Kinetic Monte Carlo simulations on electroforming in nanomanipulated conductive bridge random access memory devices.

Conductive bridge random access memory (CBRAM) devices exhibit great potential as the next-generation nonvolatile memory devices. However, they suffer from two major disadvantages, namely relatively high power consumption and large cycle-to-cycle and device-to-device variations, which hinder their more extensive commercialization. To learn how to enhance their device performance, kinetic Monte Carlo (KMC) simulations were employed to illustrate the variation of electroforming processes in nanomanipulated CBRAM devices by introducing an ion-blocking layer with scalable nanopores and tuning the microstructures of dielectric layers.

Computational Study on Interlocked-Ferroelectricity-Contributed High-Performance Memristors Based on Two-Dimensional van der Waals Ferroelectric Semiconductors.

In order to realize the prevailing artificial intelligence technology, memristor-implemented in-memory or neuromorphic computing is highly expected to break the bottleneck of von Neumann computers. Although high-performance memristors have been vigorously developed in labs or in industry, systematic computational investigations on memristors are seldom. Hence, it is urgent to provide theoretical or computational support for the exploration of memristor operating mechanisms or the screening of memristor materials.

Field-Induced Antiferroelectric-Ferroelectric Transformation in Organometallic Perovskite Displaying Giant Negative Electrocaloric Effect.

Antiferroelectric materials with an electrocaloric effect (ECE) have been developed as promising candidates for solid-state refrigeration. Despite the great advances in positive ECE, reports on negative ECE remain quite scarce because of its elusive physical mechanism. Here, a giant negative ECE (maximum Δ ∼ -33.

Computational Study on Filament Growth Dynamics in Microstructure-Controlled Storage Media of Resistive Switching Memories.

The filament growth processes, crucial to the performance of nanodevices like resistive switching memories, have been widely investigated to realize the device optimization. With the combination of kinetic Monte Carlo (KMC) simulations and the restrictive percolation model, three different growth modes in electrochemical metallization (ECM) cells were dynamically reproduced, and an important parameter, the relative nucleation distance, was theoretically defined to measure different growth modes quantitatively; hence their transition can be well described. In our KMC simulations, the inhomogeneity of storage medium is realized through introducing evolutionary void versus non-void sites within it to mimic the real nucleation during filament growth.

High-density electron transfer in Ni-metal-organic framework@FeNi-layered double hydroxide for efficient electrocatalytic oxygen evolution.

The electrochemical oxygen evolution reaction is a bottleneck reaction in hydrolysis and electrolysis because the four-step electron transfer leads to slow reaction kinetics and large overpotentials. This situation can be improved by fast charge transfer by optimizing the interfacial electronic structure and enhancing polarization. Herein, a unique metal (Ni) organic (diphenylalanine, DPA) framework Ni(DPA) (Ni-MOF) with tunable polarization is designed to bond with FeNi-LDH (layered double hydroxides) nanoflakes.

Electrochemical Resistive Switching in Nanoporous Hybrid Films by One-Step Molecular Layer Deposition.

An organic-inorganic hybrid resistive random-access memory based on a nanoporous zinc-based hydroquinone (Zn-HQ) thin film has been constructed with a Pt/Zn-HQ/Ag sandwich structure. The porous Zn-HQ functional layer was directly fabricated by a one-step molecular layer deposition. These Pt/Zn-HQ/Ag devices show a typical electroforming-free bipolar resistive switching characteristic with lower operation voltages and higher on/off ratio above 10.

Circular polarized light-dependent anomalous photovoltaic effect from achiral hybrid perovskites.

Circular polarized light-dependent anomalous bulk photovoltaic effect - a steady anomalous photovoltaic current can be manipulated by changing the light helicity, is an increasingly interesting topic in contexts ranging from physics to chemistry. Herein, circular polarized light-dependent anomalous bulk photovoltaic effect is presented in achiral hybrid perovskites, (4-AMP)BiI (ABI, 4-AMP is 4-(aminomethyl)piperidinium), breaking conventional realization that it can only happen in chiral species. Achiral hybrid perovskite ABI crystallizes in chiroptical-active asymmetric point group m (C), showing an anomalous bulk photovoltaic effect with giant photovoltage of 25 V, as well as strong circular polarized light - sensitive properties.

Mitophagy and mitochondrial dynamics in type 2 diabetes mellitus treatment.

The prevalence of type 2 diabetes is associated with inflammatory bowels diseases, nonalcoholic steatohepatitis and even a spectrum of cancer such as colon cancer and liver cancer, resulting in a substantial healthcare burden on our society. Autophagy is a key regulator in metabolic homeostasis such as lipid metabolism, energy management and the balance of cellular mineral substances. Mitophagy is selective autophagy for clearing the damaged mitochondria and dysfunctional mitochondria.

