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Solar photocatalytic hydrogen production is attracting great attention for addressing the environmental and energy challenges, while the low solar-to-hydrogen (STH) efficiency of photocatalysts hinders its industrial implementation. To enhance the STH efficiency, the construction of single-atom photocatalyst and direct Z-scheme heterojunctions (HJs) is deemed as promising strategies. This work has thoroughly studied the photocatalytic properties of WSe 2 /ZrS 2 , GaTe/ZrS 2 van der Waals HJs, as well as these HJs anchored by single atoms (Pt@WSe 2 /ZrS 2 , Pt@GaTe/ZrS 2) using the first-principles calculations. The results indicate that appropriate bandgaps, band edge positions and internal electric field effectively accelerate photogenerated carrier migration via direct Z-scheme path in WSe 2 /ZrS 2 and GaTe/ZrS 2 HJs. After anchoring Pt atoms onto the reducing agent layer of these HJs, the hydrogen evolution performance of both Pt@WSe 2 /ZrS 2 and Pt@GaTe/ZrS 2 systems are significantly enhanced, enabling spontaneous redox reactions. Furthermore, these HJs exhibit excellent light absorption capacity, with their optical absorption spectra even expanding into the near-infrared range. Especially, the STH efficiency of Pt@GaTe/ZrS 2 HJ reaches 12.94%, surpassing the threshold necessary for future industrial applications. Therefore, this study presents a novel strategy for precisely modulating photocatalytic performance and predicts that Pt@WSe 2 /ZrS 2 and Pt@GaTe/ZrS 2 HJs are promising direct Z-scheme systems for overall water splitting. [Display omitted] • A novel strategy is introduced for precisely modulating photocatalytic performance. • WSe 2 /ZrS 2 and GaTe/ZrS 2 heterojunctions possess ideal band edges and band gaps. • Single-atom Pt anchored heterojunctions further enhance hydrogen evolution. • These anchored heterojunctions efficiently harness light from visible to near-infrared. • These heterojunctions are promising Z-scheme photocatalysts for overall water splitting. [ABSTRACT FROM AUTHOR]

CaMnO3 is a promising starting point for the search of perovskites which are suitable as electrode materials for the hydrogen evolution reaction (HER). In a previous theoretical study [Phys. Status Solidi B 2022, 260, 2200427], it was established that the global hybrid functional PW1PW is well suited to obtain structural, energetic, and electronic bulk properties. Herein, the focus is extended to surface properties of CaMnO3. All symmetry‐inequivalent low‐index surfaces of CaMnO3 are investigated with PW1PW. Based on the experience with polar surfaces, it is decided to employ stoichiometric and symmetric models, in some cases with Schottky defects. From the calculated surface energies, the crystal morphologies are predicted based on the Gibbs–Wulff theorem. The (101), (100), (011), (001), and (010) surfaces (space group no. 62) and the (010), (110), (011), and (101) surfaces (space group no. 20) dominate the surfaces of respective single crystals and should be considered in future theoretical calculations of the HER. Furthermore, it is found that the modification with space group no. 20 is significantly more stable than space group no. 62 for nanoparticles with a diameter below 10 nm. [ABSTRACT FROM AUTHOR]

CaMnO3 is a promising starting point for the search of perovskites which are suitable as electrode materials for the hydrogen evolution reaction (HER). In a previous theoretical study [Phys. Status Solidi B 2022, 260, 2200427], it was established that the global hybrid functional PW1PW is well suited to obtain structural, energetic, and electronic bulk properties. Herein, the focus is extended to surface properties of CaMnO3. All symmetry‐inequivalent low‐index surfaces of CaMnO3 are investigated with PW1PW. Based on the experience with polar surfaces, it is decided to employ stoichiometric and symmetric models, in some cases with Schottky defects. From the calculated surface energies, the crystal morphologies are predicted based on the Gibbs–Wulff theorem. The (101), (100), (011), (001), and (010) surfaces (space group no. 62) and the (010), (110), (011), and (101) surfaces (space group no. 20) dominate the surfaces of respective single crystals and should be considered in future theoretical calculations of the HER. Furthermore, it is found that the modification with space group no. 20 is significantly more stable than space group no. 62 for nanoparticles with a diameter below 10 nm. [ABSTRACT FROM AUTHOR]

