scholarly journals A Molecular Dynamics Study on Rotational Nanofluid and Its Application to Desalination

Membranes ◽  
2020 ◽  
Vol 10 (6) ◽  
pp. 117
Author(s):  
Qingsong Tu ◽  
Wice Ibrahimi ◽  
Steven Ren ◽  
James Wu ◽  
Shaofan Li
Keyword(s):  
Molecular Dynamics ◽  
Angular Velocity ◽  
Large Scale ◽  
Salt Water ◽  
Dynamics Simulation ◽  
Dynamics Modeling ◽  
Molecular Dynamics Modeling ◽  
Desalination Technology ◽  
Nanofluidic Device ◽  
Fluid Hydrodynamics

In this work, we systematically study a rotational nanofluidic device for reverse osmosis (RO) desalination by using large scale molecular dynamics modeling and simulation. Moreover, we have compared Molecular Dynamics simulation with fluid mechanics modeling. We have found that the pressure generated by the centrifugal motion of nanofluids can counterbalance the osmosis pressure developed from the concentration gradient, and hence provide a driving force to filtrate fresh water from salt water. Molecular Dynamics modeling of two different types of designs are performed and compared. Results indicate that this novel nanofluidic device is not only able to alleviate the fouling problem significantly, but it is also capable of maintaining high membrane permeability and energy efficiency. The angular velocity of the nanofluids within the device is investigated, and the critical angular velocity needed for the fluids to overcome the osmotic pressure is derived. Meanwhile, a maximal angular velocity value is also identified to avoid Taylor-Couette instability. The MD simulation results agree well with continuum modeling results obtained from fluid hydrodynamics theory, which provides a theoretical foundation for scaling up the proposed rotational osmosis device. Successful fabrication of such rotational RO membrane centrifuge may potentially revolutionize the membrane desalination technology by providing a fundamental solution to the water resource problem.

Molecular Dynamics Modeling the Nano-Identation of Titanium

2021 ◽  
Author(s):  
Peiqiang Yang ◽  
Xueping Zhang ◽  
Zhenqiang Yao ◽  
Rajiv Shivpuri
Keyword(s):  
Molecular Dynamics ◽  
Plastic Deformation ◽  
Titanium Alloys ◽  
Large Scale ◽  
Mechanical Response ◽  
Pure Titanium ◽  
Dynamics Modeling ◽  
Dynamics Model ◽  
Nano Indentation ◽  
Molecular Dynamics Modeling

Abstract Titanium alloys’ excellent mechanical and physical properties make it the most popular material widely used in aerospace, medical, nuclear and other significant industries. The study of titanium alloys mainly focused on the macroscopic mechanical mechanism. However, very few researches addressed the nanostructure of titanium alloys and its mechanical response in Nano-machining due to the difficulty to perform and characterize nano-machining experiment. Compared with nano-machining, nano-indentation is easier to characterize the microscopic plasticity of titanium alloys. This research presents a nano-indentation molecular dynamics model in titanium to address its microstructure alteration, plastic deformation and other mechanical response at the atomistic scale. Based on the molecular dynamics model, a complete nano-indentation cycle, including the loading and unloading stages, is performed by applying Large-scale Atomic/Molecular Massively Parallel Simulator (LAMMPS). The plastic deformation mechanism of nano-indentation of titanium with a rigid diamond ball tip was studied under different indentation velocities. At the same time, the influence of different environment temperatures on the nano-plastic deformation of titanium is analyzed under the condition of constant indentation velocity. The simulation results show that the Young’s modulus of pure titanium calculated based on nano-indentation is about 110GPa, which is very close to the experimental results. The results also show that the mechanical behavior of titanium can be divided into three stages: elastic stage, yield stage and plastic stage during the nano-indentation process. In addition, indentation speed has influence on phase transitions and nucleation of dislocations in the range of 0.1–1.0 Å/ps.

Nano-Tribological Analysis by Molecular Dynamics Simulation—A Review

2006 ◽  
Vol 3 (2) ◽  
pp. 167-188 ◽  
Author(s):  
L. C. Zhang ◽  
K. Mylvaganam
Keyword(s):  
Molecular Dynamics ◽  
Large Scale ◽  
Surface Force ◽  
Atomic Scale ◽  
Dynamics Simulation ◽  
Asperity Contact ◽  
Dynamics Modeling ◽  
Body Contact ◽  
Cutting Regimes ◽  
Three Body

The advent of super computers for large scale atomic simulations and the invention of proximal testing devices such as atomic force microscope, friction force microscope, surface force apparatus, nanoScratcher etc., have led to the development of micro- and nano-tribology. This paper reviews some fundamental concepts and steps involved in molecular dynamics modeling of nanotribology together with some significant aspects such as the mechanisms of wear and friction, the scale effect of asperity contact size on friction, and the deformation induced by two-body and three-body contact sliding on the atomic scale with a focus on the authors' work on copper and silicon. Studies on diamond-copper sliding reveal that there exist four distinct regimes of deformation, and that no-wear deformation can be achieved by using a lower sliding speed, a smaller tip radius and a better lubrication. The variation of the frictional force is a function of contact area in all regimes except that in the cutting regime where the conventional friction law still holds. Investigations into the diamond-silicon sliding show that the amorphous phase transformation is the main deformation in silicon. In a two-body contact sliding, the deformation of silicon falls into no-wear, adhering, ploughing, and cutting regimes while in a three-body sliding it falls into no-wear, condensing, adhering, ploughing and no-damage wear regimes.

