Changes In Electronic Structure Research Articles

Ternary cobalt–iron–manganese layered double hydroxides with 1D/2D hierarchical nanostructure for oxygen evolution reaction and urea oxidation reaction

Developing high-efficient and stable electrocatalysts for oxygen evolution reaction (OER) is crucial for water splitting and metal-air batteries. Herein, ternary CoFe1−XMnX (0 <X < 1) layered double hydroxides (LDHs) grown on nickel form (NF) with nanosheet-nanowires (1D/2D) hierarchical nanostructure are synthesized. The introduction of Mn causes the change of crystal phase, morphology, and electronic structure of CoFe-LDH through electron transfer from Co/Fe to Mn, which provides the whole merit structural features and synergistic effect. Further experimental results exhibit that CoFe0.75Mn0.25-LDH possesses superior OER performance, which only requires overpotentials of 243 and 298 mV to reach 20 and 100 mA cm−2. The remodeling of LDHs in the OER process is also discussed to further explore the OER catalytic mechanism. In addition, CoFe0.75Mn0.25-LDH can also be utilized to the urea oxidation reaction (UOR), which requests a low potential of 1.367 V to reach 10 mA cm−2. A solar driven water splitting system is assembled and acquires the current density of 10 mA cm−2 at the low cell voltage of 1.58 V. This work offers an effective approach to boost the OER and UOR performance of CoFe-LDH based bifunctional electrocatalysts.

Ferroelectric control of band alignments and magnetic properties in the two-dimensional multiferroic VSe2/In2Se3

Our first-principles evidence shows that the two-dimensional (2D) multiferroic VSe2/In2Se3 experiences continuous change of electronic structures, i.e. with the change of the ferroelectric (FE) polarization of In2Se3, the heterostructure can possess type-I, -II, and -III band alignments. When the FE polarization points from In2Se3 to VSe2, the heterostructure has a type-III band alignment, and the charge transfer from In2Se3 into VSe2 induces half-metallicity. With reversal of the FE polarization, the heterostructure enters the type-I band alignment, and the spin-polarized current is turned off. When the In2Se3 is depolarized, the heterostructure has a type-II band alignment. In addition, influence of the FE polarization on magnetism and magnetic anisotropy energy of VSe2 was also analyzed, through which we reveal the interfacial magnetoelectric coupling effects. Our investigation about VSe2/In2Se3 predicts its wide applications in the fields of both 2D spintronics and multiferroics.

Unveiling the effect of gas treatment on the electronic structure of carbon nanotube-supported Pd catalysts for electroreduction of H2O2 and Heck reaction

This study explored the impact of gas treatments on the structures of multi-walled carbon nanotubes supported Pd (CNT-Pd) catalysts used for electrocatalytic H2O2 reduction and the Heck cross-coupling reaction. The CNT-Pd catalyst was prepared by anchoring Pd nanoparticles on thiolated CNTs. XPS was conducted to examine the surface composition and electronic structure changes of the CNT-Pd catalyst before and after gas treatment. The XPS results revealed that as-prepared CNT-Pd contains at least two different oxidation states on the surface, whereon their proportions depend on the gas used for treatment. Treatment with H2 leads to Pd(0) enrichment near the surface, while O2 treatment causes Pd(Ⅱ) enrichment of CNT-Pd. All catalysts containing both Pd(0) and Pd(Ⅱ) were active toward H2O2 reduction, and the Heck cross-coupling reaction of n-butyl acrylate and 4-iodotoluene; increased proportion of metallic Pd(0) boosted the catalytic reaction. However, the catalyst stability increased as the amount of Pd(II) increased.

Anomalous pressure-responsive emission enhancement of FCO-CzS due to molecular configuration and electronic structure changes

Studying the stimuli-responsive properties of luminescent materials is important for their applications, while the luminescent materials studied up to now usually exhibit emission quenching and red shift in photoluminescence (PL) energy upon compression. Designing luminescent material with abnormal pressure responses remains challenging. Here, we report the discovery of abnormal luminescent properties of FCO-CzS upon compression. A theoretical study on the excited state decay process has been carried out for FCO-CzS at high pressure by hybrid quantum mechanics/molecular mechanics (QM/MM). A significant emission enhancement and blue shift are observed as pressure increases up to 20 GPa. This is opposite to the pressure response behaviours reported for other luminescent materials. It is further revealed that both the unique molecular configuration and the electronic structure change contribute to the anomalous pressure-responsive emission of FCO-CzS, which reduces the non-radiative rate and increases the radiative rate, respectively. Our study provides a strategy for the design of luminescent materials with desired pressure responses.

