Two-dimensional ferroelectrics hold great promise for ultrathin, energy-efficient electronic and memory devices. Unlike homobilayers, where the number of candidate bilayers scales linearly with the number of monolayers, the vast design space of heterobilayers, combined with their intrinsically sparse ferroelectric occurrence, renders brute-force screening highly inefficient. Here, we address this challenge by identifying key physical descriptors through high-throughput first-principles calculations on 33 102 hexagonal stacking configurations and by developing a monolayer-informed predictive model that enables rapid identification of sliding ferroelectricity in heterobilayers without explicitly constructing bilayer structures. Relying on monolayerlevel descriptors, the model achieves high-fidelity predictions across a broad materials space. Applying this framework, we uncover more than 1000 sliding ferroelectric heterobilayers with out-of-plane polarization (OOP) exceeding that of experimentally reported MoS2/WS2. Notably, the top-performing candidate exhibits an OOP response approximately 130 times larger than MoS2/WS2. These results establish a large curated dataset of sliding ferroelectrics and demonstrate a scalable, structure-free discovery paradigm for ferroelectric heterobilayers, paving the way for accelerated design of next-generation two-dimensional ferroelectric devices.

Two-dimensional ferroelectrics with large out-of-plane polarization (OOP) are promising for the design of low-power memory and logic devices, but their experimental realization remains limited due to the scarcity of homobilayers and the complexity of heterobilayers. Here, we perform high-throughput screening of 24,960 configurations and identify 43 semiconducting heterobilayer ferroelectrics with an OOP exceeding the experimentally reported value in MoS2/WS2 while maintaining sliding barriers below 100 meV/f.u. Among them, CdO/InN exhibits an OOP nearly 50 times greater than that of MoS2/WS2, along with a low sliding barrier of around 35 meV/f.u., making it a candidate that combines strong polarization with low-energy switching. The data analysis shows that heterobilayers composed of single-atom-layer monolayers mostly exhibit enhanced sliding ferroelectric behavior, providing a library of ferroelectrics. In addition, we develop a multiscale physical model that links monolayer characteristics to the sliding ferroelectric response by combining structural projection and polarization decomposition. This physical mechanism reveals a crucial competition between interlayer and intralayer dipoles in heterobilayer systems.

Although van der Waals (vdW) heterostructures have shown significant photocatalytic applications, the discovery of high-performance vdW heterostructure photocatalysts is limited by the computational cost in the high-dimensional search space and the complexity of large-scale atomic models. Here, we utilize big-data analysis, high-throughput screening, high-fidelity calculations, and machine learning to discover Z-scheme heterostructure photocatalysts from 11 935 vdW heterostructures, constructed using 155 two-dimensional (2D) semiconductors with diverse structures from our 2DMatPedia database. We first perform high-throughput high-fidelity hybrid functional calculations on the 155 monolayer 2D semiconductors to obtain their high-accuracy band information. Using the explainable descriptor and deep reinforcement learning algorithm, we identify 1062 potential Z-scheme vdW heterostructures. Finally, the best 33 Z-scheme heterostructure photocatalysts from the pool of 1062 candidates are verified and validated through high-fidelity hybrid functional calculations. Among these Z-scheme heterojunctions, our photocatalytic calculations indicate that SnO2/WSe2, Bi2Se3/VI2, Bi2Se3/Sb, and Bi2Te2S/Sr(SnAs)2 have the best redox abilities. Using machine learning techniques, we further identified 29 new high-potential Z-scheme heterostructures from the pool, making a total of 62 candidates. The combination of high-throughput, descriptor, and machine learning techniques helps to narrow down the candidates of high-performance photocatalytic heterostructures in a very large material space and accelerate the discovery process of Z-scheme photocatalysts in the experiment.

