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The search for materials with high intrinsic carbon monoxide oxidation reaction (COOR) catalytic activity is critical for enhancing the efficiency of reducing CO contamination. COOR catalysts, however, have long relied heavily on noble metals and CeO

Benefiting from the dragging effect of yttrium, an ultrahigh overall-performance phase-change memory is reported, including low resistance drift, high data retention, low power consumption, fast operating speed, and good cycling endurance.

Despite recent advances in exfoliated vdW ferromagnets, the widespread application of 2D magnetism requires a Curie temperature (Tc) above room temperature as well as a stable and controllable magnetic anisotropy. Here we demonstrate a large-scale iron-based vdW material Fe4GeTe2 with the Tc reaching ~530 K. We confirmed the high-temperature ferromagnetism by multiple characterizations. Theoretical calculations suggested that the interface-induced right shift of the localized states for unpaired Fe d electrons is the reason for the enhanced Tc, which was confirmed by ultraviolet photoelectron spectroscopy. Moreover, by precisely tailoring Fe concentration we achieved arbitrary control of magnetic anisotropy between out-of-plane and in-plane without inducing any phase disorders. Our finding sheds light on the high potential of Fe4GeTe2 in spintronics, which may open opportunities for room-temperature application of all-vdW spintronic devices.

Machine learning (ML) is believed to have enabled a paradigm shift in materials research, and in practice, ML has demonstrated its power in speeding up the cost-efficient discovery of new materials and autonomizing materials laboratories. In this Perspective, current research progress in materials data which are the backbones of ML are reviewed, focusing on high-throughput data generation, standardized data storage, and data representation. More importantly, the challenging issues in materials data that should be overcome to unlock the full potential of ML in materials research and development, including classic 5V (volume, velocity, variety, veracity, and value) issues, 3M (multicomponent, multiscale, and multistage) challenges, co-mining of experimental and computational data, and materials data toward transferable/explainable ML or causal ML, are discussed.

High-performance functional materials are the cornerstones of the continuous advance of modern science and technology, but the development of new materials is still challenging. Here, we propose a robust design strategy for novel crystalline solids based on group-theory classification and high-throughput computation, as demonstrated by the successful identification of new optoelectronic semiconductors. First, by means of theoretical group analysis and composition engineering, we obtained 78 prototypical crystal structures and built a computational materials database containing 21,060 ternary chalcogenide compounds. Our high-throughput screening of the coordination characteristics, phase stability, and electronic structures provided 97 candidate semiconductors, including 93 completely new compounds. Among them, 22 crystals with excellent dynamical and thermal stability are predicted to show high photovoltaic conversion efficiency (30%), comparable to the currently most efficient single-junction GaAs solar cell, owing to their optimal electronic properties and outstanding optical absorption. This discovery of new chalcogenide crystals offers excellent candidates for optoelectronic applications and suggests that our design strategy is a promising way to search for unknown high-performance functional materials.

A design principle was proposed to break the linear scaling relationships of key intermediates in the NORR for promoted reaction thermodynamics via modifying the surface functionalization of MXenes.

Two-dimensional transition metal carbides (MXenes) have great potential to achieve intrinsic magnetism due to their available chemical and structural diversity. In this work, by spin-polarized density functional theory calculations, we designed and comprehensively investigated 50 double transition metal (DTM) MXenes MCr

The concentration-sensitive nitrogen-doping effects on both the stability and electrical resistivity of GST124 are understood through various configurations of N dopants.

Three new stable semiconducting Ge–Sb–Te monolayers exhibit high visible-light absorbance (105–106 cm−1) and photovoltaic efficiency (26–30% at 0.1 μm), considerably larger than the currently dominant commercial photovoltaic semiconductor Si.

The synthesis methods, properties and applications for energy storage and electrocatalysis of MBenes were summarized. Furthermore, discussions and perspectives on the existing problems, major challenges and future development of MBenes were provided.

