Charge Density Difference Calculations Research Articles

Enhanced VOCs adsorption on Group VIII transition metal-doped MoS2: A DFT study

Volatile organic compounds (VOCs) represent a significant category of toxic and harmful air pollutants. Among the various abatement techniques available for VOCs, adsorption technology is widely recognized as a cost-effective solution. In this study, density functional theory (DFT) was employed to calculate and compare the adsorption capacities of six typical VOCs on pristine MoS2 and MoS2 modified with Group VIII (MVIII) transition metals atoms. It is found that MVIII-MoS2 monolayer demonstratesa significant enhancement in adsorption capabilities for VOCsrelative to pristine MoS2. Among these Group VIII transition metals atoms, Fe, Ru and Os atoms exhibited the most significant VOCs adsorption enhancement, with Fe atoms demonstrating a particularly pronounced effect. This suggests a synergistic interaction between the metal dopants and the substrate. Density of states (DOS) and charge density difference analyses provided further insights into the mechanisms underlying improved adsorption capability. Interestingly, the introduction of MVIII atoms results in the emergence of a novel state density within the surface state of MoS2, thereby facilitating enhanced electron transfer between VOCs and the substrate. Charge density difference calculations further corroborated these findings, with certain configurations exhibiting significant electron cloud overlap. Such modification leads to more active electron transfer, thereby increasing the substrate’s affinity for VOC molecules and consequently improving the adsorption efficiency. The findings not only enhance the comprehension of VOC adsorption mechanisms on MoS2 but also underscore the potential of metal-doped two-dimensional materials for environmental applications.

Computational Insight into Transition Metal Atoms Anchored on B2C3P as Single‐Atom Electrocatalysts for Nitrogen Reduction Reaction

AbstractNH3 is not only an important chemical raw material but also a high‐energy storage chemical with zero carbon. Electrocatalytic nitrogen reduction reaction (NRR), which can be driven by clean electric energy under ambient conditions, has become a promising technology for NH3 synthesis due to its environmentally friendly properties. Because of the limitations of low yield and high overpotential, efficient catalysts are urgently needed to solve this problem. In this study, based on density functional theory method and high throughput screening strategy, the NRR was investigated on transition metal single atom anchored to 2D B2C3P surface (TM@B2C3P) as single‐atom catalysts (SACs). The results showed that V@B2C3P and Ti@B2C3P have good catalytic properties, and the limiting potentials were −0.10 and −0.24 V, respectively. Furthermore, the charge density difference and crystal orbital Hamilton population calculations demonstrated that the high catalytic activity can be attributed to the obvious charge transfer between TM@B2C3P and the adsorption intermediates. It is hoped that this work can play a certain role in exploring the application of SACs in NRR.

Effect of terminal substituents on intramolecular charge transfer in one- and two-photon absorption of zinc phthalocyanine derivatives

Zinc phthalocyanine derivatives have unique structure and photophysical properties, which make them a remarkable potential in the fields of optoelectronics as well as biomedicine. In order to reveal the effect of the terminal substituents on the electron transition mechanisms, one-photon absorption (OPA) and two-photon absorption (TPA) processes of three zinc phthalocyanines modified with different terminal substituents (PcZn-0, PcZn-1 and PcZn-2) have been analyzed by using density-functional theory (DFT) in combination with the sum-over-states (SOS) model, the visualization of the transition density matrix (TDM) as well as charge density difference (CDD) calculations. Red-shifted OPA absorption peaks with enhanced intensities, have been observed in molecules PcZn-1, PcZn-2 with long terminal substituents. However, for TPA process, a more effective charge transfer over almost the entire molecule has been observed in PcZn-1 molecule with 4-methoxybenonic acid as terminal substituents. When H-atoms in the hydroxyl groups of four terminal 4-Methoxybenzoic acid groups were substituted by dispersed red-one chains, a limited range of intramolecular charge transfer and localized excitation inside the dispersed red-one chain were observed, leading to a localized excitation absorption peak and expanding the wavelength region of TPA response. Furthermore, terminal substituents with conjugated branches exhibit a stronger cooperative effect between the terminal chains and shows larger TPA response. On the contrary, excessive dihedral angles between different groups can weaken the conjugation degree of molecules and affect intramolecular charge transfer as well as TPA response.

