Predictive power of effective intermolecular pair potentials: MD simulation results for methane up to 1000 MPa

1990 ◽  
Vol 57 (1-2) ◽  
pp. 35-46 ◽  
Author(s):  
Berthold Saager ◽  
Johann Fischer
Keyword(s):  
Md Simulation ◽  
Predictive Power ◽  
Pair Potentials ◽  
Simulation Results

Thermal Transport in Nanocrystalline Materials

2005 ◽  
Author(s):  
Zhanrong Zhong ◽  
Xinwei Wang
Keyword(s):  
Thermal Conductivity ◽  
Specific Heat ◽  
Thermal Transport ◽  
Nanocrystalline Materials ◽  
Large Scale ◽  
Md Simulation ◽  
Fundamental Physics ◽  
Grain Sizes ◽  
Simulation Results ◽  
Thermal Phenomena

In this work, thermal transport in nanocrystalline materials is studied using large-scale equilibrium molecular dynamics (MD) simulation. Nanocrystalline materials with different grain sizes are studied to explore how and to what extent the size of nanograins affects the thermal conductivity and specific heat. Substantial thermal conductivity reduction is observed and the reduction is stronger for nanocrystalline materials with smaller grains. On the other hand, the specific heat of nanocrystalline materials shows little change with the grain size. The simulation results are compared with the thermal transport in individual nanograins based on MD simulation. Further discussions are provided to explain the fundamental physics behind the observed thermal phenomena in this work.

Thermal Expansion and Isotopic Composition Effects on Lattice Thermal Conductivities of Crystalline Silicon

2006 ◽  
Author(s):  
Yunfei Chen ◽  
Guodong Wang ◽  
Deyu Li ◽  
Jennifer R. Lukes
Keyword(s):  
Thermal Conductivity ◽  
Thermal Expansion ◽  
Md Simulation ◽  
Lattice Thermal Conductivity ◽  
Mass Difference ◽  
Dynamics Simulation ◽  
Temperature Range ◽  
Simulation Results ◽  
Callaway Model ◽  
Thermal Conductivities

Equilibrium molecular dynamics simulation is used to calculate lattice thermal conductivities of crystal silicon in the temperature range from 400K to 1600K. Simulation results confirmed that thermal expansion, which resulted in the increase of the lattice parameter, caused the decrease of the lattice thermal conductivity. The simulated results proved that thermal expansion imposed another type resistance on phonon transport in crystal materials. Isotopic and vacancy effects on lattice thermal conductivity are also investigated and compared with the prediction from the modified Debye Callaway model. It is demonstrated in the MD simulation results that the isotopic effect on lattice thermal conductivity is little in the temperature range from 400K to 1600K for isotopic concentration below 1%, which implies the isotopic scattering on phonon due to mass difference can be neglected over the room temperature. The remove of atoms from the crystal matrix caused mass difference and elastic strain between the void and the neighbor atoms, which resulted in vacancy scattering on phonons. Simulation results demonstrated this mechanism is stronger than that caused by isotopic scattering on phonons due to mass difference. A good agreement is obtained between the MD simulation results of silicon crystal with vacancy defects and the data predicted from the modified Debye Callaway model. This conclusion is helpful to demonstrate the validity of Klemens' Rayleigh model for impurity scattering on phonons.

A scale-up nanoporous membrane centrifuge for reverse osmosis desalination without fouling

TECHNOLOGY ◽  
2018 ◽  
Vol 06 (01) ◽  
pp. 36-48 ◽  
Author(s):  
Qingsong Tu ◽  
Tiange Li ◽  
Ao Deng ◽  
Kevin Zhu ◽  
Yifei Liu ◽  
...  
Keyword(s):  
Angular Velocity ◽  
Reverse Osmosis ◽  
Large Scale ◽  
Md Simulation ◽  
Scale Up ◽  
Scale Separation ◽  
Nanoporous Membrane ◽  
Micron Size ◽  
Simulation Results ◽  
Reverse Osmosis Desalination

A scale-up nanoporous membrane centrifuge is designed and modeled. It can be used for nanoscale scale separation including reverse osmosis desalination. There are micron-size pores on the wall of the centrifuge and nanoscale pores on local graphene membrane patches that cover the micron-size pores. In this work, we derived the critical angular velocity required to counter-balance osmosis force, so that the reverse-osmosis (RO) desalination process can proceed. To validate this result, we conducted a large scale (four million atoms) full atom molecular dynamics (MD) simulation to examine the critical angular velocity required for reverse osmosis at nanoscale. It is shown that the analytical results derived based on fluid mechanics and the simulation results observed in MD simulation are consistent and well matched. The main advantage of such nanomaterial based centrifuge is its intrinsic anti-fouling ability to clear [Formula: see text] and [Formula: see text] ions accumulated at the vicinity of the pores due to the Coriolis effect. Analyses have been conducted to study the relation between osmotic pressure, centrifugal pressure, and water permeability.

