete potentials admit such continuous characterization [22][23][24][25][26][27][28][29][30]. However, one must be very careful when using this approach.…”

Section: Introductionmentioning

confidence: 99%

Soft representation of the square-well and square-shoulder potentials to be used in Brownian and molecular dynamics simulations

Sandoval-Puentes¹,

Torres-Carbajal²,

Zavala-Martínez³

et al. 2022

J. Phys.: Condens. Matter

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The discrete hard-sphere (HS), square-well (SW), and square-shoulder (SS) potentials have become the battle horse of molecular and complex fluids because they contain the basic elements to describe the thermodynamic, structural, and transport properties of both types of fluids. The mathematical simplicity of these discrete potentials allows us to obtain some analytical results despite the nature and complexity of the modeled systems. However, the divergent forces arising at the potential discontinuities may lead to severe issues when discrete potentials are used in computer simulations with uniform time steps. One of the few routes to avoid these technical problems is to replace the discrete potentials with continuous and differentiable forms built under strict physical criteria to capture the correct phenomenology. The match of the second virial coefficient between the discrete and the soft potentials has recently been successfully used to construct a continuous representation that mimics some physical properties of HSs (Báez et al 2018 J. Chem. Phys. 149 164907). In this paper, we report an extension of this idea to construct soft representations of the discrete SW and SS potentials. We assess the accuracy of the resulting soft potential by studying structural and thermodynamic properties of the modeled systems by using extensive Brownian and molecular dynamics computer simulations. Besides, Monte Carlo results for the original discrete potentials are used as benchmark. We have also implemented the discrete interaction models and their soft counterparts within the integral equations theory of liquids, finding that the most widely used approximations predict almost identical results for both potentials.

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Constant-force approach to discontinuous potentials

Cited by 19 publications

References 50 publications

Self-diffusion coefficient of the square-well fluid from molecular dynamics simulations within the constant force approach

Self-diffusion coefficient of the square-well fluid from molecular dynamics simulations within the constant force approach

Pseudo hard-sphere viscosities from equilibrium Molecular Dynamics

Soft representation of the square-well and square-shoulder potentials to be used in Brownian and molecular dynamics simulations

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