Optimal Interaction Energies Research Articles

A molecular dynamics assisted insight on the enhancement of interfacial adhesion of carbon fiber with polypropylene matrix via a combination of surface functionalization and defect laden carbon nanotube coating

The low compatibility of traditional carbon fibers with thermoplastics results in an inferior interfacial interaction. Therefore, it prohibits full exploitation of low-cost thermoplastics like polypropylene in developing high-strength carbon fiber reinforced composites. In the present study, atomistic and mesoscopic molecular dynamics simulations are carried out to postulate enhancement in interfacial shear strength among amine terminated carbon fiber and polypropylene. Pristine and amine functionalized carbon nanotubes are coated to the amine terminated carbon fiber separately. The influence of Stone-Wales and Di-vacancy defects of carbon nanotubes, with their varying defect concentration, is investigated. Besides, maleic anhydride-grafted-styrene ethylene butylene styrene is used as a compatibilizer. Interaction energy among maleic anhydride-grafted-styrene ethylene butylene styrene and amine terminated carbon nanotubes increases with amine weight percentage over carbon nanotube. The highest optimal interaction energy is shown by carbon nanotube functionalized with 6 wt percent amine groups and having 3 Stone-Wales defects, which is ∼41% higher than that with pristine carbon nanotubes. The pull-out coarse-grain simulations of the amine terminated carbon fiber coated with such optimal carbon nanotubes displayed the highest interfacial shear strength of 31.11 MPa, and it was ∼106% higher than the composite reinforced with neat carbon fiber.

Maximal enhancement of nanoscale boiling heat transfer on superhydrophilic surfaces by improving solid-liquid interactions: Insights from molecular dynamics

The dramatic development in electronics results in an increasing cooling challenge. Nucleate pool boiling, as an efficient phase-change heat transfer technology without external energy consumption, is highly promising for sustainable high-heat-flux dissipation. To facilitate the design of boiling surfaces, an explicit understanding of effects of further reinforcements in the solid-liquid interaction on nucleate boiling over superhydrophilic surfaces is urgently desired. Whereas, it is considerably difficult to implement the relevant study and elucidate the underlying mechanism by current experimental approaches. Here, utilizing molecular dynamics simulations, effects of solid-liquid interactions on nucleate boiling over superhydrophilic surfaces are quantitatively illustrated. Our results manifest that, even for superhydrophilic surfaces, the bubble nucleation, growth and critical-heat-flux in nanoscale sense can be still strikingly enhanced with the improvement of solid-liquid interaction. Attractively, an optimal interaction energy coefficient (α = 1.5) for achieving maximal boiling enhancement is obtained in this study. The enhanced mechanism is elaborated by the heat transfer efficiency at the solid-liquid interface and energy barrier for phase-change. Additionally, it is found that conducting separate energy analyses for different liquid layers near the substrate is vital to reveal microscopic mechanisms thoroughly. This study provides significant guidance towards surface design in state-of-the-art thermal management systems.

Super‐resolution image reconstruction using molecular docking

Molecular-docking is an essential tool in the drug designing process, where a small molecule ligand (drug) binds with disease-causing protein molecule to prevent its further activity. Docking process helps in predicting the most appropriate configuration and the optimal interaction energy between the interacting molecules (ligand and protein) to form a stable complex. Based on this idea, a new learning-based single image super-resolution reconstruction (LSI-SRR) method is proposed here. Estimation of a high resolution (HR) patch is achieved by optimising the interaction energy between the input low resolution patch and its corresponding candidate patches appropriately chosen from the training image dataset via Genetic algorithm. Structured-spatiogram based measure; a new and competent similarity criterion is proposed to select potentially efficient training images which encompass better statistical and structural co-relation with the input image. The proposed method is tested on synthetic and real-time images at different magnification factors. Performance analysis of the proposed work is compared with some of the representative state-of-the-art LSI-SRR methods. Experimental results demonstrate that the proposed method produces HR images with enhanced image details, minimal artefacts and most importantly enables an efficient trade-off between the image qualities to speed than the competing methods.

A protein self-assembly model guided by electrostatic and hydrophobic dipole moments.

