scholarly journals Molecular Dynamics Simulation on Behaviors of Water Nanodroplets Impinging on Moving Surfaces

Nanomaterials ◽  
2022 ◽  
Vol 12 (2) ◽  
pp. 247
Author(s):  
Hao Zhang ◽  
Ling Pan ◽  
Xuqing Xie
Keyword(s):  
Molecular Dynamics ◽  
Md Simulation ◽  
Solid Surfaces ◽  
Dynamics Simulation ◽  
Copper Surfaces ◽  
Dynamical Characteristics ◽  
Translation Velocity ◽  
Dynamical Behaviors ◽  
Short Period ◽  
Surface Translation

Droplets impinging on solid surfaces is a common phenomenon. However, the motion of surfaces remarkably influences the dynamical behaviors of droplets, and related research is scarce. Dynamical behaviors of water nanodroplets impinging on translation and vibrating solid copper surfaces were investigated via molecular dynamics (MD) simulation. The dynamical characteristics of water nanodroplets with various Weber numbers were studied at four translation velocities, four vibration amplitudes, and five vibration periods of the surface. The results show that when water nanodroplets impinge on translation surfaces, water molecules not only move along the surfaces but also rotate around the centroid of the water nanodroplet at the relative sliding stage. Water nanodroplets spread twice in the direction perpendicular to the relative sliding under a higher surface translation velocity. Additionally, a formula for water nanodroplets velocity in the translation direction was developed. Water nanodroplets with a larger Weber number experience a heavier friction force. For cases wherein water nanodroplets impinge on vibration surfaces, the increase in amplitudes impedes the spread of water nanodroplets, while the vibration periods promote it. Moreover, the short-period vibration makes water nanodroplets bounce off the surface.

scholarly journals Movement pattern of an ellipsoidal nanoparticle confined between solid surfaces: Theoretical model and molecular dynamics simulation

Friction ◽  
2020 ◽  
Author(s):  
Junqin Shi ◽  
Xiangzheng Zhu ◽  
Kun Sun ◽  
Liang Fang
Keyword(s):  
Molecular Dynamics ◽  
Theoretical Model ◽  
Molecular Dynamics Simulation ◽  
Movement Pattern ◽  
Axial Ratio ◽  
Surface Damage ◽  
Solid Surfaces ◽  
Dynamics Simulation ◽  
Copper Surfaces ◽  
Good Agreement

Abstract The movement pattern of ellipsoidal nanoparticles confined between copper surfaces was examined using a theoretical model and molecular dynamics simulation. Initially, we developed a theoretical model of movement patterns for hard ellipsoidal nanoparticles. Subsequently, the simulation indicated that there are critical values for increasing the axial ratio, driving velocity of the contact surface, and lowering normal loads (i.e., 0.83, 15 m/s, and 100 nN under the respective conditions), which in turn change the movement pattern of nanoparticles from sliding to rolling. Based on the comparison between the ratio of arm of force (e/h) and coefficient of friction (μ) the theoretical model was in good agreement with the simulations and accurately predicted the movement pattern of ellipsoidal nanoparticles. The sliding of the ellipsoidal nanoparticles led to severe surface damage. However, rolling separated the contact surfaces and thereby reduced friction and wear.

scholarly journals Molecular dynamics simulation of sI methane hydrate under compression and tension

2020 ◽  
Vol 18 (1) ◽  
pp. 69-76
Author(s):  
Qiang Wang ◽  
Qizhong Tang ◽  
Sen Tian
Keyword(s):  
Molecular Dynamics ◽  
Methane Hydrate ◽  
Fracture Process ◽  
Md Simulation ◽  
Maximum Stress ◽  
Dynamics Simulation ◽  
Tensile Fracture ◽  
Maximum Compressive Stress ◽  
Motion State ◽  
Stress States

