Similar Electronegativity Research Articles

La-Ni-Si: A Gold Mine with a Diamond.

The La-poor part of the ternary La-Ni-Si system has been explored leading to the discovery and structural characterization of four new polar intermetallic compounds. LaNi5Si2 [BaAu5Ga2 type, oP64, space group Pnma, a = 7.8223(7) Å, b = 6.3894(6) Å, c = 17.843(2) Å, V = 891.8(2) Å3, Z = 8] features a diamond (lonsdaleite)-like homoatomic Ni framework and is the first Ni representative of a larger family of compounds typically formed by aurides. La2Ni8Si3 [Eu2Ni8Si3 type, tP52, P42/nmc, a = 10.0278(3) Å, c = 7.5047(4) Å, V = 754.65(6) Å3, Z = 4] is characterized by homoatomic Ni4 tetrahedra and rectangles. LaNi5Si3 [SrNi5P3 type, oS36, Cmcm, a = 3.722(2) Å, b = 11.759(5) Å, c = 11.622(3) Å, V = 508.7(3) Å3, Z = 4] is governed by extensive heteroatomic bonding and characterized by homopolyhedral packing. La3Ni4Si2 [Ce3Ni4Si2 type, mC36, C2/c, a = 15.819(1) Å, b = 6.0068(5) Å, c = 7.4918(6) Å, β = 103.163(5)°, V = 693.17(10) Å3, Z = 4] is a new member of homologous series that includes La3Ni3Si2 and La3Ni3.5Si2. We conclude that the similar radii and electronegativities of Ni and Si are the reason for the incredible diversity of compositions and structures in this system.

Robustly Boosting Thermoelectric Performance of N-Type PbSe via Lattice Plainification and Dynamic Doping.

Ideal thermoelectrics shall possess a high average ZT, which relies on high carrier mobility and appropriate carrier density at operating temperature. However, conventional doping usually results in a temperature-independent carrier concentration, making performance optimization over a wide temperature range be challenging. This work demonstrates the combination of lattice plainification and dynamic doping strategies is an effective route to boost the average ZT of N-type PbSe. Because Sn and Pb have similar ionic radii and electronegativity, this allows Sn to fill the intrinsic Pb vacancies and effectively improves the carrier mobility of PbSe to 1300 cm2 V-1 s-1. Furthermore, a trace amount of Cu is introduced into the Sn-filled PbSe to optimize the carrier concentration. The extra Cu is situated in the interstitial sides of the lattice, which undergoes a dissolution-precipitation process with temperature, leading to a strongly temperature-dependent carrier density in the material. This dynamic doping effectively improves the electrical transport properties and is also valid to suppress the lattice thermal conductivity. Ultimately, the resulting PbSn0.004Se+3‰Cu obtains a maximum ZT of ≈1.7 at 800 K and an average ZT of ≈1.0, with a 7.7% power generation efficiency in a single-arm device, showing significant potential for commercial application.

Unimolecular net heterolysis of symmetric and homopolar σ-bonds

The unimolecular heterolysis of covalent σ-bonds is integral to many chemical transformations, including SN1-, E1- and 1,2-migration reactions. To a first approximation, the unequal redistribution of electron density during bond heterolysis is governed by the difference in polarity of the two departing bonding partners1–3. This means that if a σ-bond consists of two identical groups (that is, symmetric σ-bonds), its unimolecular fission from the S0, S1, or T1 states only occurs homolytically after thermal or photochemical activation1–7. To force symmetric σ-bonds into heterolytic manifolds, co-activation by bimolecular noncovalent interactions is necessary4. These tactics are only applicable to σ-bond constituents susceptible to such polarizing effects, and often suffer from inefficient chemoselectivity in polyfunctional molecules. Here we report the net heterolysis of symmetric and homopolar σ-bonds (that is, those with similar electronegativity and equal leaving group ability3) by means of stimulated doublet–doublet electron transfer (SDET). As exemplified by Se–Se and C–Se σ-bonds, symmetric and homopolar bonds initially undergo thermal homolysis, followed by photochemically SDET, eventually leading to net heterolysis. Two key factors make this process feasible and synthetically valuable: (1) photoexcitation probably occurs in only one of the incipient radical pair members, thus leading to coincidental symmetry breaking8 and consequently net heterolysis even of symmetric σ-bonds. (2) If non-identical radicals are formed, each radical may be excited at different wavelengths, thus rendering the net heterolysis highly chemospecific and orthogonal to conventional heterolyses. This feature is demonstrated in a series of atypical SN1 reactions, in which selenides show SDET-induced nucleofugalities3 rivalling those of more electronegative halides or diazoniums.