A computational methodology is briefly described, which appears to be able to accurately describe the mechanisms of redox active enzymes. The method is built on hybrid density functional theory where the inclusion of a fraction of exact exchange is critical. Two examples of where the methodology has been applied are described. The first example is the mechanism for water oxidation in photosystem II, and the second one is the mechanism for N2 activation by nitrogenase. The mechanism for PSII has obtained very strong support from subsequent experiments. For nitrogenase, the calculations suggest that there should be an activation process prior to catalysis, which is still strongly debated. [ABSTRACT FROM AUTHOR]

Sustainable hydrogen production is one of the most important topics in modern energy economics. Of technological relevance are, for example, electrochemical and thermal splitting of water. For such processes anode materials with a variable concentration of oxygen defects are required. Herein, the oxygen defect thermochemistry of a possible anode material, the perovskite CaMnO3, is investigated theoretically. The aim of this work is to identify reliable quantum chemical methods for the calculation of oxygen defect formation enthalpies and entropies, including configuration entropy, which is usually neglected. All possible defect configurations in a supercell are computed to obtain the configuration entropy using Boltzmann statistics. Various generalized gradient approximation (GGA), meta‐GGA, and hybrid functionals as implemented in the solid‐state programs CRYSTAL and VASP are evaluated for the calculation of structure parameters, electronic and magnetic properties, and reaction energies of CaMnO3. The global hybrid functional PW1PW gives the most accurate overall description of CaMnO3 and is therefore recommended for future theoretical studies of more efficient water‐splitting catalysts based on calcium manganate. [ABSTRACT FROM AUTHOR]

The presence of cubic PuH2 and PuH3, the products of hydrogen corrosion of Pu, during long-term storage is of concern because of the materials' pyrophoricity and ability to catalyse the oxidation reaction of Pu to form PuO2. Here, we modelled cubic PuH2 and PuH3 using Density Functional Theory (DFT) and assessed the performance of the PBEsol+U+SOC (0 ≤ U ≤ 7 eV) including van der Waals dispersion using the Grimme D3 method and the hybrid HSE06sol+SOC. We investigated the structural, magnetic and electronic properties of the cubic hydride phases. We considered spin–orbit coupling (SOC) and non-collinear magnetism to study ferromagnetic (FM), longitudinal and transverse antiferromagnetic (AFM) orders aligned in the <100>, <110> and <111> directions. The hybrid DFT confirmed that FM orders in the <110> and <111> directions were the most stable for cubic PuH2 and PuH3, respectively. For the standard DFT, the most stable magnetic order is dependent on the value of U used, with transitions in the magnetic order at higher U values (U > 5 eV) seen for both PuH2 and PuH3. [ABSTRACT FROM AUTHOR]

Boron‐containing III‐nitride heterostructures have recently attracted significant attention for improving the efficiency of visible and UV light emitters. However, the fundamental material properties of wurtzite (WZ) boron nitride (BN) are largely unexplored. Here, highly accurate first‐principles calculations are used to gain insight into internal strain, elastic constants, and electronic band structure deformation potentials. These parameters are key ingredients for simulating, and thus predicting, electronic and optical properties of boron‐containing III‐nitride‐based light emitters. The ab initio calculations show, for instance, that the quasi‐cubic approximation for deformation potentials is a poor approximation for WZ BN. [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) pseudohexagonal ZnSe (h -ZnSe) nanosheet has been sythesized and demonstrated to be a stable, cut-price and high-efficiency photocatalyst under the irradiation of ultraviolet light. Herein, we use hybrid density functional theory to rationally design the charge-compensated codoped h -ZnSe sheets, which are simulated by substituting Sb for Se atom, and Sc or Y for Zn atom, for visible-light-driven photocatalytic water splitting to produce hydrogen. It is demonstrated that the Sc–Sb and Y–Sb codoped sheets are energetically favorable compared with Sc, Y, Sb-monodoped sheets because dopants have strong Coulombic interactions with other atoms, and moreover, have the effectively reduced bandgap, the larger absorption region of visible light, and appropriate band edges positions with respect to the water redox level. Meanwhile, compared to monodoped sheets, the codoped sheets do not introduce charge-imbalance defects or unoccupied impurity states which promote the electron-hole recombination. Furthermore, the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) are easier driven by photogenerated carriers due to the largely reduced overpotentials and ample active sites on the codoped sheets. Thus, the Sc–Sb and Y–Sb codoped h -ZnSe sheets can be promising photocatalysts for visible-light-driven water decomposition to generate hydrogen. [Display omitted] • Sc-or Y-Sb passivated codoping can effectively reduce band gap of pseudohexagonal ZnSe sheet. • Codoped ZnSe sheets have suitable positions of band edges with respect to the water redox potentials. • Codoping can promote the visible light absorption of ZnSe sheet. • Codoping can reduce the overpotential of ZnSe sheet for OER and HER. • Sc-or Y-Sb codoped ZnSe sheets are promising visible-light-driven photocatalyst. [ABSTRACT FROM AUTHOR]

