Adjacent Mo Atoms Research Articles

Thermodynamic stability, electronic structure and mechanical properties of Mo-Re binary alloys: A first-principles calculations

Using first-principles calculations, we have systematically studied thermodynamic stability, electronic structure and mechanical properties of Mo-Re binary alloys. The alloying element Re prefers to occupy the substitution position with a formation energy of 0.10 eV in Mo rather than the tetrahedron/octahedron interstitial position. The charge transfers are obviously present between Re and Mo atoms, which can be confirmed by the Bader charge analysis. The density of states (DOS) demonstrates that the d orbitals of Re and Mo atoms are hybridized, revealing that Re and its adjacent Mo atoms can form the directional bond containing covalent components. On the basis of above studies on the most stable occupancy structure, the mechanical quantities (the elastic constants Cij, bulk modulus B, Young’s modulus E, shear modulus G, Poisson’s ratio v, and B/G) have been analyzed for three Mo-Re alloys with the low Re content, which are Mo127Re1, Mo53Re1 and Mo15Re1, respectively. All these mechanical quantities of both Mo127Re1 and Mo53Re1 alloys are nearly the same as that of perfect Mo, while all these mechanical quantities of Mo15Re1 alloy are obviously larger or smaller than that of perfect Mo. This demonstrates that Mo15Re1 alloy has significantly different mechanical characteristics from Mo127Re1 and Mo53Re1 alloys as well as perfect Mo. These results can provide a significant reference for the application of Mo-Re alloys in future fusion fields.

Heterogeneous-Structured Molybdenum Diboride as a Novel and Promising Anode for Lithium-Ion Batteries.

With the development of electric vehicles, exploiting anode materials with high capacity and fast charging capability is an urgent requirement for lithium-ion batteries (LIBs). Borophene, with the merits of high capacity, high electronic conductivity and fast diffusion kinetics, holds great potential as anode for LIBs. However, it is difficult to fabricate for the intrinsic electron-deficiency of boron atom. Herein, heterogeneous-structured MoB2 (h-MoB2) with amorphous shell and crystalline core, is prepared by solid phase molten salt method. As demonstrated, crystalline core can encapsulate the honeycomb borophene within two adjacent Mo atoms, and amorphous shell can accommodate more lithium ions to strengthen the lithium storage capacity and diffusion kinetics. According to theoretical calculations, the lithium adsorption energy in MoB2 is about -2.7 eV, and the lithium diffusion energy barrier in MoB2 is calculated to be 0.199 eV, guaranteeing the enhanced adsorption capability and fast diffusion kinetic behavior of Li+ ions. As a result, h-MoB2 anode presents high capacity of 798 mAh g-1 at 0.1 A g-1, excellent rate performance of 183 mAh g-1 at 5 A g-1 and long-term cyclic stability for 1200 cycles. This work may inspire ideas for the fabrication of borophene analogs and two-dimensional metal borides.

Tuning Local Atomic Structures in MoS2 Based Catalysts for Electrochemical Nitrate Reduction.

In recent years, there has been a substantial surge in the investigation of transition-metal dichalcogenides such as MoS2 as a promising electrochemical catalyst. Inspired by denitrification enzymes such as nitrate reductase and nitrite reductase, the electrochemical nitrate reduction catalyzed by MoS2 with varying local atomic structures is reported. It is demonstrated that the hydrothermally synthesized MoS2 containing sulfur vacancies behaves as promising catalysts for electrochemical denitrification. With copper doping at less than 9% atomic ratio, the selectivity of denitrification to dinitrogen in the products can be effectively improved. X-ray absorption characterizations suggest that two sulfur vacancies are associated with one copper dopant in the MoS2 skeleton. DFT calculation confirms that copper dopants replace three adjacent Mo atoms to form a trigonal defect-enriched region, introducing an exposed Mo reaction center that coordinates with Cu atom to increase N2 selectivity. Apart from the higher activity and selectivity, the Cu-doped MoS2 also demonstrates remarkably improved tolerance toward oxygen poisoning at high oxygen concentration. Finally, Cu-doped MoS2 based catalysts exhibit very low specific energy consumption during the electrochemical denitrification process, paving the way for potential scale-up operations.