Two-dimensional double transition metal MXene ScCr2C2F2-based van der Waals magnetic tunnel junctionss with 2H-MoS2 layers as the tunnel barriers have been proposed to show the maximum tunnel magnetoresistance ratios of 6.95 × 106%.

By controlling the amorphous-to-crystalline relative volume, chalcogenide phase-change memory materials can provide multi-level data storage (MLS), which offers great potential for high-density storage-class memory and neuro-inspired computing. However, this type of MLS system suffers from high power consumption and a severe time-dependent resistance increase (“drift”) in the amorphous phase, which limits the number of attainable storage levels. Here, we report a new type of MLS system in yttrium-doped antimony telluride, utilizing reversible multi-level phase transitions between three states, i.e., amorphous, metastable cubic and stable hexagonal crystalline phases, with ultralow power consumption (0.6–4.3 pJ) and ultralow resistance drift for the lower two states (power-law exponent

Two-dimensional (2D) transition metal carbides (MXenes) with intrinsic magnetism and half-metallic features show great promising applications for spintronic and magnetic devices, for instance, achieving perfect spin-filtering in van der Waals (vdW) magnetic tunnel junctions (MTJs). Herein, combining density functional theory calculations and nonequilibrium Green's function simulations, we systematically investigated the spin-dependent transport properties of 2D double transition metal MXene ScCr

The selective hydrogenation of acetylene to ethylene in ethylene-rich gas streams is an important process in the manufacture of polyethylene. Conventional thermal hydrogenation routes require temperatures above 100 °C and excess hydrogen to achieve a satisfactory C2H2 conversion efficiency. Here, we report a room-temperature electrochemical acetylene reduction system based on a layered double hydroxide (LDH)-derived copper catalyst that offers an ethylene Faradaic efficiency of up to ~80% and inhibits alkane and hydrogen formation. The system affords an acetylene conversion of over 99.9% at a flow rate of 50 ml min−1 in a simulated gas feed, yielding high-purity ethylene with an ethylene/acetylene volume ratio exceeding 105 and negligible residual hydrogen (0.08 vol.%). These acetylene conversion metrics are superior to most other state-of-the-art strategies. The findings therefore conclusively demonstrate an electrochemical strategy as a viable alternative to current technologies for acetylene-to-ethylene conversions with potential advantages in energy and atom economies. The selective semihydrogenation of acetylene in ethylene-rich gas streams is an important process in the manufacture of polyethylene, which is traditionally performed thermocatalytically. Now, a room-temperature electrochemical acetylene reduction system with excellent performance is presented.

Searching for highly efficient and eco-friendly photocatalysts for water splitting is essential for renewable conversion and storage of inexhaustible solar energy but remains a great challenge. Herein, based on the new emerging two-dimensional (2D) material of MoSi2N4, we report novel Janus MoSiGeN4 and WSiGeN4 structures with excellent stabilities and great potentials in photocatalytic applications through first-principles calculations. Comprehensive studies show that MoSi2N4, MoSiGeN4, and WSiGeN4 exhibit semiconductor characteristics with an indirect gap, appropriate band gaps, and strong optical absorbance in the visible spectrum. Excitingly, by constructing Janus structures, an intrinsic electric field is realized that enhances the spatial separation and anisotropic migration of photoexcited electrons and holes. Further, this strategy can also alter the band alignment to provide an adequate photoexcited carrier driving force for water redox reactions. Moreover, the surface N vacancy can effectively lower the energy demand of both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) so that the catalytic process can be self-sustained under the potential provided by the photocatalyst alone. Particularly, the overall water splitting can proceed simultaneously and spontaneously on the surface of MoSiGeN4 and WSiGeN4 when pH is 3 or ≥8, respectively. These explorations offer new prospects for the design of highly efficient photocatalysts.

