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In this paper, density-functional theory calculations are performed to explore how the biaxial strain and electric field affect the electronic properties of MoS2/ScCl3 van der Waals (vdW) heterostructure. The pristine MoS2/ScCl3 vdW heterostructure is a semiconductor with an indirect bandgap of 1.55 eV which is also with type II band alignment. The results show that the bandgap, band alignment, and effective mass of the MoS2/ScCl3 heterostructure can be effectively modulated by mechanical strain and external electric field. The bandgap decreases for both tensile and compressive strains and a transition from type II band alignment to type I upon tensile strain. When positive field applying (from MoS2 to the ScCl3), the type II heterostructure transforms to type I and the bandgap remains about 1.55 eV. The type II heterostructure can remain but the bandgap is reduced as the negative electric field is applied. These results suggest that MoS2/ScCl3 heterostructure is a possible candidate for high-performance nanoelectronic devices. [ABSTRACT FROM AUTHOR]

The threshold displacement energies (TDEs) of lattice atoms in lithium ferrite (LiFe5O8) are calculated using first‐principles molecular dynamics simulations. The TDEs vary with crystal direction and sublattice. The weighted average TDEs are 34.65, 28.54, 38.85, 37.92, and 34.31 eV for FeTetra, FeOct, Li, OI, and OII atoms in LiFe5O8, respectively. The FeOct primary knock‐on atom (PKA) has the smallest TDE. Various defects, including vacancies (VFeTetra, VFeOct, VLi, VOI, and VOII), interstitials (IFe, ILi and IO), antisite defects (LiFeOct, LiFeTetra and FeLi), split interstitials (DFeFe, DLiLi, DLiFe, and DOO), crowding defects (CrowFeFeFe) and exchange defects (OO), are formed by low‐energy recoil events. The effect of the presence of these defects on the magnetic behavior in LFO is investigated using density functional theory. The occupation of the octahedral and tetrahedral sublattice in LiFe5O8 has an important effect on magnetization. The net magnetization decreases or increases when a Fe atom at an octahedral or tetrahedral site is replaced by a nonmagnetic atom, respectively. These results are helpful for using irradiation to tune the magnetic behavior of LiFe5O8 and applying magnetic devices based on LiFe5O8 in the presence of irradiation. [ABSTRACT FROM AUTHOR]

Semiconductor quantum dots (QDs) have attracted tremendous attention in the field of photocatalysis, owing to their superior optoelectronic properties for photocatalytic reactions, including high absorption coefficients and long photogenerated carrier lifetimes. Herein, by choosing 2‐(3,4‐dimethoxyphenyl)‐3‐oxobutanenitrile as a model substrate, we demonstrate that the stereoselective (>99 %) C−C oxidative coupling reaction can be realized with a high product yield (99 %) using zwitterionic ligand capped CsPbBr3 perovskite QDs under visible light illumination. The reaction can be generalized to different starting materials with various substituents on the phenyl ring and varied functional moieties, producing stereoselective dl‐isomers. A radical mediated reaction pathway has been proposed. Our study provides a new way of stereoselective C−C oxidative coupling via a photocatalytic means using specially designed perovskite QDs. [ABSTRACT FROM AUTHOR]

Monolayer MoS2 has attracted much attention due to its catalytic performance in water splitting. However, the low electronic conductivity and limited number of active catalytic sites of monolayer MoS2 limit the hydrogen production efficiency. In this work, the effect of phosphorus doping on the electronic characteristics and catalytic activity of the hydrogen evolution reaction in monolayer MoS2 was studied using density functional theory. A semiconductor to conductor transformation occurs in monolayer MoS2(1-x)Px for x larger than 0.25. The Gibbs free energy is greatly reduced from 2.18 to 0.03 eV for the adsorption of hydrogen on monolayer MoS0.5P0.75. The Gibbs free energy for hydrogen atom adsorption on monolayer MoS0.5P0.75 is between 0.03 and 0.16 eV with hydrogen coverage θH = 1/12-7/12 ML. The Gibbs free energy is close to zero, indicating that phosphorus doping can trigger the basal plane active sites on monolayer MoS2; thus, this work provides a new design for the improvement of the catalytic activity of two-dimensional transition metal dichalcogenide-based catalysts by phosphorus doping. [ABSTRACT FROM AUTHOR]