Understanding the structural relation and electrochemical evolution between ZnGeP2 and ZnSiP2 twin phosphides for advanced Li-ion batteries

Ternary ZnGeP2 with large capacity and suitable plateau is considered to be alternative anode for LIBs, while it suffers heavy-use of Ge raw-material inducing high cost-price thus failure of commercialization. Herein, a unique atomic substitution strategy is proposed by using Si-atom to totally replace Ge site in ZnGeP2. Interestingly, novel ZnSiP2 as twin-analogue is achieved, keeping the great advantages of high ICE (90 %), low plateau (∼0.35 V) and comparable rate performance (4000 mA/g, 629 mAh/g) for LIBs. More specially, such ZnSiP2 twin even exhibits higher thermo-stability (1046 vs 891 °C), larger capacity (1554 vs 1387 mAh/g) and lower voltage-hysteresis (0.28 vs 0.44 V) than ZnGeP2, which are unexpected and attractive for battery-safety and energy improvement. The above unusual phenomena are investigated in-detail, and the results show that owing to the similar radius and electronegativity between Si&Ge, the ZnSiP2 enables the same structural phase with ZnGeP2 matrix thus keeping its electrochemical advantages. Meanwhile, the ZnSiP2 exhibits larger formation energy (−1.24 eV) toward better structural-stability, lighter Si-component to higher capacity, lower Si-lithiated potential oriented smaller voltage-hysteresis, thus showing high performances in LiCoO2//ZnSiP2 full-cell. The above atomic substitution strategy can be easily extended to other good performance yet high cost electrode materials toward application.

Polarization loss in rutile TiO2 doped with acceptor ions for microwave absorption

With an increase in electromagnetic (EM) pollution, inducing polarization loss using lattice defects has become one of the main strategies for the design and optimization of a new generation of microwave absorbers. In this study, point defects in TiO2 absorbers are designed and controlled using a sol–gel method. The influences of the electronegativity difference and the ionic valence states of the dopant ions on the microwave absorption (MA) performance of rutile TiO2 composites are investigated. The results show that the defects such as oxygen vacancy (VO∙∙) and Ti3+ can be adjusted continuously at a high-temperature sintering process. Cu2+, which has a larger electronegativity than Ti4+ (Cu2+χ = 1.90 > Ti4+χ = 1.54) promotes the localization of electrons. Furthermore, compared with Ag+, which has a similar electronegativity (Ag+χ = 1.93 ≈ Cu2+χ = 1.90), polyvalent copper ions (Cu2++e→Cu+) enhance the electron-hopping process. The formed electron-pinning defect dipole clusters (TiTi′, VO∙∙, CuTi″, CuTi″′, Ti3+→VO∙∙←Ti3+, Ti3+→VO∙∙←Cu2++e, Cu2++e→Cu+, Ti4++e→Ti3+) produce a stronger polarization relaxation process, which regulates the MA performance of TiO2 absorbers. Therefore, this study provides an essential reference for refining the EM wave attenuation performance of simple oxide absorbers.