Gas Detecting Evaluation by Graphitic-based Silicon Carbide Nanosurface doped with Manganese: A Promising Device for Air Pollution Monitoring

Silicon carbide (SiC) as a direct broad bandgap semiconducting material has the potential to bring a considerable developement into optoelectronic and electronic devices. This article aims to investigate Physico-chemical properties of manganese (Mn)–doped graphene-like silicon carbide (SiC) monolayer sheet by the first-principles methods based on the density functional theory (DFT) for scavenging of CO, CO2, NO, NO2 gas molecules. The results recommend that the adsorption of these gas molecules on Mn-embedded SiC sheet monolayer is more energetically desired than that on the pristine ones. Gas molecules of CO, CO2, NO, NO2 have been adsorbed on the Mn site of doped SiC monolayer through the formation of covalent bonds. The assumption of chemical adsorptions has been approved by the projected density of states (PDOS) and charge density difference plots. Charge density difference calculations also indicate that the electronic densities were mainly accumulated on the adsorbate of CO, CO2, NO, NO2 gas molecules. The ability of SiC nanosheet for monitoring of CO, CO2, NO and NO2 is fluctuated by their selectivity and sensitivity through NMR, NQR, IR and HOMO/LUMO approaches which can represent the efficiency of Mn–doped SiC surface as the promising sensors toward air pollution detecting.

COF‐Topological Quantum Material Nano‐heterostructure for CO2 to Syngas Production under Visible Light

AbstractEfficient solar‐driven syngas production (CO+H2 mixture) from CO2 and H2O with a suitable photocatalyst and fundamental understanding of the reaction mechanism are the desired approach towards the carbon recycling process. Herein, we report the design and development of an unique COF‐topological quantum material nano‐heterostructure, COF@TI with a newly synthesized donor‐acceptor based COF and two dimensional (2D) nanosheets of strong topological insulator (TI), PbBi2Te4. The intrinsic robust metallic surfaces of the TI act as electron reservoir, minimising the fast electron‐hole recombination process, and the presence of 6s2 lone pairs in Pb2+ and Bi3+ in the TI helps for efficient CO2 binding, which are responsible for boosting overall catalytic activity. In variable ratio of acetonitrile‐water (MeCN : H2O) solvent mixture COF@TI produces syngas with different ratios of CO and H2. COF@TI nano‐heterostructure enables to produce higher amount of syngas with more controllable ratios of CO and H2 compared to pristine COF. The electron transfer route from COF to TI was realized from Kelvin probe force microscopy (KPFM) analysis, charge density difference calculation, excited state lifetime and photoelectrochemical measurements. Finally, a probable mechanistic pathway has been established after identifying the catalytic sites and reaction intermediates by in situ DRIFTS study and DFT calculation.

Triboelectric Charging Properties of the Functional Groups of Common Pharmaceutical Materials Using Density Functional Theory Calculations.

Triboelectrification is a ubiquitous and poorly understood phenomenon in powder processing, particularly for pharmaceutical powders. Charged particles can adhere to vessel walls, causing sheeting; they can also cause agglomeration, threatening the stability of powder formulations, and in extreme cases electrostatic discharges, which present a serious fire and explosion hazard. Triboelectrification is highly sensitive to environmental and material conditions, which makes it very difficult to compare experimental results from different publications. In this work, density functional theory (DFT) is used to investigate the charge transfer characteristics of several functional groups of paracetamol in order to better understand the mechanisms of charging at the nanoscale and the influence of the environmental and material properties on charge transfer. This is achieved by studying the structure and electronic properties at the molecule-substrate interface. Using this molecule-substrate approach, the charging contributions of individual functional groups are explored by examining the Hirschfeld charges, the charge density difference between the molecule and substrate, the density of states, and the location of the frontier orbitals (HOMO and LUMO) of a paracetamol molecule. Charge density difference calculations indicate a significant transfer of charge from the molecule to the surface. Observable regions of electron density enrichment and depletion are evident around the electron-donating and -withdrawing groups, respectively. The density of states for the paracetamol molecule evolves as it approaches the surface, and the band gap disappears upon contact with the substrate. Hirshfeld charge analysis reveals asymmetry in the charge redistribution around the molecule, highlighting the varying charging tendencies of different atoms.