Carbon nanotubes decorated with Pt as a viable electrocatalyst system using electrochemical atomic layer deposition

Surface limited redox replacement (SLRR) is an electrochemical deposition method designed to deposit metal thin films, typically onto other metals, that are mere monolayers in thickness, where such low dimensions allows catalyst-support interactions to affect catalyst efficiency. Here we explore the growth of Pt, using iterative Cu-mediated SLRR cycles, directly onto carbon nanotubes (CNTs) which are potentially good candidates as electrocatalyst supports due to their electrical conductivity and chemical resistance. Scanning electron microscope images showed that Pt grew as nanoparticles, and hydrogen underpotential deposition from cyclic voltammetry showed that the active surface area approached an asymptotic value around eight iterations. Catalytic activity, measured using the oxygen reduction reaction, reached a maximum at ten iterations. Both are shown to be influenced by the growth mode, but electrochemical modeling indicates that the trend in activity is also due to a change in activation energy, possibly due to changes in Pt electronic structure due to interactions with the CNTs. Durability cycling showed a greater than 85% retention of surface area for the first 10,000 cycles of accelerated stress testing but decayed steadily to about 50% after 30,000 cycles. This performance may be related to the phenomenon that limits surface area growth.

Lix(C5H5N)yFe2-zSe2: A Defect-Resilient Expanded-Lattice High-Temperature Superconductor.

Two-dimensional iron chalcogenide intercalates display a remarkable correlation of the interlayer spacing with enhancement of the superconducting critical temperature (Tc). In this work, synchrotron X-ray absorption (XAS; at the Fe and Se K-edges) and emission (XES; at the Fe Κβ) spectroscopies allow one to discuss how the important rise of Tc (∼44 K) in the molecule-intercalated Lix(C5H5N)yFe2-zSe2 relates to the electronic and local structural changes felt by the inorganic host upon doping (x). XES shows that widely separated layers of edge-sharing FeSe4 tetrahedra carry low-spin moieties, with a local Fe magnetic moment slightly reduced compared to the parent β-Fe2-zSe2. Pre-edge XAS expresses the progressively reduced mixing of metal 3d-4p states upon lithiation. Doping-mediated local lattice modifications, probed by conventional Tc optimization measures (cf. the anion height and FeSe4 tetrahedra regularity), become less relevant when layers are spaced far away. On the basis of extended X-ray absorption fine structure, such distortions are compensated by a softer Fe network that relates to Fe-site vacancies, alleviating electron-lattice correlations and superconductivity. Density functional theory (DFT) guided modification of the isolated Fe2-zSe2 (z, vacant sites) planes, resembling the host layers, identify that Fe-site deficiency occurs at low energy cost, giving rise to stretched Fe sheets, in accordance with experiments. The robust high-Tc in Lix(C5H5N)yFe2-zSe2, arises from the interplay of electron-donating spacers and the iron selenide layer's tolerance to defect chemistry, a tool to favorably tune its Fermi surface properties.

Influence of Vacancy on Structural Stability, Mechanical Properties and Electronic Structures of a Ti5Sn3 Compound from First-Principles Calculations

Titanium alloy is widely used in biomedical materials. Ti-Sn alloy is a new type β titanium alloy with no toxicity. In this paper, the mechanical and electronic properties of Ti5Sn3 with vacancy defects have been studied by using first-principles method. The vacancy formation energy, vacancy formation enthalpy, elastic constant, elastic modulus, hardness and electronic structure of perfect Ti5Sn3 and Ti5Sn3 with different vacancies were also calculated and discussed. The results show that Ti5Sn3 is more likely to form vacancies at VTi2. In addition, the bulk deformation resistance of Ti5Sn3 is weakened by the vacancy, and the shear resistance, stiffness and hardness of Ti5Sn3 are increased by the Ti vacancy, but the brittleness of Ti5Sn3 is increased. On the contrary, the presence of Sn vacancy decreases the shear resistance, stiffness and hardness of Ti5Sn3, and increases the toughness of Ti5Sn3. By analyzing the change of electronic structure, it is found that removing the Ti atom at the VTi2 position can improve the interaction between atoms, while Sn vacancy can weaken the interaction.

The N3/TiO2 interfacial structure is dependent on the pH conditions during sensitization.