Phase engineering strategies in two-dimensional transition metal dichalcogenides (2D-TMDs) have garnered significant attention due to their potential applications in electronics, optoelectronics, and energy storage. Various methods, including direct synthesis, pressure control, and chemical doping, have been employed to manipulate structural transitions in 2D-TMDs. Metal intercalation emerges as an effective technique to modulate phase transition dynamics by inserting external atoms or ions between the layers of 2D-TMDs, altering their electronic structure and physical properties. Here, we investigate the significant structural phase transitions in Pb(Ta1+xSe2)2 single crystals induced by Ta intercalation using a combination of Raman spectroscopy and first-principles calculations. The results highlight the pivotal role of Ta atoms in driving these transitions and elucidate the interplay between intercalation, phase transitions, and resulting electronic and vibrational properties in 2D-TMDs. By focusing on Pb(Ta1+xSe2)2 as an ideal case study and investigating like metal intercalation, this study advances understanding in the field and paves the way for the development of novel applications for 2D-TMDs, offering insights into the potential of these materials for future technological advancements.

Many exotic properties in rhombohedral (or ABC-stacked) multilayer graphene have recently been reported experimentally. In this Letter, we first reveal the underlying mechanism of spin degeneracy lifting in rhombohedral trilayer graphene. Then, we propose a design concept for all-rhombohedral graphene-based magnetic tunnel junctions (MTJs) by utilizing pristine, back-gated, and top-gated ABC-stacked trilayer graphene, which exhibit semimetallic (conducting), semiconducting (insulating), and half-metallic (ferromagnetic) behavior, respectively. This enables the realization of an "all-in-one" magnetic tunnel junction based entirely on trilayer graphene. This design enables voltage-controlled spintronics (lower power than conventional MTJs) with perfect interfacial matching and subnanometer thickness uniformity across 4-in. wafers. Using first-principles calculations and the nonequilibrium Green's function, we comprehensively study electronic structures and transport properties of these all-graphene MTJs. Furthermore, we demonstrate that their characteristics can be tuned via a perpendicular electric field and electron doping. Our findings offer a new concept for the development of fully graphene-based spintronic devices utilizing the three distinct electronic phases of rhombohedral trilayer graphene.

Ferroelectric Rashba semiconductors (FRS) are highly demanded for their potential capability for nonvolatile electric control of electron spins. An ideal FRS is characterized by a combination of room temperature ferroelectricity and a strong Rashba effect, which has, however, been rarely reported. Herein, we designed a room-temperature FRS by vertically stacking a Sb monolayer on a room-temperature ferroelectric In2Se3 monolayer. Our first-principles calculations reveal that the Sb/In2Se3 heterostructure exhibits a clean Rashba splitting band near the Fermi level and a strong Rashba effect coupled to the ferroelectric order. Switching the electric polarization direction enhances the Rashba effect, and the flipping is feasible with a low energy barrier of 22 meV. This Rashba-ferroelectricity coupling effect is robust against changes of the heterostructure interfacial distance and external electric fields. Such a nonvolatile electrically tunable Rashba effect at room temperature enables potential applications in next-generation data storage and logic devices operated under small electrical currents.

The interaction of molecular iodine on Mgn (n = 2–18) clusters has been investigated using first-principles calculations. Structural, adsorption energy and electronic properties of these systems are reported. After structure optimization, the iodine molecule undergoes dissociative adsorption, where the I–I covalent bond of molecular iodine is broken and the dissociative iodine atoms adsorb on the surfaces of the magnesium clusters. The adsorption energy ranging from − 4.335 to − 5.740 eV indicates the chemisorption of I on Mgn clusters. In the same way, for n > 4, Mg-I compounds have bond lengths of 2.694 to 2.937 Å forming ionic bonds and the values of charge transfer in MgnI2 reach − 0.829 to − 0.977 e. The projected density of states (PDOS) of Mg7I2, which has the highest absolute adsorption energy, and Mg16I2, which has the highest amount of charge transfer, demonstrate the strong hybridization between the Mg 3s and the I 5p orbitals. Overall, the change in electronic structure suggests that Mgn clusters might serve as promising adsorbents for the removal of gaseous radioactive iodine.

The interstitial charge in 2D HfI 2 exhibits high mobility due to weak lattice perturbation, and the high mobility induces a high power factor and ZT value.