Adsorption of CO, CO2 and NO2 molecules on Li/Pt decorated C-57 nanostructures and effect of applied external electric field: A DFT study

The adsorption behavior of CO2, NO2, and CO gasses on C-57 carbon nanotubes is presently being investigated in this work. Utilizing density functional theory (DFT) computations at the vdW-DF3-OPT2 and PBEsol theoretical levels, the adsorption characteristics of these gases on Li-decorated nanostructures are being investigated. This article examines the NEB (Nudged Elastic Band) technique for gas adsorption on carbon nanotubes. The results of the study can help with the development and improvement of gas adsorption systems based on carbon nanotubes. Furthermore, at various strengths of external electrical fields, the adsorption behavior of CO2 and CO gasses on Pt-decorated C-57 carbon nanosheets is being investigated. The findings provide insights into how the electric field affects the adsorption energy. The objective of this study is to further our knowledge of gas adsorption on C-57 carbon nanostructures and to demonstrate how external electric fields can be used to modify the adsorption properties for a range of energy and environmental applications. We are currently studying the geometries of 1 up to 2 adsorbed gas molecules on the exterior of the nanotube and identifying preferred Li-decorated sites in terms of gas adsorption energy. The charge density difference and electronic band structures are currently being used to assess the adsorption system's characteristics. The charge accumulation between the interacting atoms is being revealed by charge density difference calculations, suggesting the possibility of covalent bond formation. This nanostructure may make a good material for gas adsorption, according to the adsorption energy data (-0.4 to 1.6 (eV)). The efficiency of gas capture and storage systems can be improved by varying the adsorption behavior through the application of an external electrical field.

COF-Topological Quantum Material Nano-heterostructure for CO2 to Syngas Production under Visible Light.

Efficient solar-driven syngas production (CO+H2 mixture) from CO2 and H2O with a suitable photocatalyst and fundamental understanding of the reaction mechanism are the desired approach towards the carbon recycling process. Herein, we report the design and development of an unique COF-topological quantum material nano-heterostructure, COF@TI with a newly synthesized donor-acceptor based COF and two dimensional (2D) nanosheets of strong topological insulator (TI), PbBi2Te4. The intrinsic robust metallic surfaces of the TI act as electron reservoir, minimising the fast electron-hole recombination process, and the presence of 6s2 lone pairs in Pb2+ and Bi3+ in the TI helps for efficient CO2 binding, which are responsible for boosting overall catalytic activity. In variable ratio of acetonitrile-water (MeCN : H2O) solvent mixture COF@TI produces syngas with different ratios of CO and H2. COF@TI nano-heterostructure enables to produce higher amount of syngas with more controllable ratios of CO and H2 compared to pristine COF. The electron transfer route from COF to TI was realized from Kelvin probe force microscopy (KPFM) analysis, charge density difference calculation, excited state lifetime and photoelectrochemical measurements. Finally, a probable mechanistic pathway has been established after identifying the catalytic sites and reaction intermediates by in situ DRIFTS study and DFT calculation.

Unveiling an S-scheme F–Co3O4@Bi2WO6 heterojunction for robust water purification

Devising a desirable nano-heterostructured photoelectrode based on the charge transfer kinetics mechanism is a pivotal strategy for implementing efficient photoelectrocatalytic (PEC) technology, since the charge separation and utilization efficiency of a photoelectrode is critical to its PEC performance. Herein, we fabricate a F–Co3O4@Bi2WO6 core–shell hetero-array photoanode by coupling Bi2WO6 nanosheets with F–Co3O4 nanowires using a simple solvothermal solution method. The three-dimensional hierarchical heterostructure has a homogeneous chemical interface, helping it to promote an S-scheme-based carrier transport kinetics and maintain excellent cycling stability. Charge density difference calculations verify the electron migration trend from F–Co3O4 to Bi2WO6 upon hybridization and the formation of an internal electric field in the heterojunction, consistent with the S-scheme mechanism, which is identified by in situ irradiation X-ray photoelectron spectroscopy and by ultraviolet photoelectron spectroscopy. The optimized F–Co3O4@Bi2WO6-2 photoelectrode achieves high carrier utilization efficiency and exhibits superior PEC degradation performance for various organic pollutants, including reactive brilliant blue KN-R, rhodamine B, sulfamethoxazole, and bisphenol A. This work not only reveals that F–Co3O4@Bi2WO6-2 is effective for PEC water remediation but also provides a strategy to enhance carrier transport kinetics by designing binary oxides.