The electronic structure of the N3/TiO2 interface can directly influence the performance of a dye sensitized solar cell (DSSC). Therefore, it is crucial to understand the parameters that control the dye's orientation on the semiconductor's surface. A typical step in DSSC fabrication is to submerge the nanoparticulate semiconductor film in a solution containing the dye, the sensitizing solution. The pH of the N3 sensitizing solution determines the distribution of the N3 protonation states that exist in solution. Altering the pH of the sensitizing solution changes the N3 protonation states that exist in solution and, subsequently, the N3 protonation states that anchor to the TiO2 substrate. We utilize the surface specific technique of heterodyne detected vibrational sum frequency generation spectroscopy to determine the binding geometry of N3 on a TiO2 surface as a function of the sensitizing solution pH conditions. It is determined that significant reorientation of the dye occurs in pH ≤2.0 conditions due to the lack of N3-dye carboxylate anchoring groups participating in adsorption to the TiO2 substrate. Consequently, the change in molecular geometry is met with a change in the interfacial electronic structure that can hinder electron transfer in DSSC architectures.

Evolution of the Electronic Structure of Ultrathin MnBi2Te4 Films.

Ultrathin films of intrinsic magnetic topological insulator MnBi2Te4 exhibit fascinating quantum properties such as the quantum anomalous Hall effect and the axion insulator state. In this work, we systematically investigate the evolution of the electronic structure of MnBi2Te4 thin films. With increasing film thickness, the electronic structure changes from an insulator type with a large energy gap to one with in-gap topological surface states, which is, however, still in drastic contrast to the bulk material. By surface doping of alkali-metal atoms, a Rashba split band gradually emerges and hybridizes with topological surface states, which not only reconciles the puzzling difference between the electronic structures of the bulk and thin-film MnBi2Te4 but also provides an interesting platform to establish Rashba ferromagnet that is attractive for (quantum) anomalous Hall effect. Our results provide important insights into the understanding and engineering of the intriguing quantum properties of MnBi2Te4 thin films.

Synergistic effect of interstitial C doping and oxygen vacancies on the photoreactivity of TiO2 nanofibers towards CO2 reduction

TiO2 nanofiber membranes were prepared by calcinating the electrospun TiO2 nanofibers precursor. Sample calcined at 400 °C (T400) exhibited high CO2 to CH4 conversion efficiency (55.17 μmol·g−1·h−1) and electron selectivity (98.3%) under simulated sunlight. In-situ DRIFTS and the calculated Gibbs free energy revealed CO* to be a major intermediate with the formation of COH* intermediate being the rate-limiting step. The considerable CO2 photoreduction behavior obtained on T400 sample can be attributed to the following causes: (1) the existence of surface OVs gives the change in electronic structure by upshifting CB position to be capable of CO2 photoreduction; (2) the surface Ti terminals acted as reaction sites, resulting in the accumulation of CO* intermediates to continually produce CH4 with the support of sufficient electrons. These results lay the foundation for advancing the mechanistic insight on CO2 photoreduction and its selectivity to CO2 to CH4.

Solid State Batteries – Chemistry, Electrochemistry and Mechanical Concerns

High energy long life rechargeable battery is considered as key enabling technology for deep de-carbonization. Energy storage in the electrochemical form is attractive because of its high efficiency and fast response time. Besides the technological importance, electrochemical devices also provide a unique platform for fundamental and applied materials research since ion movement is often accompanied by inherent complex phenomena related to phase changes, electronic structure changes and defect generation. In this talk, I will discuss key chemical, electrochemical and mechanical considerations in all solid state batteries. With recent advances in characterization tools and computational methods, we are able to explore ionic mobility, charge transfer and phase stability in electrode and electrolyte, as well as their interphases in operando, and map out the complex relations in novel solid state materials for next generation energy storage and conversion.

(Digital Presentation) Investigations into the Capacity Degradation Due to an Electronic Structural Change in Homogenous Boron-Substituted Ni-Rich Layered Oxides