Exploring the mechanism of nerve agent (Tabun and Sarin) adsorption on carbon nanocones: Computational insights

Carbon NanoCones (CNCs), distinguished by their conical shape and large surface area, are evaluated for their potential application in nerve gas [tabun (GA) and sarin (GB)] adsorption. Density Functional Theory (DFT) calculations, Molecular Dynamics (MD), and Monte Carlo (MC) simulations are employed to investigate this phenomenon comprehensively. The study findings indicate that tabun (GA) and sarin (GB) undergo spontaneous adsorption, characterized by significant negative energy values. Density Functional Theory (DFT) calculations indicate electron donation tendencies of nerve agents to CNC surfaces. Computational analysis shows higher adsorption efficiency in the inner portion (P1) of CNCs. Molecular Dynamics (MD) and Monte Carlo (MC) simulations confirm planar adsorption configurations parallel to CNC surfaces. The DFT calculations show that GA has a far greater adsorption energy on a Carbon Nanocone compared to GB (−44.96 kcal/mol for GA, whereas GB has an adsorption energy of −35.95 kcal/mol). Furthermore, the analysis reveals significant differences between Sarin and Tabun nerve agents. Sarin exhibits higher global hardness, indicating increased stability, while Tabun shows higher overall softness, suggesting greater reactivity. Despite similar electronegativities, Sarin’s greater ionization energy and electron affinity imply enhanced stability and reactivity. Differences in HOMO and LUMO energies highlight unique reactivity profiles, with Sarin being more susceptible to nucleophilic attacks and Tabun to electrophilic attack. Sarin’s larger energy gap between HOMO and LUMO orbitals signifies its superior stability under electronic disturbances.

High-efficiency activated phosphorus-doped Ni2S3/Co3S4/ZnS nanowire/nanosheet arrays for energy storage of supercapacitors

Transition metal sulfides (TMS) have been considered as a promising group of electrode materials for supercapacitors as a result of their strong redox activity, but high volumetric strain of the materials during electrochemical reactions causes rapid structural collapse and severe capacity loss. Herein, we have synthesized phosphorus-doped (P-doped) Ni2S3/Co3S4/ZnS battery-type nanowire/nanosheet arrays as an advanced cathode for supercapacitor through a two-step process of hydrothermal and annealing treatments. The material has a one-dimensional nanowire/two-dimensional nanosheet-like coexisting microscopic morphology, which facilitates the exposure of abundant active centers and promotes the transport and migration of ions in the electrolyte, while the doping of P significantly enhances the conductivity of the electrode material. Simultaneously, the element phosphorus with similar atomic radii and electronegativity to sulfur may act as electron donors to regulate the electron distribution, thus providing more effective electrochemically active sites. In gratitude to the synergistic effect of microstructure optimization and electronic structure regulation induced by the doing of P, the P-Ni2S3/Co3S4/ZnS nanoarrays provide a superior capacity of 2716 F g−1 at 1 A/g, while the assembled P-Ni2S3/Co3S4/ZnS//AC asymmetric supercapacitor exhibits a high energy density of 48.2 Wh kg−1 at a power density of 800 W kg−1 with the capacity retention of 89 % after 9000 cycles. This work reveals a possible method for developing high-performance transition metal sulfide-based battery-like electrode materials for supercapacitors through microstructure optimization and electronic structure regulation.

Dielectric properties of (Eu,Ca)Cu3Ti4O12 ceramics prepared by a sol-gel method

CaCu3Ti4O12 perovskite-type phase possesses promising dielectric properties; however, the giant permittivity phenomenon in this material has not been satisfactorily described yet. Eu with similar electronegativity and ionic radius as Ca was selected for testing of partly and completely substituted materials. Here, we prepared a series with a composition of CaCu3Ti4O12, Eu0.4Ca0.6Cu3Ti4O12 and EuCu3Ti4O12. A sol-gel method was used to synthetize precursors, followed by sintering in a temperature range of 1000 °C-1120 °C. Europium was substituted in full stoichiometry of CaII with the aim to observe whether i) EuII is stabilized in the perovskite structure and/or ii) possible secondary phases induced by the excess of EuIII positively affect the dielectric characteristics. Samples were characterized by XPS, XRD, SEM. Influence of the microstructure and phase composition on the dielectric properties of the samples (also in relation to the sintering temperature) is discussed. Secondary phases and microstructure played an important role in improving the permittivity values. The obtained values of permittivity measured at room temperature are giant up to higher frequencies, but differ significantly for some individual compositions.