AbstractMolecular dynamics (MD) analysis of methane hydrate is important for the application of methane hydrate technology. This study investigated the microstructure changes of sI methane hydrate and the laws of stress–strain evolution under the condition of compression and tension by using MD simulation. This study further explored the mechanical property and stability of sI methane hydrate under different stress states. Results showed that tensile and compressive failures produced an obvious size effect under a certain condition. At low temperature and high pressure, most of the clathrate hydrate maintained a stable structure in the tensile fracture process, during which only a small amount of unstable methane broke the structure, thereby, presenting a free-motion state. The methane hydrate cracked when the system reached the maximum stress in the loading process, in which the maximum compressive stress is larger than the tensile stress under the same experimental condition. This study provides a basis for understanding the microscopic stress characteristics of methane hydrate.

Molecular Dynamics Simulation of AFM-Based Nanomachining Processes

2011 ◽  
Author(s):  
Rapeepan Promyoo ◽  
Hazim El-Mounayri ◽  
Kody Varahramyan ◽  
Ashlie Martini
Keyword(s):  
Molecular Dynamics ◽  
Friction Coefficient ◽  
Md Simulation ◽  
Computational Models ◽  
Dynamics Simulation ◽  
Radius Of Curvature ◽  
Force Microscopy ◽  
Indentation Force ◽  
Atomic Force ◽  
Development And Validation

Recently, atomic force microscopy (AFM) has been widely used for nanomachining and fabrication of micro/ nanodevices. This paper describes the development and validation of computational models for AFM-based nanomachining (nanoindentation and nanoscratching). The Molecular Dynamics (MD) technique is used to model and simulate mechanical indentation and scratching at the nanoscale in the case of gold and silicon. The simulation allows for the prediction of indentation forces and the friction force at the interface between an indenter and a substrate. The effects of tip curvature and speed on indentation force and friction coefficient are investigated. The material deformation and indentation geometry are extracted based on the final locations of atoms, which are displaced by the rigid tool. In addition to modeling, an AFM was used to conduct actual indentation at the nanoscale, and provide measurements to validate the predictions from the MD simulation. The AFM provides resolution on nanometer (lateral) and angstrom (vertical) scales. A three-sided pyramid indenter (with a radius of curvature ∼ 50 nm) is raster scanned on top of the surface and in contact with it. It can be observed from the MD simulation results that the indentation force increases as the depth of indentation increases, but decreases as the scratching speed increases. On the other hand, the friction coefficient is found to be independent of scratching speed.

MOLECULAR DYNAMICS SIMULATION OF PULSED LASER ABLATION

2011 ◽  
Vol 25 (04) ◽  
pp. 543-550 ◽  
Author(s):  
XIU-FANG GONG ◽  
GONG-XIAN YANG ◽  
PENG LI ◽  
YIN WANG ◽  
XI-JING NING
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulation ◽  
Pulsed Laser ◽  
Pulsed Laser Ablation ◽  
Laser Pulses ◽  
Solid Surfaces ◽  
Dynamics Simulation ◽  
Angular Distributions ◽  
Adiabatic Expansion ◽  
Expansion Model

We have developed a simplified molecular-dynamical model for simulating ablation of solid surfaces by laser pulses, and specifically investigated expansion of Cu cloud in vacuum vaporized on the surface, showing that the angular distributions of the plume depend on the shape of the laser spot on the surface. In particular, experimentally observed flipover effects have been obtained, and an adiabatic constant determined from our simulations via an adiabatic expansion model agrees well with previous measurements.