Ni-rich layered oxides (LiNixCoyMnzO2, x≥0.8, x+y+z=1) would fulfil the energy density requirements of the automobile industry since they offer outstanding capacities at relatively high mean voltages and sufficient power densities1-3. However, the materials still show significant capacity and voltage fade which requires substantial research. Recently we have shown that the electronic structure is the key to understand the performance but also the failure of the materials1. Thus, we intend to modify the electronic structure using anionic dopants such as Boron. Thus, homogenous B-substituted NCM811s (BNCM811_x%, x% means the x at. % of Boron) are synthesized and the materials reveal a significant change in the electronic structure as evident from x-ray photoelectron spectroscopy (XPS) and near edge x-ray absorption spectroscopy (NEXAFS). Interestingly, a shift of the so called H2-H3 peak4 to higher potentials was observed by Boron substitution and BNCM811s_2% shows relative higher initial discharge capacity (Figure 1A.) at a slightly higher mean voltage, but a lower cycling stability compared to NCM811 (Figure 1B.).The H2-H3 differential capacity peak (Figure 1C) might also include oxygen release5, which is one of the main reasons restricting the cycling stability. Near edge x-ray absorption spectroscopy (NEXAFS) shows that the H2-H3 peak corresponds to a reaction from Ni3+ to Ni2+ (upon charge) and Ni2+ to Ni3+ (upon discharge) which suggest a reaction like NiO2 ⥂ NiO + ½ O2 as the underlying process. At the same time, an Oxygen K peak at 531 eV appears in the NEXAFS spectra, which was assigned to O-O formation in the host structure of Li-rich materials6, 7. Note that the electronic structure of the materials was determined in 5 mAh/g steps over the H2-H3 peak and due to the high resolution, this process became visible for the first time. The findings suggest that dimer formation is not only a phenomenon of Li-rich materials but can also be found in Ni-rich layered oxides at high states of charge.The origin of dimer formation and oxygen release can be traced back to the electronic configuration of Ni. Charge transfer multiplet calculations reveal, that Ni2+ reacts to covalent Ni3+ upon charge (and vice versa upon discharge)1. Ni3+ has a 3d7 electronic state, whose low spin configuration is more preferred than its high spin configuration. Thus, Ni3+ is more prone to Jahn-Teller (JT) distortions and tends to form covalent bonds. Consequently, the electrons are more bound to the individual sites making a further oxidation of the transition metal almost impossible. In conclusion, Boron substitution helps us to understand the function and failure of layered oxides in Li-ion batteries on an atomistic scale and the findings can be used as a design guide for future materials. K. Kleiner, C. A. Murray, C. Grosu, B. Ying, M. Winter, P. Nagel, S. Schuppler and M. Merz, Journal of The Electrochemical Society, 2021.J. Zhao, W. Zhang, A. Huq, S. T. Misture, B. Zhang, S. Guo, L. Wu, Y. Zhu, Z. Chen and K. Amine, Advanced Energy Materials, 2017, 7, 1601266.S.-J. Yoon, K.-J. Park, B.-B. Lim, C. S. Yoon and Y.-K. Sun, Journal of the Electrochemical Society, 2014, 162, A3059.S. Jamil, G. Wang, L. Yang, X. Xie, S. Cao, H. Liu, B. Chang and X. Wang, Journal of Materials Chemistry A, 2020, 8, 21306-21316.K. Märker, P. J. Reeves, C. Xu, K. J. Griffith and C. P. Grey, Chemistry of Materials, 2019, 31, 2545-2554.E. Hu, X. Yu, R. Lin, X. Bi, J. Lu, S. Bak, K.-W. Nam, H. L. Xin, C. Jaye and D. A. Fischer, Nature Energy, 2018, 3, 690-698.K. Kleiner, B. Strehle, A. R. Baker, S. J. Day, C. C. Tang, I. Buchberger, F.-F. Chesneau, H. A. Gasteiger and M. Piana, Chemistry of Materials, 2018, 30, 3656-3667. Figure 1

Bonding in nitrile photo-dissociating ruthenium drug candidates-A local vibrational mode study.