Design of a belt-like single-phase solid-solution Cu-Zn selenide with superior potassium-ion storage properties via a facile cation-exchange process

To produce high-performance potassium ion batteries (KIBs), it is essential to fabricate anode materials with an appropriately controlled structure and chemical composition. In this study, we successfully fabricate porous solid-solution Cu-Zn selenide nanobelts (NBs) coated with N-doped carbon (p-CZSe@NC NBs) using a facile cation-exchange process. The p-ZnSe@NC NBs are prepared using a polymer coating on ZnSe[diethylenetriamine]0.5 followed by carbonization. Because Zn and Cu have a similar atomic radius and electronegativity, the Zn in p-ZnSe@NC NBs is easily substituted with Cu in a spontaneous reaction without heating. The synergistic effect of the combination of the electrochemically active Zn and inactive Cu in response to K ions and the inner pores of the NBs is conducive to buffering the change in volume and improving ion accessibility. The N-doped carbon shell also provides additional conductive pathways and improves the structural robustness of the electrode. As a result, the p-CZSe@NC NB electrode achieves a high specific capacity of 288.3 mA h g−1 with superior cycling stability over 500 cycles at 0.5 A g−1 and 132.4 mA h g−1 at 3.0 A g−1. Our work thus outlines a facile method for the design of high-performance anodes for energy storage via the control of their chemical composition and structure.

Electronic modulation of fiber-shaped-CoFe2O4 via Mg doping for improved PMS activation and sustainable degradation of organic pollutants

Advanced oxidation processes (AOPs) driven by transition metal oxides are promising systems for the removal of organic pollutants. However, the catalytic activity is still limited by the low redox property of the active site. In this study, a novel and robust fiber-shaped cobalt ferrite catalyst was synthesized through a magnesium doping strategy. Detailed structural characterization and theoretical calculations demonstrated that the doping of Mg into CoFe2O4 maintains the spinel structure but increased the electron density of Co sites due to its similar atomic radius but different electronegativity to Co. Remarkably, the optimized MCFO-0.4 achieved superior capability for peroxymonosulfate (PMS) activation and outstanding performance for the catalytic degradation of Ponceau 2R (PR). Furthermore, the inherent crystal stability and magnetic nature of spinel allows for magnetically reusability and ultra-low cobalt leaching of MCFO-0.4. Radical quenching and EPR results confirmed the involvement of singlet oxygen and hydroxyl radicals during PMS activation, and a possible catalytic mechanism was finally proposed. This work provides a case study on microstructural regulation and electron modulation in spinel catalysts, which may provide now clues to further improve the activity of oxidation catalysts for large-scale wastewater treatment.

Electron-donating N−–Ti3+–Ov interfacial sites with high selectivity for the oxidation of primary C–H bonds

Element doping can fabricate different types of oxygen vacancies (O v ) on TiO 2 , but the effects of O v coordination and configuration on the oxidation reaction remain unclear. Here, we modify the local geometric ligand environment of O v by doping N and B into anatase TiO 2 (N-TiO 2 and B-TiO 2 ). N − –Ti 3+ –O v is induced in N-TiO 2 by substituting O with N, which has similar ionic size and electronegativity, and Ti 3+ –O v is found in TiO 2 and B-TiO 2 . Density functional theory calculations indicate that N − –Ti 3+ –O v is more reactive than Ti 3+ –O v toward O 2 activation. The resultant N-TiO 2 -0.25 enriched in N − –Ti 3+ –O v contributes to a rapid formation of superoxygen species (•O 2 − ), which increase the oxidation rate of primary C–H bonds in toluene, and thus exhibits much higher selectivity and yield. The fabrication of N − –Ti 3+ –O v develops doped catalysts with improved O v reactivity and enhanced primary C–H bond oxidation selectivity. • N − –Ti 3+ –O v is more reactive than Ti 3+ –O v toward O 2 activation to generate ⋅O 2 − • The generation of ⋅O 2 − is the rate-determining step in selective oxidation of toluene • The introduced photo energy does not change the thermal selective oxidation process • A higher yield of products is attributed to the increased selective oxidation rate Oxygen vacancies in TiO 2 influence catalytic activity differently depending on their coordination environment. Chen et al. explore N and B doping and show that N − –Ti 3+ –O v is more reactive than Ti 3+ –O v toward O 2 activation, enhancing the primary C–H bond oxidation of toluene.