Molecular dynamics simulation of homogeneous nucleation of supersaturated potassium chloride (KCl) in aqueous solutions

CrystEngComm ◽  
2019 ◽  
Vol 21 (48) ◽  
pp. 7507-7518 ◽  
Author(s):  
Soroush Ahmadi ◽  
Yuanyi Wu ◽  
Sohrab Rohani
Keyword(s):  
Molecular Dynamics ◽  
Aqueous Solution ◽  
Molecular Dynamics Simulation ◽  
Aqueous Solutions ◽  
Potassium Chloride ◽  
Homogeneous Nucleation ◽  
Md Simulation ◽  
Crystal Nucleation ◽  
Dynamics Simulation

Molecular dynamics (MD) simulation is used to investigate the mechanism of crystal nucleation of potassium chloride (KCl) in a supersaturated aqueous solution at 293 K and 1 atm.

scholarly journals Material Analysis and Molecular Dynamics Simulation for Cavitation Erosion and Corrosion Suppression in Water Hydraulic Valves

Materials ◽  
2020 ◽  
Vol 13 (2) ◽  
pp. 453 ◽  
Author(s):  
Masoud Kamoleka Mlela ◽  
He Xu ◽  
Feng Sun ◽  
Haihang Wang ◽  
Gabriel Donald Madenge
Keyword(s):  
Molecular Dynamics ◽  
Md Simulation ◽  
Essential Role ◽  
Corrosion Inhibitors ◽  
Cavitation Erosion ◽  
Dynamics Simulation ◽  
Preference Ranking ◽  
Water Hydraulics ◽  
The Impact ◽  
Hydraulic Valves

In the milestone of straggling to make water hydraulics more advantageous, the choice of coating polymer for water hydraulics valves plays an essential role in alleviating the impact of cavitation erosion and corrosion, and this is a critical task for designers. Fulfilling the appropriate selection, we conflicted properties that are vital for erosion and corrosion inhibitors, as well as the tribology in the sense of coefficient of friction. This article aimed to choose the best alternative polymer for coating on the selected substrate, that is, Cr2O3, Al2O3, Ti2O3. By applying PROMETHEE (Preference Ranking Organization Method for Enrichment Evaluations), the best polymer obtained with an analyzed performance attribute is Polytetrafluoroethylene (PTFE) that comes up with higher outranking (0.5932052). A Molecular Dynamics (MD) simulation was conducted to identify the stronger bonding with the regards of the better cleave plane between Polytetrafluoroethylene (PTFE) and the selected substrate. Polytetrafluoroethylene (PTFE)/Al2O3 cleaved in (010) plane was observed to be the strongest bond in terms of binding energy (3188 kJ/mol) suitable for further studies.

scholarly journals Molecular Dynamics Simulation and Kinetic Study of Fluoride Binding to V21C/V66C Myoglobin with a Cytoglobin-like Disulfide Bond

2020 ◽  
Vol 21 (7) ◽  
pp. 2512
Author(s):  
Lu-Lu Yin ◽  
Jia-Kun Xu ◽  
Xiao-Juan Wang ◽  
Shu-Qin Gao ◽  
Ying-Wu Lin
Keyword(s):  
Molecular Dynamics ◽  
Disulfide Bond ◽  
Rational Design ◽  
Double Mutant ◽  
Md Simulation ◽  
Experimental Studies ◽  
Heme Iron ◽  
Dynamics Simulation ◽  
Fluoride Ion ◽  
Artificial Proteins

Protein design is able to create artificial proteins with advanced functions, and computer simulation plays a key role in guiding the rational design. In the absence of structural evidence for cytoglobin (Cgb) with an intramolecular disulfide bond, we recently designed a de novo disulfide bond in myoglobin (Mb) based on structural alignment (i.e., V21C/V66C Mb double mutant). To provide deep insight into the regulation role of the Cys21-Cys66 disulfide bond, we herein perform molecular dynamics (MD) simulation of the fluoride–protein complex by using a fluoride ion as a probe, which reveals detailed interactions of the fluoride ion in the heme distal pocket, involving both the distal His64 and water molecules. Moreover, we determined the kinetic parameters of fluoride binding to the double mutant. The results agree with the MD simulation and show that the formation of the Cys21-Cys66 disulfide bond facilitates both fluoride binding to and dissociating from the heme iron. Therefore, the combination of theoretical and experimental studies provides valuable information for understanding the structure and function of heme proteins, as regulated by a disulfide bond. This study is thus able to guide the rational design of artificial proteins with tunable functions in the future.