Polarization, a fundamental property of light, has been widely exploited from quantum physics to high-dimensional optics. Materials with intrinsic optical anisotropy, such as dichroism and birefringence, are central to light polarization control, including the development of polarizers, waveplates, mirrors and phase-matching elements. Therefore, materials with strong optical anisotropy have been long-sought. Recently, two-dimensional van der Waals crystals show high optical anisotropy but are mostly restricted to the out-of-plane direction, which is challenging to access in optical engineering. Here we report a two-dimensional van der Waals material, NbOCl2, that exhibits sharp electronic and structural contrast between its in-plane orthogonal axes. Colossal in-plane optical anisotropy-linear dichroism (up to 99% in ultraviolet) and birefringence (0.26-0.46 within a wide visible-near-infrared transparency window)-is experimentally demonstrated. Our findings provide a powerful and easy-to-access recipe for ultracompact integrated polarization industries.

Reconstructive phase transitions are characterized by significant changes in the crystal structure of a material, typically accompanied by dramatic changes in its physical properties. In this Letter, via first-principles calculations, we report a reconstructive phase transition between nonlayered and layered tungsten dinitride (WN2) with kinetic energy barriers of 0.19 and 0.61 eV per formula unit depending on the transition direction. The nonlayered-to-layered transition can be triggered when an in-plane biaxial strain reaches 9.3%, while the layered-to-nonlayered transition happens at 53.5% of an out-of-plane uniaxial strain. The nonlayered and layered WN2 phases exhibit distinct structural, bonding, and electronic characteristics. Another intrinsic advantage of the reconstructive transition between layered and nonlayered phases is that it can be easily extended to two-dimensional (2D) nanoscale regions. Our results predict a rich phase diagram for 2D WN2 under strains, appealing for advanced nanoelectronics applications such as phase-change electronics or pressure sensors.

The technique of conventional ferromagnet/heavy-metal spin-orbit torque (SOT) offers significant potential for enhancing the efficiency of magnetic memories. However, it faces fundamental physical limitations, including hunting effects from the metallic layer, broken symmetry for enabling antidamping switching, spin scattering caused by interfacial defects, and sensitivity to stray magnetic fields. To address these issues, we here propose a van der Waals (vdW) field-free SOT antiferromagnetic memory using a vdW bilayer LaBr$_2$ (an antiferromagnet with perpendicular magnetic anisotropy) and a monolayer T$_d$ phase WTe$_2$ (a Weyl semimetal with broken inversion symmetry). By systematically employing density functional theory in conjunction with non-equilibrium Green's function methods and macrospin simulations, we demonstrate that the proposed vdW SOT devices exhibit remarkably low critical current density approximately 10 MA/cm$^2$ and rapid field-free magnetization switching in 250 ps. This facilitates excellent write performance with extremely low energy consumption. Furthermore, the device shows a significantly low read error rate, as evidenced by a high tunnel magnetoresistance ratio of up to 4250%. The superior write and read performance originates from the unique strong on-site (insulating phase) and off-site (magnetic phase) Coulomb interactions in electride LaBr$_2$, a large non-zero z-component polarization in WTe$_2$, and the proximity effect between them.

Toward high-density single atom catalysts (SACs), the interaction between neighboring SACs and the induced non-linear loading effect become crucial for their intrinsic catalytic performance. Despite recent investigations on homonuclear SACs, understanding such effect in heteronuclear SACs remains limited. Using Fe and Co SACs co-supported on the nitrogen-doped graphene as a model system, the loading effect on the site-specific activity of heteronuclear SACs toward oxygen reduction reaction (ORR) is here reported by density functional theory calculations. The Fe site exhibits an oscillatory decrease in activity with the loading. In contrast, the Co site has a volcano-like activity with the optimum performance achieved at ≈16.8 wt.% (average inter-site distance: ≈7 Å). At the ultra-high loading of 38.4 wt.% (inter-site distance: ≈4 Å), the Co site is the only ORR active site, whereas Fe sites turn into spectators. This distinct loading-dependent activity between the Fe and Co sites can be ascribed to their difference in the binding capability with the substrate and the dxz and dyz orbitals' occupation. These findings highlight the importance of the loading effect in heteronuclear SACs, which could be useful for the development of high-performance heteronuclear and high-entropy SACs toward various catalytic reactions in the high-loading regime.

