scholarly journals Ring Mechanism of Fast Na+Ion Transport in Na2LiFeTeO6: Insight from MolecularDynamics Simulation

2021 ◽  
Author(s):  
Kartik Sau ◽  
Tamio Ikeshoji
Keyword(s):  
Molecular Dynamics ◽  
Diffusion Mechanism ◽  
Layered Oxides ◽  
Ion Distribution ◽  
Theoretical Simulation ◽  
Solid State Battery ◽  
Ring Mechanism ◽  
Dynamics Simulations ◽  
Fast Ion ◽  
Potential Parameters

Honeycomb layered oxides have attracted recent attention because of their rich crystal chemistry. However, the atomistic mechanisms of cationic transport in these structures remain vastly unexplored. Herein, we perform an extensive, systematic molecular dynamics study on Na2LiFeTeO6 using combined force-field and first-principles-based molecular dynamics simulations. We use are fined set of inter-atomic potential parameters of a previously reported potential model that represents various structural and transport properties of this recently reported promising material for all-solid-state battery applications. The present simulation study elucidates the roles of octahedral ordering and entropic contributions in Na+-ion distribution in the ab-plane. Our theoretical simulation also develops a ring-like atomistic diffusion mechanism and relevant atomistic energy barriers that help to understand the origin of fast ion conduction in honeycomb layered oxides.

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’.

Molecular-Dynamics Analysis of the Structural Properties of Silica during Cooling

2008 ◽  
Vol 139 ◽  
pp. 101-106 ◽  
Author(s):  
Byoung Min Lee ◽  
Shinji Munetoh ◽  
Teruaki Motooka ◽  
Yeo Wan Yun ◽  
Kyu Mann Lee
Keyword(s):  
Molecular Dynamics ◽  
Glass Transition ◽  
Transition Temperature ◽  
Structural Properties ◽  
Diffusion Coefficients ◽  
The Self ◽  
Dynamics Analysis ◽  
Self Diffusion ◽  
Dynamics Simulations ◽  
Potential Parameters

The structural properties of SiO2 liquid during cooling have been investigated by molecular dynamics simulations. The interatomic forces acting on the particles are calculated by the modified Tersoff potential parameters. The glass transition temperature and structural properties of the resulting SiO2 system at various temperatures have been investigated. The fivefold coordinations of Si and threefold coordinations of O atoms were observed, and the coordination defects of system decrease with decreasing temperature up to 17 % at 300 K. The self-diffusion coefficients for Si and O atoms drop to almost zero below 3000 K. The structures were distorted at high temperatures, but very stable atomic network persisted up to high temperature in the liquid state.

scholarly journals Role of Interlayer Distance on Cationic Diffusion of Nickel-Based Honeycomb Layered Tellurates

2021 ◽  
Author(s):  
Kartik Sau ◽  
Tamio Ikeshoji ◽  
Godwill Mbiti Kanyolo ◽  
Titus Masese
Keyword(s):  
Molecular Dynamics ◽  
Transport Properties ◽  
Crystal Chemistry ◽  
Interatomic Potential ◽  
Layered Oxides ◽  
Ionic Radii ◽  
Diffusion Channel ◽  
Exponential Increase ◽  
Potential Parameters

<b>Although the fascinatingly rich crystal chemistry of honeycomb layered oxides has been accredited as the propelling force behind their remarkable electrochemistry, the atomistic mechanisms surrounding their operations remain unexplored. Thus, herein, we present an extensive molecular dynamics study performed systematically using a refined set of inter-atomic potential parameters of <i>A</i><sub>2</sub>Ni<sub>2</sub>TeO<sub>6</sub> (where <i>A</i> = Li, Na, and K). We demonstrate the effectiveness of the Vashishta-Rahman form of the interatomic potential in reproducing various structural and transport properties of this promising class of materials and predict an exponential increase in cationic diffusion with larger interlayer distances. The simulations further demonstrate the correlation between broadened inter-layer (inter-slab) distances associated with the larger ionic radii of K and Na compared to Li and the enhanced cationic conduction exhibited in K<sub>2</sub>Ni<sub>2</sub>TeO<sub>6</sub> and Na<sub>2</sub>Ni<sub>2</sub>TeO<sub>6</sub> relative to Li<sub>2</sub>Ni<sub>2</sub>TeO<sub>6</sub>. Whence, our findings connect a wider bottleneck along the cationic diffusion channel within frameworks comprised of larger mobile cations to the improved cationic diffusion experimentally observed in honeycomb layered oxides. </b>

Molecular Dynamics Simulations of Water and Ion Structures Near Charged Surfaces

2007 ◽  
Author(s):  
Dongyan Xu ◽  
Deyu Li ◽  
Yongsheng Leng
Keyword(s):  
Molecular Dynamics ◽  
Surface Charge ◽  
Molecular Dynamics Simulations ◽  
Single Molecule ◽  
Research Field ◽  
Water Molecules ◽  
Wall Region ◽  
Surface Charges ◽  
Ion Distribution ◽  
Dynamics Simulations

Extensive research has been devoted to nanofluidics in the past decade because of its potential applications in single molecule sensing and manipulations. Fundamental studies have attracted significant attention in this research field since the success of nanofluidic devices depends on a thorough understanding of the fluidic, ionic, and molecular behavior in highly confined nano-environments. In this paper, we report on molecular dynamics simulations of the effect of surface charge densities on the ion distribution and the water density profile close to a charged surface. We demonstrate that surface charges not only interact with mobile ions in the electrolyte, but also interact with water molecules due to their polarizability, and hence influence the orientation of water molecules in the near wall region. For the first time, we show that as the surface charge density increases, the water molecules within ∼ 5 Å of the {100} silicon surface will evolve from one layer into two layers. Meanwhile, the orientation of the water molecules is more aligned instead of randomly distributed. This layering effect may have important implications on electroosmotic flow through nanochannels and heat transfer across the solid-liquid interface.