A Selenenium-Bridged 10-Boratriptycene Lewis Acid

AbstractA non-planar triarylborane and a new member of the boratriptycene family bearing a selenium atom in bridgehead position of triptycene scaffold was generated and isolated as a boron-‘ate’ complex paired with a weakly coordinating anion. With similar electronegativity while possessing longer atom radius with respect to sulfur, the introduction a selenium atom, in the form of a selenenium moiety, at the bridgehead of a triptycene scaffold allows a very precise modification of the pyramidalization of the boron atom environment. Experimental and computational evaluation of the Lewis acidity of this new boratriptycene derivative gave qualitative information on how a modification of the pyramidalization of the boron environment affects alone Lewis acidity parameters of such pyramidal triarylborane.

Intrinsic defects and the influences on electrical transport properties in quaternary diamond-like compounds: Cd2Cu3In3Te8 as an example

Over the years, the fact that the quaternary diamond-like thermoelectric materials show much lower carrier mobilities than ternary compounds remains mysterious. In this work, by adopting first-principles defect chemistry and electrical transport calculations, the fundamental origin of the difference on carrier mobility between quaternary and ternary diamond-like compounds is addressed, exemplified by Cd2Cu3In3Te8. The results of defect chemistry show that the main intrinsic defects in quaternary compound Cd2Cu3In3Te8 are substitutional defects, i.e., CdIn and CdCu, differing from the copper vacancy defect in ternary Cu-based compound such as CuInTe2. The low defect formation energies in Cd2Cu3In3Te8 result in high defect concentrations, which is caused by the similar atomic radii and electronegativities between CdIn and CdCu. Further calculations show that the low-energy defects are mainly located around the valence band maximum in Cd2Cu3In3Te8. The electrical transport calculations, considering both the acoustic phonon scattering and ionized impurity scattering, demonstrate that mainly due to the higher concentration of the ionized defects, the mobility of the quaternary Cd2Cu3In3Te8 is much lower than that of ternary CuInTe2. Our work sheds light on the intrinsic defects in quaternary diamond-like compounds and their influence on charge transport.

Nitrogen and Sulfur Co‐Doped Carbon Quantum Dots for Sensing Applications: A Review

AbstractCarbon quantum dots (CQDs) have emerged in the last decade, outperforming other members of the carbon family due to remarkable properties such as fluorescence, cytocompatibility, photostability, and other chemical properties, which have led to an increasing number of applications in bioimaging, sensing, photovoltaic, and medicine. Nature is a treasure trove of exciting precursors, which inspires constant persuasion of safe synthetic routes. Doped CQDs, in particular, exhibit excellent luminous characteristics and have been effectively used in various applications. Among the different doping methods used to tune the properties of CQDs, nitrogen (N) and sulfur (S) are the most commonly used elements with comparable atomic sizes, strong valence bonds, and similar electronegativity. As a result, the last lustrum has seen a significant increase in several synthetic approaches to NSCQDs. This is an attempt to review the journey of NSCQDs through green and chemical sources of synthesis and their sensing applications.