Conventional two-dimensional (2D) Janus materials are featured by the different anions on the two sides of the structures. In this work, we report a new type of Janus structures, Janus electrenes with different cation layers. By substituting one of the two zirconium cation layers in Zr2Cl2 with group I to III elements, we generated nine Janus 2D materials ZrXCl2, where X = Na, K, Rb, Ca, Sr, Ba, Sc, Y or La. The phonon spectra demonstrate the dynamical stability of ZrScCl2, ZrYCl2 and ZrCaCl2, confirming the feasible formation of cationic Janus electrenes. Interestingly, the different groups of Janus structures have dramatically different electronic and magnetic properties. While the substitution of group III elements introduces ferromagnetic anionic electrons to the ZrXIIICl2 systems, ZrXIICl2 are semiconductors with band gaps of around 0.2 eV with flat valence bands (band width from 175 to 234 meV), and ZrXICl2 are ferromagnetic half-metals. Our results open up a new dimension of freedom to effectively tune the electronic and magnetic properties of electrenes, paving the way for their novel applications.

Direct formic acid fuel cells (DFAFCs) are among the promising energy sources in the future low-carbon economy. A key challenge hindering their scale-up and commercialization is the lack of efficient electrocatalysts for anodic formic acid oxidation (FAO). Very recently, the FAO performance of palladium hydrides (PdHx) has been found to be superior to the pristine Pd that is well known for its high intrinsic FAO activity. However, there is enormous space for the controlled synthesis and electrocatalytic behaviors of PdHx-based nanomaterials awaiting to be explored. Herein, the hydrogen intercalation-induced crystallization of PdNiP alloy nanoparticles is reported, and the obtained PdNiP-H nanoparticles exhibit excellent FAO performance. Of particular note, the FAO stability of PdNiP-H is much better than that of pristine Pd-H. Furthermore, the PdNiP-H nanoparticles are used as the anode catalyst in a prototype DFAFC, which demonstrate much higher power density than commercial Pd/C. Density functional theory calculations show that the synergistic effect of alloying Ni and P endows the PdNiP-H with a higher preference toward FAO via the direct pathway and better anti-CO* poisoning capability. This work shines new light on the development of PdHx-based nanoalloys with good activity and stability for DFAFC applications.

Two-dimensional (2D) transition metal dichalcogenides (TMDs) exhibit a broad spectrum of remarkable physical properties, making them appealing for many applications such as nanoelectronics, optoelectronics, and wearable devices. Due to the atomically thin thickness of 2D TMDs, electron-lattice interaction, spin-orbit coupling, Coulomb interaction, and light-matter interaction manifest themselves in 2D TMDs. These endow various emerging properties, including strong excitonic effect, polaron states, charge density wave, valley polarization, and superconductivity. In this chapter, we start with a brief introduction to the electronic band structures and optical properties of 2D TMDs, and then focus on the emerging properties of 2D TMDs.

Interest in enhancing magnetic performances of low-sintered ceramic materials by co-doping of oxide nanoparticle and low-melting glass has thrived. Usually this process includes performance enhancement of ceramic attributed to grain growth and deterioration caused by excess additives. Here, we study the grain growth and magnetic properties of Bi-substituted LiZnTi (LiZnTiBi) ferrites doped with various Al2O3- modified ZnO-B2O3-SiO2 (Al-ZBS) glass additives. XRD patterns indicate that the Al-ZBS glass has no effect on lattice constant of ferrite, which means that the Al-ZBS glasss is only existed in grain boundary. SEM results indicate that the LiZnTiBi ferrites has two changes due to the interaction between substituted of Bi2O3 and doping of Al-ZBS glasses. Firstly, grain growth of the ferrite is dominant and its relative density gradually increases when contents of Al-ZBS glass (x) is less than 0.10. Moreover, the grain growth of the ferrite is suppressed because of competition between the two additives when value of x more than 0.10. Finally, one kind of LiZnTiBi ferrite (x = 0.10) with large average grains size (-8.11 mu m) and good magnetic properties (4 pi Ms =3747.3 Gs, Hc=165.7 A/m and Bs =324.9 mT) is obtained at-900 oC. (c) 2022 Elsevier B.V. All rights reserved.

