Papers by Keyword: Molecular Dynamic Simulation

Abstract: Succinic acid is a potential co-former to produce co-crystal, thus an understanding of the dissolution behaviour of succinic acid crystal is crucial for designing the co-crystal. In this works, α-succinic acid was chosen as a model compound for this study regardless its attractive crystal chemistry and its diverse surface properties. The aims of this study are to analyse the morphology of succinic acid crystal (form A) and to analyse the dissolution behaviour of succinic acid crystal (form A) in the ethanol solution using molecular dynamic simulation. Prediction of form A succinic acid morphology were conducted with different combination of charge set and potential function i.e ESP and CVFF which produces hexagonal needle-like shape morphology and shows good agreement with the experimental crystal shape. Dissolution of α-succinic acid in ethanol solvent was investigated using dynamic simulation. Visual observation and mobility assessment shows that the molecules at the edge of the crystal tends to dissolve faster compared to the molecules at other position on the facet.

Abstract: Protein encapsulated gold nanoclusters has attracted great attention for their excellent fluorescent properties and potential biomedical applications. Glucose Binding Protein (GBP) has a high sensitivity and selectivity to glucose binding that makes them ideal for biosensor development. It is anticipated that GBP encapsulated gold nanoclusters could be a promising glucose sensor. Here we investigated the growth of gold nanoclusters in GBP using Molecular Dynamics (MD) simulation. To facilitation the nucleation of gold nanoclusters at specific sites, cysteine mutations were introduced in GBP. It is found that the nucleation site of gold nanoclusters inside mutant GBP are different from those in native GBP. Gold nanoclusters were formed near the mutated cysteine and tyrosine residues. Glucose remained in the binding site of a mutant GBP with gold nanoclusters although no conformational change was observed in MD simulation, similar to a native GBP. This work suggests the possibility of growing gold nanoclusters in the designed site within GBP and a new glucose sensor based on mutated GBP protected gold nanoclusters.

Abstract: Three-dimensional depth of field microscope (3-D FM), scanning electronic microscope (SEM) and molecular dynamic simulation (MD) were used to evaluate the surface morphology, behaviors and failure mechanisms of mortar and fine aggregate mixture (FAM). The effects of ultraviolet (UV) light and moisture for FAM, the interfacial behaviors of bitumen-aggregate were investigated. Results showed that in the pure mortar, the UV-ageing could increase the adhesion between the bitumen and fine aggregates, and the cohesion failure was dominant after UV-ageing. Due to the lower air voids in the pure mortar, the moisture did not cause the adhesion failure. The molecular dynamic simulation implied that UV ageing and moisture-treatment could reduce the interfacial energy, and the aromatic and asphaltene played a great role in the adhesion between bitumen and aggregate.

Abstract: With honeycomb lattice of sp² hybridized carbon atoms, graphene has demonstrated excellent electrical and mechanical properties. One of its promising applications is to fabricate graphene-ceramic composite to improve the mechanical properties. In order to quantify the strength between graphene-ZrB₂ interactions, molecular dynamic method was utilized to simulate typical interface of graphene/ZrB₂ ceramic structure. Berendsen method was used to control the temperature and pressure during the whole simulation process. Universal potential function was employed to simulate the force filed between graphene and ZrB₂ structure. The binding structures of graphene/ZrB₂ (0001) interface were analyzed in detail and the bonding energy of the interface was calculated. The influence of numbers of graphene layer and sandwich structures on the bonding energy of interface is discussed. The study helped to understand the influence of graphene on mechanical properties of ZrB₂ ceramic.

Abstract: The compatibilities of polymer blends, Polypropylene (PP) and Polyamide12(PA12) with the quantity ratio 10/90, was simulated by Molecular Dynamics (MD) and Mesoscopic Dynamic simulation (MesoDyn) simulations. Cohesive energy density (CED) and solubility parameters (δ) of pure substances and PP/PA12 blends were got by MD simulations. Flory-Huggins parameter was calculated based on CED values. The mesoscale simulation was related to the molecular simulation through Flory-Huggins parameter. Free energy density and the density profiles were got through MesoDyn simulation. Results showed that solubility parameter difference (Δδ) of PP/PA12 is 4.092 and free energy density value is 0.17 in the equivalent system. And phase separation behavior was observed in the density profiles. All these indicates that PP and PA12 is not miscible which is the same as the experiment results.

Abstract: The molecular dynamics simulation studies on the microstructure evolution properties of amorphous Ca₇Mg₃ alloy during the isothermal annealing have been performed. The simulated structure factor S(q) of Ca₇Mg₃ is well agreed with the experimental data. Results indicate that the icosahedron structure plays dominate role in the structure transformation, and the smaller Mg atoms are much more probable to be the central atoms of the basic clusters of icosahedron.

Abstract: The molecular dynamics simulation studies on the microstructure evolution properties of liquid Ca-Mg alloys during the rapid solidifications have been performed. The simulated structure factor S(q) of Ca₇Mg₃ is well agreed with the experimental data. Results indicate that the glass transition temperatures of CaMg₂ and Ca₇Mg₃ are 590 K and 550 K respectively with the cooling rate of 1×10¹² K/s. It also found that icosahedron is much easier to form in CaMg₂ system, and Ca-Mg alloys with more Mg content indicate higher glass forming ability.

Abstract: In this paper, we have developed an empirical formula describing the equation of state of argon fluid using cluster expansion technique and commonly used force parameters. To test the reliability of the formula, we have further simulated the equation of state for argon at corresponding states employing molecular dynamic method. The comparisons have shown that the empirical formula gives much better prediction than that from the simple form equation of ideal gases and the inclusion of the third virial terms in expansions is prominently important.

Abstract: This paper briefly reviews the overseas and domestic research status of the mechanics of hetero film-substrate interface based on molecular dynamics simulation, on this basis building the accurate model of diamond coatings/WC interface and executing the molecular dynamic simulation, exactly measuring the adhesive strength of the diamond coatings/WC interface, finally exploring the influence of interface scales on the adhesive strength of the diamond coatings/WC interface and verifying the feasibility of studying the microscopic structure by molecular dynamics simulation to characterize the mechanical properties of macrostructure, which has important significance for optimizing deposition process of diamond coatings to improve the adhesive strength of the interface.

Abstract: Recently, there were many accident of small dam break of reservoir in China, which reflects a problem in construction and management of small reservoir. By studying over 306 reservoirs which have been reinforced, the main problems to the safety operation of reservoir were concluded. The main 17 problems and 10 questions were discussed in this paper and the answers and suggestions are also made.