Nitric oxide removal by synergistic photooxidation and adsorption using Pd1/g-C3N4-UiO-66-NH2 P-A heterojunction

Simultaneous avoidance of secondary air pollution and catalyst deactivation remains a challenge for existing photocatalytic removal of nitric oxide (NO). Herein, a photocatalysis-adsorption (P-A) heterojunction is synthesized for eco-friendly NO removal by facilely grinding Pd single atoms (Pd1) anchored g-C3N4 (48CN/Pd) with UiO-66-NH2 (UION). Under visible-light irradiation, the 40UION-CN/Pd composite shows 93.91 % of NO removal efficiency with only 2.73 % of NO2 emissions and negligible catalyst deactivation. The DeNOx index increases remarkably from −0.66 for 48CN/Pd to 0.86 for 40UION-CN/Pd. Furthermore, the synthesized P-A heterojunction efficiently removes NO from real flue gases produced by a domestic coal-fired stove and from SO2-rich flue gases. The mechanism exploration based on experimental investigations and density functional theory (DFT) calculations reveals that UION captures the NO2 selectively produced by 48CN/Pd, simultaneously suppressing NO2 emissions and refreshing active sites for NO photooxidation. Moreover, the results of X-ray photoelectron spectroscopy (XPS), charge density difference calculation, energy-resolved distribution of electron traps (ERDT) and in-situ Kelvin probe force microscopy (KPFM) reveal that the built-in electric field and Type-II heterojunction formed between 48CN/Pd and UION promote the separation of photogenerated carriers, enhancing the catalytic activity of the composite. This work provides an innovative strategy to avoid NO2 emission and catalyst deactivation during photocatalytic NO removal.

Nitrogen modification enhances conductivity and reactivity of sulfidated zero-valent iron: Mechanism and Cr(VI) removal

The incorporation of electronegative elemental nitrogen into zero-valent iron (ZVI)/sulfidated zero-valent iron (S-ZVI) has emerged as an outstanding and promising way to improve decontamination performance. However, the impact of nitrogen modification on the electrical structure of ZVI/S-ZVI remains unclear. Herein, nitrogen-modified sulfidated zero-valent iron (S-N-ZVI) was successfully obtained utilizing cheap and accessible ammonium chloride as the nitrogen source. Raman spectra, FTIR, and density functional theory (DFT) calculations demonstrated that NH3 acts as the dominant nitrogen species. According to the projected density of states and charge-density difference calculations, N is successfully bound to Fe, resulting in a redistribution of surface charge and an increase in electron density of S-N-ZVI, which is reflected in the improved conductivity of S-N-ZVI. Compared with S-ZVI, S-N-ZVI demonstrates better performance in terms of Cr(VI) removal kinetics (kobs improved by 2.075 folds), resistance to air aging, reusability and ability to preserve FeSX stability. This study highlights that the electronic structure significantly impacts the physicochemical properties of S-ZVI and reveals the mechanism of nitrogen modification on the electronic structure of S-ZVI.

Trifunctional electrocatalysts of single transition metal atom doped g-C4N3 with high performance for OER, ORR and HER

