Sodium-ion batteries (SIBs) have attracted considerable attention due to the intrinsic safety and high abundance of sodium. However, the lack of high-performance anode materials becomes a main obstacle for the development of SIBs. Here, we identify an ideal anode material, a metallic TiC monolayer with not only remarkably high storage capacity of 1278 mA h g but also low barrier energy and open-circuit voltage, through first-principles swarm-intelligence structure calculations. TiC still keeps metallic after adsorbing two-layer Na atoms, ensuring good electrical conductivity during the battery cycle. Besides, high melting point and superior dynamical stability are in favor of practical application. Its excellent performance can be mainly attributed to the presence of an unusual n-biphenyl unit in the TiC monolayer. High cohesive energy, originating from multibonding coexistence (e.g., covalent, ionic, and metal bonds) in the TiC monolayer, provides strong feasibility for experimental synthesis. In comparison with TiC, functionalized TiC with oxygen shows a higher storage capacity; meanwhile, it keeps nearly the same barrier energy. This is in sharp contrast with metal-rich MXenes. These intriguing properties make the TiC monolayer a promising anode material for SIBs.

to observe jerks follows a power law spectrum with energy exponents close to α ≈ 2. At even lower temperatures, the boundary kinetics becomes erratic even in our large (one million atoms) system. The lateral movement of twin walls is found for our thin twin walls (w = 3 layers) to operate by kinks which propagate along the twin wall. The needle domains nucleate either from the surface or from other existing twin walls. Intersections of twin walls constitute pinning centers which impede the free movement of the kinks in the walls. These intersection points act then as a pattern of intrinsic, self-induced defects which lead ultimately to the power law distribution of the crackling noise of the domain walls.

Graphene and phosphorene are two major types of atomically thin two-dimensional materials under extensive investigation. However, the zero band gap of graphene and the instability of phosphorene greatly restrict their applications. Here, we make first-principle unbiased structure search calculations to identify a new buckled graphene-like PC6 monolayer with a number of desirable functional properties. The PC6 monolayer is a direct-gap semiconductor with a band gap of 0.84 eV, and it has an extremely high intrinsic conductivity with anisotropic character (i.e., its electron mobility is 2.94 × 105 cm2 V–1 s–1 along the armchair direction, whereas the hole mobility reaches 1.64 × 105 cm2 V–1 s–1 along the zigzag direction), which is comparable to that of graphene. On the other hand, PC6 shows a high absorption coefficient (105 cm–1) in a broad band, from 300 to 2000 nm. Additionally, its direct band gap character can remain within a biaxial strain of 5%. All these appealing properties make the predicted PC6 monolayer a promising candidate for applications in electronic and photovoltaic devices.

Electrides are unique compounds where most of the electrons reside at interstitial regions of the crystal behaving as anions, which strongly determines its physical properties. Interestingly, the magnitude and distribution of interstitial electrons can be effectively modified either by modulating its chemical composition or external conditions (e.g., pressure). Most of the electrides under high pressure are nonmetallic, and superconducting electrides are very rare. Here we report that a pressure-induced stable Li 6 P electride, identified by first-principles swarm structure calculations, becomes a superconductor with a predicted superconducting transition temperature T c of 39.3 K, which is the highest among the already known electrides. The interstitial electrons in Li 6 P, with dumbbell-like connected electride states, play a dominant role in the superconducting transition. Other Li-rich phosphides, Li 5 P, Li 11 P 2 , Li 15 P 2 , and Li 8 P, are also predicted to be superconducting electrides, but with a lower T c. Superconductivity in all these compounds can be attributed to a combination of a weak electronegativity of phosphorus (P) with a strong electropositivity of lithium (Li), and opens up the interest to explore high-temperature superconductivity in similar binary compounds.

Sodium-ion batteries (SIBs) have become one of the most promising energy storage devices due to the high abundance and safety of sodium.

A novel mechanism for the generation of device materials with very high domain boundary densities is described: we shear the sample in a computer experiment and achieve higher twin densities than in rapid quench. These domain patterns are very stable. Elastically soft materials (image with 6.4$ \times $10(5) atoms) has greater twin densities than hard materials, even for nano-crystals.

Two dimensional TaC2is a promising anode material from the standpoint of a high specific capacity, fast Li diffusion rate, low operating voltage, and good electronic conductivity.

An important goal in chemistry is to prepare Frich transition metal fluorides due to the high oxidation states and potential applications such as oxidating and fluorinating agents. Thus far, the highest F stoichiometry in the neutral transition metal fluorides is 7. Here, we identify a hitherto unknown IrF 8 compound through first-principles swarmintelligence structure search calculations under high pressure. The three identified IrF 8 phases exhibit typical molecular crystal characters, showing +8 oxidation state in Ir. The spatial symmetry of the basic building block in the three IrF 8 phases gradually increases with pressure (e.g., dodecahedron → square antiprism → quasicube). The pressure-induced faster increase of Ir 5d orbital energy level with respect to F 2p provides a strong charge transfer driving force from Ir 5d to F 2p, facilitating the formation of F-rich compounds. More interestingly, the predicted electron affinities of the three predicted IrF 8 phases are comparable/larger than that of PtF 6 , the strongest oxidation agent in the third row transition metal hexafluorides. The built high-pressure phase diagram of Ir−F binary compounds provides useful information for experimental synthesis.