First-principles study of oxygen segregation and its effect on the embrittlement of molybdenum symmetrical tilt grain boundaries

Elemental segregation can pronouncedly affect the cohesion of grain boundary (GB), which shows tremendous potential in altering the thermal stability and mechanical properties of metals. In this work, we systematically investigate the segregation behavior of oxygen (O) atoms at a series of GBs in molybdenum (Mo), using first principles calculations, to reveal the effect of O segregation on the embrittlement of Mo GBs. It is found that O atoms energetically prefer to segregate at sites in both the GB core and the vicinity of the GB plane. The strengthening energy is strongly associated with the GB structure, and it linearly decreases with the continuous deformation of the GB. O segregation can lead to an increase in the volume of polyhedron sites and a decrease in the charge density among adjacent Mo atoms across the GB plane. The weakened Mo-Mo bonds are believed to disrupt the GB cohesion, thereby increasing the intergranular cleavage tendency of Mo. Interestingly, O segregation does not always trigger GB embrittlement. The Σ5(310)[001] symmetric tilt grain boundary (STGB) with an O atom doped at the cap trigonal prism (CTP) site possesses a strength as strong as the clean GB. O segregation promotes the generation of Mo-O bonds across the GB plane, which counteracts the adverse effect of weakened Mo-Mo bonds. This work deepens the understanding of the possible effect of O segregation on GB cohesion of Mo from the atomic and electronic scales, providing guidance for enhancing the mechanical properties of Mo via GB structure optimization.

Breaking the Scaling Relationship on Single-Atom Embedded MBene for Selective CO2 Electroreduction.

Highly active and selective electrochemical CO2 reduction reaction (CO2RR) to chemicals and fuels is crucial for clean energy production and environmental remediation. Although transition metals and their alloys are widely used to catalyze CO2RR, their activity and selectivity are generally unsatisfactory, hindered by energy scaling relationships among the reaction intermediates. Herein, we generalize the multisite functionalization strategy to single-atom catalysts in order to circumvent the scaling relationships for CO2RR. We predict that single transition metal atoms embedded in two-dimensional Mo2B2 could be exceptional catalysts for CO2RR. We show that the single-atoms (SAs) and their adjacent Mo atoms can only bind to carbon and oxygen atom, respectively, thus enabling dual site functionalization to circumvent the scaling relationships. Following extensive first-principles calculations, we discover two SA-Mo2B2 single-atom catalysts (SA = Rh and Ir) that can produce methane and methanol with an ultralow overpotential of -0.32 and -0.27 V, respectively.

Mo-embedded Ir-based electrocatalyst for nitrogen reduction reaction: A computational study

Ammonia has a wide range of applications, including as a fertilizer and important chemical feedstock. Therefore, its catalytic synthesis is critical to global agricultural and industrial production. A widely used method of NH3 synthesis in industry is the Haber–Bosch process. However, the energy consumption of this process is high, making it an environmentally unfriendly technology. As a result, methods for NH3 synthesis at room temperature and pressure are urgently required. The electrocatalytic nitrogen reduction reaction (NRR) is widely regarded as a green and sustainable method for NH3 production because the reaction can be carried out under ambient conditions, and the electricity required to drive the reaction can be generated from renewable resources. In this work, an NRR catalyst based on Ir doped with Mo was modeled using density functional theory calculations, and the effect of the degree of doping on the catalytic activity was investigated. We found that the Ir(100) surface doped with a single Mo atom and that doped with two adjacent Mo atoms (Mo@Ir(100) and Mo@Ir(100)-ortho, respectively) exhibit the best NRR catalytic activities, having free energy barriers of 0.54 and 0.57 eV, respectively. In addition, by comparing the strength of adsorption of N2 and H on the active sites, we found that the competitive hydrogen evolution reaction could be inhibited. These results suggest that Mo@Ir(100) and Mo@Ir(100)-ortho are promising NRR catalysts for use under ambient conditions.