With the rapid development of renewable energy technologies, the quest for efficient and cost-effective trifunctional catalysts capable of simultaneously driving the Hydrogen Evolution Reaction (HER), Oxygen Reduction Reaction (ORR), and Oxygen Evolution Reactions (OER) has become a focal point of research. In this study, we employed first-principles calculations to investigate the catalytic activities of the synthetic material g-C4N3 as an electrocatalyst for HER, OER, and ORR by incorporating various transition metal atoms into the numerous 3 N vacancies (TM@g-C4N3) naturally occurring in its primitive structure. Our calculations reveal that Cu@g-C4N3 holds promise as a trifunctional electrocatalyst, exhibiting low OER/ORR overpotentials (ηOER = ηORR = 0.44 V) and a |ΔG∗H| value of only 0.08 eV. Furthermore, Ni@g-C4N3_S1N2 exhibits a lower OER overpotential (ηOER = 0.34 V). Bader charge analysis, charge density difference calculations, and D-band center investigations confirm that the catalytic performance is fundamentally rooted in the electronic properties of these materials. Thus, g-C4N3 embedded with transition metal atoms shows promise as an efficient electrocatalyst for OER/ORR/HER, with implications for the development of high-efficiency trifunctional electrocatalysts.

Titanium-doped graphite-type silicon carbide biosensor for detecting and eliminating gaseous pollution: A green chemistry approach by molecular simulation study

Regarding thermal strength, chemical stability and surface reactivity of silicon carbide (SiC), it is possible to allocate it as a suitable gas detector for commercial application. Therefore, this research was focused on the investigation of the chemo-resistivity properties of SiC nanosheet through doping with the transition metal. Thermochemical, electric and magnetic properties of titanium (Ti)-doped graphene-like monolayer silicon carbide (SiC) sheet have been studied by the first-principles methods based on the density functional theory (DFT) for scavenging of gas molecules of CO, CO2, NO, NO2. The results recommend that the adsorption of these gas molecules on Ti-embedded monolayer SiC sheet is more energetically desired than that on the pristine ones. Gas molecules of CO, CO2, NO, NO2 have been adsorbed on the Ti site of doped monolayer SiC through the formation of covalent bonds. The assumption of chemical adsorptions has been approved by the projected density of states (PDOS) and charge density difference plots. Charge density difference calculations also indicate that the electronic densities were mainly accumulated on the adsorbate of CO, CO2, NO, NO2 gas molecules. The results in this investigation can indicate the competence of transition metal doped silicon carbide nanosheet in sensor devices.

Electronic structure, magnetism and martensitic transformation in all-d-metal Heusler alloys Mn2PtZ (Z = Sc, Ti, V)

The atomic ordering, electronic structure, magnetic properties and martensitic transformation of three new all-d-metal Heusler alloys Mn2PtZ (Z = Sc, Ti and V) have been investigated theoretically to discover new magnetic shape memory alloys (MSMAs). Depending on the different third transition metal element Z, Mn2PtSc and Mn2PtTi tend to form XA structure while Mn2PtV forms L21 structure. This difference is related to their DOS structures. Charge density difference calculations indicate enhanced d-d hybridization in these all-d-metal Heusler alloys. Mn2PtZ are all ferrimagnets with their Mn-Mn or Mn-V local spin moments antiparallel coupled. In these alloys, Mn2PtTi is a possible new MSMA with the energy difference ΔEM between the martensite and austenite as large as −262 meV/f.u., which indicates a high martensitic transformation temperature and is related to the Jahn-Teller effect in the electronic structure. A large volume effect of 2.9% cell shrinkage occurs during the martensitic transformation. All this makes Mn2PtTi a promising candidate for MSMAs with wide applications.

Enhanced photocatalytic performance of a stable type-II PtSe2/GaSe van der Waals heterostructure.

In this investigation, the structural, electronic, and optical properties of two-dimensional van der Waals heterostructure (vdwHS) PtSe2/GaSe with three different configurations have been studied using density functional theory with the generalized gradient approximation. All three optimized vdwHSs PtSe2/GaSe have positive phonon frequencies and hexagonal unit cells. The hybrid exchange-correlation functional has been employed to study the electronic properties of vdwHSs PtSe2/GaSe. The vdwHSs PtSe2/GaSe shows semiconducting behavior with indirect Type-II bandgaps, which have been confirmed by the charge density difference, electrostatic potential, work function, and band edge calculations. Additionally, from the band edge positions, the vdwHSs PtSe2/GaSe are analyzed for photocatalytic activities. The optical properties such as extinction coefficient, refractive index, reflectivity, energy loss spectrum, and absorption coefficient have been studied using norm-conserving pseudo-potentials. The vdwHSs PtSe2/GaSe exhibit consistent absorption from the visible to the ultraviolet region of the electromagnetic spectrum. From the obtained results, we conclude that vdwHSs PtSe2/GaSe could be utilized for H2 production through photocatalytic activity as well as for optoelectronic devices and their application.