In this work, we investigated bonding features of 15 ruthenium(II) nitrile complexes of the type [Ru(tpy)(L)-(CH3CN)]n+, containing the tridentate tpy ligand (tpy = 2,2':6',2″-terpyridine) and various bidentate ancillary ligands L; 12 compounds originally synthesized by Loftus et al. [J. Phys. Chem. C 123, 10291-10299 (2019)] and three new complexes. We utilized local vibrational force constants derived from the local mode theory as a quantitative measure of bond strength complemented with the topological analysis of the electron density and the natural bond orbital analysis. Loftus et al. suggested that nitrile dissociation occurs after light induced singlet-triplet transition of the original complexes and they used as a measure of nitrile release efficiency quantum yields for ligand exchange in water. They observed larger quantum yields for complexes with smaller singlet-triplet energy gaps. The major goal of this work was to assess how the Ru-NC and Ru-L bond strengths in these 15 compounds relate to and explain the experimental data of Loftus et al., particularly focusing on the question whether there is a direct correlation between Ru-NC bond strength and measured quantum yield. Our study provides the interesting result that the compounds with the highest quantum yields also have the strongest Ru-NC bonds suggesting that breaking the Ru-NC bond is not the driving force for the delivery process rather than the change of the metal framework as revealed by first results of a unified reaction valley approach investigation of the mechanism. Compounds with the highest quantum yield show larger electronic structure changes upon singlet-triplet excitation, i.e., larger changes in bond strength, covalency, and difference between the singlet and triplet HOMOs, with exception of the compound 12. In summary, this work provides new insights into the interplay of local properties and experimental quantum yields forming in synergy a useful tool for fine tuning of existing and future design of new nitrile releasing ruthenium compounds. We hope that this work will bring theoretical and experimental studies closer together and serves as an incubator for future collaboration between computational chemists and their experimental colleagues.

Synchrotron X-ray spectroscopic study of the antiferromagnetic-ferromagnetic transition in Ni-doped FeRh epitaxial thin films

We investigate the change of magnetism and electronic structure across the antiferromagnetic (AFM) -ferromagnetic (FM) transition of Ni-doped FeRh epitaxial thin films by x-ray magnetic circular dichroism (XMCD) and hard x-ray photoemission spectroscopy (HAXPES). The Rh L edge XMCD results indicate that the remnant FM phase at low temperature possesses smaller Rh moment than the normal FM phase which can undergo AFM-FM transition. The HAXPES results confirm an increase of Rh 4d density of state at the Fermi level and a possible “well-screened” state at the Ni 2p photoemission in the FM phase. FM fluctuation of the inter-site Fe-Fe exchange coupling within the AFM phase can be interpreted from the temperature dependence of the Fe 2p HAXPES results.

Theoretical study of potential n-type and p-type dopants in GaN from data mining and first-principles calculation

Impurity doping is one of the important means to control the physical properties of intrinsic semiconductors. By combining data mining and first principles calculation, a series of potential dopable elements in gallium nitride (GaN) were predicted by Shannon radius and probability model methods in this study. The Shannon radius difference and replacement probability were used as the criterion to screen the dopable elements and a total of 36 dopants were predicted. Then the structural stability and electronic structure of these doped structures were systematically studied by the first principles calculations. Among these dopants, the defect formation energy of 14 kinds is less than 3 eV, namely O, Zr, Ti, Si, F, Ge, Nb, S, Se for n-type and Be, Mg, Ca, Zn and Mn for p-type. In these potential doping systems, the changes of electronic structure can be divided into two types according to whether the impurity energy level is introduced or not. The doping of Ti, Nb, F and Mn can introduce significant impurity levels in the band gap, the electrons of which are directly involved in the carrier transition. For other dopants, no obvious impurity energy level is introduced in the band gap. Compared with the undoped GaN, the electronic density of states of the doped systems are significantly enhanced at the conduction band minimum. These results are expected to provide an effective theoretical reference for the experimental screening of appropriate GaN dopants

Mechanical properties of pyrophyllite under the coupling of high temperature-pressure: A first-principle study

Pyrophyllite [Al2Si4O10(OH)2] is known to be the pressure transmission medium in the high temperature-pressure synthesis industry of super-hard materials, which is attributed to its exceptional support properties, heat resistance, and pressure transmission. Therefore, it is of utmost importance to characterize the mechanical behavior of pyrophyllite under the coupling action of high temperature-pressure (the combined effect of temperature-pressure is called T-P coupling in this work). In this work, the optimal structures, elastic constant, elastic modulus, and anisotropy index of pyrophyllite under T-P coupling are investigated systematically based on the first principle calculation for the first time. Several structure parameters, including lattice constants and layer spacing, indicate that the effect of T-P coupling on the structure mainly acts on internal layer spacing (dI). The elastic modulus (B: Bulk modulus, E: Young's modulus, G: Shear modulus) of pyrophyllite increase gradually with augmented pressure and decreases with the process of heating. Under T-P coupling, high pressure weakens the degree of influence caused by temperature on the elastic modulus of pyrophyllite. This phenomenon is mainly attributed to the structural compactness of pyrophyllite caused by pressure, which weakens the thermal expansion effect caused by heating. As a result, the impact of temperature on the stiffness of pyrophyllite was weakened with rising pressure. At the same time, the changes in crystal structure and atomic distribution density under different T-P conditions also change the toughness and elastic anisotropy of pyrophyllite. The 3D spatial distribution diagrams of anisotropy reflect that temperature increases the elastic mechanical anisotropy of pyrophyllite, in contrast to pressure which tends to decrease it. The sealed pressure transmission medium should not only have good mechanical and thermodynamic properties, but also have insulation. The change of electronic structure under T-P coupling shows that pyrophyllite always maintains good insulation characteristics. These results reveal new insight into the application of pyrophyllite in the synthesis of super-hard materials. And all of these studies are expected to be a guideline for others in their experimental investigations.