Protein self-assembling is studied under the light of the Biological Membrane model. To this purpose we define a simplified formulation of hydrophobic interaction energy in analogy with electrostatic energy stored in an electric dipole. Self-assembly is considered to be the result of the balanced influence of electrostatic and hydrophobic interactions, limited by steric hindrance as a consequence of the relative proximity of their components. Our analysis predicts the type of interaction that drives an assembly. We study the growth of both electrostatic and hydrophobic energies stored by a protein system as it self-assembles. Each type of assembly is studied by using two examples, PDBid 2OM3 (hydrophobic) and PDBid 3ZEE (electrostatic). Other systems are presented to show the application of our procedure. We also study the relative orientation of the monomers constituting the first dimer of a protein assembly to check whether their relative position provides the optimal interaction energy (energy minimum). It is shown that the inherent orientation of the dimers corresponds to the optimum energy (energy minimum) of assembly compatible with steric limitations. These results confirm and refine our Biological Membrane model of protein self-assembly valid for all open and closed systems.

Understanding the Enhanced Activity of Pt-Alloys Toward Hydrogen Oxidation Reaction in Alkaline Media

Recent advances in anion exchange membranes (AEMs) and catalysts with greatly improved ORR kinetics are tempered by the two orders of magnitude higher overvoltages for the hydrogen oxidation/evolution reaction (HOR/HER) rates as compared to acidic pH. It has been demonstrated that Pt in conjunction with additional transition metalsm (Pt-M), either alloyed or as an ad-atom exhibit enhanced HOR activity in high pH media compared to pure Pt. However, the mechanistic origin of the activity enhancement induced by the second metal has been under extensive debate and remains unclear. Some researchers propose that the enhanced HOR activity exhibited by Pt-M is attributable to the bifunctional effects whereby optimal interaction energies of adsorption/dissociation of H2 and adsorption of hydroxyl species (OHad) on metal surfaces are achieved;1 whereas others argue that the Pt-H binding energy is the dominant factor determining the HOR activity of Pt-alloys in alkaline media.2 Herein, a series of nanoscale Pt-alloys including PtRu/C, PtNb/C, and PtCo/C with various composition and particle morphology were investigated by rotating disk electrode testing and surface-sensitive in situ x-ray absorption spectroscopy (XAS) method. In an attempt to fully rationalize all the experimental results, we propose a fundamentally novel rendition of the electrochemical double-layer structure wherein the hydroxide-species formed in the compact part of the double-layer, either on an adjacent non-precious alloying metal (-OHad in the Inner Helmholtz Plane of the double-layer) or on the precious metal (-OHad in the Outer Helmholtz Plane of the double-layer), plays an important role in enhancing HOR kinetics at high pH media. A complex relationship, heretofore unknown, exists between electrocatalysis and the electrochemical double-layer structure which will unraveled here in more detail with both theoretical and experimental results. Acknowledgements: The authors gratefully acknowledge the financial support from Arpa-e, US DOE under a grant lead by Proton On-Site, Walingford, CT. Use of the Stanford Synchrotron Radiation Light-source, SLAC National Accelerator Laboratory, is supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Contract No. DE-AC02-76SF00515. Use of Beamline 2-2 at SSRL was partially supported by the National Synchrotron Light Source II, Brookhaven National Laboratory, under U.S. Department of Energy Contract No. DE-SC0012704. Use of the beamline 9-BM in Advanced Photon Source, an Office of Science User Facility operated for the U.S. Department of Energy (DOE) Office of Science by Argonne National Laboratory, was supported by the U.S. DOE under Contract No. DE-AC02-06CH11357. MRCAT operations are supported by the Department of Energy and the MRCAT member institutions. This research used resources of the Advanced Photon Source, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357. References (1) Strmcnik, D.; Uchimura, M.; Wang, C.; Subbaraman, R.; Danilovic, N.; van der, V.; Paulikas, A. P.; Stamenkovic, V. R.; Markovic, N. M. Nat Chem 2013, 5, 300. (2) Durst, J.; Siebel, A.; Simon, C.; Hasche, F.; Herranz, J.; Gasteiger, H. A. Energy & Environmental Science 2014, 7, 2255. Figure 1

How to simulate affinities for host–guest systems lacking binding mode information: application to the liquid chromatographic separation of hexabromocyclododecane stereoisomers