Rationalizing hydrogen evolution mechanism on the slab of Zn-reduced 2H–MoS2 monolayer by density functional theory calculations

In this paper, the H2 evolution mechanism and activity on Zn-reduced 2H–MoS2 were explored by density functional theory (DFT) calculations based on the possible active sites including nZn-MoS2 and nZn-S vacancy (SV) (n = 1, 2, 3), which were built by replacing one, two, three adjacent Mo atoms in MoS2 and at SV by Zn, respectively. The calculations indicate that the amount of Zn incorporation can significantly affect the H2 evolution activities and mechanisms of Zn-doped MoS2 and Zn-doped SV and Zn-doped SV is more favorable to the production of H2. The formation of 3Zn–MoS2 and 3Zn-SV is less favorable to H2 evolution reactions (HER) due to their too high or low ΔGH. The replacement of one Mo in MoS2 by Zn can reduce the ΔGH of S atom to −0.18 eV, and S bonded by one Zn (SA) in Zn–MoS2 cannot catalyze HER. In 2Zn–MoS2, S bonded by two Zn atoms (SB) catalyzes HER by the Heyrovsky-step-controlled Volmer-Heyrovsky mechanism, and the rate determining step (RDS) has a barrier of 47.8 kcal/mol. Moreover, Zn doping is beneficial for generating Zn-doped SV. Zn-SV catalyzes HER via the same mechanism with 2Zn–MoS2, and the barrier of RDS is 30.7 kcal/mol. After replacing two adjacent Mo atoms of SV with Zn, the resulting 2Zn-SV follows the Volmer-Heyrovsky mechanism to catalyze HER, and the RDS is the Volmer step with a barrier of 27.2 kcal/mol.

Boosting the efficiency of Fe-MoS2/peroxymonosulfate catalytic systems for organic powllutants remediation: Insights into edge-site atomic coordination

Fe atoms were highly isolated by the edge Mo vacancies and the adjacent Mo atoms could provide electrons smoothly for the regeneration of Fe(II). • Fe-MoS 2 catalyst with Fe atomically anchored at the edge Mo vacancies was prepared. • Fe(II) can be rapidly regenerated through the Mo-S 2 -Fe-S 2 -Mo edge configuration. • The electron transfer between edge Mo, S and Fe atoms were well clarified. • Both the adsorption and activation of PMS were systemically investigated. • Fe-MoS 2 was highly stable for the AOPs of varied persistent organic pollutants. Here, we designed and prepared edge defect-rich Fe-MoS 2 nanohybrid catalysts via a facile post-confined strategy, in which single Fe atoms were isolated by the newly formed edge Mo vacancies. Evaluation of the decontamination efficiency, using the model herbicide 2,4-dichlorophenoxyacetic acid (2,4-D), showed that the rate constant for the Fe-MoS 2 /peroxymonosulfate (PMS)/2,4-D system was (0.2777 min −1 ), seven times higher than that of a Fe-MoS 2 nanocluster counterpart (0.0323 min −1 ). The unique Mo-S 2 -Fe-S 2 -Mo edge configuration of Fe-MoS 2 promoted the regeneration of active sites during the activation reaction in which Fe(III) was reduced to Fe(II), Mo(IV) was oxidized to Mo(V), and the adjacent S atoms acted as bridges for electron transfer. Thus, PMS could be constantly activated by low valence Fe atoms resulting in superior catalytic performance. Quenching experiments and Electron Paramagnetic Resonance (EPR) signals indicated that hydroxyl radicals, sulfate radicals (SO 4 •- ), superoxide anion radicals and singlet oxygen ( 1 O 2 ) were all involved in the oxidative degradation of 2,4-D, in which 1 O 2 and SO 4 •- predominated. In addition, PMS adsorption and its activation were identified as key steps in the process, and the Fe-MoS 2 /PMS system demonstrated good robustness during continuous operation. This study provides new insights into the Fe-MoS 2 edge coordination mechanism for the PMS activated decontamination of organic pollutants.