This work investigates, using density functional theory (DFT), the localization of electrons and holes produced by irradiation in LiF crystals doped with Ti. We show that the Ti can act either as an electron trap, when located at an interstitial position of the LiF lattice, or as a trap for holes by substituting a Li atom. We also observe that an excess electron is localized in a Ti p-state while a hole localizes in a Ti d-state. The localization of the hole in this state when the Ti substitutes a Li is supported by results reported in the literature where it was assumed that the Ti substitute is a hole trap. The defect energy levels obtained in this work agree quite well with those reported in experiments. • Electronic structure calculations of Ti-doped LiF are performed from first principles. • Ti impurity shows a dual character behaving as an electron trap when interstitial and a hole trap when substitutional. • Excess electron is localized in a Ti p-state while a hole localizes in a Ti d-state. [ABSTRACT FROM AUTHOR]

The presence of cubic PuH2 and PuH3, the products of hydrogen corrosion of Pu, during long-term storage is of concern because of the materials’ pyrophoricity and ability to catalyse the oxidation reaction of Pu to form PuO2. Here, we modelled cubic PuH2 and PuH3 using Density Functional Theory (DFT) and assessed the performance of the PBEsol+U+SOC (0 ≤ U ≤ 7 eV) including van der Waals dispersion using the Grimme D3 method and the hybrid HSE06sol+SOC. We investigated the structural, magnetic and electronic properties of the cubic hydride phases. We considered spin–orbit coupling (SOC) and non-collinear magnetism to study ferromagnetic (FM), longitudinal and transverse antiferromagnetic (AFM) orders aligned in the , and directions. The hybrid DFT confirmed that FM orders in the and directions were the most stable for cubic PuH2 and PuH3, respectively. For the standard DFT, the most stable magnetic order is dependent on the value of U used, with transitions in the magnetic order at higher U values (U > 5 eV) seen for both PuH2 and PuH3.

Abstract Advanced semiconductor superlattices play important roles in critical future high-tech applications such as aerospace, high-energy physics, gravitational wave detection, astronomy, and nuclear related areas. Under such extreme conditions like high irradiative environments, these semiconductor superlattices tend to generate various defects that ultimately may result in the failure of the devices. However, in the superlattice like GaAs/AlAs, the phase stability and impact on the device performance of point defects are still not clear up to date. The present calculations show that in GaAs/AlAs superlattice, the antisite defects are energetically more favorable than vacancy and interstitial defects. The AsX (X = Al or Ga) and XAs defects always induce metallicity of GaAs/AlAs superlattice, and GaAl and AlGa antisite defects have slight effects on the electronic structure. For GaAs/AlAs superlattice with the interstitial or vacancy defects, significant reduction of band gap or induced metallicity is found. Further calculations show that the interstitial and vacancy defects reduce the electron mobility significantly, while the antisite defects have relatively smaller influences. The results advance the understanding of the radiation damage effects of the GaAs/AlAs superlattice, which thus provide guidance for designing highly stable and durable semiconductor superlattice based electronic and optoelectronics for extreme environment applications.

High-throughput density functional theory calculations have been typically performed with reduced accuracy and notable error in the band gap. Here we suggest several approaches to calculate the optoelectronic properties by using coarser k -point meshes for the Fock exchange potential. In our benchmark calculations, we were able to obtain the optical properties of zinc-blende and wurtzite materials with reasonable accuracy. We also propose an approach of high-throughput calculations using a pre-converged wavefunction by the reduced k -point meshes for the Fock exchange and performing the subsequent non-self-consistent-field calculations. • Methods to reduce the cost of hybrid DFT not losing the accuracy significantly. • Cost-effective calculation of the density of states and dielectric functions. • Suggested methods to perform high-throughput hybrid DFT calculations. [ABSTRACT FROM AUTHOR]