The measurement of crop nutrition is considerably significant in agricultural practices, especially in the application of mechanized variable rate fertilization. Feature extraction and model building are two important links in crop nutrition measurement by digital image. In this paper, a feature set of fusion multi-colour space in field prototype is extracted and an evaluation approach using stepwise-based ridge regression (SBRR) that uses correlation-based evaluation method is employed. First the image features of three known colour spaces are extracted, meanwhile a new colour space named rgb is constructed according to the characteristics that RGB colour space easily affected by light. Then the SBRR with nested cross validation is used to find the best evaluation model. By performance evaluation, the optimal SBRR model is obtained ( R 2 = 0.718 RMSE = 5.111). Additionally, compared with two other nutritional evaluation approach named back-propagation artificial neural network (BP-ANN) and k-nearest neighbors (KNN), SBRR achieves better performance in both R2 and RMSE. Furthermore the proposed model’s reliability is verified using the image dataset taken from the same wheat field in the next year. The R 2 and RMSE values are 0.794 and 4.304, respectively. The comparisons and verification show that our proposed SBRR approach can achieve better experimental results and can be considered a reliable and low-cost alternative for estimating the chlorophyll content of wheat leaves in field.

Yes-associated protein (YAP), as a co-activator of transcription factors, is a downstream protein in the Hippo signaling pathway with important functions in cell proliferation, apoptosis, invasion and migration. YAP also plays a key role in the development of CCl4-induced liver fibrosis. However, the mechanism of YAP during hepatic fibrosis progression and reversion is still unclear. Mild liver fibrosis was developed after 4 months of high-fat diet (HFD) stimulation, and we found that the YAP signaling pathway was activated. Here, we aim to reveal whether specific knockout of Yap gene in the liver can improve liver fibrosis induced by insulin resistance (IR) stimulated by HFD, and further explain its specific mechanism. We found that liver-specific Yap gene knockout improved IR-induced liver fibrosis and liver dysfunction, and this mechanism is related to the inhibition of the insulin signal pathway at the FoxO1 level. These findings provide a new insight, and Yap is expected to be a new target to reverse the early stage of liver fibrosis induced by IR.

Ultrawide bandgap semiconductors are fundamentally important in solid-state lighting, transparent electrodes and power electronics, but their 2D forms are rarely reported and less studied. By means of ab initio simulations, we predict new trigonal YOBr and monolayered crystals with ultrawide bandgaps and exceptional properties. It is demonstrated that trigonal YOBr is energetically, dynamically and mechanically stable and shows lower energy compared with other known experimental phases. We present that, under hydrostatic pressure, the bulk YOBr crystal undergoes a structural transformation from Rm to P4/nmm, accompanied by an indirect–direct band transition. By further exploring relevant metal oxyhalides MOX (M = Sc/Y and X = Cl/Br), we suggest that, owing to the small exfoliation energy, the monolayers promise experimental fabrication by mechanical cleavage, as for graphene. These MOX monolayers possess excellent stability, large bandgaps and high carrier mobilities. We reveal interesting indirect–direct bandgap transitions in uniaxially strained ScOCl and trigonal YOBr monolayers. In addition, we highlight that remarkable ultraviolet light absorption and appreciable band edges render these MOX monolayers great candidates for potential applications in UV-electronics and photocatalysis. Our findings open a new avenue to explore phase transitions in rare-earth oxyhalides under pressure/strain and provide promising ultrawide-bandgap semiconductors for future optoelectronic devices.

Constructing heterostructure solar cells using donor and acceptor semiconductors has attracted global interest owing to their high power conversion efficiency. In this paper, based on density functional theory calculations, we comprehensively evaluated 64 two-dimensional transition metal carbides (MXenes) to explore them as appropriate semiconductors for solar cells by material screening. The results highlight that Zr2CO2 (Hf2CO2) and Ti2CO2 are promising donor and acceptor materials, respectively. Interestingly, the heterostructures have a moderate band gap of 1.22 eV and exhibit a noticeable absorbance coefficient of 105 cm−1 in the visible light region. Moreover, the type-II nature of the heterostructures could induce effective electron–hole separation. Furthermore, the photocurrents of Ti2CO2/Zr2CO2 and Ti2CO2/Hf2CO2 heterostructure solar cell devices are competitive with those of silicon devices. In particular, Ti2CO2/Zr2CO2 and Ti2CO2/Hf2CO2 heterostructure solar cells deliver a very high power conversion efficiency of 22.74% and 19.56%, respectively. Our present study paves the way for facilitating the potential application of MXenes as photovoltaic materials.

