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Herein, via first‐principle calculations and theoretical analysis, a new Dirac semimetal carbon system called C32, which is composed of pentagonal, hexagonal, heptagonal, and octagonal carbon rings is systematically investigated. The stability of C32 is verified by calculating the phonon dispersion, elastic constants, etc., and an appropriate pathway for experimental synthesis is proposed. Besides, it is discovered that the system holds the quadruple rotation and inversion symmetry, resulting in the emergence of eight twisted Dirac cones (D1 and D2) with a highly anisotropic Fermi velocity from 3.83 × 105 to 8.96 × 105 m s−1 along different k directions. To substantiate the semimetallic nature of C32, its nontrivial topological properties are confirmed through the presence of topologically protected edge states, and the nonzero ℤ2 topological invariant. More importantly, by introducing biaxial strain, it is uncovered that Dirac cones can gradually evolve into a nodal line, and the perfect nodal line can be obtained when the biaxial strain is 13.3%. Furthermore, by constructing the tight‐binding model, the appearance of the Dirac cone is perfectly repeated and its evolution into the nodal line under biaxial strain is explained. [ABSTRACT FROM AUTHOR]

Spin current generation from charge current in nonmagnetic materials promises an energy-efficient scheme for manipulating magnetization in spintronic devices. In some asymmetric two-dimensional (2D) materials, the Rashba and valley effects coexist owing to strong spin–orbit coupling (SOC), which induces the spin Hall effect due to spin-momentum locking of both effects. Herein, we propose a new Janus structure MoSiAs2Se with both valley physics and the Rashba effect and reveal an effective way to modulate the properties of this structure. The results demonstrated that applying an external electric field is an effective means to modulating the electronic properties of MoSiAs2Se, leading to both type I–II phase transitions and semiconductor–metal phase transitions. Furthermore, the coexistence of the Rashba and valley effects in monolayer MoSiAs2Se contributes to the spin Hall effect (SHE). The magnitude and direction of spin Hall conductivity can also be manipulated with an out-of-plane electric field. Our results enrich the physics and materials of the Rashba and valley systems, opening new opportunities for the applications of 2D Janus materials in spintronic devices. [ABSTRACT FROM AUTHOR]

The past decade witnessed substantial attention toward metal‐organic frameworks (MOFs) for photocatalytic water splitting owing to their versatile structural and optoelectronic characteristics. However, MOFs capable of efficient photocatalytic overall water splitting (OWS) remain notably scarce. Although MOF‐based photocatalysts with OWS potential are highly promising due to their diverse building blocks and topological configurations, the vast number of possible MOFs renders traditional trial‐and‐error materials discovery approaches impractical. Herein, a data‐driven methodology that integrates machine learning with high‐throughput first‐principles computations to identify MOFs with OWS capability is presented. By systematically assessing factors including water stability, band gap, band positions, charge carrier transport, and optical absorption properties, 14 MOFs from the Quantum‐MOF (QMOF) database containing over 20,000 MOFs as promising candidates for visible‐light‐driven OWS are identified. Notably, five of them exhibit exceptional electronic and optical properties, outperforming previously reported MOF OWS photocatalysts, such as UIO66(Zr)‐NH2, MIL125(Ti)‐NH2, and MIL53(Al)‐NH2 is established. This work represents a large‐scale, data‐driven exploration of MOF‐based photocatalysts for water splitting, shedding light on the untapped potential of photocatalysis in MOFs. [ABSTRACT FROM AUTHOR]

In carbon allotropes, a series of topological semi-metals have been predicted, but both novel electronic properties and mechanical characteristics, e.g. , a negative Poisson's ratio (NPR), are rarely discovered in the same sp 2 type system. Here, a new three-dimensional carbon network, named WZGN, constructed from distorted one-dimensional zigzag graphene nanoribbons is proposed. The stability of the system is fully ensured by the phonon dispersion, AIMD simulation, and binding energy calculations. Besides, it is found that the system holds both topologically protected nodal line semi-metal properties together with an NPR property. Especially, the value of the NPR can exceed -0.36 when 21% uniaxial tensile strain along the c '-direction is applied. Our findings point out that nodal line semi-metals can be compatible with intrinsic NPR properties in a wide strain range in carbon systems with sp 2 hybridization, suggesting possible applications in mechanical and electronics fields.

Spin current generation from charge current in nonmagnetic materials promises an energy-efficient scheme for manipulating magnetization in spintronic devices. In some asymmetric two-dimensional (2D) materials, the Rashba and valley effects coexist owing to strong spin-orbit coupling (SOC), which induces the spin Hall effect due to spin-momentum locking of both effects. Herein, we propose a new Janus structure MoSiAs 2 Se with both valley physics and the Rashba effect and reveal an effective way to modulate the properties of this structure. The results demonstrated that applying an external electric field is an effective means to modulating the electronic properties of MoSiAs 2 Se, leading to both type I-II phase transitions and semiconductor-metal phase transitions. Furthermore, the coexistence of the Rashba and valley effects in monolayer MoSiAs 2 Se contributes to the spin Hall effect (SHE). The magnitude and direction of spin Hall conductivity can also be manipulated with an out-of-plane electric field. Our results enrich the physics and materials of the Rashba and valley systems, opening new opportunities for the applications of 2D Janus materials in spintronic devices.

The valley polarization, induced by the magnetic proximity effect, in monolayer transition metal dichalcogenides (TMDCs), has attracted significant attention due to the intriguing fundamental physics. However, the enhancement and modulation of valley polarization for real device applications is still a challenge. Here, using first-principles calculations we investigate the valley polarization properties of monolayer TMDCs CrS 2 and CrSe 2 and how to enhance the valley polarization by constructing Janus CrSSe (with an internal electric field) and modulate the polarization in CrSSe by applying external electric fields. Janus CrSSe exhibits inversion symmetry breaking, internal electric field, spin-orbit coupling, and compelling spin-valley coupling. A magnetic substrate of the MnO 2 monolayer can induce a modest magnetic moment in CrSe 2 , CrSe 2 , and CrSSe. Notably, the Janus structure with an internal electric field has a much larger valley p compared with its non-Janus counterparts. Moreover, the strength of valley polarization can be further modulated by applying external electric fields. These findings suggest that Janus materials hold promise for designing and developing advanced valleytronic devices.

7-Atomic-layer materials have attracted much attention recently because of their rich structures and more-abundant properties than 3- and 5-atomic-layer materials. However, the thermoelectric properties of the new monolayer materials have not been explored yet. Here, we investigate the thermoelectric conversion efficiency of a 7-atomic-layer structure ZrGe 2 N 4 , which is selected from a series of 7-atomic-layer structures according to their stabilities and thermoelectric properties. The results indicate that this material is an excellent candidate for high-performance thermoelectric materials. Its figure of merit ZT value is close to 4.0 at high temperature. The high efficiency originates from two factors: one is the lower thermal conductivity of ZrGe 2 N 4 and the other is the decoupling of electron and phonon transport in the 7-atomic-layer structures.