Anisotropic Interfacial Force Field for Interfaces of Water with Hexagonal Boron Nitride

This study introduces an anisotropic interfacial potential that provides an accurate description of the van der Waals (vdW) interactions between water and hexagonal boron nitride (h-BN) at their interface. Benchmarked against the strongly constrained and appropriately normed (SCAN) functional, the developed force field demonstrates remarkable consistency with reference data sets, including binding energy curves and sliding potential energy surfaces for various configurations involving a water molecule adsorbed atop the h-BN surface. These findings highlight the significant improvement achieved by the developed force field in empirically describing the anisotropic vdW interactions of the water/h-BN heterointerfaces. Utilizing this anisotropic force field, molecular dynamics simulations demonstrate that atomically-flat pristine h-BN exhibits inherent hydrophobicity. However, when atomic-step surface roughness is introduced, the wettability of h-BN undergoes a significant change, leading to a hydrophilic nature. The calculated water contact angle (WCA) for the roughened h-BN surface is approximately 64{\deg}, which closely aligns with experimental WCA values ranging from 52{\deg} to 67{\deg}. These findings indicate the high probability of the presence of atomic steps on the surfaces of experimental h-BN samples, emphasizing the need for further experimental verification. The development of the anisotropic interfacial force field for accurately describing interactions at the water/h-BN heterointerfaces is a significant advancement in accurately simulating the wettability of two-dimensional (2D) materials, offering a reliable tool for studying the dynamic and transport properties of water at these interfaces, with implications for materials science and nanotechnology.Comment: 22 pages, 5 figure

A New Semantic Approach on Yelp Review-star Rating Classification

This paper introduces a new semantic approach for yelp review star rating prediction. Our approach extracts feature vectors from user reviews to develop star prediction models. User review text contains detailed information about reviewers’ experience, and directly reflects reviewer’s satisfaction level. Our approach can extract sentimental words from review text, and convert these information into different feature vectors. Reviewer’s personal preference may be extremely skewed from each other, to eliminate these effects, we use belief propagation methods to calculate review star probability distributions for different types of reviewers. Our machine learning algorithm predicts review star based on reviewers’ preference and voting habit. We extract different feature vectors and apply them to several machine learning algorithms. To evaluate all the 2.2 million user reviews, we build spark system on three laptops. To achieve a better prediction accuracy, we perform sentiment analysis of reviews in terms of the number of positive, negative, negation words, and apply belief propagation methods to get rid of personal preference effects. Our system can evaluate 2.2 million data entries in less than two minutes and achieve an accuracy of 55%

Bulk β-Te to few layered β-tellurenes: indirect to direct band-Gap transitions showing semiconducting property

Herein we report a prediction of a highly kinetic stable layered structure of tellurium (namely, bulk beta-Te), which is similar to these layered bulk materials such as graphite, black phosphorus, and gray arsenic. Bulk beta-Te turns out to be a semiconductor that has a band gap of 0.325 eV (HSE06: 0.605 eV), based on first-principles calculations. Moreover, the single-layer form of the bulk beta-Te, called beta-tellurene, is predicted to have a high stability. When the bulk beta-Te is thinned to one atomic layer, an indirect semiconductor of band gap is changed to 1.265 eV (HSE06: 1.932 eV) with a very high kinetic stability. Interestingly, an increase of the number of the beta-tellurene layers from one to three is accompanied by a shift from an indirect to direct band gap. Furthermore, the effective carrier masses, the optical properties and phonon modes of few-layer beta-tellurenes are characterized. Few-layer beta-tellurenes strongly absorb the ultraviolet and blue-violet visible lights. The dramatic changes in the electronic structure and excellent photo absorptivities are expected to pave the way for high speed ultrathin transistors, as well as optoelectronic devices working in the UV or blue-green visible regions. © Copyright 2017 IOP Publishing Terms & conditions Disclaime

Superflexible C-68-graphyne as a promising anode material for lithium-ion batteries