Crystalline solids with ultralow thermal conductivity are paramount for the development of thermoelectric materials and thermal barrier coatings for efficient thermal energy management. Here, by high-throughput ab initio calculations, we predict a group of 56 novel layered semiconducting IV–V–VI (IV = Si, Ge Sn, Pb; V = As, Sb, Bi; VI = S, Se, Te) compounds that are energetically, mechanically and dynamically stable. We demonstrate that these hitherto-unknown semiconductors exhibit intrinsically ultralow lattice thermal conductivity between 0.28 and 2.02 W m−1 K−1 at room temperature, most of which fall below 1 W m−1 K−1. Such ultralow thermal conductivity can be attributed to the presence of avoided-crossing behavior between low-lying optical phonons and acoustic modes, which leads to the significant reduction of phonon group velocities and induces ultrahigh Gruneisen parameters causing strong anharmonic phonon–phonon scattering, thus short phonon mean free path and low κl. In addition, we reveal that these IV–V–VI compounds show significant anisotropy κl along different directions, arising from the anisotropic group velocity and anharmonicity due to the weak VI–VI interlayer interactions along the c-axis. Our work not only provides a large family of novel semiconductors with exceptionally low κl but also highlights the design of new low-κl materials.

Searching for highly efficient and cost-effective bifunctional electrocatalysts for the oxygen evolution reaction (OER), oxygen reduction reaction (ORR) and hydrogen evolution reaction (HER), which can be applied to water splitting, fuel cells and metal–air batteries, is critical for developing clean and renewable energies. Yet it remains a great challenge. By means of first-principles calculations, we have studied the OER, ORR and HER catalytic activity of Mo2B2 MBene-supported single-atom catalysts (SACs) by embedding a series of transition metal atoms in the Mo vacancy (TM@Mo2B2, TM = Ti, V, Cr, Mn, Fe, Co, Ni and Cu) as electrocatalysts. All TM@Mo2B2 SACs show excellent metallic conductivity, which would be favorable for the charge transfer in electrocatalytic reactions. Importantly, Ni@Mo2B2 can be used as a HER/OER bifunctional electrocatalyst with a lower |ΔGH| (−0.09 eV) for the HER under 1/4H coverage and a lower overpotential (ηOER = 0.52 V) than that of IrO2 (ηOER = 0.56 V) for the OER, while Cu@Mo2B2 can be used as an OER/ORR bifunctional electrocatalyst with a lower overpotential (ηOER = 0.31 V) than that of IrO2 (ηOER = 0.56 V) and RuO2 (ηOER = 0.42 V) for the OER and a lower overpotential of 0.34 V than that of Pt (ηORR = 0.45 V) for the ORR, for both of which the transition metal atoms serve as the active sites. This work could open up an avenue for the development of non-noble-metal-based bifunctional MBene electrocatalysts.

Two-dimensional (2D) Janus structures such as MoSSe and Janus graphene have grabbed global attention for their novel properties and interesting behaviors. In this study, via first-principles calculations, we have systematically explored the structural, electronic, and magnetic properties of Janus-functionalized Sc2CTT′ (T, T′ = H, O, OH, F, Cl). Interestingly, four Sc2COT′ were found to be ferrimagnetic half-metals with high predicted Curie temperatures, indicating their feasibility in spintronic applications. On the other hand, Sc2COHCl, Sc2CHCl, and Sc2CFCl are suitable photocatalysts for photocatalytic water splitting. In particular, Sc2COHCl with a bandgap of 0.99 eV is highlighted as an infrared light-driven photocatalyst. Sc2COHH, possessing an ideal direct band gap of 1.08 eV and noticeable optical absorption in the visible light region, is very promising as the donor material for solar cells. It is highlighted that the designed type II Sc2COHH/InS heterostructure solar cell could present a high power conversion efficiency of up to 21.04% by inducing effective photo-excited electron–hole separation, which is favorable for photodetection harvesting. We believe that our study will provide a feasible strategy for the design and application of MXenes.