A novel approach for the simulation of host-guest systems by systematically scanning the host molecule's orientations within the guest cavity is presented along with a thermodynamic strategy for determining preferential binding modes and corresponding optimal interaction energies between host and guest molecules. By way of example, the elution order of hexabromocyclododecane stereoisomers from high performance liquid chromatography separation on a permethylated β-cyclcodextrin stationary phase has been computed using classical molecular dynamics simulations with the explicit solvents water and acetonitrile. Comparison of estimated with experimental separation data reveals remarkable squared coefficients of correlation with R(2) = 0.87 and a very high correlation R(LOO2) = 0.72 using the leave-one-out cross-validation method and water as solvent. In particular, the approach presented shapes up as very robust in terms of the evaluated time range under consideration, reflecting well thermodynamic equilibria. These and further observations correlating with experimental results suggest the suitability of the underlying force fields and our multi-mode approach for the estimation of relative binding affinities for host-guest systems with unknown binding modes.

Ab Initio Study of Solvent Effects on Rate of 1,3-Dipolar Cycloadditions of Benzonitrile Oxide and Various Dipolarophiles

Ab initio molecular orbital calculations have been used to investigate the structures and the transition states of 1,3-dipolar cycloadditions between benzonitrile oxide with ethylene, cyclopentene, acrylonitrile and tetracyanoethylene in heptane and water: calculations reveal enhanced hydrogen bonding of a water molecule to the transition states for the cycloaddition 1,3-dipolar of reaction of benzonitrile oxide with cyclopentene, the optimal interaction energies being 0.7 kcal/mol more favourable for hydrogen bonding to the oxygen atom in the transition states than for the reactants.

Enhanced Hydrogen Bonding of Water to Diels-Alder Transition States. Ab Initio Evidence

Ab initio molecular orbital calculations reveal enhanced hydrogen bonding of a water molecule to the transition states for the Diels-Alder reactions of cyclopentadiene with methyl vinyl ketone (MVK) and acrylonitrile. The optimal interaction energies are found to be 1.5-2.0 kcal/mol more favorable for hydrogen bonding to the oxygen or nitrogen in the transition states than for the dienophiles. This support the assertion from a prior simulation study that the observed rate accelerations for Diels-Alder reactions in aqueous solution arise from this hydrogen-bonding effect in addition to a relatively constant hydrophobic term

XC and HFD-B potential energy curves for Xe-Xe and related physical properties

The XC (exchange-Coulomb) and the HFD (Hartree-Fock-dispersion) potential models for the interaction of two closed shell atoms are reviewed briefly. It is shown that while the original XC potential model (XC-1) does not lead to an optimal potential for the Xe-Xe interaction, two variants, XC-2 and XC-3, do lead to optimal interaction energies for this interaction as a function of the interatomic distance R. The three XC potentials, two HFD-B type potentials, and three other literature potentials are compared with respect to their predictive ability for various microscopic and (dilute gas) macroscopic properties of Xe. One of the HFD-B potentials, developed here, is a modification of the original HFD-B potential for Xe-Xe and this HFD-B2 potential, and the XC-3 potential, are apparently the most reliable representations of the two-body Xe-Xe interaction available. The two-bodypotentials are also used to help discuss the problems associated with the representation of many-body interactions in rare gas systems.

Energy Profile of Cs+in Gramicidin A in the Presence of Water. Problem of the Ion Selectivity of the Channel

The effect of water present at the mouth and inside the channel of Gramicidin A on the energy profile calculated for a caesium ion is determined. The total optimal interaction energy computed for the system GA-Cs+-(22 waters) leads to an energy profile characterized by a deep minimum at 11 A followed by an entrance energy barrier of 7 Kcal/mol expanding until 9 A from the center. After this point, a second minimum less deep than the previous one is observed, itself followed by a central barrier. The shape of the profile at the entrance is governed by the balance between the progressive desolvation process of the ion and the increase of favorable hydrogen bond interactions implying both the water molecules and GA. The comparison of this energy profile with that obtained in vacuo shows that the presence of water molecules does not modify the pathway of the ion which, owing to its size, is constrained essentially to remain on the channel axis. The comparison Na+ versus Cs+ indicates that although the phenomena involved are globally the same, differences between the two profiles appear due firstly to the difference in the affinity of the two ions for water and secondly to their respective size. This last difference implies that the number of water molecules present in the interior of the channel during the cation progression is reduced roughly by one in the case of caesium. The desolvation barrier computed for Cs+ is half the corresponding value for Na+, a result in agreement with the observed selectivity.