The breakthrough in the synthesis of graphyne, graphdiyne and graph-4-yne stimulates interest in studying new members of the graphyne family for promising applications. In this work, a new allotrope of graphyne with excellent stability and an ultrahigh specific surface area of 4255 m(2) g(-1), named C-68-graphyne, is predicted by first principles calculations. Mechanical tests reveal that C-68-graphyne exhibits much smaller in-plane tensile stiffness (similar to 50.5 N m(-1)) and out-of-plane bending stiffness (similar to 0.5 eV) than graphene (in-plane tensile stiffness 350 N m(-1) and out-of-plane bending stiffness 1.4 eV), suggesting C-68-graphyne as a superflexible material. Meanwhile, our results show that monolayer C-68-graphyne is a semiconductor with a direct band gap of 1.0 eV, which can be tuned by strain-engineering, and the calculated carrier mobility is as high as 1.81 x 10(5) to 2.97 x 10(5) cm(2) V-1 s(-1) at 300 K. Finally, the potential application of C-68-graphyne as an anode material for lithium-ion batteries is explored and predicted. The calculated results show highly efficient charge transfer from the adsorbed Li ions to C-68-graphyne yet a low diffusion barrier for Li ions in C-68-graphyne for fast charge/discharge rates. The storage capacities for Li in monolayer and bilayer C-68-graphyne are calculated to be as high as 1954 and 1675 mA h g(-1), respectively. These features make C-68-graphyne a promising anode material for lithium-ion batteries with excellent energy storage capacities as well as fast charge/discharge rates

Registry-Dependent Potential for Interfaces of Water with Graphene

An anisotropic interlayer potential that can accurately describe the van der Waals interaction of the water–graphene interface is presented. The force field is benchmarked against the many-body dispersion-corrected density functional theory. The parametrization of the interlayer potential demonstrates a satisfactory agreement with the reference data set of binding energy curves and sliding potential energy surfaces for various configurations of a water molecule deposited on monolayer graphene, indicating that the developed force field significantly enhances the accuracy in the empirical description of water–graphene interfacial interactions. The water contact angles of monolayer and multilayer graphene extracted from molecular dynamics simulations based on this force field are close to the experimental measurements and predict the hydrophilic nature of graphene. The theoretical approach proposed in this work can be easily adapted to heterointerfaces formed with water and other two-dimensional materials, providing a reliable and versatile platform for studying the wetting properties of these materials

Highly Stable Single-Phase FeCoNiMnX (X = Cr, Mo, W) High-Entropy Alloy Catalysts with Submicrometer Size for Efficient Oxygen Evolution

The activity and stability of oxygen evolution reaction (OER) catalysts are often trade-offs and are both size-dependent. Theoretical calculations have predicted that some noble-metal-free high-entropy alloys (HEAs) are promising OER catalysts. However, their catalytic properties have not been proven because of the lack of a facile method to synthesize small-sized homogeneous HEA particles. Here, submicrometer-sized single-phase FeCoNiMnW HEA particles were prepared by electrochemical metallization in 900 s (at 900 °C). FeCoNiMnW shows the best OER activity (η = 355 mV at 500 mA cm–2) and durability of the three HEAs because the large total density of states of FeCoNiMnW accelerates the electrons’ transport speed for OER. More importantly, the single-phase FeCoNiMnW continuously operated for 50 days at 500 mA cm–2 with an almost unchanged overpotential. Overall, this work offers a rapid and simple method to prepare various effective and long-lasting single-phase HEA catalysts with controllable sizes and enhanced OER performances

Chemical inhomogeneity–induced profuse nanotwinning and phase transformation in AuCu nanowires

Abstract Nanosized metals usually exhibit ultrahigh strength but suffer from low homogeneous plasticity. The origin of a strength–ductility trade-off has been well studied for pure metals, but not for random solid solution (RSS) alloys. How RSS alloys accommodate plasticity and whether they can achieve synergy between high strength and superplasticity has remained unresolved. Here, we show that face-centered cubic (FCC) RSS AuCu alloy nanowires (NWs) exhibit superplasticity of ~260% and ultrahigh strength of ~6 GPa, overcoming the trade-off between strength and ductility. These excellent properties originate from profuse hexagonal close-packed (HCP) phase generation (2H and 4H phases), recurrence of reversible FCC-HCP phase transition, and zigzag-like nanotwin generation, which has rarely been reported before. Such a mechanism stems from the inherent chemical inhomogeneity, which leads to widely distributed and overlapping energy barriers for the concurrent activation of multiple plasticity mechanisms. This naturally implies a similar deformation behavior for other highly concentrated solid-solution alloys with multiple principal elements, such as high/medium-entropy alloys. Our findings shed light on the effect of chemical inhomogeneity on the plastic deformation mechanism of solid-solution alloys