scholarly journals A Molecular Interpretation of the Dynamics of Diffusive Mass Transport of Water Within a Glassy Polyetherimide

2021 ◽  
Author(s):  
Andrea Correa ◽  
Antonio De Nicola ◽  
Giuseppe Scherillo ◽  
Valerio Loianno ◽  
Domenico Mallamace ◽  
...  
Keyword(s):  
Mass Transport ◽  
Chemical Potential ◽  
Fluid Model ◽  
Diffusion Mechanism ◽  
Sorption Kinetics ◽  
Glassy Matrix ◽  
Lattice Fluid ◽  
Molecular Interpretation ◽  
Dynamics Simulations ◽  
Hydrogen Bondings

The diffusion process of water molecules within a polyetherimide (PEI) glassy matrix has been analyzed by combining the experimental analysis of water sorption kinetics performed by FTIR spectroscopy with theoretical information gathered from Molecular Dynamics simulations and with the expression of water chemical potential provided by a non-equilibrium lattice fluid model able to describe the thermodynamics of glassy polymers. This approach allowed to construct a convincing description of the diffusion mechanism of water in PEI providing molecular details of the process related to the effects of the cross- and self-hydrogen bondings established in the system on the dynamics of water mass transport.

scholarly journals A Molecular Interpretation of the Dynamics of Diffusive Mass Transport of Water within a Glassy Polyetherimide

2021 ◽  
Vol 22 (6) ◽  
pp. 2908
Author(s):  
Andrea Correa ◽  
Antonio De Nicola ◽  
Giuseppe Scherillo ◽  
Valerio Loianno ◽  
Domenico Mallamace ◽  
...  
Keyword(s):  
Mass Transport ◽  
Chemical Potential ◽  
Fluid Model ◽  
Diffusion Mechanism ◽  
Sorption Kinetics ◽  
Glassy Matrix ◽  
Water Molecules ◽  
Lattice Fluid ◽  
Molecular Interpretation ◽  
Dynamics Simulations

The diffusion process of water molecules within a polyetherimide (PEI) glassy matrix has been analyzed by combining the experimental analysis of water sorption kinetics performed by FTIR spectroscopy with theoretical information gathered from Molecular Dynamics simulations and with the expression of water chemical potential provided by a non-equilibrium lattice fluid model able to describe the thermodynamics of glassy polymers. This approach allowed us to construct a convincing description of the diffusion mechanism of water in PEI providing molecular details of the process related to the effects of the cross- and self-hydrogen bonding established in the system on the dynamics of water mass transport.

scholarly journals Influence of Br − /S 2− site-exchange on Li diffusion mechanism in Li 6 PS 5 Br: a computational study

2021 ◽  
Vol 379 (2211) ◽  
Author(s):  
Marcel Sadowski ◽  
Karsten Albe
Keyword(s):  
Rotation Axis ◽  
Computational Study ◽  
Diffusion Mechanism ◽  
Range Transport ◽  
Site Exchange ◽  
Dynamics Simulations ◽  
Low Degrees ◽  
Fast Ion ◽  
Free Material ◽  
Superionic Conduction

We investigate how low degrees of Br − / S 2 − site-exchange influence the Li + diffusion in the argyrodite-type solid electrolyte Li 6 PS 5 Br by ab initio molecular dynamics simulations. Based on the atomic trajectories of the defect-free material, a new mechanism for the internal Li + reorganization within the Li + cages around the 4 d sites is identified. This reorganization mechanism is highly concerted and cannot be described by just one rotation axis. Simulations with Br − / S 2 − defects reveal that Li + interstitials ( L ii . ) are the dominant mobile charge carriers and originate from Frenkel pairs. These are formed because B rS . defects on the 4 d sites donate one or even two L ii . to the neighbouring cages. The L ii . then carry out intercage jumps via interstitial and interstitialcy mechanisms. With that, one single B rS . defect enables Li + diffusion over an extended spatial area explaining why low degrees of site-exchange are sufficient to trigger superionic conduction. The vacant sites of the Frenkel pairs, namely V Li   ′ , are mostly immobile and bound to the B rS . defect. Because S Br ′ defects on 4 a sites act as sinks for L ii . they seem to be beneficial only for the local Li + transport. In their vicinity T4 tetrahedral sites start to get occupied. Because the Li + transport was found to be rather confined if S Br ′ and B rS . defects are direct neighbours, their relative arrangement seems to be crucial for effective long-range transport. This article is part of the Theo Murphy meeting issue ‘Understanding fast-ion conduction in solid electrolytes’.

