Structure, Mechanical Properties, and Dynamic Fracture in Nanophase Silicon Nitride via Parallel Molecular Dynamics

1996 ◽  
Vol 457 ◽  
Author(s):  
Kenji Tsuruta ◽  
Andrey Omeltchenko ◽  
Aiichiro Nakano ◽  
Rajiv K. Kalia ◽  
Priya Vashishta
Keyword(s):  
Mechanical Properties ◽  
Molecular Dynamics ◽  
Grain Size ◽  
Silicon Nitride ◽  
Dynamic Fracture ◽  
Elastic Moduli ◽  
Md Simulations ◽  
Multiphase Model ◽  
Order Of Magnitude ◽  
Parallel Molecular Dynamics

ABSTRACTMillion-atom molecular-dynamics (MD) simulations are performed to study the structure, mechanical properties, and dynamic fracture in nanophase Si3N4. We find that intercluster regions are highly disordered: 50% of Si atoms in intercluster regions are three-fold coordinated. Elastic moduli of nanophase Si3N4 as a function of grain size and porosity are well described by a multiphase model for heterogeneous materials. The study of fracture in the nanophase Si3N4 reveals that the system can sustain an order-of-magnitude larger external load than crystalline Si3N4. This is due to branching and pinning of the crack front by nanoscale microstructures.

Molecular Dynamics Simulations of Nanoindentation of Silicon Nitride

1998 ◽  
Vol 539 ◽  
Author(s):  
Phillip Walsh ◽  
Andrey Omeltchenko ◽  
Hideaki Kikuchi ◽  
Rajiv K. Kalia ◽  
Aiichiro Nakano ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Molecular Dynamics ◽  
Silicon Nitride ◽  
Elastic Moduli ◽  
Local Stress ◽  
Md Simulations ◽  
Stress Distributions ◽  
Surface Adhesion ◽  
Amorphous Silicon Nitride ◽  
Dynamics Simulations

AbstractThis is a report of work in progress on 10 million atom Molecular Dynamics (MD) simulations of nanoindentation of crystalline and amorphous silicon nitride (Si3N4). Nanoindentation is used to determine mechanical properties of extremely thin films such as hardness and elastic moduli. We report load-displacement curves for several Si3N4 configurations using an idealized non-deformable indenter and analyze the local stress distributions in the vicinity of the indenter tip. Preliminary results for surface adhesion using Si3N4 for both tip and substrate are also reported.

Structure, Mechanical Properties, and Thermal Transport in Microporous Silicon Nitride Via Parallel Molecular Dynamics

1995 ◽  
Vol 408 ◽  
Author(s):  
Andrey Omeltchenko ◽  
Aiichiro Nakano ◽  
Rajiv K. Kalia ◽  
Priya Vashishta
Keyword(s):  
Mechanical Properties ◽  
Thermal Conductivity ◽  
Molecular Dynamics ◽  
Silicon Nitride ◽  
Elastic Constants ◽  
Thermal Transport ◽  
Entire System ◽  
Amorphous Silicon Nitride ◽  
Parallel Molecular Dynamics ◽  
Dynamics Simulations

AbstractMolecular dynamics simulations are performed to investigate structure, mechanical properties, and thermal transport in amorphous silicon nitride under uniform dilation. As the density is lowered, we observe the formation of pores below ρ = 2.6 g/cc and at 2.0 g/cc the largest pore percolates through the entire system. Effects of porosity on elastic constants, phonons and thermal conductivity are investigated. Thermal conductivity and Young's modulus are found to scale as ρ1.5 and ρ3.6, respectively.

Early Stages of Sintering of Si3N4 Nanoclusters Via Parallel Molecular Dynamics

1995 ◽  
Vol 408 ◽  
Author(s):  
Kenji Tsuruta ◽  
Andrey Omeltchenko ◽  
Rajiv K. Kalia ◽  
Priya Vashishta
Keyword(s):  
Molecular Dynamics ◽  
Silicon Nitride ◽  
Neck Region ◽  
Md Simulations ◽  
Parallel Computers ◽  
Early Stages ◽  
Parallel Molecular Dynamics ◽  
Rapid Diffusion ◽  
A Chain

AbstractWe investigate early stages of sintering of silicon nitride (Si3N4) nanoclusters by molecular-dynamics (MD) simulations on parallel computers. Within 100 pico seconds, an asymmetric neck is formed between nanocrystals at 2,000K. In the neck region, there are more four-fold than three-fold coordinated Si atoms. In contrast, amorphous nanoclusters develop a symmetric neck, which has nearly the same number of three-fold and four-fold coordinated Si atoms. In the case of sintering among three nanoclusters, a chain-like structure forms in 200 pico seconds. The present study shows that sintering is driven by rapid diffusion of surface atoms and cluster rearrangement.

Fracture of Nanophase Ceramics: A Molecular-Dynamics Study

1996 ◽  
Vol 457 ◽  
Author(s):  
Aiichiro Nakano ◽  
Rajiv K. Kalia ◽  
Andrey Omeltchenko ◽  
Kenji Tsuruta ◽  
Priya Vashishta
Keyword(s):  
Molecular Dynamics ◽  
Silicon Nitride ◽  
Load Balancing ◽  
Molecular Dynamics Simulations ◽  
Dynamic Fracture ◽  
Parallel Computers ◽  
Fracture Surfaces ◽  
Affine Structures ◽  
Dynamics Simulations ◽  
Multiscale Algorithms

ABSTRACTNew multiscale algorithms and a load-balancing scheme are combined for molecular-dynamics simulations of nanocluster-assembled ceramics on parallel computers. Million-atom simulations of the dynamic fracture in nanophase silicon nitride reveal anisotropie self-affine structures and crossover phenomena associated with fracture surfaces.

