Molecular Dynamics Investigation of Water Behavior Through Nanopores

2020 ◽  
Author(s):  
Kimia Montazeri ◽  
Penghui Cao ◽  
Yoonjin Won
Keyword(s):  
Molecular Dynamics ◽  
Bulk Water ◽  
Energy Storage And Conversion ◽  
Water Molecules ◽  
Transport Mechanisms ◽  
Confined Water ◽  
Nanoscale Transport ◽  
Wetting Properties ◽  
Velocity Autocorrelation ◽  
Water Behavior

Abstract The transport of fluids through nanoscale pores, channels, and membranes has been of great importance in our daily life. Nanoscale transport is relevant to many applications such as agriculture, energy and environmental fields. Considering these applications, it is important to characterize detailed mechanisms of liquid transport through nanoscale defects and pores on surfaces. Such characterization requires a detailed understanding of the deviation of water behavior and its transport mechanisms in nanoscale from bulk water. Molecular dynamics provide proper means to understand the dynamics and mechanisms of motions of water molecules confined in ultra-small spaces. This work examines the water transport through an individual pore which has a nanoscale dimensions ranging from 1.0 to 1.8 nm from molecular dynamics perspective. The effects of the nanopore dimensions as well as the surface wetting properties on the behavior of confined water are studied. The translational and rotational dynamics of water molecules are characterized by examining velocity autocorrelation functions and the calculation of the density of states, which supports the presence of unusual, solid-like behaviors of water molecules. A good understanding of the transport mechanisms and their origins are crucial to address common challenges in many engineering applications such as energy storage and conversion and could pave the way towards more efficient water-energy systems.

scholarly journals Dynamic Properties of Water Confined in Graphene-Based Membrane: A Classical Molecular Dynamics Simulation Study

Membranes ◽  
2019 ◽  
Vol 9 (12) ◽  
pp. 165 ◽  
Author(s):  
One-Sun Lee
Keyword(s):  
Molecular Dynamics ◽  
Hydrogen Bond ◽  
Free Energy ◽  
Graphene Sheets ◽  
Water Molecules ◽  
Energy Profile ◽  
Confined Water ◽  
Graphene Surface ◽  
Dynamics Simulations ◽  
Density Of Water

We performed molecular dynamics simulations of water molecules inside a hydrophobic membrane composed of stacked graphene sheets. By decreasing the density of water molecules inside the membrane, we observed that water molecules form a droplet through a hydrogen bond with each other in the hydrophobic environment that stacked graphene sheets create. We found that the water droplet translates as a whole body rather than a dissipate. The translational diffusion coefficient along the graphene surface increases as the number of water molecules in the droplet decreases, because the bigger water droplet has a stronger van der Waals interaction with the graphene surface that hampers the translational motion. We also observed a longer hydrogen bond lifetime as the density of water decreased, because the hydrophobic environment limits the libration motion of the water molecules. We also calculated the reorientational correlation time of the water molecules, and we found that the rotational motion of confined water inside the membrane is anisotropic and the reorientational correlation time of confined water is slower than that of bulk water. In addition, we employed steered molecular dynamics simulations for guiding the target molecule, and measured the free energy profile of water and ion penetration through the interstice between graphene sheets. The free energy profile of penetration revealed that the optimum interlayer distance for desalination is ~10 Å, where the minimum distance for water penetration is 7 Å. With a 7 Å interlayer distance between the graphene sheets, water molecules are stabilized inside the interlayer space because of the van der Waals interaction with the graphene sheets where sodium and chloride ions suffer from a 3–8 kcal/mol energy barrier for penetration. We believe that our simulation results would be a significant contribution for designing a new graphene-based membrane for desalination.