In this study, the B3LYP hybrid density functional theory was used to investigate the electromechanical characteristics of C70 fullerene with and without point charges to model the effect of the surface of the gate electrode in a C70 single-electron transistor (SET). To understand electron tunneling through C70 fullerene species in a single-C70 transistor, descriptors of geometrical atomic structures and frontier molecular orbitals were analyzed. The findings regarding the node planes of the lowest unoccupied molecular orbitals (LUMOs) of C70 and both the highest occupied molecular orbitals (HOMOs) and the LUMO of the C70 anion suggest that electron tunneling of pristine C70 prolate spheroidal fullerene could be better in the major axis orientation when facing the gate electrode than in the major (longer) axis orientation when facing the Au source and drain electrodes. In addition, we explored the effect on the geometrical atomic structure of C70 by a single-electron addition, in which the maximum change for the distance between two carbon sites of C70 is 0.02 Å.

Using hybrid density functional theory calculations, we systematically study the biaxial strain and electric field modulated electronic properties of g-ZnO/SnS 2 , g-ZnO/SnSe 2 , and g-ZnO/SnSSe S-scheme van der Waals heterostructures (vdWHs). g-ZnO/SnS 2 and g-ZnO/SnSSe are found to be promising photocatalysts for water splitting with high solar-to-hydrogen efficiencies, even under acidic, alkaline, and high-stress conditions. The strain effect on the bandgaps of g-ZnO/SnXY is explained in detail according to the correlation between geometry structure and orbital hybridization of SnXY, which could help understand the strain-induced band structure evolutions in other SnXY (X, Y = S, Se)-based vdWHs. It is surprising that under an external electric field, g-ZnO/SnS 2 , g-ZnO/SnSe 2 , and g-ZnO/SnSSe can offer the occupied nearly free-electron (NFE) states. In many materials, NFE states are usually unoccupied and is not conducive to the charge transport. The NFE state in g-ZnO/SnSe 2 is the most sensitive to the electric field and might be promising electron transport channel in nanoelectronic devices. g-ZnO/SnSe 2 might also have application potential in gas sensors and high-temperature superconductors.