The threshold displacement energies (TDEs) of lattice atoms in lithium ferrite (LiFe5O8) are calculated using first‐principles molecular dynamics simulations. The TDEs vary with crystal direction and sublattice. The weighted average TDEs are 34.65, 28.54, 38.85, 37.92, and 34.31 eV for FeTetra, FeOct, Li, OI, and OII atoms in LiFe5O8, respectively. The FeOct primary knock‐on atom (PKA) has the smallest TDE. Various defects, including vacancies (VFeTetra, VFeOct, VLi, VOI, and VOII), interstitials (IFe, ILi and IO), antisite defects (LiFeOct, LiFeTetra and FeLi), split interstitials (DFeFe, DLiLi, DLiFe, and DOO), crowding defects (CrowFeFeFe) and exchange defects (OO), are formed by low‐energy recoil events. The effect of the presence of these defects on the magnetic behavior in LFO is investigated using density functional theory. The occupation of the octahedral and tetrahedral sublattice in LiFe5O8 has an important effect on magnetization. The net magnetization decreases or increases when a Fe atom at an octahedral or tetrahedral site is replaced by a nonmagnetic atom, respectively. These results are helpful for using irradiation to tune the magnetic behavior of LiFe5O8 and applying magnetic devices based on LiFe5O8 in the presence of irradiation. [ABSTRACT FROM AUTHOR]

Halide perovskites have distinguished themselves among the numerous optoelectronic materials due to their versatile processing technology and exceptional optical response. Unfortunately, their stability and toxicity from heavy metals severely hamper their development, in addition to the challenge of further improving photovoltaic performance. Hence, a lead-free perovskite-based heterojunction, C 2 N/CsGeI 3 , is investigated using a hybrid density functional, including electron structures, charge density differences, optical properties and more. The study reveals the presence of a built-in electric field directed from the CsGeI 3 to the C 2 N layer. Moreover, based on the work function, it is confirmed that the electrons are transferred in a Z-scheme mechanism after the CsGeI 3 contacts with the C 2 N layer. Under light irradiation, the construction of the C 2 N/CsGeI 3 heterojunction significantly enhances optical absorption within the range of visible-light wavelengths. Additionally, the impact of interfacial strain on the C 2 N/CsGeI 3 is explored and discussed. These findings not only suggest that the C 2 N/CsGeI 3 heterojunction holds promise for photovoltaic applications but also provide a theoretical insight into lead-free perovskite-based functional materials.

Single-atom catalysts (SACs) have attracted wide attention to be acted as potential electrocatalysts for nitrogen reduction reaction (NRR). However, the coordination environment of the single transition metal (TM) atoms is essential to the catalytic activity for NRR. Herein, we proposed four types of 3-, 4-coordinated and π-d conjugated TM x B 3 N 3 S 6 (x=2, 3, TM=Ti, V, Cr, Mn, Fe, Zr, Nb, Mo, Tc, Ru, Hf, Ta, W, Re and Os) monolayers for SACs. Based on density functional theory (DFT) calculations, I-TM 2 B 3 N 3 S 6 and III-TM 3 B 3 N 3 S 6 are the reasonable 3-coordinated and 4-coordinated structures screening by structure stable optimizations, respectively. Next, the structural configurations, electronic properties and catalytic performances of 30 kinds of the 3-coordinated I-TM 2 B 3 N 3 S 6 and 4-coordinated III-TM 3 B 3 N 3 S 6 monolayers with different single transition metal atoms were systematically investigated. The results reveal that B 3 N 3 S 6 ligand is an ideal support for TM atoms due to existence of strong TM-S bonds. The 3-coordinated I-V 2 B 3 N 3 S 6 is the best SAC with the low limiting potential (U L ) of -0.01 V, excellent stability (E f =-0.32 eV, U diss =0.02 V) and remarkable selectivity characteristics. This work not only provides novel π-d conjugated SACs, but also gives theoretical insights into their catalytic activities and offers reference for experimental synthesis., (© 2023 Wiley-VCH GmbH.)

We propose a reconfigurable spin tunnel diode based on a small spin-gapped semiconductor (non-doped VS 2 monolayer) and semi-metallic magnets (doped VS 2 monolayer) separated by a thin insulating tunneling barrier (h-BN). By using first-principles calculations assisted by the nonequilibrium Green's function method, we have carried out a comprehensive study of spin-dependent current and spin transport properties while varying the bias. The device exhibited a magnetization-controlled diode-like behavior with forward-allowed current under antiparallel magnetizations and reverse-forbidden current under parallel magnetizations at the two electrodes. The threshold voltage is tunable by the hole doping density of VS 2 monolayers. The doping effect on VS 2 monolayers indicates that the magnetic moments, the Heisenberg exchange parameters and Curie temperatures can be monotonically reduced by a larger hole doping density. Our study on VS 2 heterostructures has presented a simple and practical device strategy with very promising applications in spintronics.

Thermoelectric (TE) materials have attracted great attention in solving the problems in the waste heat field, while low figure of merit and poor material stability drastically limit their practical applications. In this work, a two-dimensional (2D) Sc 2 Si 2 Te 6 monolayer was systematically explored as a promising TE material via ab initio methods. The results reveal that the Sc 2 Si 2 Te 6 monolayer possesses an indirect band gap with a rhombohedral crystal phase and exhibits excellent dynamic stability. The lower electronic/lattice thermal conductivity and higher electron carrier mobility result in good n-type power factor parameters between 6.24 × 10 10 and 1.5 × 10 11 W m -1 s -1 K -2 from 300 to 700 K. Such combined merits of low thermal conductivity and high power factor parameters endow the Sc 2 Si 2 Te 6 monolayer with superior thermoelectric properties with figure of merit ( ZT ) values of 1.41 and 3.81 at 300 K and 700 K, respectively. This study presented here can shed light on the future design of various 2D materials for thermoelectric applications.