Analysis of the Instability for Two Nano-Scale Liquid Threads Coexisting in a Periodic Fundamental Cell

2011 ◽  
Author(s):  
Chun-Lang Yeh
Keyword(s):  
Stability Criterion ◽  
Md Simulation ◽  
Density Field ◽  
Stability Criteria ◽  
Stable Domain ◽  
Nano Scale ◽  
Critical Wavelength ◽  
Molecular Scale ◽  
Vaporization Process ◽  
Simulation Results

This paper investigates the vaporization process of two nano-scale liquid threads coexisting in a periodic fundamental cell by molecular dynamics (MD) simulation. The influences of liquid thread radius, fundamental cell length, and relative position of the two threads are discussed. Snapshots of molecules, the number of liquid particles formed, and density field are analyzed. Two linear stability criteria, namely, Rayleigh’s stability criterion and Kim’s stability criterion, are accessed for their validity in molecular scale. It is found that more liquid particles are formed when the separation of the two threads is larger. Moreover, vaporization is slower when the two liquid threads are close to each other. It is also found that the trends of Rayleigh’s stability criterion and Kim’s stability criterion agree with MD simulation results. However, when the two threads coalesce into a single thread and remain intact, the critical wavelength of perturbation may be increased and the stable domain is broadened. Under such a situation, Rayleigh’s stability criterion and Kim’s stability criterion underpredict the stable domain.

Multiple Time-Scale Molecular Simulations: Modeling Realistic Loading Rates

2007 ◽  
Author(s):  
S. N. Medyanik ◽  
E. Guleryuz
Keyword(s):  
Time Scales ◽  
Md Simulation ◽  
Multiple Time ◽  
Strain Rates ◽  
Simulation Methods ◽  
Multiple Time Scale ◽  
Loading Rates ◽  
Simulation Results ◽  
Experimental Values

The vast gap between the molecular dynamics (MD) and experimental time scales poses serious problems to direct comparison between the MD simulation and experimental results. The inability of the traditional MD simulation methods to model long enough time scales also results in modeling unrealistically high loading rates and strain rates that are usually at least six or seven orders of magnitude higher than the corresponding experimental values. This may have a tremendous effect on the realism and quality of the simulation results.

scholarly journals Simulation Study of Helium Effect on the Microstructure of Nanocrystalline Body-Centered Cubic Iron

Materials ◽  
2018 ◽  
Vol 12 (1) ◽  
pp. 91 ◽  
Author(s):  
Chunping Xu ◽  
Wenjun Wang
Keyword(s):  
Lattice Constant ◽  
Tensile Strain ◽  
Room Temperature ◽  
Md Simulation ◽  
Uniaxial Tensile ◽  
Body Centered Cubic ◽  
X Ray Diffraction ◽  
X Ray ◽  
Swelling Rate ◽  
Simulation Results

Helium (He) effect on the microstructure of nanocrystalline body-centered cubic iron (BCC-Fe) was studied through Molecular Dynamics (MD) simulation and simulated X-ray Diffraction (XRD). The crack generation and the change of lattice constant were investigated under a uniaxial tensile strain at room temperature to explore the roles of He concentration and distribution played in the degradation of mechanical properties. The simulation results show that the expansion of the lattice constant decreases and the swelling rate increases while the He in the BCC region diffuses into the grain boundary (GB) region. The mechanical property of nanocrystalline BCC-Fe shows He concentration and distribution dependence, and the existence of He in GB is found to benefit the generation and growth of cracks and to affect the strength of GB during loading. It is observed that the reduction of tensile stress contributed by GB He is more obvious than that contributed by grain interior He.

