AB INITIO MOLECULAR DYNAMICS STUDY OF DISSOLVED SiO2 IN SUPERCRITICAL WATER

2007 ◽  
Vol 06 (01) ◽  
pp. 49-62 ◽  
Author(s):  
N. L. DOLTSINIS ◽  
M. BURCHARD ◽  
W. V. MARESCH ◽  
A. D. BOESE ◽  
T. FOCKENBERG
Keyword(s):  
Molecular Dynamics ◽  
Ab Initio ◽  
Supercritical Water ◽  
Statistical Error ◽  
Distribution Functions ◽  
Time Span ◽  
Ab Initio Molecular Dynamics ◽  
Spontaneous Polymerization ◽  
Dynamics Simulations ◽  
Pair Distribution Functions

Ab initio molecular dynamics simulations of SiO 2 in supercritical water at temperatures of 900 K and 1200 K and a pressure of 1.5 GPa at concentrations of 5 wt% and 16 wt% have been carried out. The different polymeric forms SiO 4 H 4, Si 2 O 7 H 6, and Si 3 O 10 H 8 are found to be energetically similar within the statistical error, suggesting that all three polymeric forms play an important role in solutions at the above conditions. However, neither spontaneous polymerization nor depolymerization has been observed during the 10-ps time span of the simulations. The dynamic and structural properties of the supercritical solutions have been analyzed in terms of diffusion coefficients, vibrational spectra, and radial pair distribution functions.

scholarly journals Proton Transport Mechanism and Pathways in the Superprotonic Phase of M3H(AO4)2 Solid Acids from Ab Initio Molecular Dynamics Simulations

2021 ◽  
Author(s):  
Boris Merinov ◽  
Sergey Morozov
Keyword(s):  
Molecular Dynamics ◽  
Ab Initio ◽  
Proton Transport ◽  
Transport Mechanism ◽  
Solid Acids ◽  
Ab Initio Molecular Dynamics ◽  
Theoretical Studies ◽  
Dynamics Simulations ◽  
Experimental And Theoretical Studies ◽  
Superprotonic Phase

The proton transport mechanism in superprotonic phases of solid acids is a subject of experimental and theoretical studies for a number of years. Despite this, details of the mechanism still...

scholarly journals OH− and H3O+ Diffusion in Model AEMs and PEMs at Low Hydration: Insights from Ab Initio Molecular Dynamics

Membranes ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 355
Author(s):  
Tamar Zelovich ◽  
Mark E. Tuckerman
Keyword(s):  
Molecular Dynamics ◽  
Fuel Cell ◽  
Ab Initio ◽  
Cost Effective ◽  
Clean Energy ◽  
Proton Exchange ◽  
Ab Initio Molecular Dynamics ◽  
Anion Exchange Membranes ◽  
Diffusion Mechanisms ◽  
Dynamics Simulations

Fuel cell-based anion-exchange membranes (AEMs) and proton exchange membranes (PEMs) are considered to have great potential as cost-effective, clean energy conversion devices. However, a fundamental atomistic understanding of the hydroxide and hydronium diffusion mechanisms in the AEM and PEM environment is an ongoing challenge. In this work, we aim to identify the fundamental atomistic steps governing hydroxide and hydronium transport phenomena. The motivation of this work lies in the fact that elucidating the key design differences between the hydroxide and hydronium diffusion mechanisms will play an important role in the discovery and determination of key design principles for the synthesis of new membrane materials with high ion conductivity for use in emerging fuel cell technologies. To this end, ab initio molecular dynamics simulations are presented to explore hydroxide and hydronium ion solvation complexes and diffusion mechanisms in the model AEM and PEM systems at low hydration in confined environments. We find that hydroxide diffusion in AEMs is mostly vehicular, while hydronium diffusion in model PEMs is structural. Furthermore, we find that the region between each pair of cations in AEMs creates a bottleneck for hydroxide diffusion, leading to a suppression of diffusivity, while the anions in PEMs become active participants in the hydronium diffusion, suggesting that the presence of the anions in model PEMs could potentially promote hydronium diffusion.

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