Hierarchical heterostructure of NiFe2O4 nanoflakes grown on the tip of NiCo2O4 nanoneedles with enhanced interfacial polarization effect to achieve highly efficient electrocatalytic oxygen evolution

In this work, a heterostructure oxygen evolution reaction (OER) electrocatalyst consisting of NiFe2O4 nanoflakes grown on the tip of NiCo2O4 nanoneedles arrays supported on nickel foam (NCO-NNs@NFO-NFs/NF) was obtained via simultaneous cation (Co3+ by Fe3+) and ligand exchange (-OH by 1,4-benzenedicarboxylic acid) and further annealing of the hydroxide/MOF precursor in air. HRTEM and Raman characterizations confirm the formation of NCO/NFO heterostructure. XPS characterization and charge density difference calculations clarify the electron transfer from Fe to Ni and Co at the NCO/NFO heterointerface. Electrochemical tests show that NCO-NNs@NFO-NFs/NF possesses excellent OER electrocatalytic activity (overpotential of 265 mV@50 mA cm−2) and durability (stable for 100 h@1 A cm−2). NCO-NNs@NFO-NFs/NF‖20 % Pt/C two-electrode system can achieve 10 mA cm−2 at 1.398 V for anion exchange membrane (AEM) water splitting in 1.0 M KOH at 85 °C, which exceeds the activity of using commercial RuO2 as an anode at 25 °C, combined with the stability of 100 h at 10 mA cm−2 at 25 °C, demonstrating the practical application in industrial AEM process. XPS and HRTEM characterizations of NCO-NNs@NFO-NFs/NF after the OER V-t test, along with ex-situ Raman characterization, confirm that Co and Fe sites undergo surface reconstruction to form specific CoOOH/FeOOH interfaces, as to exert the synergistic effect of Co and Fe dual active sites during OER process. DOS calculations reveal that the density of state at Fermi energy level increases after the introduction of Fe, thereby improving conductivity and facilitating the activation of adsorbed oxygen species. This study shows a significant methodology for simultaneous improvement of the electrocatalytic stability and activity of spinel oxides-based heterostructures, which is critical for practical application.

Interlayer Charge Transfer Over Graphitized Carbon Nitride Enabling Highly-Efficient Photocatalytic Nitrogen Fixation.

Exploiting cost-effective, high-efficiency, and contamination-free semiconductors for photocatalytic nitrogen reduction reaction (N2 RR) is still a great challenge, especially in sacrificial-free system. On basis of the electron "acceptance-donation" concept, a boron-doped and carbon-deficient g-C3 N4 (Bx CvN)isherein developed through precise dopant and defect engineering. The optimized B15 CvN exhibisted an NH3 production rate of 135.3µmolh-1 g-1 in pure water with nine-fold enhancement to the pristine graphitic carbon nitride (g-C3 N4 ), on account of the markedly elevated visible-light harvesting, N2 activation, and multi-directional photoinduced carriers transfer. The decorated B atoms with coexistent occupied and empty sp3 hybridized orbitals are theoretically proved to be in charge of the increase of N2 adsorption energy from -0.08 to -0.26eV and the change in N2 adsorption model from one-way to two-way end-on pattern. Noticeably, the elaborate coordination of doped B atoms and carbon vacancies greatly facilitated the interlayer interaction and vertical charge migration of Bx CvN, whichisdistinctly revealed through the charge density difference calculations. The current study provides an alternative groundbreaking perspective for advancing photocatalytic N2 RR through the targeted configuration of the defect and dopant sites.

