Chemical Potential and Thermodynamic Properties of Self-Assembled Monolayers: A Method of External Fields in a Monte Carlo Simulation

Ustinov, E. A.; Горбунов, В. А.; Akimenko, S. S.

doi:10.1021/acs.jpcc.0c05308

Cited by 8 publications

(33 citation statements)

References 61 publications

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“…Damping Field and Its Effect on Intermolecular Potentials and Pressure. In our previous work, 71 we introduced a kind of hypothetical external field that affects intermolecular interactions rather than individual molecules in the following form:…”

Section: Theoretical Modelmentioning

confidence: 99%

“…The benefit is obvious: the chemical potential of the ideal gas is determined analytically, so the chemical potential of the crystal has the same value because the system is in equilibrium. This idea seems to be especially promising in cases of very rigid crystals, and it was first applied in our previous paper 71 to the thermodynamic analysis of self-assembly phenomenon in a 2D molecular layer of trimesic acid molecules. An interesting consequence of imposing the damping field on the system is the appearance of the pressure change along the damping field gradient.…”

Section: Theoretical Modelmentioning

confidence: 99%

“…Model of Trimesic Acid Molecule. In our previous papers, 71,72 we used an oversimplified model that accounted for dispersion and electrostatic interactions. Each carboxylic group was presented by a pair of opposite charges positioned at the same distance from the center of the molecule at an angle of 30°.…”

Section: External Potentialmentioning

confidence: 99%

“…Figure 1 presents the scheme of a TMA molecule obtained with the density functional theory 71 and the simplified scheme used in this study.…”

Section: External Potentialmentioning

confidence: 99%

“…In the second case, we performed simulations of the gas− crystal system with the kinetic Monte Carlo algorithm in an elongated cell with the lengths ratio L x /L y = 8/3 1/2 according to our method of two external fields. 71 The dense phase was positioned in the central part of the simulation cell.…”

Section: Simulation Detailsmentioning

confidence: 99%

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Thermodynamics of Rigid Self-Assembled Crystals: Molecular Simulation of Two-Phase Systems under External Fields

2021

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A general methodology for determining the thermodynamic characteristics of orientationally ordered rigid crystals is presented. The basic problem here is associated with a very small flux of primary molecules that are released from a narrow interface and carry main information on thermodynamic properties of the crystal. The proposed approach is based on the kinetic Monte Carlo simulation of the gas−crystal system with an external "damping field" that reduces the intermolecular potential at the crystal edges and switches it off in the gas phase. Such a technique increases the primary molecular flux by several orders of magnitude, which is crucial for accurate determination of thermodynamic functions. In this study, we applied the approach to the thermodynamic analysis of the trimesic acid monolayer, explicitly accounting for hydrogen bonds, the dispersion, and electrostatic potentials. We considered equations of state, heat capacities, Helmholtz free energies, and entropies of three polymorphous structures: honeycomb, flower-like, and hexagonally close-packed structures in a wide range of temperatures and pressures. The calculated free energy and entropy excellently obey the Gibbs−Duhem equation, which confirms the thermodynamic consistency of our approach. The role of hydrogen bonds in the stability of different phases, as well as the condition of phase transitions, was also considered.

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Section: Theoretical Modelmentioning

confidence: 99%

Section: Theoretical Modelmentioning

confidence: 99%

Section: External Potentialmentioning

confidence: 99%

“…Figure 1 presents the scheme of a TMA molecule obtained with the density functional theory 71 and the simplified scheme used in this study.…”

Section: External Potentialmentioning

confidence: 99%

Section: Simulation Detailsmentioning

confidence: 99%

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Thermodynamics of Rigid Self-Assembled Crystals: Molecular Simulation of Two-Phase Systems under External Fields

2021

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Crystal Agglomeration and Microscopic Molecular Exchange Mechanism in Antisolvent Crystallization

Qin,

Yang

2024

Crystal Growth & Design

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Agglomeration is a significant challenge in antisolvent crystallization, especially when it comes to crystallizing insoluble drugs. This study aimed to address this issue by taking a unique, dynamic molecular perspective and proposing a solution based on microscopic molecular exchange. Atorvastatin calcium, a widely prescribed medication for lowering blood lipids, was used as a case for antisolvent crystallization, which is also prone to agglomeration. Kinetic experiments revealed the rapid exchange between solvent and antisolvent, leading to precipitation occurring within a mere 0.0333 s. Thermodynamic investigations further showed that each droplet had the potential to generate an astonishing equivalent nucleation rate of up to 5 billion nuclei per second. The rapid precipitation and small nucleation region, coupled with a large number of nuclei, worsened the crystal agglomeration problem. However, it was found that this molecular exchange process can be slowed by the solvent composition. Specifically, when the methanol mole fraction in the crystallization system reached approximately 50%, the equivalent nucleation rate decreased significantly to about 100 million per second. Armed with this crucial finding, a strategy was devised to overcome agglomeration by simultaneously adding the solution and antisolvent to maintain a lower exchange rate, which effectively avoided agglomeration and promoted the purification of atorvastatin calcium.

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Boundary-Monte Carlo Method for Neutral and Charged Confined Fluids

Forsman

Woodward

2022

J. Chem. Theory Comput.

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In this work, we describe a new Monte Carlo (MC) simulation method to investigate highly coupled fluids in confined geometries at a constant chemical potential. This method is based on so-called multiscale Hamiltonian methods, wherein the chemical potential is determined using a more amenable Hamiltonian for a fluid in an "outer" region, which facilitates standard methods, such as grand canonical MC simulations or Widom's particle insertion method. The (inner region) fluid of interest is placed in diffusive contact with the simpler outer fluid via a boundary zone wherein the Hamiltonian is transformed. The current method utilizes an ideal fluid for the outer regions, which allows for implicit rather than explicit simulations. Only the boundary and inner region need explicit consideration; hence, the nomenclature used is boundary-Monte Carlo. We illustrate the utility of the method for simple neutral and charged fluids in cylindrical and planar pores. In the latter case, we use a dense room-temperature ionic liquid model and illustrate how the boundary zone establishes a proper Donnan equilibrium between inner and outer fluids in the presence of charged planar electrodes. Thus, the method allows direct calculation of properties such as the differential capacitance, without the need for additional difficult calculations of the requisite Donnan potential.

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Chemical Potential and Thermodynamic Properties of Self-Assembled Monolayers: A Method of External Fields in a Monte Carlo Simulation

Cited by 8 publications

References 61 publications

Thermodynamics of Rigid Self-Assembled Crystals: Molecular Simulation of Two-Phase Systems under External Fields

Thermodynamics of Rigid Self-Assembled Crystals: Molecular Simulation of Two-Phase Systems under External Fields

Crystal Agglomeration and Microscopic Molecular Exchange Mechanism in Antisolvent Crystallization

Boundary-Monte Carlo Method for Neutral and Charged Confined Fluids

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