Metal oxides are particularly promising high-temperature thermoelectric (TE) materials due to their excellent high-temperature stability, eco-friendliness and cost-effectiveness. Yet, their poor TE performance has become the main bottleneck for their wide application. As a result, it is imperative to find novel oxide materials with superior thermoelectric performance for applications at high temperatures. In this work, a high-throughput (HT) materials-discovery effort has been made to discover promising TE oxides using the ALKEMIE platform. A novel type of oxide MTa2O6 (M = Mg, Ca) was discovered for high-temperature TE applications. In addition, another screened oxide, SrTiO3, a well-known n-type perovskite oxide, was used as a benchmark for comparison. The calculated results indicate that CaTa2O6 possesses a similar band structure to SrTiO3 and thus superior electrical-transport performance. MgTa2O6 exhibits a peak value of the thermoelectric figure of merit, ZT, of larger than unity at 1000 K. We find that MgTa2O6 has a superior Seebeck coefficient compared with SrTiO3 or CaTa2O6. Further analysis of the electronic structure suggests that the flat conduction-band edge in MgTa2O6 produces a highly energy-dependent electronic density of states, and thus the high Seebeck coefficient. Furthermore, a significant reduction of the phonon relaxation time is the origin of the observed decrease in the calculated thermal conductivity between 300 K and 1000 K. The present work demonstrates the results of a rapid and successful HT screening of high-temperature TE materials, and can be extended to the exploration of other new materials.

2D van der Waals (vdW) heterostructures as potential materials for solar energy-related applications have been brought to the forefront for researchers. Here, by employing first-principles calculations, we proposed that the PtS2/GaSe vdW heterostructure is a distinguished candidate for photocatalytic water splitting and solar cells. It is shown that the PtS2/GaSe heterostructure exhibits high thermal stability with an indirect band gap of 1.81 eV. We further highlighted the strain induced type-V to type-II band alignment transitions and band gap variations in PtS2/GaSe heterostructures. More importantly, the outstanding absorption coefficients in the visible light region and high carrier mobility further guarantee the photo energy conversion efficiency of PtS2/GaSe heterostructures. Interestingly, the natural type-V band alignments of PtS2/GaSe heterostructures are appropriate for the redox potential of water. On the other hand, the power conversion efficiency of ZnO/(PtS2/GaSe heterostructure)/CIGS (copper indium gallium diselenide) solar cells can achieve ∼17.4%, which can be further optimized up to ∼18.5% by increasing the CIGS thickness. Our present study paves the way for facilitating the potential application of vdW heterostructures as a promising photocatalyst for water splitting as well as the buffer layer for solar cells.

China produces half of the world’s vegetables. The production uses 1.7% of the global harvest area of crops but accounts for 7.8% of the chemical fertilizers and 6.6% of crop-sourced greenhouse gas (GHG) emissions worldwide. Using an innovative management programme, the integrated knowledge and products strategy (IKPS), we demonstrate opportunities for producing more vegetables with lower environmental impacts in China’s vegetable production systems. Combining soil–crop system management practices with enhanced-efficiency fertilizer products, IKPS was tested through 54 site-year field experiments in China’s major agro-ecological zones by a national research network over 12 years. Compared with current farming practices, the adoption of IKPS decreased the nitrogen (N) application rate by 38%, N surplus by 65% and GHG emissions by 28%, while increasing yield by 17%. Scenario analyses showed that adoption of IKPS in China’s vegetable production could mitigate resource and environmental burdens while enhancing food and nutrition security. Chinese vegetable production accounts for 1.7% of the global harvest area of crops but uses 7.8% of the chemical fertilizer and produces 6.6% of the crop-sourced greenhouse gas emissions of the global agricultural sector. An innovative management programme offers opportunities for producing more vegetables with lower environmental impacts.