Mechanical Properties of α-Helices Estimated Using Molecular Dynamics and Finite Element Simulations

2008 ◽  
Author(s):  
Peyman Honarmandi ◽  
Philip Bransford ◽  
Roger D. Kamm
Keyword(s):  
Mechanical Properties ◽  
Molecular Dynamics ◽  
Finite Element ◽  
Solid Mechanics ◽  
Normal Mode Analysis ◽  
Computational Cost ◽  
Md Simulations ◽  
Elastic Stiffness ◽  
Mode Analysis ◽  
Molecular Volume

Mechanical properties of biomolecules and their response to mechanical forces may be studied using Molecular Dynamics (MD) simulations. However, high computational cost is a primary drawback of MD simulations. This paper presents a computational framework based on the integration of the Finite Element Method (FEM) with MD simulations to calculate the mechanical properties of polyalanine α-helix proteins. In this method, proteins are treated as continuum elastic solids with molecular volume defined exclusively by their atomic surface. Therefore, all solid mechanics theories would be applicable for the presumed elastic media. All-atom normal mode analysis is used to calculate protein’s elastic stiffness as input to the FEM. In addition, constant force molecular dynamics (CFMD) simulations can be used to predict other effective mechanical properties, such as the Poisson’s Ratio. Force versus strain data help elucidate the mechanical behavior of α-helices upon application of constant load. The proposed method may be useful in identifying the mechanical properties of any protein or protein assembly with known atomic structure.

Unusually high flexibility of graphene–Cu nanolayered composites under bending

2019 ◽  
Vol 21 (31) ◽  
pp. 17393-17399 ◽  
Author(s):  
Yuxin Zhao ◽  
Xiaoyi Liu ◽  
Jun Zhu ◽  
Sheng-Nian Luo
Keyword(s):  
Mechanical Properties ◽  
Molecular Dynamics ◽  
Analytical Model ◽  
Md Simulations ◽  
High Flexibility

The mechanical properties of graphene–Cu nanolayered (GCuNL) composites under bend loading are investigated via an energy-based analytical model and molecular dynamics (MD) simulations.

Permeability variation with porosity, pore space geometry, and cement type: A case history from the Snøhvit field, the Barents Sea

Geophysics ◽  
2015 ◽  
Vol 80 (1) ◽  
pp. D43-D49 ◽  
Author(s):  
Sissel Grude ◽  
Jack Dvorkin ◽  
Martin Landrø
Keyword(s):  
Grain Size ◽  
Elastic Moduli ◽  
Barents Sea ◽  
Pore Space ◽  
Rock Physics ◽  
Additional Information ◽  
Order Of Magnitude ◽  
Porosity And Permeability ◽  
Lower Permeability ◽  
Permeability Variation

Laboratory permeability data from the brine-filled Tubåen Formation in the Snøhvit field show an order of magnitude permeability variation for approximately the same porosity. This variation in permeability is explained by a modified Kozeny-Carman equation that exploits the relationships among permeability, porosity, cementation, and pore geometry. The expression correlates the slope in a logarithmic plot of porosity versus permeability with the amount of contact cement and sorting, and the intercept with the grain size. Additional information about sorting and/or cementation can be used to better constrain the slope of the plot. Based on this equation, we found that the grain size and the amount of contact cement increased with depth in the lowermost Tubåen 1–3 sandstone units, this led to an increasing permeability with depth, in the same porosity range. The permeability variation in the shallowest Tubåen 4 sandstone unit was affected by sorting to a larger degree than the remaining Tubåen intervals, which influenced the cementation factor, porosity, and permeability simultaneously. These findings were supported by the depositional environment of the formation, a petrology study of grain size and sorting and a rock-physics study. The rock-physics study indicated that the samples with higher permeability had higher elastic moduli compared with the samples with lower permeability. This correlation between permeability and elastic moduli can be explained by the increasing amount of contact cement for the stiffer, high-permeability samples.

The Effects of Thermal Loading on the Mechanical Properties of Interfaces of Dissimilar Materials by Nanoindentation Simulations

2011 ◽  
Vol 133 (2) ◽  
Author(s):  
Ningbo Liao ◽  
Ping Yang ◽  
Miao Zhang ◽  
Wei Xue
Keyword(s):  
Heat Transfer ◽  
Mechanical Properties ◽  
Molecular Dynamics ◽  
Thermal Cycling ◽  
Thermal Loading ◽  
Mechanical Test ◽  
Dissimilar Materials ◽  
Md Simulations ◽  
Test Models ◽  
Critical Consideration

Heat transfer across the interfaces of dissimilar materials is a critical consideration in a wide variety of scientific and engineering applications. In this paper, molecular dynamics (MD) simulations are conducted to investigate the effects of thermal loading on mechanical properties of Al–Cu and Cr–Cu interfaces. The mechanical properties are investigated by MD simulations of nanoindentation. Both the results of MD simulations and experiments show the Young’s modulus decrease after thermal cycling, and the Cr–Cu interface is more sensitive to the thermal loading than the Al–Cu interface. The thermal loading and mechanical test models proposed here can be used to evaluate interfacial properties under the effects of heat transferring.

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