Molecular Dynamics Study of a KCl Aqueous Solution: Dynamical Results

1987 ◽  
Vol 42 (3) ◽  
pp. 227-230 ◽  
Author(s):  
M. Migliore ◽  
S. L. Fornili ◽  
E. Spohr ◽  
K. Heinzinger
Keyword(s):  
Diffusion Coefficients ◽  
Md Simulation ◽  
Bulk Water ◽  
Water Molecules ◽  
Hydration Water ◽  
Self Diffusion ◽  
Average Temperature ◽  
Velocity Autocorrelation ◽  
Dynamical Properties ◽  
Velocity Autocorrelation Functions

In this paper we report on dynamical properties of a 2.2 molal aqueous KCl solution as obtained from an 8.7 ps MD simulation at an average temperature of 289 K. Velocity autocorrelation functions, self-diffusion coefficients and spectral densities of the hindered translational and librational motions of the ions and the water molecules assigned to three subsystems - hydration water of the cations, hydration water of the anions and bulk water - are discussed.

scholarly journals Molecular insights on confined water in the nanochannels of self-assembled ionic liquid crystal

2021 ◽  
Vol 7 (31) ◽  
pp. eabf0669
Author(s):  
Yoshiki Ishii ◽  
Nobuyuki Matubayasi ◽  
Go Watanabe ◽  
Takashi Kato ◽  
Hitoshi Washizu
Keyword(s):  
Molecular Dynamics ◽  
Ionic Liquid ◽  
Water Transport ◽  
Density Functional ◽  
Large Scale ◽  
The Self ◽  
Water Molecules ◽  
Diffraction Measurement ◽  
Confined Water ◽  
Self Assembled

Self-assembled ionic liquid crystals can transport water and ions via the periodic nanochannels, and these materials are promising candidates as water treatment membranes. Molecular insights on the water transport process are, however, less investigated because of computational difficulties of ionic soft matters and the self-assembly. Here we report specific behavior of water molecules in the nanochannels by using the self-consistent modeling combining density functional theory and molecular dynamics and the large-scale molecular dynamics calculation. The simulations clearly provide the one-dimensional (1D) and 3D-interconnected nanochannels of self-assembled columnar and bicontinuous structures, respectively, with the precise mesoscale order observed by x-ray diffraction measurement. Water molecules are then confined inside the nanochannels with the formation of hydrogen bonding network. The quantitative analyses of free energetics and anisotropic diffusivity reveal that, the mesoscale geometry of 1D nanodomain profits the nature of water transport via advantages of dissolution and diffusion mechanisms inside the ionic nanochannels.

scholarly journals Crystalline Hydrogen Bond of Water Molecules Confined in a Metal-Organic Framework

2021 ◽  
Author(s):  
Jinhee Bae ◽  
Sun Ho Park ◽  
Dohyun Moon ◽  
Nak Cheon Jeong
Keyword(s):  
Hydrogen Bond ◽  
Metal Organic Framework ◽  
Bulk Water ◽  
Coordination Bond ◽  
Ex Situ ◽  
Water Molecules ◽  
Confined Water ◽  
Metal Organic ◽  
Cu Bonding ◽  
Organic Framework

Abstract Hydrogen bond (H-bond) of water molecules confined in nanopores is of particular interest because it is expected to exhibit chemical features different from bulk water molecules due to its interaction with the wall lining the pores. Herein, we show a crystalline behavior of hydrogen-bonded water molecules residing in the nanocages of a paddlewheel metal-organic framework, providing in situ and ex situ synchrotron single-crystal X-ray diffraction and Raman spectroscopy studies. The crystalline H-bond is demonstrated by proving the vibrational chain connectivity arising between hydrogen bonding and paddlewheel Cu−Cu bonding in sequentially connected Cu–Cu⋅⋅⋅⋅⋅coordinating H2O⋅⋅⋅⋅⋅H-bonded H2O and proving the spatial ordering of H-bonded water molecules at room temperature, where they are anticipated to be disordered with a high degree of freedom in their molecular motions. Additionally, we show a substantial distortion of the paddlewheel Cu2+ centers that arises simultaneously with water coordination. Also, we suggest the dynamic coordination bond character of the H-bond of the confined water molecules, by which an H-bond transitions to a coordination bond at the Cu2+ center instantaneously after dissociating a previously coordinated water molecule.

