Computational discovery of two-dimensional tetragonal group IV-V monolayers.

The two-dimensional (2D) hexagonal group IV-V family has attracted significant attention due to their unique properties and potential applications in electronics, spintronics, and photocatalysis. In this study, we report the discovery of a stable tetragonal allotrope, termed the Td4 phase, of 2D IV-V monolayers through a structural search utilizing an adaptive genetic algorithm. We investigate the geometric structures, structural stabilities, and band structures of the Td4-phase 2D IV-V monolayers (where IV = Si, Ge, Sn; V = P, As, Sb) based on the first-principles calculations.

2D-MnC: An Optimal Electrocatalyst with Nonbonding Multiple Single Centers for CO-to-CH Conversion.

The CO reduction reaction (CORR) is a promising method that can both mitigate the greenhouse effect and generate valuable chemicals. The 2D-MC with high-density transition metal single atoms is a potential catalyst for various catalytic reactions. Using an effective strategy, we screened 1s-MnC as the most promising electrocatalyst for the CORR in the newly reported 2D-MC family.

Influence of Zr aggregation on Li-ion conductivity of amorphous solid-state electrolyte Li-La-Zr-O.

In our study, we investigated the influence of the local structure of amorphous Li-La-Zr-O (a-LLZO) on Li-ion conductivity using ab initio molecular dynamics (AIMD). A-LLZO has shown promising properties in inhibiting the growth of lithium dendrites, making it a potential candidate for solid electrolytes in all-solid-state lithium batteries. The low Li-ion conductivity of a-LLZO is currently limiting its practical applications.

In Situ Induced Lattice-Matched Interfacial Oxygen-Passivation-Layer Endowing Li-Rich and Mn-Based Cathodes with Ultralong Life.

The high capacity of Li-rich and Mn-based (LRM) cathode materials is originally due to the unique hybrid anion- and cation redox, which also induces detrimental oxygen escape. Furthermore, the counter diffusion of released oxygen (into electrolyte) and induced oxygen vacancies (into the interior bulk phase) that occurs at the interface will cause uncontrolled phase collapse and other issues. Therefore, due to its higher working voltage (>4.

First-Principles Observation of Bonded 2D BC Bilayers.

Two-dimensional (2D) B-C compounds possess rich allotropic structures with many applications. Obtaining new 2D BC structures is highly desirable due to the novel applications of three-dimensional (3D) BC in protections. In this work, we proposed a new family of 2D BC from the first-principles calculations.

Significant second-harmonic generation and bulk photovoltaic effect in trigonal selenium and tellurium chains.

One-dimensional (1D) selenium and tellurium crystalize in helical chainlike structures and thus exhibit fascinating properties. By performing first-principles calculations, we have researched the linear and nonlinear optical (NLO) properties of 1D Se and Te, and find that both systems exhibit pronounced NLO responses. In particular, 1D Se is found to possess a large second-harmonic generation coefficient with the χ value being up to 7 times larger than that of GaN, and is even several times larger than that of the bulk counterpart.

Anionic Redox Processes in Maricite- and Triphylite-NaFePO of Sodium-Ion Batteries.

In recent years, NaFePO has been regarded as one of the most promising cathode materials for next-generation rechargeable sodium-ion batteries. There is significant interest in the redox processes of rechargeable batteries for high capacity applications. In this paper, the redox processes of triphylite-NaFePO and maricite-NaFePO materials have been analyzed based on first-principles calculations and analysis of Bader charges.

Manipulating External Electric Field and Tensile Strain toward High Energy Density Stability in Fast-Charging Li-Rich Cathode Materials.

Li-rich layered oxides (LLOs) are promising cathodes for lithium-ion batteries because of their high energy density provided by anionic redox. Although great improvements have been achieved in electrochemical performance, little attention has been paid to the energy density stability during fast charging. Indeed, LLOs have severe capacity fading and voltage decay especially at a high state of charge (SOC), disabling the application of the frequently used constant-current-constant-voltage mode for fast charging.