Effect of w/c ratio and cement content on diffusivity of chloride ion in concrete: A molecular dynamics study

2019 ◽  
Vol 10 (4) ◽  
pp. 83
Author(s):  
Rokonuzzaman Rokon ◽  
Md. Shafiqul Islam ◽  
Nusrat E. Mursalin
Keyword(s):  
Molecular Dynamics ◽  
Diffusion Coefficient ◽  
Diffusion Coefficients ◽  
Md Simulation ◽  
Cement Content ◽  
Chloride Ion ◽  
Simulation Method ◽  
Chloride Induced Corrosion ◽  
Simulation Results ◽  
And Performance

When a reinforced structure is exposed to marine environments, chloride-induced corrosion occurs and it decreases the durability and performance of the structure. The degree of humidity, the presence of cracks, environmental conditions, w/c ratio, and cement content are the influencing factors for chloride ion ingress into concrete. All of them, w/c ratio and cement content are treated as the most crucial factors on diffusion. This paper focus on Molecular Dynamics (MD) simulation method to determine the diffusion coefficient of chloride ion in concrete. The effect of w/c ratio and cement content on the diffusivity of chloride ion is also evaluated. The diffusion coefficients are obtained 2.88x10-12 m2/s, 3.13x10-12 m2/s, and 3.61x10-12 m2/s respectively for different w/c ratio of 0.40, 0.45 and 0.50 with constant cement content. Again the diffusion coefficient are calculated 4.6x10-12 m2/s, 3.13x10-12 m2/s, 2.78x10-12 m2/s respectively for different cement content of 300 kg/m3, 350 kg/m3 and 400 kg/m3 with constant w/c ratio. The simulation results clearly indicate that the diffusion coefficient of chlorine was affected by w/c ratio and cement content significantly.

Mobility of Self-Interstitial Clusters in FE and CU

1998 ◽  
Vol 527 ◽  
Author(s):  
Yu.N. Osetsky ◽  
A. Serra ◽  
V. Priego
Keyword(s):  
Cluster Size ◽  
Md Simulation ◽  
Three Dimensional ◽  
Migration Energy ◽  
Jump Frequency ◽  
Extensive Simulation ◽  
One Dimensional ◽  
Thermally Activated ◽  
Pair Potentials ◽  
Bias Model

ABSTRACTMolecular dynamics (MD) simulation has been used to study the thermally activated mobility of clusters of self-interstitial atoms (SIAs) in Fe and Cu. Such clusters are formed in metals during irradiation with energetical particles and, according to the cascade production bias model, they play an important role in the microstructure evolution of metals under irradiation. An extensive simulation of clusters from 2 to 30 interstitials has been carried out for the temperature range ≍360-1200K using long-range interatomic pair potentials. The results show that clusters bigger than two SIAs are one-dimensionally mobile. Di-interstitials have two migration mechanisms depending on the temperature. At low temperature the mechanism is one-dimensional whereas at high temperature the probability of rotation and three-dimensional migration increases. It was found that in both metals the effective migration energy of clusters estimated via their jump frequency does not depend on the cluster size, although the cluster jump frequency decreases as the cluster size increases. The mechanism of cluster migration and problems of the treatment of one-dimensional mobility are discussed.

scholarly journals Molecular Dynamics Simulation-Based Study on Enhancing Thermal Properties of Graphene-Reinforced Thermoplastic Polyurethane Nanocomposite for Heat Exchanger Materials

2020 ◽  
Author(s):  
Animesh Talapatra ◽  
Debasis Datta
Keyword(s):  
Thermal Conductivity ◽  
Molecular Dynamics ◽  
Glass Transition ◽  
Thermal Properties ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Md Simulation ◽  
Thermoplastic Polyurethane ◽  
Simulation Based ◽  
Simulation Results

Molecular dynamics (MD) simulation-based development of heat resistance nanocomposite materials for nanoheat transfer devices (like nanoheat exchanger) and applications have been studied. In this study, MD software (Materials Studio) has been used to know the heat transport behaviors of the graphene-reinforced thermoplastic polyurethane (Gr/TPU) nanocomposite. The effect of graphene weight percentage (wt%) on thermal properties (e.g., glass transition temperature, coefficient of thermal expansion, heat capacity, thermal conductivity, and interface thermal conductance) of Gr/TPU nanocomposites has been studied. Condensed-phase optimized molecular potentials for atomistic simulation studies (COMPASS) force field which is incorporated in both amorphous and forcite plus atomistic simulation modules within the software are used for this present study. Layer models have been developed to characterize thermal properties of the Gr/TPU nanocomposites. It is seen from the simulation results that glass transition temperature (Tg) of the Gr/TPU nanocomposites is higher than that of pure TPU. MD simulation results indicate that addition of graphene into TPU matrix enhances thermal conductivity. The present study provides effective guidance and understanding of the thermal mechanism of graphene/TPU nanocomposites for improving their thermal properties. Finally, the revealed enhanced thermal properties of nanocomposites, the interfacial interaction energy, and the free volume of polymer nanocomposites are examined and discussed.

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