In the wake of the considerable investigation of two-dimensional (2D) materials, van der Waals (vdW) heterostructures based on atomically thin 2D materials show large potential for functional elect...

The disadvantages of high power consumption and slow operating speed hinder the application of phase-change materials (PCMs) for a universal memory. In this work, based on a rigorous experimental scheme, we synthesized a series of YxSb2-xTe3 (0 ≤ x ≤ 0.333) PCMs and demonstrated that Y0.25Sb1.75Te3 (YST) is an excellent candidate material for the universal phase-change memory. This YST PCM, even being integrated into a conventional T-shaped device, exhibits an ultralow reset power consumption of 1.3 pJ and a competitive fast set speed of 6 ns. The ultralow power consumption is attributed to the Y-reduced thermal and electrical conductivity, while the maintained crystal structure of Sb2Te3 and the grain refinement provide the competitive fast crystallization speed. This work highlights a novel way to obtain new PCMs with lower power consumption and competitive fast speed toward a universal memory.

Inorganic electrides have gained remarkable attention for their intrinsic physical properties derived from loosely bound anionic electrons. Herein, using ab initio evolutionary structure search, we...

Novel tetragonal PrVO4 nanocubes have been fabricated by a simple and green hydrothermal method. The excellent catalytic activity of the samples was investigated for the degradation of methylene blue aqueous solution under visible light irradiation. As compared with pure PrVO4 and H2O2, the photocatalytic efficiency of the PrVO4/H2O2 system was enhanced about 1.5 and 9 folds, respectively. In the whole photocatalytic process, h+ and ·OH radicals played the dominant roles on the basis of the trapping test. The significantly enhanced photocatalytic activity was attributed to the synergistic effect between photocatalytic oxidation of PrVO4 and heterogeneous photo-Fenton-like reaction of V(V)/H2O2. Finally, a possible photocatalytic mechanism was proposed.

Ultrathin semiconductors with great electrical and photovoltaic performance hold tremendous promise for fundamental research and applications in next-generation electronic devices. Here, we report new 2D direct-bandgap semiconductors, namely mono- and few-layer In2Ge2Te6, with a range of desired properties from ab initio simulations. We suggest that 2D In2Ge2Te6 samples should be highly stable and can be experimentally fabricated by mechanical exfoliation. They are predicted to exhibit extraordinary optical absorption and high photovoltaic conversion efficiency (≥31.8%), comparable to the most efficient single-junction GaAs solar cell. We reveal that, thanks to the presence of van Hove singularities in the band structure, unusual quantum-phase transitions could be induced in monolayers via electrostatic doping. Furthermore, taking bilayer In2Ge2Te6 as a prototypical system, we demonstrate the application of van der Waals pressure as a promising strategy to tune the electronic and stacking property of 2D crystals. Our work creates exciting opportunities to explore various quantum phases and atomic stacking, as well as potential applications of 2D In2Ge2Te6 in future nanoelectronics.

In recent years, a new large family of two dimensional transition metal carbides, carbonitrides, and nitrides, so-called MXenes, have grabbed considerable attention, owing to their many fascinating physical and chemical properties that are closely related to the rich diversity of their elemental compositions and surface terminations. In particular, it is easy for MXenes to form composites with other materials such as polymers, oxides, and carbon nanotubes, which further provides an effective way to tune the properties of MXenes for various applications. Not only have MXenes and MXene-based composites come into prominence as electrode materials in the energy storage field as is widely known, but they have also shown great potential in environment-related applications including electro/photocatalytic water splitting, photocatalytic reduction of carbon dioxide, water purification and sensors, thanks to their high conductivity, reducibility and biocompatibility. In this review, we summarize the synthesis and properties of MXenes and MXene-based composites and highlight their recent advances in environment-related applications. Challenges and perspectives for future research are also outlined.