We investigate theoretically the waiting time distribution (WTD) of the sub-gap electron transport through a quantum dot which is coupled to two normal metal leads and one Majorana bound state of a topological superconductor. Using the generalized master equation approach, we calculate and present the analytical expressions of the WTDs. It is found that the WTD is an even function of the energy level of the dot. For comparison, we also consider the case that the quantum dot is side coupled to an ordinary fermionic state. For an ordinary fermionic state, the WTD indicates quite different behavior when tuning the dot energy level with opposite signs. Moreover, we discuss the information contained in the g(2) function to investigate the bunching and antibunching of electron tunneling processes.

Elemental carbon has been successfully used to tune the light emission properties of zinc oxide (ZnO) through artificially doping but the underlying mechanism remains controversial. At present, carbon-related defect complexes are the main explanation. Nevertheless, the possibility of forming semiconducting Zn-C compounds has not been discussed. In this study, we reveal the existence of various stable semiconducting Zn-C compounds. Based on particle swarm optimization and first-principles calculations, we perform a structural search of Zn-C binary compounds and report four stable semiconducting structures, in which the covalent Zn-C bonding characteristics are stronger compared with that in the metal rocksalt zinc carbide (ZnC). Crucially, three of the four Zn-C compounds have direct or quasi-direct band gaps in the range of 1.09-2.94 eV which are energies highly desirable for optoelectronic applications. Electronic transitions across the band gaps of these Zn-C structures could contribute to blue and near-infrared light emissions of C-doped ZnO. Our results have not only unraveled a new perspective to explain and tailor the light emission properties of ZnO but also provide a deeper understanding of possible Zn-C compounds.

Two-dimensional (2D) electrides, characterized by excess interstitial anionic electron (IAE) in a crystalline 2D material, offer promising opportunities for the development of electrode materials, in particular in rechargeable metal-ion batteries applications. Although a few such potential electride materials have been reported, they generally show low metal-ion storage capacity, and the effect of IAE on the ion storage performance remains elusive so far. Here we report a novel 2D electride, [Sc3Si2]1+·1e-, with fascinating IAE-driven high alkali metal-ion storage capacity. In particular, its K-ion specific capacity can reach up to 1497 mA h g-1, higher than any previously reported 2D materials-based anodes in K-ion batteries (PIBs). The IAE in the [Sc3Si2]1+·1e- crystal accounts for such high capacity behavior, which can drift away and balance the charge on the metal-cation, playing a crucial role in stabilizing the metal-ion adsorption and enhancing multilayer-ions adsorption. This proposed IAE-driven storage mechanism provides an unprecedented avenue for the future design of high storage capacity electrode materials.

Inter-site interactions between single atom catalysts (SACs) in the high loading regime are critical to tuning the catalytic performance. However, the understanding on such interactions and their distance dependent effects remains elusive, especially for the heteronuclear SACs. In this study, we reveal the effects of the distance-dependent inter-site interaction on the catalytic performance of SACs. Using the density functional theory calculations, we systematically investigate the heteronuclear iron and cobalt single atoms co-supported on the nitrogen-doped graphene (FeN4-C and CoN4-C) for oxygen reduction reaction (ORR). We find that as the distance between Fe and Co SACs decreases, FeN4-C exhibits a reduced catalytic activity, which can be mitigated by the presence of an axial hydroxyl ligand, whereas the activity of CoN4-C shows a volcano-like evolution with the optimum reached at the intermediate distance. We further unravel that the transition towards the high-spin state upon adsorption of ORR intermediate adsorbates is responsible for the decreased activity of both FeN4-C and CoN4-C at short inter-site distance. Such high-spin state transition is also found to significantly shift the linear relation between hydroxyl (*OH) and hydroperoxyl (*OOH) adsorbates. These findings not only shed light on the SAC-specific effect of the distance-dependent inter-site interaction between heteronuclear SACs, but also pave a way towards shifting the long-standing linear relations observed in multiple-electron chemical reactions.