Strength Analyses of FE2O3+Al Nanocomposites Using Classical Molecular Dynamics

Aerospace ◽

10.1115/imece2005-79282 ◽

2005 ◽

Author(s):

Vikas Tomar ◽

Min Zhou

Keyword(s):

Molecular Dynamics ◽

Voronoi Tessellation ◽

Bulk Single Crystal ◽

Polycrystalline Aluminum ◽

Grain Sizes ◽

Classical Molecular Dynamics ◽

Potential Form ◽

Tension And Compression ◽

Strength Asymmetry ◽

Polycrystalline Structures

Classical molecular dynamics (CMD) simulation is an important technique for analyzing custom-designed nanostructured materials and nano-sized systems such as nanowires and nanobelts. This research focuses on analyzing the strength of Fe2O3+Al energetic nanocomposites using CMD. A generic potential form is used to describe the behavior of the Fe+Al+Fe2O3+Al2O3 system. The potential is able to describe bulk single crystal behavior of Fe, Al, Fe2O3, Al2O3 as well as interfacial transitions among them. The nanostructures analyzed include polycrystalline Aluminum, Fe2O3 as well as their composites with two different volume fractions (0.6/0.4 and 04/0.6). The polycrystalline structures are generated using voronoi tessellation. Quasi-static strength analyses are carried out using a massively parallel CMD code for both tension and compression. The analyses reveal that reverse Hall-Petch (H-P) effect is operative for polycrystalline Al under both tension and compression. However, for polycrystalline Fe2O3 reverse H-P effect is operative under tension only. Compression still shows direct H-P effect. This effect transcends into the strength of both composites at all grain sizes. In addition, we also observe tension-compression strength asymmetry in the all polycrystalline systems. This framework offers an important tool for nanoscale design of advanced nanocomposite materials.

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Characterization of Defect Nucleation and Propagation in Fe2O3+FCC-Al Nanocomposites During Uniaxial Tensile and Compressive Deformations

Applied Mechanics ◽

10.1115/imece2006-13629 ◽

2006 ◽

Author(s):

Vikas Tomar ◽

Min Zhou

Keyword(s):

Molecular Dynamics ◽

Grain Size ◽

Defect Formation ◽

Voronoi Tessellation ◽

Orientation Distribution ◽

Uniaxial Tensile ◽

Grain Sizes ◽

Classical Molecular Dynamics ◽

Average Grain Size ◽

Nanocrystalline Structures

The objective of this research is to analyze uniaxial tensile and compressive mechanical deformations of α-Fe2O3 + fcc Al nanoceramic-metal composites using classical molecular dynamics (MD). Specifically, variations in the nucleation and the propagation of defects (such as dislocations and stacking faults etc.) with variation in the nanocomposite phase morphology and their effect on observed tensile and compressive strengths of the nanocomposites are analyzed. For this purpose, a classical molecular dynamics (MD) potential that includes an embedded atom method (EAM) cluster functional, a Morse type pair function, and a second order electrostatic interaction function is developed, see Tomar and Zhou (2004) and Tomar and Zhou (2006b). The nanocrystalline structures (nanocrystalline Al, nanocrystalline Fe2O3 and the nanocomposites with 40% and 60% Al by volume) with average grain sizes of 3.9 nm, 4.7 nm, and 7.2 nm are generated using a combination of the well established Voronoi tessellation method with the Inverse Monte-Carlo method to conform to prescribed log-normal grain size distributions. For comparison purposes, nanocrystalline structures with a specific average grain size have the same grain morphologies and the same grain orientation distribution. MD simulations are performed at the room temperature (300 K). Calculations show that the deformation mechanism is affected by a combination of factors including the fraction of grain boundary (GB) atoms and the electrostatic forces between atoms. The significance of each factor is dependent on the volume fractions of the Al and Fe2O3 phases. Depending on the relative orientations of the two phases at an interface, the contribution of the interface to the defect formation varies. The interfaces have stronger effect in structures with smaller average grain sizes than in structures with larger average grain sizes.

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Heterogeneity in the microstructure and dynamics of tetraalkylammonium hydroxide ionic liquids: insight from classical molecular dynamics simulations and Voronoi tessellation analysis

Physical Chemistry Chemical Physics ◽

10.1039/c9cp06796e ◽

2020 ◽

Vol 22 (6) ◽

pp. 3466-3480 ◽

Cited By ~ 5

Author(s):

Th. Dhileep N. Reddy ◽

Bhabani S. Mallik

Keyword(s):

Molecular Dynamics ◽

Ionic Liquids ◽

Molecular Dynamics Simulations ◽

Voronoi Tessellation ◽

Md Simulations ◽

Tetrabutylammonium Hydroxide ◽

Classical Molecular Dynamics ◽

Tetraethylammonium Hydroxide ◽

Tetrapropylammonium Hydroxide ◽

Dynamics Simulations

Microscopic structural and dynamic heterogeneities were investigated for three ionic liquids (ILs), tetraethylammonium hydroxide, tetrapropylammonium hydroxide, and tetrabutylammonium hydroxide employing classical molecular dynamics (MD) simulations.

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A Conserved Asparagine in a Ubiquitin Conjugating Enzyme Positions the Substrate for Nucleophilic Attack

10.26434/chemrxiv.7019579.v1 ◽

2018 ◽

Cited By ~ 1

Author(s):

Walker M. Jones ◽

Aaron G. Davis ◽

R. Hunter Wilson ◽

Katherine L. Elliott ◽

Isaiah Sumner

Keyword(s):

Molecular Dynamics ◽

Quantum Mechanics ◽

Molecular Mechanics ◽

Reaction Rates ◽

Nucleophilic Attack ◽

Classical Molecular Dynamics ◽

Ubiquitin Conjugating Enzyme ◽

Conjugating Enzyme

We present classical molecular dynamics (MD), Born-Oppenheimer molecular dynamics (BOMD), and hybrid quantum mechanics/molecular mechanics (QM/MM) data. MD was performed using the GPU accelerated pmemd module of the AMBER14MD package. BOMD was performed using CP2K version 2.6. The reaction rates in BOMD were accelerated using the Metadynamics method. QM/MM was performed using ONIOM in the Gaussian09 suite of programs. Relevant input files for BOMD and QM/MM are available.

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