A COARSE-GRAINED MODEL OF MONOOLEIN: COMPARISON WITH THE ATOMISTIC MODEL

2009 ◽  
Vol 08 (01n02) ◽  
pp. 169-173
Author(s):  
J. H. KIM ◽  
S. H. CHOI ◽  
D. H. JUNG ◽  
C. S. CHO ◽  
Y. J. CHOI
Keyword(s):  
Molecular Dynamics ◽  
Lipid Bilayer ◽  
Dissipative Particle Dynamics ◽  
Dynamics Simulation ◽  
Coarse Grained ◽  
Atomistic Model ◽  
Coarse Grained Model ◽  
Cosmetic Industry ◽  
Dynamics Simulations ◽  
Potential Parameters

Monoolein (2,3-dihydroxypropyl (Z)-octadec-9-enoate) is one of the monoacylglycerol and has been studied for various applications in food, pharmaceutical, and cosmetic industry. Those applications make use of the phase behavior of monoolein. In order to understand the lipid bilayer phase of monoolein in mesoscale, a coarse-grained model has been built and tested in this work. The monoolein molecule was represented by two hydrophilic heads and six hydrophobic tails. The three water molecules were also represented as one bead. For comparison, the atomistic model has also been used for molecular dynamics simulation on the lipid bilayer phase in isothermal-isobaric (NPT) ensemble. The interaction and bond bending potential parameters for dissipative particle dynamics (DPD) were obtained with molecular dynamics simulations on lipid bilayer in water. And we also obtained the interaction parameters of the coarse-grained model, which agree well with the atomistic model. We compared the simulated phases using the coarse-grained model with using the atomistic model. With these parameters, we successfully reproduced the lamella phase of monoolein in DPD simulations.

Toward Rational Design of Fast Ion Conductors: Molecular Dynamics Modeling of Interfaces of Nanoscale Planar Heterostructures

2002 ◽  
Vol 17 (7) ◽  
pp. 1686-1691 ◽  
Author(s):  
J-J. Liang ◽  
P.W-C. Kung
Keyword(s):  
Molecular Dynamics ◽  
Ionic Conductivity ◽  
Periodic Boundary Condition ◽  
Rational Design ◽  
Periodic Boundary ◽  
Dynamics Modeling ◽  
Molecular Dynamics Modeling ◽  
Conductivity Increase ◽  
Dynamics Simulations ◽  
Fast Ion

Increased ionic conductivity at nanoscale planar interfaces of the CaF2|BaF2 system was successfully modeled using molecular dynamics simulations. A criterion was established to construct simulation cells containing any arbitrarily lattice-mismatched interfaces while permitting periodic boundary condition. The relative (to the bulk) ionic conductivity increase at the 111 (CaF2)|111 (BaF2) interface was qualitatively reproduced. Higher conductivity, by a factor of 7.6, was predicted for the 001 (CaF2)|001 (BaF2) interface. A crystalline nanocomposite of the CaF2|BaF2 system, in which the [001] morphology is encouraged and crystallite dimensions are approximately 4 nm, was proposed to give ionic conductivity approaching that predicted for the 001 (CaF2)|001 (BaF2) interface.

The Diffusion Isotope Effect and Diffusion Mechanism in Liquid Cu-Ag and Cu-Ni Alloys

2021 ◽  
Vol 413 ◽  
pp. 136-145
Author(s):  
Ujjal Sarder ◽  
Tumpa R. Paul ◽  
Irina V. Belova ◽  
Graeme E. Murch
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulations ◽  
Isotope Effect ◽  
Composition Dependence ◽  
Diffusion Mechanism ◽  
Liquid Alloys ◽  
Ni Alloys ◽  
Effect Parameter ◽  
Dynamics Simulations ◽  
And Diffusion

In this paper, the diffusion isotope effect and diffusion mechanism are investigated by means of molecular dynamics simulations in two liquid alloys, Ni-Ag and Ni-Cu. The values for the diffusion isotope effect parameter allow for the estimate of the number of atoms which are moving cooperatively in a basic diffusion event as experienced by a given atomic species. It is shown that the composition dependence of ND is typically very small. However, the temperature dependence of this parameter is much more pronounced. In addition, it is shown that, on average, in these alloys and temperatures considered, ND is limited to the range: 5<ND<17. This is consistent with results of molecular dynamics simulations on the average coordination number calculations. This would suggest that, together with a given atom, depending on temperature, the neighbouring atoms are all involved in the basic diffusion event.

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