Hydrazine Hydrate Intercalated 1T-Dominant MoS2 with Superior Ambient Stability for Highly Efficient Electrocatalytic Applications.

Metallic 1T-phase MoS2 exhibits superior hydrogen evolution reaction (HER) performance than natural 2H-phase MoS2 owing to its higher electrical conductivity and abundance of active sites. However, the reported 1T-MoS2 catalysts usually suffer from extreme instability, which results in quick phase transformation at ambient conditions. Herein, we present a facile approach to engineer the phase of MoS2 by introducing intercalated hydrazine. Interestingly, the as-synthesized 1T-dominant MoS2 sample demonstrates excellent ambient stability without noticeable degradation for 3 months. Additionally, the 1T-dominant MoS2 exhibits superior electrical conductivity (∼700 times higher than that of 2H-MoS2) and improved electrochemical catalytic performance (current density ∼12 times larger than that of 2H-MoS2 at an overpotential of 300 mV vs the reversible hydrogen electrode, RHE). Through experimental characterizations and density functional theory (DFT) calculation, we conclude that the stabilization of the metallic phase could be attributed to the electron donation from hydrazine molecules to the adjacent Mo atoms. The phase control strategy in this work provides a guideline to develop other highly efficient and stable two-dimensional (2D) electrocatalysts.

Study of the core-shell structure MoSi2@ Al2O3 powder prepared by the sol-gel method in a low-vacuum atmosphere

Molybdenum disilicide (MoSi 2 ) is a novel crack-healing material used in the traditional thermal barrier coating , which reacts with ZrO 2 to attain a corresponding volume expansion of approximately 138%. However, the pre-oxidation of MoSi 2 causes the “pesting” phenomenon, which degrades the microstructure and mechanical properties throughout the service. To address this issue, the aluminum oxide was fabricated on the MoSi 2 surface using the sol-gel method and low-pressure post-heat treatment to prevent oxygen penetration. The orthogonal experiment investigated the effect of pH, temperature, and water amount on sol generation. Because the Zeta potential difference has reached its maximum value (about 27 mV) at pH 4, the aluminum sol was notably adsorbed on the MoSi 2 particles. The modified MoSi 2 @Al 2 O 3 particles were characterized to understand their morphologies, surface adsorption energy, and crystal structures. The oxygen adsorption energy on the MoSi 2 (103) surface was lower than that on the Mo 5 Si 3 (411) surface, which indicated that the oxidization process can be divided into two independent steps. The Al 2 O 3 shell was uniformly formed on the MoSi 2 particles, especially in the low-vacuum environment (10 MPa) for 3 h post-treatment. The dense core-shell structure can prevent oxygen penetration into the MoSi 2 surface, thus prolonging the self-healing property of MoSi 2 . • Heterogeneous charge between MoSi 2 and C 9 H 21 AlO 3 is maximum at pH 4.0. • “Pesting” phenomenon occurs by the preferential oxidization of adjacent Mo atoms. • MoSi 2 @Al 2 O 3 core-shell structure is uniformly generated in a low-vacuum atmosphere. • MoSi 2 @Al 2 O 3 can prevent oxygen from reacting with the MoSi 2 surface.