Nitrogenated Holey Graphene (C2N-h2D): An excellent sensor for neurotransmitter amino acids

Interactions of amino acids with organic surfaces are highly relevant to the development of modern synthetic biomaterials with biocompatibility and low biotoxicity. Biomolecule-surface interactions vary differently according to the molecule orientation, charge state, and distance from the surface. Furthermore, the electron transfer through molecule/surface could also play a key role in biological recognition and signaling systems. Here, using density functional theory (DFT), we investigated the interactions of three neurotransmitter amino acids (NAAs), namely, glycine (Gly), γ-aminobutyric acid (Gaba), and glutamate (Glu), onto a nanosheet of holey nitrogenated graphene (C2N-h2D). In general, the interactions between amino acids and carbon-based surfaces are mediated through weak van der Waals interactions. However, based on interaction energy and charge density difference calculations, there is a strong physisorption process between NAAs and the C2N structure. In particular, Gaba and Glu can act as exclusive electron donor and acceptor, respectively. Our calculations also reveal that, by changing the orientations from neutral to zwitterionic, the Gly molecule changes from a donor to a strong acceptor of electrons. In the case of electron donation, the resistivity on the C2N surface should be reduced. These findings indicate that the C2N surface is an excellent candidate for high-performance biosensor applications. From the band structure point of view, the NAAs molecules introduce occupied flat bands within the bandgap of the C2N single layer, while the surface energy levels keep the bulk characteristics of the semiconductor system. Finally, the optical absorption spectrum of NAAs-C2N systems reveals that these NAAs seem to improve the photoactivity performance of the C2N structure, with the appearance of intraband transitions.

Crystal structure and electronic properties of BrF under high-pressure

The bromine monofluoride (BrF)’s structural and electronic properties are widely investigated under high pressure through ab initio computations using the density functional theory. At first, five new high-pressure BrF structures are uncovered with space groups P21, Cmc21, Pmc21, P2/m, and R-3m symmetry under pressure. According to the elastic constants and phonon scattering curves, the mechanical and dynamical stability of Cmc21, Pmc21, P2/m, and R-3m structures under pressures can be demonstrated. The band structure and density of states show that the P21 and the Cmc21 structures are non-metallic. In contrast, the Pmc21, P2/m, and R-3m structures are metallic. Band structure computations indicate that the Cmc21 structure is a semiconductor containing a direct band gap (Eg) of 0.90 eV (PBE) or 2.19 eV (HSE06). The electron localization function (ELF), Crystal Orbital Hamilton Population (COHP), and charge density difference calculations indicate that the Cmc21 structure is covalent. Besides, we find that the BrF (at ambient pressure) transition temperature of 144 K (∼−129 °C) is compatible with the previous experiment that reported that the temperature when BrF precipitates into a fine yellow powder is below −130 °C. The results enrich the BrF's high-pressure phases and establish the basis for subsequent theoretical and experimental studies.

Investigation of the W/Y2O3 heterogeneous interface properties and its effect on hydrogen behavior using first-principles calculations

Here, first-principles calculations were employed to study the properties of the W/Y2O3 interface and its effect on H dissolution and migration. Two W/Y2O3 interface structures were selected to investigate the influence of terminal structures and stacking sequences on the interface properties. The Y4O6–W (bridge) and O–W type A terminal interface exhibited the lowest interface energy at the W (110)/Y2O3 (222) interface with the orientation of W (1-10) ()/Y2O3 (2-1-1) () and at the W (200)/Y2O3 (400) interface with the orientation of W (001) (3 × 3)/Y2O3 (001) (1 × 1). The work of adhesion of the O–W type terminal interface is larger than those of the Y–W type and Y n O m –W terminal interfaces, indicating that the O–W type A terminal interface has the most stable structure. Atomic-bonding analysis confirmed that the W–O bond plays an essential role in stabilizing the interface structure, and the stability improves as the density of the W–O bonds at the interface increases. These conclusions are further verified by charge-density difference calculations, which revealed that strong ionic bonds are formed between the W and O atoms at the W/Y2O3 interface. With regard to the H behavior at the W (200)/Y2O3 (400) interface, the segregation energy confirmed that the interface plays an important role in the segregation of H. The migration energy barrier of interstitial H along the interface is greater than that in the bulk. This means that the interface retains a significant number of injected H atoms, leading to an increase in the local concentration of H atoms at the interface. These results provide theoretical insights into the profound understanding of the interface properties and its effect on H behavior in Y2O3-dispersion-strengthened W.