HOT Graphene and HOT Graphene Nanotubes: New Low Dimensional Semimetals and Semiconductors.

We report a new graphene allotrope named HOT graphene containing carbon hexagons, octagons, and tetragons. A corresponding series of nanotubes are also constructed by rolling up the HOT graphene sheet. Ab initio calculations are performed on geometric and electronic structures of the HOT graphene and the HOT graphene nanotubes.

Dependence of Electronic and Optical Properties of MoS Multilayers on the Interlayer Coupling and Van Hove Singularity.

In this paper, the structural, electronic, and optical properties of MoS multilayers are investigated by employing the first-principles method. Up to six-layers of MoS have been comparatively studied. The covalency and ionicity in the MoS monolayer are shown to be stronger than those in the bulk.

Lithium Deficiencies Engineering in Li-Rich Layered Oxide LiMnNiCoO for High-Stability Cathode.

Li-rich layered oxides have been in focus because of their high specific capacity. However, they usually suffer from poor kinetics, severe voltage decay, and capacity fading. Herein, a long-neglected Li-deficient method is demonstrated to address these problems by simply reducing the lithium content.

A Guideline for Tailoring Lattice Oxygen Activity in Lithium-Rich Layered Cathodes by Strain.

Lattice oxygen activity plays a dominant role in balancing discharge capacity and performance decay of lithium-rich layered oxide cathodes (LLOs). On the basis of density functional theory (DFT) and tight-binding theory, the activity of lattice oxygen can be improved by tensile strain and suppressed by compressive strain. To verify this conclusion, LLOs with large lattice parameters (L-LLOs) were synthesized taking advantage of the lattice expansion effect in nanomaterials.

Electronic Properties of Vanadium Atoms Adsorption on Clean and Graphene-Covered Cu(111) Surface.

The electronic properties of vanadium atoms adsorbed on clean and graphene-covered Cu(111) surface have been systematically studied using ab initio theoretical method. Two coverages (1/9 ML and 1 ML) of vanadium adsorption are considered in this work. Our calculations indicate that V staying underneath the Cu surface is found to be the most stable adsorption site at the aforementioned two coverages for V/Cu(111).

Chemically initiated liquid-like behavior and fabrication of periodic wavy Cu/CuAu nanocables with enhanced catalytic properties.

Solid crystalline materials have long range order in their atomic arrangement while liquids have short range order, and the transition between them is usually caused by heat and/or pressure. Herein, we report the finding that chemical processes may play a similar role as heat and initiate liquid-like behavior of crystalline nanomaterials at a temperature far below their melting points. When the straight Cu/CuAu crystalline nanocables are dispersed in organic amine at 80 °C under ambient conditions, the continuous oxidation of Cu atoms on the surface and diffusion of Cu atoms from the core to the surface would break up the long-range ordered arrangement of atoms and lead to the transformation of an anisotropic crystal into an isotropic liquid-like state, which resulted in the evolution of the straight morphology of the nanocables into periodic wavy structures following the Rayleigh instability.

Recent advances in the chemical transformations of functionalized alkylidenecyclopropanes (FACPs).

During the past several years, functionalized alkylidenecyclopropanes (FACPs) have attracted intensive attention in synthetic chemistry. Many interesting transformations of FACPs have been developed to synthesize a lot of structurally diverse and valuable polycyclic and heterocyclic compounds. This review will classify FACPs into aryl-FACPs, alkyl-FACPs and ring-FACPs for the first time, and recent interesting chemical transformations in these research fields will be included, respectively, from 2011.

CrNbO Nanowires with High Electronic Conductivity for High-Rate and Long-Life Lithium-Ion Storage.

Intercalation-type TiNbO (x = 2, 5, and 24) anode materials have recently become more interesting for lithium-ion batteries (LIBs) due to their large theoretical capacities of 388-402 mAh g. However, the Ti/Nb ions in TiNbO with empty 3d/4d orbitals usually lead to extremely low electronic conductivity of <10 S cm, greatly restricting their practical capacity and rate capability. Herein, we report a class of highly conductive CrNbO nanowires as an intercalation-type anode material for high-performance LIBs.