The activation of porous atomic layered MoS2 basal-plane to induce adjacent Mo atom pairs promoting high efficiency electrochemical N2 fixation

MoS2 has been proven to be an efficient NRR electrocatalyst, the activation of inert basal plane and rational utilization of basal plane have become the key to further increasing the activity. The defects of basal plane help to expose active sites, however, they cannot activate basal plane to promote NRR. Herein, based on the calculation results, we designed porous atomic layered 2H-MoS2(PAL-MoS2) by one-step calcination treatment. The porosity of the basal plane effectively utilizes basal plane atoms while the presence of adjacent Mo atom pairs improves the NRR performance. A high Faradic efficiency of 44.36 % and a sizeable NH3 yield of 3405.55 μg h−1 mgcat−1 (1.98 μg h−1 cm−2) at ‒0.1 V vs. reversible hydrogen electrode are obtained in 0.1 M HCl under ambient conditions, as far as we know, outperforming most of Mo-based NRR electrocatalysts reported before. Furthermore, this catalyst also exhibits high selectivity, electrochemical stability and good performance characterization.

Non-Metal Single-Phosphorus-Atom Catalysis of Hydrogen Evolution.

Non-metal-based single-atom catalysts (SACs) offer low cost, simple synthesis methods, and effective regulation for substrates. Herein, we developed a simplified pressurized gas-assisted process, and report the first non-metal single-atom phosphorus with atomic-level dispersion on unique single-crystal Mo2 C hexagonal nanosheet arrays with a (001) plane supported by carbon sheet (SAP-Mo2 C-CS). The SAP-Mo2 C-CS is structurally stable and shows exceptional electrocatalytic activity for the hydrogen evolution reaction (HER). A so-called high-active "window" based on the active sites of P atoms and their adjacent Mo atoms gives a ΔGH* close to zero for hydrogen evolution, which is the most ideal ΔGH* reported so far. Meanwhile, the moderate d-band center value of SAP-Mo2 C-CS can be also used as an ideal standard value to evaluate the HER performance in non-metal-based SACs.

Non‐Metal Single‐Phosphorus‐Atom Catalysis of Hydrogen Evolution

AbstractNon‐metal‐based single‐atom catalysts (SACs) offer low cost, simple synthesis methods, and effective regulation for substrates. Herein, we developed a simplified pressurized gas‐assisted process, and report the first non‐metal single‐atom phosphorus with atomic‐level dispersion on unique single‐crystal Mo2C hexagonal nanosheet arrays with a (001) plane supported by carbon sheet (SAP‐Mo2C‐CS). The SAP‐Mo2C‐CS is structurally stable and shows exceptional electrocatalytic activity for the hydrogen evolution reaction (HER). A so‐called high‐active “window” based on the active sites of P atoms and their adjacent Mo atoms gives a ΔGH*close to zero for hydrogen evolution, which is the most ideal ΔGH*reported so far. Meanwhile, the moderate d‐band center value of SAP‐Mo2C‐CS can be also used as an ideal standard value to evaluate the HER performance in non‐metal‐based SACs.

Covalent 0D–2D Heterostructuring of Co9S8–MoS2 for Enhanced Hydrogen Evolution in All pH Electrolytes

AbstractUltrasmall Co9S8 nanoparticles are introduced on the basal plane of MoS2 to fabricate a covalent 0D–2D heterostructure that enhances the hydrogen evolution reaction (HER) activity of electrochemical water splitting. In the heterostructure, separate phases of Co9S8 and MoS2 are formed, but they are connected by Co–S–Mo type covalent bonds. The charge redistribution from Co to Mo occurring at the interface enhances the electron‐doped characteristics of MoS2 to generate electron‐rich Mo atoms. Besides, reductive annealing during the synthesis forms S defects that activates adjacent Mo atoms for further enhanced HER activity as elucidated by the density functional theory (DFT) calculation. Eventually, the covalent Co9S8–MoS2 heterostructure shows amplified HER activity as well as stability in all pH electrolytes. The synergistic effect is pronounced when the heterostructure is coupled with a porous Ni foam (NF) support to form Co9S8–MoS2/NF that displays superior performance to those of the state‐of‐the‐art non‐noble metal electrocatalysts, and even outperforms a commercial Pt/C catalyst in a practically meaningful, high current density region in alkaline (>170 mA cm−2) and neutral (>60 mA cm−2) media. The high HER performance and stability of Co9S8–MoS2 heterostructure make it a promising pH universal alternative to expensive Pt‐based electrocatalysts for practical water electrolyzers.