Cu-Based Multicomponent Metallic Compound Materials as Electrocatalyst for Water Splitting.

In this study, Cu-based multicomponent metallic compound materials M-Cu (M = Mn, Fe, Co, Ni, and Pt) were studied as electrocatalytic materials for water splitting. Different metal materials attached to the copper foam substrate can change the valence states of copper and oxygen, resulting in the change of electronic structure of the materials, thus changing its catalytic activity.

Tailoring of Bandgap and Spin-Orbit Splitting in ZrSe2 with Low Substitution of Ti for Zr

Tuning the bandgap in layered transition metal dichalcogenides (TMDCs) is crucial for their versatile applications in many fields. The ternary formation is a viable method to tune the bandgap as well as other intrinsic properties of TMDCs, because the multi-elemental characteristics provide additional tunability at the atomic level and advantageously alter the physical properties of TMDCs. Herein, ternary Ti x Zr1 – x Se2 single crystals were synthesized using the chemical-vapor-transport method. The changes in electronic structures of ZrSe2 induced by Ti substitution were revealed using angle-resolved photoemission spectroscopy. Our data show that at a low level of Ti substitution, the bandgap of Ti x Zr1 – x Se2 decreases monotonically, and the electronic system undergoes a transition from a semiconducting to a metallic state without a significant variation of dispersions of valence bands. Meanwhile, the size of spin-orbit splitting dominated by Se 4p orbitals decreases with the increase of Ti doping. Our work shows a convenient way to alter the bandgap and spin-orbit coupling in TMDCs at the low level of substitution of transition metals.

Symmetry and strain analysis of combined electronic and structural instabilities in tungsten trioxide, WO3

Lattice parameter data from the literature have been used to provide a complete description of spontaneous strain variations across each of the six known phase transitions of WO3 in the temperature interval 5–1273 K. Analysis of strain/order parameter coupling reveals the character of each phase transition, a unified description of strain across the full temperature range, the relationship between strain and electronic effects, and new insights into the strain gradients likely to be present in each of the different domain walls that develop in four different ferroelastic phases. Tetragonal and orthorhombic shear strains have values of 4%–6% and 2%–3%, respectively, and are dominated by coupling with the order parameter for antiferroelectric-type displacements. Conversely, shear strains, e4, e5, and e6, of up to 2% are controlled by octahedral tilting. Changes in electronic structure and properties have been related back to the susceptibility of W6+ to develop cooperative second-order-Jahn–Teller distortions. Proximity to tilt instabilities along with group–subgroup relationships in the P4/nmm parent structure results in two overlapping sequences of structural phase transitions, which differ in the form of their electronic structure. The possibility of a ground state structure in space group P21/c can be rationalized in terms of the efficiency by which different combinations of shearing and tilting of the WO6 octahedra can reduce the unit cell volume and would imply that WO3 has a re-entrant phase transition. Gradients in up to three order parameters coupled with gradients in strain of up to 12% across ferroelastic domain walls indicate that the different ferroelastic phases of WO3 should have domain walls with varied and potentially exotic electronic properties for device applications such as in nanoelectronics and neuromorphic computing.

The effects of defects on the defect formation energy, electronic band structure, and electron mobility in 4H–SiC

With the first-principle method, we studied the effects of the type and position of defects on the defect formation energy, electronic band structure, and electron mobility of the 4-layer hexagonal system silicon carbon (4H–SiC). The vacancy defect formation energy is smaller than the interstitial defect formation energy. The C vacancy defect formation energy is the smallest, while the Si interstitial defect formation energy is the largest. The defect formation energy is little affected by the defect position. The electronic band structure shows semi-metallic property due to the vacancy defect and the interstitial defect, and it shows a smaller bandgap due to the antisite defect. The electronic band structure changes little while the defect position changes. The electron mobility is reduced in varying degrees according to different defect types. The electron mobility changes little while the defect position changes.