Antioxidant, Cytotoxic and Antidiabetic Activities of Protein Hydrolysates Prepared from Chinese Pond Turtle ().

Research Background: Cardiovascular diseases and diabetes are the biggest causes of death globally. Bioactive peptides derived from many food proteins using enzymatic proteolysis and food processing have a positive impact on the prevention of these diseases. The bioactivity of Chinese pond turtle muscle proteins and their enzymatic hydrolysates has not received much attention, thus this study aims to investigate their antioxidant, antidiabetic and cytotoxic activities.

Molecular Design of Three-Dimensional Metal-Free A(NH)X Perovskites for Photovoltaic Applications.

The intense research activities on the hybrid organic-inorganic perovskites (HOIPs) have led to the greatly improved light absorbers for solar cells with high power conversion efficiency (PCE). However, it is still challenging to find an alternative lead-free perovskite to replace the organohalide lead perovskites to achieve high PCE. This is because both previous experimental and theoretical investigations have shown that the Pb cations play a dominating role in contributing the desirable frontier electronic bands of the HOIPs for light absorbing.

Acquiring High-T Layered Metal Halide Ferroelectrics via Cage-Confined Ethylamine Rotators.

Two-dimensional (2D) organic-inorganic hybrid perovskite (OIHP) ferroelectrics have attracted widespread interest in the field of optoelectronics due to the combination of excellent semiconducting and ferroelectric properties. The Curie temperature (T ), below which ferroelectricity exists, is a crucial parameter for ferroelectrics. However, the lack of research on T tuning of 2D OIHP ferroelectrics hinders their further progress.

PCl: A Unique Post-Phosphorene 2D Material with Superior Properties against Oxidation.

Herein, a unique class of post-phosphorene materials, namely, phosphorene halogenides (e.g., α-PCl) with superior oxidation resistance and desirable bandgap characteristics, are proposed.

CaP: A New Two-Dimensional Functional Material with Desirable Band Gap and Ultrahigh Carrier Mobility.

Two-dimensional (2D) semiconductors with direct and modest band gap and ultrahigh carrier mobility are highly desired functional materials for nanoelectronic applications. Herein, we predict that monolayer CaP is a new 2D functional material that possesses not only a direct band gap of 1.15 eV (based on HSE06 computation) but also a very high electron mobility up to 19 930 cm V s, comparable to that of monolayer phosphorene.

Stability of Metal-Encapsulating Boron Fullerene B40.

The structural stability of MB40 (M = Li, Na, K, Ba, and Tl) is investigated on the basis of density-functional theory calculations at the PBE0 level. Particular attention is placed on the relative stability between the endohedral and exohedral configurations of metalloborospherenes. It is found that the Na and Ba atoms can be stably encapsulated inside the B40 cage, whereas the Li, K, and Tl atoms favor the exohedral configuration where the dopant caps one of heptagons of B40 cage.

Polygermanes: bandgap engineering via tensile strain and side-chain substitution.

Successful synthesis of the phenylisopropyl hexagermane (Chem. Commun. 2013, 49, 8380) offers an exciting opportunity to synthesize a new class of low-dimensional germanium compounds with novel optical and electronic properties.

Boron-nitride and aluminum-nitride "Pringles" and flapping motion.

Motivated by the recent successful synthesis of a new nanocarbon, namely, a warped, double-concave graphene "Pringle" (Nat. Chem., 2013, 5, 739), we investigate properties of warped boron-nitride (BN) and aluminum-nitride (AlN) analogues, i.

First-principles simulations on suspended coinage-metal nanotubes composed of different atomic species.

Substitutional doping of gold and copper atoms in a (4, 4) silver single-wall nanotube has been investigated using first-principles simulations. It is found that the Au- and Cu-substitutional doping of the tip-suspended (4, 4) Ag tube can maintain the hollow tubular structure at different alloy compositions due to the existence of a local minimum in the string tension variation with their unit cell lengths. The bonding energy differences between the mono-elements and hetero-elements and string tension may play important roles in suppressing the "self-purification" effects so that the nanoalloy tubes can be formed.

Coinage metal (4, 4) nanotubes, simulated by first-principles calculations.

The structural stability of coinage metal nanotubes with a square cross-section has been investigated by the first-principles numerical simulations. In addition to the reported (4, 4) silver tube, it is found that the hollow (4, 4) copper and gold nanotubes can also be formed by applying an appropriate stress to an 8(A)/8(B) fcc wire. The stability of these coinage metal (4, 4) nanotubes, formed by tip-stretching the wires, has been explained by a local minimum in the string tension variation with their tube lengths.