Molecule template method for precise synthesis of Mo-based alloy clusters and electrocatalytic nitrogen reduction on partially reduced PtMo alloy oxide cluster

Alloy clusters are attractive electrocatalysts that have adjustable activity through the synergistic effects of alloy components. However, the synthesis of atomically-precise alloy clusters is still a challenge. Here, we report a molecular template method in which phosphomolybdic acid adsorbs foreign noble metal ions, and then anneals into a series of Mo-based alloy oxide clusters (PtMo, IrMo, AuMo and PdMo), where oxygen is the terminal oxygen outside the cluster. The as-prepared alloy clusters have tunable atomic ratio and uniform size around 1 nm. Taking PtMo clusters as an example, their electrocatalytic nitrogen reduction reaction (NRR) has been investigated in depth. Among all compositions, PtMo-6 cluster (Pt:Mo atomic ratio 1:2) exhibits the highest NRR activity with a Faradaic efficiency of 14.37% and a NH 3 yield rate of 65.3 μg h −1 mg −1 cat. in 0.1 M KOH, surpassing the known Mo-based catalysts. The combination of operando X-ray absorption spectroscopy and DFT calculations reveals that the oxide cluster in working state is the partially reduced. An unusual synergy is discovered, namely that Pt acts as a proton donor, providing *H to promote the hydrogenation of N 2 on the adjacent Mo atom. This work provides a simple and universal method for the precise synthesis of alloy clusters and new guidance for designing highly efficient NRR catalysts. A molecule template method is developed to prepare Mo-based alloy clusters (PtMo, IrMo, AuMo and PdMo) with uniform particle size of 1–2 nm and controllable atomic ratio. Among all PtMo compositions, PtMo-6 cluster exhibits the highest electrocatalytic activity towards nitrogen reduction reaction. The combination of X-ray absorption spectroscopy and DFT calculations reveals the synergistic mechanism of NRR on PtMo-6 clusters, that is, Pt acts as a proton donor, providing *H (* represents active site) to promote the hydrogenation of N 2 on nearby Mo atoms. • A molecule template method is developed to prepare Mo-based alloy clusters. • Partially oxidized PtMo cluster exhibits high electrocatalytic activity towards nitrogen reduction reaction. • Operando observation of nitrogen reduction reaction on PtMo cluster by X-ray absorption spectroscopy. • An unusual synergy is discovered, that is, Pt providing *H to promote the hydrogenation of N 2 on Mo.

A sacrificial Zn strategy enables anchoring of metal single atoms on the exposed surface of holey 2D molybdenum carbide nanosheets for efficient electrocatalysis

A sacrificial Zn strategy is reported to anchor non-noble metal single atoms on 2D holey Mo2C nanosheets, enabling these individual metal atoms being coordinated with three adjacent Mo atoms on the surfaces for efficient water splitting.

The structural, electronic, and magnetic properties of the stoichiometric (001) surface of double perovskite Sr2FeMoO6