Improved Recovery and Selectivity of Lanthanide-Ion-Binding Cyclic Peptide Hosts by Changing the Position of Acidic Amino Acids

The development of an effective host molecule to separate lanthanide (Ln) ions and a method for predicting its guest recognition/self-assembly behavior based on primary chemical structures are highly sought after in both academia and industry. Herein, we report the improvement of one-pot Ln ion recovery and a performance prediction method for four new cyclic peptide hosts that differ in the position of acidic amino acids. These cyclic peptide hosts could recognize Ln3+ directly through a 1:1 complexation–precipitation process and exhibited high Lu3+ selectivity in spite of similar ion size and electronegativity when the positions of the acidic amino acids were changed. This unpredictable selectivity was explained by considering the dipole moment, lowest unoccupied molecular orbital, and cohesion energy. In addition, a semi-empirical function using these parameters was proposed for screening the sequence and estimating the isolated yields without long-time molecular dynamics calculations. The insights obtained from this study can be employed for the development of high-performance peptides for the selective recovery of Ln and other metal ions, as well as for the construction of diverse supramolecular recognition systems.

Alkanes versus Oligosilanes: Conformational Effects on σ-Electron Delocalization.

Observations and computations both suggest that the extent and the conformational dependence of σ-electron delocalization in frontier molecular orbitals are quite different in alkanes CnH2n+2 and oligosilanes SinH2n+2, the isosteric and isoelectronic saturated chains built from carbon or silicon atoms, respectively. We find that the different conformational effects can be understood in simple intuitive terms. There are two modes of σ-electron delocalization, strongly conformation-sensitive skeletal delocalization through backbone X-X bonds (σ-conjugation and σ-hyperconjugation) and only weakly conformation-sensitive lateral delocalization through lateral X-H bonds (σ-hyperconjugation and σ-homoconjugation). In alkanes, both modes are active and complement each other, leading to delocalization in all conformations. In oligosilanes, only skeletal delocalization of holes is important in frontier orbitals, and the even simpler ladder C model provides an adequate intuitive description of the strong conformational dependence of σ-electron delocalization. Ultimately, the difference is primarily due to the similar electronegativity of carbon and hydrogen as opposed to the lower electronegativity of silicon, which causes a polarization of Si-H bonds. This understanding has been derived from an analysis of approximate algebraic solutions of a simple Hückel-level extended ladder H model for an infinite regular helical chain, using the effective mass of a hole as a measure of delocalization. This model is derived from the classical Sandorfy H model, and is parametrized by fitting to results of density functional or Hartree-Fock theory.

Ultra-High Sulfur-Doped Hierarchical Porous Hollow Carbon Sphere Anodes Enabling Unprecedented Durable Potassium-Ion Hybrid Capacitors.

Sulfur doping is a promising path to ameliorate the kinetics of carbon-based anodes. However, the similar electronegativity of sulfur and carbon and the poor thermal stability of sulfur severely restrict the development of high-sulfur-content carbon-based anodes. In this work, ultra-high sulfur-doped hierarchical porous hollow carbon spheres (SHCS) with a sulfur content of 6.8 at % are synthesized via a direct high-temperature sulfur-doping strategy. An SHCS has sulfur bonded to the carbon framework including C-S-C and C-SOx-C, which enlarges its interlayer distance (0.411 nm). In the K half-cell, benefiting from the considerable content and the reasonable architecture of sulfur, the SHCS exhibits significantly improved reversible specific capacity, initial Coulombic efficiency, and cyclability than hierarchical porous hollow carbon spheres without sulfur. Remarkably, the potassium ion hybrid capacitor device fabricated with the SHCS anode achieves excellent energy/power density (135.6 W h kg-1/17.7 kW kg-1) and unprecedented durability over 26,000 cycles at 2 A g-1. This research provides a superior strategy to design high-sulfur-content carbon-based anodes with excellent potassium storage performance.