Magnetic properties of transition-metal-doped tubular gold clusters: M@Au(24) (M = V, Cr, Mn, Fe, Co, and Ni).

The energetic and magnetic properties of the tubular cluster Au(24), doped endohedrally by a 3d transition-metal atom M (M = V, Cr, Mn, Fe, Co, and Ni) have been investigated by the scalar relativistic density functional simulations. It is found that (1) these 3d transition-metal atoms can be encapsulated stably into the tubular Au(24) and do not significantly perturb the atomic and electronic structures of the parent tubular Au(24), (2) the infrared (IR) spectra of the tubular Au(24) cluster are significantly changed by the dopant atoms, inducing a characteristic absorption peak in the IR spectra of all the M@Au(24), and (3) protected by the tubular Au(24), the 3d states of the dopant atoms are largely localized, and the atom-like magnetism is retained for all the doped gold clusters, exhibiting 3, 6, 5, 4, 3, and 2 mu(B) for V-Ni, respectively.

Ferroelectric ordering in ice nanotubes confined in carbon nanotubes.

The ice nanotubes with odd number of side faces formed inside carbon nanotubes (CNTs) are found to exhibit spontaneous electric polarizations along their tube axes by means of molecular dynamics simulations. The physical mechanism underlying the quasi-one-dimensional (Q1D) ferroelectricity is an interplay between the Q1D geometrical confinement of CNTs and the distinct orientational ordering of the hydrogen bonds dictated by the "ice rule". This mechanism is fundamentally different from the conventional one seen in three-dimensional ferroelectric (FE) materials or in two-dimensional FE ice films.

Stability of suspended gold and silver alloy monatomic chains.

Using the first-principles plane wave pseudopotential method, we have studied the structures and stability of gold and silver alloy monatomic chains. It is found that minimizing system's enthalpy instead of its energy is critical to identify the stability of stretched alloy chains at zero temperature since the string tension can efficiently suppress the self-purification. Our simulations show that all the gold-containing chains do exhibit a local enthalpy minimum, giving a reasonable interpretation for the experimental observations of gold and silver alloy chains with different Ag concentrations [Bettini et al.

Structures of MAu16 (-) (M=Ag, Li, Na, and K): how far is the endohedral doping?

The structural and electronic properties of MAu16 (-) (M=Ag, Li, Na, and K) have been studied by the scalar relativistic all-electron density-functional calculations, in which particular attention is paid to the stability of the endohedral Au16 (-) cage doped by different dopant atoms. It is found that only the smaller atoms, such as Cu, Li, and Na, can be stably encapsulated in the Au16 (-) cage, while the addition of the larger Ag or K atom prefers to locate in the surface or outside of the cage, which is inconsistent with the previous hypothesis that the Au16 (-) cage could act as a container to hold an arbitrary heterometal atom. The stable endohedral Li@Au16 (-) and Na@Au16 (-) have a large energy gap between the highest occupied molecular orbital and the lowest unoccupied molecular orbital gap, indicating that they are chemically stable and may be used as potential building blocks for designing cluster-assembled materials.

Tuning ferroelectricity of niobium clusters by oxygen chemisorption.

The chemisorption of atomic oxygen on Nb(N) (N=2-16) has been investigated by the scalar relativistic all-electron density-functional calculations with emphasis on its effect on the ferroelectricity of Nb(N). We have shown that the binding of O atom to niobium clusters is site- and size-dependent, for which the bridge-site doping is preferred in the smaller size range from N=2 to 8 and the threefold hollow site one for the larger Nb(N) with 9 < or = N < or = 16. Though the geometrical structures of Nb(N) are modified slightly when doped with an oxygen atom, their ferroelectric properties vary considerably, depending on cluster size and the O adsorption sites, which is mainly caused by the charge transfer between the oxygen atom and niobium clusters.

Coexistence of ferroelectricity and ferromagnetism in tantalum clusters.

The atomic and electronic structures of Ta(N) (N=2-23) clusters have been determined in the framework of pseudopotential density-functional calculations, based upon an unbiased global search with guided simulated annealing to an empirical potential. It is found that the ground-state structures of Ta(N) are very similar to those of Nb(N), showing no preference for the icosahedral growth. Also, a size- and structure-dependent ferroelectricity is found in these tantalum clusters.

Adsorption of O2 on tubelike Au24 and Au24- clusters.

The nondissociative adsorptions of O(2) on the neutral and anionic Au(24) have been studied using the density functional theory (DFT) in the generalized gradient approximation. Their geometrical structures are optimized by using a combination of the relativistic effective core potential and all-electron potential with scalar relativistic corrections. It is found that the adsorptions of O(2) on the tubelike Au(24) and Au(24) (-) are more stable than it on their space-filled counterparts.