Molecular Dynamics Simulation on Micro Couette Flow of Nanofluids

2011 ◽  
Vol 284-286 ◽  
pp. 658-661
Author(s):  
Wen Zheng Cui ◽  
Min Li Bai ◽  
Ji Zu Lv ◽  
Xiao Jie Li
Keyword(s):  
Heat Transfer ◽  
Molecular Dynamics ◽  
Heat Transfer Enhancement ◽  
Couette Flow ◽  
Liquid Argon ◽  
Visual Observation ◽  
Solid Surfaces ◽  
Dynamics Simulation ◽  
Transfer Enhancement ◽  
Base Liquid

This research applied molecular dynamics method to micro Couette flow of nanofluids, in order to examine the absorption layer near solid surfaces, and propose mechanisms of heat transfer enhancement due to flow. The model of nanofluids consisted of 4 nm Cu nanoparticles and liquid argon as base liquid, Lennard-Jones potential function was adopted to deal with the interactions between atoms. Through visual observation and analysis, it was found that the even-distributed liquid argon atoms near solid surfaces could be seemed as a reform to base liquid and had contributed to heat transfer enhancement. In the process of Couette flow, nanoparticles were rotating and vibrating besides moving translationally. The micro-motions of nanoparticles could disturb the continuity of fluid and strengthen partial flow nearby nanoparticles, and enhance heat transfer in nanofluids.

scholarly journals Preparation and Molecular Dynamics Simulation of RDX/MUF Nanocomposite Energetic Microspheres with Reduced Sensitivity

Processes ◽  
2019 ◽  
Vol 7 (10) ◽  
pp. 692
Author(s):  
Jia ◽  
Hu ◽  
Xu ◽  
Liu ◽  
Ma ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Binding Energy ◽  
Emulsion Polymerization ◽  
Md Simulation ◽  
Urea Formaldehyde ◽  
Urea Formaldehyde Resin ◽  
Experimental Results ◽  
Dynamics Simulation ◽  
Formaldehyde Resin ◽  
Process Conditions

In order to improve the general problem of irregular coating morphology and low mechanical strength of the coating layer in existing coating desensitization technology, nano-cyclotrimethylene trinitramine/melamine-urea-formaldehyde (RDX/MUF) composite energetic microspheres were prepared by an improved emulsion polymerization, taking the MUF as the binder and RDX as the main explosive. In order to judge whether RDX/MUF possessed good stability, the combination of differential scanning calorimetry (DSC) and molecular dynamics (MD) simulation was used to determine the level of binding binding energy between urea-formaldehyde resin binder (UF) and RDX. In addition, to investigate the optimal reaction temperature for the preparation of MUF/RDX, the binding energy between UF and RDX at different temperatures was simulated. And then the morphology and thermal properties of the as-prepared composite energetic microspheres were analyzed by scanning electron microscopy (SEM) and DSC, the impact sensitivity and friction sensitivity of the resultant samples were tested as well. Moreover, RDX/MUF with the same MUF content was prepared by physical mixing for comparative analysis. MD simulation demonstrated that UF and RDX possessed good binding ability at 298 K. The DSC method indicatec that UF and RDX had good compatibility, and the comprehensive performance of RDX after coating was not significantly deteriorated; The optimal binding temperature between UF and RDX was 60~70 °C which is consistent with the experimental results. The experimental results showed that the optimum process conditions for the preparation of RDX/MUF could be listed as follows: the temperature for preparing RDX/MUF composite energetic microspheres by the improved emulsion polymerization was 70 °C the optimal pH value of the urea-formaldehyde resin prepolymer solution was 3, and the optimal melamine-urea molar ratio was 0.4.

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