An electronic origin to the oscillatory segregation behavior in Ni-Cr and other BCC defects in FCC metals

Ni-Cr alloys exhibit oscillatory segregation behaviors near low index surfaces, in which the preferred segregation species changes from Ni in the first layer to Cr in the second layer. In many dilute-alloy systems, this oscillatory pattern is attributed to the elastic release of stresses in the local lattice around the segregating solute or impurity atom. These stresses are mostly thought to originate from mismatches in the atomic size of the solute and host atoms. In Ni-Cr alloys, however, an appreciable mismatch in atomic size is not present, leading to questions about the origins of the oscillatory behavior in this alloy. Using density functional theory, we have modeled the segregation of a single Cr atom in the (100) and (111) surfaces of FCC Ni, an alloy which exhibits this oscillatory behavior. Using Bader charge analysis, we show that the negative energy correlates directly with the amount of charge on the Cr atom. As Ni atoms strip valence charge from the Cr, the Cr contracts slightly in size. The greatest contraction and highest positive charge for the Cr occurs when it is in the second layer of the surface where the system exhibits the oscillating negative segregation energy. We then find that this behavior persists in other alloy systems (Ag-Nb, Cu-Cr, Pt-Nb, and Pt-V), which exhibit similar atomic radii and electronegativity differences between host and solute to Ni-Cr. These represent alloys in which the host metal exhibits an FCC ground-state structure while the solute metal exhibits a BCC ground-state structure.

Computational investigation of structural, magnetic, electronic and optical properties of the cluster Mn-X6 (X=P, S, Cl, Br or Te) doped monolayer WSe2

• The Mn-S 6 doped monolayer WSe 2 under the W-rich condition is the most stable. • The Mn-S 6 , Mn-Cl 6 and Mn-Br 6 doped monolayer WSe 2 systems become magnetic half-metal. • The Mn-P 6 and Mn-Te 6 doped monolayer WSe 2 systems turn into magnetic semiconductor. • The Mn-X 6 doped monolayer WSe 2 systems exhibit red shift and enhanced absorption. We perform systematic first-principles calculations to clarify the effects of the cluster Mn-X 6 (X=P, S, Cl, Br or Te) doping on the structural, electronic, magnetic and optical properties of monolayer WSe 2 . The smaller formation energy shows that all doping systems are more stable under W-rich condition than Se-rich condition. The cluster Mn-S 6 doped monolayer WSe 2 has the smallest formation energy may be due to S and Se elements having similar electronegativity, while the maximum formation energy of the cluster Mn-Te 6 doping may be due to the lowest electronegativity of the Te element. Although pure monolayer WSe 2 is a non-magnetic semiconductor, the Mn-P 6 and Mn-Te 6 doped monolayer WSe 2 become magnetic semiconductor, while the Mn-S 6 , Mn-Cl 6 and Mn-Br 6 doped monolayer WSe 2 turn into magnetic half-metal. Compared with the pure monolayer WSe 2 , the cluster Mn-X 6 doped monolayer WSe 2 have not only a red-shift phenomenon but also an enhanced absorption in infrared and far-ultraviolet region and thus a potential application in infrared and far-ultraviolet light detectors.

Spontaneous formation of filled-shell CsI-Xenon solid solutions under high temperature and high pressure

Different stoichiometries compounds formed by filled-shell (FS) insulators (e.g., xenon) have been extensively predicted and successfully synthesized under extreme conditions. However, theoretical prediction on solid solution formed by FS materials is lacking. Here, by combining structure searching and ab initiohybrid Metropolis-Monte Carlo/molecular dynamics simulations, we predict that the noble gas xenon and CsI can form thermodynamically stable substitutional solid solutions with hexagonal close-packed at high temperature and high pressure, in which Xe, Cs and I exhibit similar electronegativity and strong metallic feature that are analogous to the solid solution alloys. The existence of short-range order among constituent compositions improves the stability of solid solution. These results shed a new insight on the chemical reactivity between noble gases and alkali-halide compounds and provide valuable reference to understand the formation of multicomponent solid solutions under extreme conditions.