A low thermal conductivity and a high power factor are essential for efficient thermoelectric materials. The lattice thermal conductivity can be reduced by reducing the dimensions of the materials, thus improving the thermoelectric performance. In this work, the electronic, carrier and phonon transport and the thermoelectric properties of ZrNX (X = Cl, Br, and I) monolayers were investigated using density functional theory and Boltzmann transport theory. The electronic and phonon transport show anisotropic properties. The thermal conductivities are 20.8, 14.6 and 12.4 W m -1 K -1 at room temperature along the y -direction for the ZrNCl, ZrNBr, and ZrNI monolayers, respectively. Combining the low lattice thermal conductivity and the high power factor results in an excellent thermoelectric performance of the ZrNX monolayers. The thermoelectric figure of merit of ZrNX monolayers can reach magnitudes of ∼0.49-3.15 by optimal hole and electron concentrations between 300 and 700 K. ZrNX monolayers with high ZT values for n- and p-type materials would thus be novel, promising candidate 2D thermoelectric materials for heat-electricity conversion.

Semiconductor quantum dots (QDs) have attracted tremendous attention in the field of photocatalysis, owing to their superior optoelectronic properties for photocatalytic reactions, including high absorption coefficients and long photogenerated carrier lifetimes. Herein, by choosing 2-(3,4-dimethoxyphenyl)-3-oxobutanenitrile as a model substrate, we demonstrate that the stereoselective (>99 %) C-C oxidative coupling reaction can be realized with a high product yield (99 %) using zwitterionic ligand capped CsPbBr 3 perovskite QDs under visible light illumination. The reaction can be generalized to different starting materials with various substituents on the phenyl ring and varied functional moieties, producing stereoselective dl-isomers. A radical mediated reaction pathway has been proposed. Our study provides a new way of stereoselective C-C oxidative coupling via a photocatalytic means using specially designed perovskite QDs., (© 2020 Wiley-VCH GmbH.)

Lead-free perovskites and their analogues have been extensively studied as a class of next-generation luminescent and optoelectronic materials. Herein, we report the synthesis of new colloidal Cs4M(ii)Bi2Cl12 (M(ii) = Cd, Mn) nanocrystals (NCs) with unique luminescence properties. The obtained Cs4M(ii)Bi2Cl12 NCs show a layered double perovskite (LDP) crystal structure with good particle stability. Density functional theory calculations show that both samples exhibit a wide, direct bandgap feature. Remarkably, the strong Mn-Mn coupling effect of the Cs4M(ii)Bi2Cl12 NCs results in an ultra-short Mn photoluminescence (PL) decay lifetime of around 10 μs, around two orders of magnitude faster than commonly observed Mn2+ dopant emission in NCs. Diluting the Mn2+ ion concentration through forming Cs4(Cd1-xMnx)Bi2Cl12 (0 < x < 1) alloyed LDP NCs leads to prolonged PL lifetimes and enhanced PL quantum yields. Our study provides the first synthetic example of Bi-based LDP colloidal NCs with potential for serving as a new category of stable lead-free perovskite-type materials for various applications.

Concerns about the toxicity of lead-based perovskites have aroused great interest for the development of alternative lead-free perovskite-type materials. Recently, theoretical calculations predict that Pb 2+ cations can be substituted by a combination of Cu 2+ and Sb 3+ cations to form a vacancy-ordered layered double perovskite structure with superior optoelectronic properties. However, accessibilities to this class of perovskite-type materials remain inadequate, hindering their practical implementations in various applications. Here, we report the first colloidal synthesis of Cs 4 CuSb 2 Cl 12 perovskite-type nanocrystals (NCs). The resulting NCs exhibit a layered double perovskite structure with ordered vacancies and a direct band gap of 1.79 eV. A composition-structure-property relationship has been established by investigating a series of Cs 4 Cu x Ag 2-2 x Sb 2 Cl 12 perovskite-type NCs (0 ≤ x ≤ 1). The composition induced crystal structure transformation, and thus, the electronic band gap evolution has been explored by experimental observations and further confirmed by theoretical calculations. Taking advantage of both the unique electronic structure and solution processability, we demonstrate that the Cs 4 CuSb 2 Cl 12 NCs can be solution-processed as high-speed photodetectors with ultrafast photoresponse and narrow bandwidth. We anticipate that our study will prompt future research to design and fabricate novel and high-performance lead-free perovskite-type NCs for a range of applications.