A Molecular Dynamics Study of Aqueous Solutions

1979 ◽  
Vol 34 (12) ◽  
pp. 1424-1435 ◽  
Author(s):  
P. Bopp ◽  
W. Dietz ◽  
K. Heinzinger
Keyword(s):  
Molecular Dynamics ◽  
Fourier Transformation ◽  
Bulk Water ◽  
Dynamics Simulation ◽  
Force Model ◽  
Hydration Water ◽  
Nacl Solution ◽  
Velocity Autocorrelation ◽  
Hydration Shells ◽  
Velocity Autocorrelation Functions

Abstract The central force model for water has been employed in a molecular dynamics simulation of a 2.2 molal NaCl solution. The structural properties of the solution obtained are compared with results of previous simulations where the ST2 model of water was used. Preliminary results on the influence of the ions on the water molecule geometry in the hydration shells are reported. The spectral densities calculated from the hydrogen velocity autocorrelation functions by Fourier transformation indicate differences in the librational and vibrational frequencies between bulk water and hydration water of Na+ and Cl-.

Thermodynamic, structural, and dynamical properties of nano-confined water using SPC/E and TIP4P models by molecular dynamics simulations

2018 ◽  
Vol 42 (19) ◽  
pp. 16258-16272 ◽  
Author(s):  
Elham Jalalitalab ◽  
Mohsen Abbaspour ◽  
Hamed Akbarzadeh
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulations ◽  
Water Molecules ◽  
Confined Water ◽  
Dynamical Properties ◽  
Dynamics Simulations

Different morphologies of water molecules are confined between two parallel graphene surfaces.

Hydrogen Transport in Single-Walled Carbon Nanotube by Molecular Dynamics Simulation

2007 ◽  
Author(s):  
Kyung Su Oh ◽  
Seungho Park ◽  
Ohmyoung Kwon ◽  
Young Ki Choi ◽  
Joon Sik Lee
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulation ◽  
Dynamics Simulation ◽  
Hydrogen Transport ◽  
Transport Mechanisms ◽  
Single Walled Carbon Nanotube ◽  
Single Walled Carbon ◽  
Hydrogen Molecules ◽  
Velocity Autocorrelation ◽  
Carbon Nano Tubes

Carbon nanotubes have been strongly considered as promising hydrogen storage materials. In this paper, hydrogen transport mechanisms in single-walled carbon nano-tubes (SWNTs) for various temperatures and chiral indices were studied using molecular dynamics simulation. The SWNT models of zigzag (10,0), chiral (10,5) and armchair (10,10) with hydrogen molecules inside were simulated at temperatures ranging from 253K to 373K. Movements of hydrogen molecules (H2) inside a SWNT were analyzed using mean-square displacements and velocity autocorrelation functions.

Molecular Dynamics Simulation of Water Transporting Through Nanotube Driven by Concentration Difference

2011 ◽  
Author(s):  
Ning Zhang ◽  
Weizhong Li ◽  
Jing Cui
Keyword(s):  
Molecular Dynamics ◽  
Md Simulation ◽  
Flow Behavior ◽  
Bulk Water ◽  
Dynamics Simulation ◽  
Water Molecules ◽  
Flowing Water ◽  
Water Density ◽  
Concentration Difference ◽  
Water Chain

A flowing water chain in a (6, 6) carbon nanotube (CNT) driven by concentration difference is studied by molecular dynamics (MD) simulation. Water molecules in the CNT form a continuous water chain, which occupy the space of a 2 Å radius along the axis of channel. By computing the trajactory from the simulation run, the water density profile along the CNT is obtained and the flow behavior of water in the CNT is studied. The simulated results show that the density distribution in the CNT is lower than that in the bulk water and the solution, but the free energy distribution appears a contrary tendency. In addition, the quantity of hydrogen-bonds (H-bonds) forming in the CNT appears a fluctuation along with time, by analyzing which, it is found that the formation of H-bonds in the CNT is related to flow rate of water.

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