The structural, electronic, and magnetic properties of the stoichiometric (001) surface of double perovskite Sr2FeMoO6 have been studied by using a 10‐layer FeMoO4 and SrO terminated (001)‐oriented slab model and the first‐principles projector augmented wave potential within the generalized gradient approximation as well as taking into account the on‐site Coulomb repulsive (U = 2.0 eV for Fe and 1.0 eV for Mo). An outwards relaxation is observed for several layers near surface, and the accompanying layer rumpling has a decrease tend from surface layer to inner layer. Along Fe–O–Mo–O–Fe or Mo–O–Fe–O–Mo chains, the oxygen atom is closer to the adjacent Mo atom than to the adjacent Fe atom. In FeO6 or MoO6 octahedra, the two axial TM−O bonds are not equal, and especially, the surface dangling bond makes the remaining one axial TM−O bond slightly shorter than four equally equatorial TM−O bonds. The half‐metallic nature and a complete (100%) spin polarization character ensure the FeMoO4 and SrO terminated (001)‐oriented slab of double perovskite Sr2FeMoO6 a potential application in spintronics devices. The Fe+3 and Mo+5 ions are still in the (3d5, S = 5/2) and (4d1, S = 1/2) states with positive and negative magnetic moments respectively and thus antiferromagnetic coupling via oxygen between them. There is no direct interaction between two nearest Fe–Fe or Mo–Mo pairs, whereas the hybridizations between Fe 3d and 4s, O 2s and 2p, as well as Mo 4d, 5s and 5p orbitals are fairly significant. Copyright © 2016 John Wiley & Sons, Ltd.

A Cyanide-Bridged Molybdenum Bis(maleonitriledithiolate) Square

[Et4N]2[Mo(IV)O(mnt)2] (mnt = maleonitriledithiolate) reacts, as a synthon, with Me3SiCN under an acidic medium to produce the square complex [Et4N]4[Mo4(μ-CN)4(mnt)8] (1) in high yield. Complex 1 shows strong antiferromagnetic interactions between adjacent Mo atoms in the cluster. The presence of redox-active mnt as a capping ligand strongly influences the magnetic property of 1. The physicochemical properties of 1 have been rationalized by density functional theory level of calculations.

The structural, electronic and magnetic properties of a symmetrical FeMoO terminated (001)-oriented slab of double perovskite Sr2FeMoO6

The structural, electronic and magnetic properties of a 9-layer symmetrical FeMoO terminated (001)-oriented slab of double perovskite Sr2FeMoO6 have been studied by using the first-principle projector augmented wave potential within the generalized gradient approximation taking into account the on-site Coulomb repulsive (U=2.0eV for Fe and 1.0eV for Mo). An outward relaxation is observed for each layer of the first four layers and the accompanying layer's rumpling has a decreasing trend from layer 1 to layer 4. Along Fe–O–Mo–O–Fe or Mo–O–Fe–O–Mo chain, the oxygen atom is closer to the adjacent Mo atom than to the adjacent Fe atom. The half-metallic nature ensures the symmetrical FeMoO terminated (001)-oriented slab of double perovskite Sr2FeMoO6 to be a potential application in spintronic devices. The Jahn–Teller structural distortions and the outward relaxations lead to the differences between pz state and similar px and py states, between dxy state and similar dyz and dxz states as well as between dz2 and dx2−y2. The reduction in the restrictions from the reduction in the number of the near neighbors, especially the vanishing of the nearest neighbor oxygen atom just above the transition-metal (TM) atoms on the first layer makes not only the remaining axial TM–O distances slightly shorter than the four equatorial TM–O distances but also shifts toward higher energy region the occupied up-spin and down-spin states with respect to the cases of the TM atoms on the third and fifth layers.

K-Enriched MoO3 Nanobundles: A Layered Structure with High Electric Conductivity

We present a surprisingly simple procedure to synthesize potassium-intercalated MoO3 nanobundles with the integrity of the layered structure remaining intact. While the material displays semiconductor-like behavior, dramatic enhancement of the electric conductivity from 10–6 S m–1 of MoO3 to 24 S m–1 upon potassium uptake was observed. Density functional theory calculations were performed to assist in structural determination and to elucidate the electronic property of the nanobundles. It was found that the K atoms occupy the oxygen vacancy sites in the lattice. The ionization of the K atoms gives rise to the reduction of the adjacent Mo atoms, leading to electron population in the conduction band.