STUDY ON NANOMETRIC CUTTING MECHANISM AND BURR FORMATION USING MOLECULAR DYNAMICS SIMULATION

2006 ◽  
Vol 05 (04n05) ◽  
pp. 547-551 ◽  
Author(s):  
H. WU ◽  
F. Z. FANG ◽  
Q. X. PEI
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulation ◽  
Dynamics Simulation ◽  
Burr Formation ◽  
Work Piece ◽  
Dynamics Modeling ◽  
Modeling And Analysis ◽  
Nanometric Cutting ◽  
Molecular Dynamics Modeling ◽  
Elastic Rebound

Since no physical approach can be employed to study the mechanism in micro cutting, the molecular dynamics simulation is becoming more and more important. In this study, the results of molecular dynamics modeling and analysis on the nanometric machining on silicon surface are presented. According to the simulation, some phenomena in the nanometric cutting process are found. First, surface elastic rebound happens on the cut surface after cutter moving away. The value of the surface elastic rebound is calculated in the simulation. Second, the atoms near the corner of work piece swirl up following the cutter moving direction at the initial stage of removing atoms from the work piece. Third, the simulation results show that no matter how small material removal is, the burr is always formed at the edge of work piece.

scholarly journals Mechanistic Understanding From Molecular Dynamics Simulation in Pharmaceutical Research 1: Drug Delivery

2020 ◽  
Vol 7 ◽  
Author(s):  
Alex Bunker ◽  
Tomasz Róg
Keyword(s):  
Drug Delivery ◽  
Molecular Dynamics ◽  
Molecular Dynamics Simulation ◽  
Drug Loading ◽  
Pharmaceutical Research ◽  
Design Tool ◽  
Dynamics Simulation ◽  
Strong Impact ◽  
Dynamics Modeling ◽  
Molecular Dynamics Modeling

In this review, we outline the growing role that molecular dynamics simulation is able to play as a design tool in drug delivery. We cover both the pharmaceutical and computational backgrounds, in a pedagogical fashion, as this review is designed to be equally accessible to pharmaceutical researchers interested in what this new computational tool is capable of and experts in molecular modeling who wish to pursue pharmaceutical applications as a context for their research. The field has become too broad for us to concisely describe all work that has been carried out; many comprehensive reviews on subtopics of this area are cited. We discuss the insight molecular dynamics modeling has provided in dissolution and solubility, however, the majority of the discussion is focused on nanomedicine: the development of nanoscale drug delivery vehicles. Here we focus on three areas where molecular dynamics modeling has had a particularly strong impact: (1) behavior in the bloodstream and protective polymer corona, (2) Drug loading and controlled release, and (3) Nanoparticle interaction with both model and biological membranes. We conclude with some thoughts on the role that molecular dynamics simulation can grow to play in the development of new drug delivery systems.

Molecular Dynamics Modeling of Buckling Behavior of Hydrogenated Graphyne

NANO ◽  
2015 ◽  
Vol 10 (07) ◽  
pp. 1550105 ◽  
Author(s):  
A. Montazeri ◽  
S. Ebrahimi ◽  
A. Rajabpour ◽  
H. Rafii-Tabar
Keyword(s):  
Molecular Dynamics ◽  
Hydrogen Adsorption ◽  
Graphene Nanoribbons ◽  
Dynamics Simulation ◽  
Dynamics Modeling ◽  
Stability Behavior ◽  
Molecular Dynamics Modeling ◽  
Buckling Behavior ◽  
Out Of Plane ◽  
The Stability

Molecular dynamics simulation is employed to explore the influence of hydrogen adsorption on the stability behavior of graphyne (GY) as a new allotrope of carbon. The strain for the onset of buckling is determined for pristine GY and the results are compared with those for perfect graphene nanoribbons under identical conditions. The results reveal that due to the presence of triple C–C bonds in the GY structure, which are harder to rotate and bend in compression compared to single bonds, the new allotrope is stiffer than graphene during buckling phenomenon. In addition, the effect of hydrogen adsorption on the stability behavior of GY is examined with different H coverage in the range 0–50%. It is concluded that this adsorption promotes a rapid buckling which is attributed to the conversion of the stiff in-plane carbon bonding in the GY structure to the out-of-plane bonding which is weaker and easier to bend in compression. Finally, a critical value of adsorption is found above in which such a trend is not observed.

Combustion Driven by Fragment-based Ab Initio Molecular Dynamics Simulation

2019 ◽  
Author(s):  
Liqun Cao ◽  
Jinzhe Zeng ◽  
Mingyuan Xu ◽  
Chih-Hao Chin ◽  
Tong Zhu ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Ab Initio ◽  
Large Scale ◽  
Methane Combustion ◽  
Combustion Method ◽  
Dynamics Simulation ◽  
Ab Initio Molecular Dynamics ◽  
Computational Time ◽  
Combustion Mechanism ◽  
Daily Lives

Combustion is a kind of important reaction that affects people's daily lives and the development of aerospace. Exploring the reaction mechanism contributes to the understanding of combustion and the more efficient use of fuels. Ab initio quantum mechanical (QM) calculation is precise but limited by its computational time for large-scale systems. In order to carry out reactive molecular dynamics (MD) simulation for combustion accurately and quickly, we develop the MFCC-combustion method in this study, which calculates the interaction between atoms using QM method at the level of MN15/6-31G(d). Each molecule in systems is treated as a fragment, and when the distance between any two atoms in different molecules is greater than 3.5 Å, a new fragment involved two molecules is produced in order to consider the two-body interaction. The deviations of MFCC-combustion from full system calculations are within a few kcal/mol, and the result clearly shows that the calculated energies of the different systems using MFCC-combustion are close to converging after the distance thresholds are larger than 3.5 Å for the two-body QM interactions. The methane combustion was studied with the MFCC-combustion method to explore the combustion mechanism of the methane-oxygen system.

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