Electrolyte Solutions. The Measurement and Interpretation of Conductance, Chemical Potential and Diffusion in Solutions of Simple Electrolytes.

AbstractThe interplay between stress and chemical processes is a fundamental aspect of how rocks evolve, relevant for understanding fracturing due to metamorphic volume change, deformation by pressure solution and diffusion creep, and the effects of stress on mineral reactions in crust and mantle. There is no agreed microscale theory for how stress and chemistry interact, so here I review support from eight different types of the experiment for a relationship between stress and chemistry which is specific to individual interfaces: (chemical potential) = (Helmholtz free energy) + (normal stress at interface) × (molar volume). The experiments encompass temperatures from -100 to 1300 degrees C and pressures from 1 bar to 1.8 GPa. The equation applies to boundaries with fluid and to incoherent solid–solid boundaries. It is broadly in accord with experiments that describe the behaviours of free and stressed crystal faces next to solutions, that document flow laws for pressure solution and diffusion creep, that address polymorphic transformations under stress, and that investigate volume changes in solid-state reactions. The accord is not in all cases quantitative, but the equation is still used to assist the explanation. An implication is that the chemical potential varies depending on the interface, so there is no unique driving force for reaction in stressed systems. Instead, the overall evolution will be determined by combinations of reaction pathways and kinetic factors. The equation described here should be a foundation for grain-scale models, which are a prerequisite for predicting larger scale Earth behaviour when stress and chemical processes interact. It is relevant for all depths in the Earth from the uppermost crust (pressure solution in basin compaction, creep on faults), reactive fluid flow systems (serpentinisation), the deeper crust (orogenic metamorphism), the upper mantle (diffusion creep), the transition zone (phase changes in stressed subducting slabs) to the lower mantle and core mantle boundary (diffusion creep).

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Chemical potential of model electrolyte solutions consisting of hard sphere ions and hard dipoles from molecular simulations

Fluid Phase Equilibria ◽

10.1016/j.fluid.2016.08.039 ◽

2016 ◽

Vol 429 ◽

pp. 205-213 ◽

Cited By ~ 4

Author(s):

Florian Drunsel ◽

Joachim Gross

Keyword(s):

Hard Sphere ◽

Chemical Potential ◽

Molecular Simulations ◽

Electrolyte Solutions

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Influence mechanism of excipients on drug crystallization: experimental investigation and model analysis and prediction

10.22541/au.164185956.61081002/v1 ◽

2022 ◽

Author(s):

Qiao Chen ◽

Jingyun Weng ◽

Gabriele Sadowski ◽

Yuanhui Ji

Keyword(s):

Crystal Growth ◽

Growth Kinetics ◽

Surface Reaction ◽

Chemical Potential ◽

Potential Gradient ◽

Reaction Model ◽

Reaction Rate Constant ◽

Crystal Growth Kinetics ◽

Kinetics Of ◽

And Diffusion

The influence of temperature, stirring speed, and excipients on crystal growth kinetics of mesalazine and allopurinol was investigated through experiment and chemical potential gradient model. The results indicated that the Diffusion-Surface Reaction model (DSR (1,2)) showed good performance in modeling API crystal growth kinetics within the ARDs of 4%. Excipients played a crucial role in inhibiting crystal growth in all the systems. It can not only improve the API solubility, but also reduce the crystal growth rate. By comparing diffusion rate and surface-reaction rate constant within the DSR (1,2) model, it was found that the controlling step of mesalazine crystallization was surface-reaction. Allopurinol crystallization was dominated by both surface-reaction and diffusion. Meanwhile, the crystal growth kinetics of mesalazine and allopurinol were predicted successfully with the ARDs of 2.53% and 4.78%. This work provided a mechanistic understanding of polymer influence on the inhibition of API crystal growth.

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Atomic Understanding of the Swelling and Phase Transition of Polyacrylamide Hydrogel

International Journal of Applied Mechanics ◽

10.1142/s1758825116400020 ◽

2016 ◽

Vol 08 (07) ◽

pp. 1640002 ◽

Cited By ~ 9

Author(s):

Shuai Xu ◽

Ying Wang ◽

Jianying Hu ◽

Zishun Liu

Keyword(s):

Phase Transition ◽

Continuum Mechanics ◽

Chemical Potential ◽

Polymer Network ◽

Point Of View ◽

Dynamics Simulation ◽

Mechanics Model ◽

Basic Parameters ◽

Solvent Molecules ◽

And Diffusion

A polymer network can imbibe copious amounts of solvent (water) and swell, and the resulting state is known as a hydrogel. In this study, we have made the modification for the all-atom consistent valence force field (CVFF) to investigate the swelling property of polyacrylamide (PAM) hydrogel by molecular dynamics simulation. We have built 21 hydrogel models with different solvent contents and calculate the average chemical potential and diffusion coefficient of solvent molecules in PAM hydrogel. We find that when the mass fraction of solvent is about 90%, PAM hydrogel reaches its free swelling limitation and loses the motivation of absorbing solvent. Furthermore, it is also found that PAM hydrogel has a phase transition phenomenon when the values of solvent chemical potential are between [Formula: see text][Formula: see text]kcal/mol and [Formula: see text][Formula: see text]kcal/mol. This study will provide insight into the basic parameters which are widely used in continuum mechanics analysis of hydrogels from atomic point of view and help researchers to improve the continuum mechanics model for neutral hydrogel.

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