Fe3O4 is a promising anode material for Li-ion batteries because of its high theoretical capacity, low cost, and natural abundance. Nevertheless, the intrinsically sluggish reaction kinetics and huge volume variation severely limit its reversible capacity and cycle life. Herein, we synthesized a few-layered Ti3C2 (f-Ti3C2)-wrapped carbon-coated Fe3O4 (C-Fe3O4) composite (C-Fe3O4/Ti3C2) with a three-dimensional (3D) spring-roll-like structure to circumvent the intrinsic limits and prolong the cycling life of Fe3O4. As an anode for a Li-ion battery, the 3D C-Fe3O4/Ti3C2 composite not only inherits the high electrochemical activity of Fe3O4, but also exhibits excellent electrical and ionic conductivity. The f-Ti3C2 can effectively increase the electrical and ionic conductivity of C-Fe3O4, and the f-Ti3C2 partially accommodates the huge volume change in Fe3O4 caused by the Li+ insertion/extraction processes. Furthermore, the self-restacking of f-Ti3C2 is significantly prevented by C-Fe3O4, which contributes a larger surface area and more accessible active sites. The C-Fe3O4/Ti3C2 anodes displayed remarkable electrochemical properties and ultralong cycling life at high current density. A reversible capacity of 997 mA h g−1 can be delivered at 1 A g−1 even after 2000 cycles, and as high as 543 mA h g−1 can be retained at 5 A g−1. These results indicate that the 3D C-Fe3O4/Ti3C2 composite is a promising candidate anode for a high-energy density battery with a long lifespan.

Sb2Te3 phase-change material possesses the highest crystallization speed and hence the highest operating speed among investigated phase-change systems. Doping with Y or Sc has been exploited to optimize the performance of Sb2Te3, yet the substituted Y atoms are strongly clustered, while Sc is extremely expensive and thus is unfavourable for commercialization. In this work, we have successfully obtained better-performance and moderate-cost phase-change materials by co-doping Sc and Y based on ab initio calculations and ab initio molecular-dynamics simulations (AIMD). Sc can shrink the lattice while Y expands the lattice, which makes a perfect match between original and co-doped configurations and hence can benefit by maximizing the release of lattice strain. The co-doping increases the band gap to around 0.5 eV, and the concentration ratio of Sc and Y dopants provides an advantageous tool for controlling the electronic structure. Results of calculations using the BoltzTraP code show that co-doping can result in a significant reduction in the electrical conductivity at room temperature. AIMD simulation of amorphous co-doped Sb2Te3 shows that the incorporation of Sc and Y atoms can effectively improve the thermal stability of amorphous Sb2Te3. Overall, co-doping Sc and Y is a feasible way to improve the properties of Sb2Te3 for phase-change memory applications.

Single-layer 1T-TaSe2 has recently been found to host a Mott insulating ground state entwined with a commensurate charge density wave (CDW). However, the interplay between the CDW order and the Mott state remains unclear and elusive. Using first-principles calculations, we show that the CDW order with Star of David lattice distortions induces the formation of two different types of Ta-d orbitals (one is localized and the other is extended), and the Mott insulating state is brought on by the electron correlation in the localized orbital which is separated from the extended orbitals in energy. Interestingly, when a compressive biaxial strain is applied on monolayer 1T-TaSe2, the Mott insulating phase will first transform into a charge-transfer insulating phase and then into a normal metallic phase with increasing strain. The CDW always persists and is even enhanced under the strain, indicating that the Mottness collapse is unexpectedly not at the expense of suppression of the long-range CDW order. We further reveal that the realization of metallization in the CDW phase occurs because the localized orbital is immersed into the extended-orbital-spanned Fermi sea and its Hubbard splitting is quenched by orbital hybridization. Our findings may provide significant implications for fine control over correlated electronic states, possessing potential applications in ultrafast resistive switching.