Superlight and Superflexible Three-Dimensional Semiconductor Frameworks A(X≡Y) (A=Si, Ge; X/Y=C, B, N) with Tunable Optoelectronic and Mechanical Properties from First-Principles.

Silicon carbide materials, as leading wide band gap semiconductors, hold significant importance in semiconductor technologies. Herein, diamond-like 3D materials with low density, but high elasticity properties, have been designed from first-principles calculations. They are porous single-crystalline materials composed of sp -hybridized silicon (or germanium) and sp-type C≡C (or B≡N) linear moieties; their stabilities are comparable to those of recently prepared SiC materials.

Electronic halocyclization and radical haloazidation of benzene-linked 1,7-dienes for the synthesis of functionalized 3,1-benzoxazines.

A novel electronic halocyclization and radical haloazidation of benzene-linked 1,7-dienes for the formation of functionalized 3,1-benzoxazines has been achieved by using TMSN as an azido source and NBS as a halogen source. This methodology is highlighted by its mild conditions and wide substrate scope, which concomitantly introduces one C-N and two C-halogen bonds into one molecule.

Palladium-catalyzed cascade cyclization of allylamine-tethered alkylidenecyclopropanes: facile access to iodine/difluoromethylene- and perfluoroalkyl-containing 1-benzazepine scaffolds.

The unprecedented palladium-catalyzed cascade cyclization of allylamine-tethered alkylidenecyclopropanes with an ethyl difluoroiodoacetate or perfluoroalkylated reagent is developed, providing facile access to a variety of synthetically and medicinally valuable iodine/difluoromethylene- and perfluoroalkyl-containing 1-benzazepine frameworks. These reactions exhibited good yields and functional group tolerance via a radical mechanism.

Atomic-scale insights into structural and thermodynamic stability of Pd-Ni bimetallic nanoparticles.

Atomic-scale understanding of structures and thermodynamic stability of core-shell nanoparticles is important for both their synthesis and application. In this study, we systematically investigated the structural stability and thermodynamic evolution of core-shell structured Pd-Ni nanoparticles by molecular dynamics simulations. It has been revealed that dislocations and stacking faults occur in the shell and their amounts are strongly dependent on the core/shell ratio.

Copper(I)-Catalyzed Intramolecular Trifluoromethylation of Methylenecyclopropanes.

Copper(I)-catalyzed intramolecular trifluoromethylation of methylenecyclopropanes has been developed to produce a variety of CF3-substituted dihydronaphthalenes in moderate to good yields, relying on the construction of C(sp(2))-CF3 bonds under mild conditions. The reactions proceed through a radical process under copper(I) catalysis with a good compatibility for the functional group.

Defective Ti2Nb10O27.1: an advanced anode material for lithium-ion batteries.

To explore anode materials with large capacities and high rate performances for the lithium-ion batteries of electric vehicles, defective Ti2Nb10O27.1 has been prepared through a facile solid-state reaction in argon. X-ray diffractions combined with Rietveld refinements indicate that Ti2Nb10O27.

Substrate-controlled Rh(II)-catalyzed single-electron-transfer (SET): divergent synthesis of fused indoles.

Rh(II)-catalyzed diversified ring expansions controlled by single-electron-transfer (SET) have been disclosed in this communication, producing a series of indole-fused azetidines and 1H-carbazoles or related derivatives in moderate to good yields via Rh2(III,II) nitrene radical intermediates. The direction of ring expansion branches according to different ring sizes of methylenecycloalkanes.

Exploration of tetrahedral structures in silicate cathodes using a motif-network scheme.

Using a motif-network search scheme, we studied the tetrahedral structures of the dilithium/disodium transition metal orthosilicates A2MSiO4 with A = Li or Na and M = Mn, Fe or Co. In addition to finding all previously reported structures, we discovered many other different tetrahedral-network-based crystal structures which are highly degenerate in energy. These structures can be classified into structures with 1D, 2D and 3D M-Si-O frameworks.