Calculation of chemical potential for structured molecules using osmotic molecular dynamics simulations

Henrichsen, Matthew; Rowley, Richard L.

doi:10.1016/s0378-3812(97)00073-3

Cited by 7 publications

(3 citation statements)

References 15 publications

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“…The method was tested using Lennard-Jones particles and shown to be much more accurate than direct insertion techniques such as Widom’s method, implying that it is also superior to standard GCMC. There is some similarity between our method and a modified Widom method using a penalty potential by Powles et al and so-called osmotic MD, − both used for bulk fluids. That similarity is further highlighted when considering charged systems where the Donnan potential is traditionally used to describe two electrolytes in osmotic equilibrium.…”

Section: Discussionmentioning

confidence: 93%

“…Our method relies on establishing a gas/liquid interface by introducing a penalty potential, which creates a density difference between nominal internal and external regions of the pore. This approach shares some aspects in common with the so-called osmotic molecular dynamics method. − In that case a pure fluid is modeled as a virtual two-component mixture of identical particles (discriminated by labeling). One of the components, the “solvent”, is allowed to pass through a semipermeable membrane, while the “solute” is restricted to a region of high density by the membrane.…”

Section: Introductionmentioning

confidence: 99%

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Local Grand Canonical Monte Carlo Simulation Method for Confined Fluids

et al. 2019

J. Chem. Theory Comput.

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We describe a new local grand canonical Monte Carlo method to treat fluids in pores in chemical equilibrium with a reference bulk. The method is applied to Lennard-Jones particles in pores of different geometry and is shown to be much more accurate and efficient than other techniques such as traditional grand canonical simulations or Widom’s particle insertion method. It utilizes a penalty potential to create a gas phase, which is in equilibrium with a more dense liquid component in the pore. Grand canonical Monte Carlo moves are employed in the gas phase, and the system then maintains chemical equilibrium by “diffusion” of particles. This creates an interface, which means that the confined fluid needs to occupy a large enough volume so that this is not an issue. We also applied the method to confined charged fluids and show how it can be used to determine local electrostatic potentials in the confined fluid, which are properly referenced to the bulk. This precludes the need to determine the Donnan potential (which controls electrochemical equilibrium) explicitly. Prior approaches have used explicit bulk simulations to measure this potential difference, which are significantly costly from a computational point of view. One outcome of our analysis is that pores of finite cross-section create a potential difference with the bulk via a small but nonzero linear charge density, which diminishes as ∼1/ln(L), where L is the pore length.

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Section: Discussionmentioning

confidence: 93%

Section: Introductionmentioning

confidence: 99%

Local Grand Canonical Monte Carlo Simulation Method for Confined Fluids

et al. 2019

J. Chem. Theory Comput.

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“…After equilibration, the chemical potentials of the two cells are equal. 24,25 OMD uses a semipermeable membrane to achieve chemical equilibrium between two compartments on either side of the membrane. GEMC avoids the formation of an interface between the two phases.…”

Section: Introductionmentioning

confidence: 99%

Chemical potential perturbation: A method to predict chemical potentials in periodic molecular simulations

Moore

Wheeler

2011

The Journal of Chemical Physics

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A new method, called chemical potential perturbation (CPP), has been developed to predict the chemical potential as a function of density in periodic molecular simulations. The CPP method applies a spatially varying external force field to the simulation, causing the density to depend upon position in the simulation cell. Following equilibration the homogeneous (uniform or bulk) chemical potential as a function of density can be determined relative to some reference state after correcting for the effects of the inhomogeneity of the system. We compare three different methods of approximating this correction. The first method uses the van der Waals density gradient theory to approximate the inhomogeneous Helmholtz free energy density. The second method uses the local pressure tensor to approximate the homogeneous pressure. The third method uses the Triezenberg-Zwanzig definition of surface tension to approximate the inhomogeneous free energy density. If desired, the homogeneous pressure and Helmholtz free energy can also be predicted by the new method, as well as binodal and spinodal densities of a two-phase fluid region. The CPP method is tested using a Lennard-Jones (LJ) fluid at vapor, liquid, two-phase, and supercritical conditions. Satisfactory agreement is found between the CPP method and an LJ equation of state. The efficiency of the CPP method is compared to that for Widom's method under the tested conditions. In particular, the new method works well for dense fluids where Widom's method starts to fail.

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