Estimation of the Chemical Potential and the Activity of NaCl in Molten DyCl3-NaCl by Molecular Dynamics Simulation

1998 ◽  
Vol 53 (8) ◽  
pp. 655-658
Author(s):  
Masanori Sakurai ◽  
Ryuzo Takagi ◽  
Ashok K. Adyaa ◽  
Marcelle Gaune-Escard
Keyword(s):  
Molecular Dynamics ◽  
Phase Diagram ◽  
Molecular Dynamics Simulation ◽  
Molecular Dynamics Simulations ◽  
Chemical Potential ◽  
Dynamics Simulation ◽  
Dynamics Simulations ◽  
Positional Data ◽  
Liquidus Temperatures

Abstract Molecular dynamics simulations of molten DyCl3-NaCl were carried out at liquidus temperatures of the phase diagram. The chemical potential and the activity of NaCl was successfully estimated with the method proposed by Powles et al., which requires only positional data of the ions at the temperatures in question.

Migrating Interfaces in Sapphire Bicrystals and Tricrystals

2000 ◽  
Vol 6 (S2) ◽  
pp. 386-387
Author(s):  
N. Ravishankar ◽  
M.T. Johnson ◽  
C. Barry Carter
Keyword(s):  
Mass Transport ◽  
Liquid Film ◽  
Grain Boundaries ◽  
Ostwald Ripening ◽  
Chemical Potential ◽  
Driving Forces ◽  
Boundary Migration ◽  
Liquid Phase Sintering ◽  
Polycrystalline Materials ◽  
Second Phase

The migration of grain boundaries in polycrystalline materials can occur under a variety of driving forces. Grain growth in a single-phase material and Ostwald ripening of a second phase are two common processes involving boundary migration. The mass transport in each of these cases can be related to a chemical potential difference across the grains; due to curvature in the former case and due to a difference in the chemistry in the latter case. The mass transport across grains controls the densification process during sintering. In the case of liquid-phase sintering (LPS), a liquid film may be present at the grain boundaries which results in an enhanced mass transport between grains leading to faster densification. Hence, in LPS, it is important to understand mass transport across and along a boundary containing a liquid film. The use of bicrystals and tricrystals with glass layers in the boundary can provide a controlled geometry by which to study this phenomenon.

scholarly journals Computational discovery of chemically patterned surfaces that effect unique hydration water dynamics

2018 ◽  
Vol 115 (32) ◽  
pp. 8093-8098 ◽  
Author(s):  
Jacob I. Monroe ◽  
M. Scott Shell
Keyword(s):  
Surface Coverage ◽  
Chemical Potential ◽  
Water Dynamics ◽  
Hydration Water ◽  
Thermodynamic Quantities ◽  
Chemical Surface ◽  
Functional Dynamics ◽  
Water Diffusivity ◽  
Computational Discovery ◽  
Dynamics Simulations

The interactions of water with solid surfaces govern their apparent hydrophobicity/hydrophilicity, influenced at the molecular scale by surface coverage of chemical groups of varied nonpolar/polar character. Recently, it has become clear that the precise patterning of surface groups, and not simply average surface coverage, has a significant impact on the structure and thermodynamics of hydration layer water, and, in turn, on macroscopic interfacial properties. Here we show that patterning also controls the dynamics of hydration water, a behavior frequently thought to be leveraged by biomolecules to influence functional dynamics, but yet to be generalized. To uncover the role of surface heterogeneities, we couple a genetic algorithm to iterative molecular dynamics simulations to design the patterning of surface functional groups, at fixed coverage, to either minimize or maximize proximal water diffusivity. Optimized surface configurations reveal that clustering of hydrophilic groups increases hydration water mobility, while dispersing them decreases it, but only if hydrophilic moieties interact with water through directional, hydrogen-bonding interactions. Remarkably, we find that, across different surfaces, coverages, and patterns, both the chemical potential for inserting a methane-sized hydrophobe near the interface and, in particular, the hydration water orientational entropy serve as strong predictors for hydration water diffusivity, suggesting that these simple thermodynamic quantities encode the way surfaces control water dynamics. These results suggest a deep and intriguing connection between hydration water thermodynamics and dynamics, demonstrating that subnanometer chemical surface patterning is an important design parameter for engineering solid−water interfaces with applications spanning separations to catalysis.

Lattice-Fluid Model for Solvation Force Oscillations in Nonionic Fluid Films

1995 ◽  
Vol 170 (2) ◽  
pp. 407-420 ◽  
Author(s):  
Vladimir S. Mitlin ◽  
Mukul M. Sharma
Keyword(s):  
Fluid Model ◽  
Fluid Films ◽  
Lattice Fluid
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