As future photocatalyst require high activity and structural stability, the demand for high-performance photocatalyst that increases photocatalytic conversion efficiency is of significant interest. In this study, Ce–ZrO2–GO nanocomposite was fabricated by a co-precipitation technique and used for the photocatalytic degradation of eosin yellow (EY) dye under visible light irradiation. A hybrid DFT calculation was employed to analyse the electronic properties and the underlying mechanism of the observed photoactivity. The as-prepared Ce–ZrO2–GO (0.3% Ce) nanocomposite showed enhanced photodegradation of EY dye, which was about 15.98-fold higher than pure ZrO2. The enhanced performance of Ce–ZrO2–GO nanocomposite for EY dye degradation is due to the synergistic effect between the GO sheets and Ce–ZrO2. From the computational study, Ce ion could act as an electron mediator to capture the photoinduced electrons from ZrO2 to restrain the recombination rate of charge carriers. Testing with different scavengers showed that hydroxyl radicals play a major contribution to the degradation of EY dye with a pseudo first-order reaction kinetics. Total Organic Carbon analysis showed 76% mineralisation of EY dye over Ce–ZrO2–GO (0.3% Ce) nanocomposite, which is photostable and its efficiency remained almost the same after five cycles without any photocorrosion. The present study could offer an alternative approach to develop highly efficient photocatalysts for organic pollutant degradation using metal ion as a mediator to enhance charge migration, activity and structural stability of the nanocomposite. A series of Ce–ZrO2–GO nanocomposite were employed as a photocatalytic to degrade eosin yellow dye from wastewater. The present study offers an alternative approach to develop highly efficient photocatalysts for organic pollutant degradation using Ce ion as a mediator to enhance charge migration, activity and structural stability of the nanocomposite. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Gd-TiO 2 -GO was investigated using a combined experimental and DFT studies. • Gd ion enhanced the visible–light harvesting by donating electrons to GO sheets. • The smaller effective masses of Gd-TiO 2 -GO ensured effective degradation of IC dye. • The contribution of different orbitals (C 2p and Gd 5d) to the CB improved the photoactivity. • This theoretical finding offers evidence supporting the experimental reports. Abstract In recent years, there has been a growing interest in developing highly efficient photocatalysts with a visible light active semiconductor as one of its components. Herein, visible-light-driven photocatalytic activity of Gd-TiO 2 -GO nanocomposites were fabricated by sol–gel method. The photocatalytic property was evaluated for photodegradation of indigo carmine (IC) dye. The structural properties of the fabricated samples were characterised using SEM, XRD, PL, TEM, Raman, BET, EDS, elemental mapping and XPS analysis. To provide further insights into the synergistic effect, a hybrid density functional theory calculation was used to study the charge transfer, electronic and structural properties of Gd–TiO 2 –GO nanocomposite. The as-fabricated nanocomposites showed improved visible light photocatalytic performance and degradation efficiency over pure TiO 2. The optimal Gd content was found to be 0.6 wt%, and the apparent pseudo-first order photodegradation rate of IC dye was 14.19-fold higher than that of pure TiO 2 nanoparticles under visible–light irradiation. Moreover, hydroxide radicals and holes were the main active species, and the hybrid nanocomposites exhibited high stability and recyclability during the IC dye degradation process. Herein, both GO sheets and Gd3+ ion were excellent co-catalysts and their presence promote the reaction sites and synergistically enhanced the photocatalytic degradation of IC dye. Also, the smaller effective mass caused a high separation of photogenerated charge carriers, thereby promoting the photodegradation efficiency. This work offers a new understanding of designing high-performance TiO 2 -based photocatalysts for wastewater treatment. [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) gallium sulfide (GaS), hexagonal boron nitride (h-BN) and graphitic carbon nitride (g-C 3 N 4 ) have been fabricated and expected to be promising photocatalysts under ultraviolet irradiation. Here, we employ hybrid density functional calculations to explore the potential of the 2D GaS-based heterojunctions GaS/h-BN (g-C 3 N 4 ) for the design of efficient water redox photocatalysts. Both heterostructures can be formed via van der Waals (vdW) interaction and are direct bandgap semiconductors, whose bandgaps are reduced comparing with isolated GaS, h-BN or g-C 3 N 4 monolayers and whose bandedges straddle water redox potentials. Furthermore, the optical absorption of GaS/h-BN (g-C 3 N 4 ) heterostructures is observably enhanced in the ultraviolet–visible (UV–vis) light range. The electron–hole pairs in GaS/h-BN (g-C 3 N 4 ) heterostructures are completely separated from different layers. In addition, the in-plane biaxial strain can effectively modulate the electronic properties of GaS/h-BN (g-C 3 N 4 ) heterostructures. Thus the GaS/h-BN (g-C 3 N 4 ) heterostructures are anticipated to be promising candidates for photocatalytic water splitting to produce hydrogen. [ABSTRACT FROM AUTHOR]

The geometric, electronic structure and thermodynamic stability of Sc 2 O@C 92 has been characterized by using hybrid density functional theory calculations combined with statistical thermodynamic analyses. Results indicate that the isolated pentagon rule (IPR) isomers Sc 2 O@ C s (126339)-C 92 , Sc 2 O@ C 1 (126367)-C 92 and Sc 2 O@ C 1 (126390)-C 92 are favorable. Noteworthy, it is the first time to declare that fullerene isomer C s (126339)-C 92 could be considered as the suitable cage to encapsulate metallic cluster. The electronic properties of these three isomers were performed with frontier molecular orbital (HOMO and LUMO) analyses and bond order calculations. Finally, 13 C NMR and UV-vis-NIR spectra were simulated to provide valuable information for future experiments. [ABSTRACT FROM AUTHOR]

Graphite-like carbon nitride (g-C 3 N 4 )-based heterostructures have received much attention due to their prominent photocatalytic activity. The g-C 3 N 4 /Bi 2 WO 6 and g-C 3 N 4 /Bi 2 MoO 6 heterostructures, which follow a typical hetero-junction charge transfer mechanisms show a weak potential for hydrogen evolution and reactive radical generation under visible light irradiation. A mediator-free Z-scheme g-C 3 N 4 /Bi 2 MoO 6 (010) and g-C 3 N 4 /Bi 2 WO 6 (010) heterostructures photocatalyst are designed for the first time using first-principles studies. Moreover, theoretical understanding of the underlying mechanism, the effects of interfacial composition and the role the interface play in the overall photoactivity is still unexplained. The calculated band gap of the heterostructures is reduced compared to the bulk Bi 2 WO 6 and Bi 2 MoO 6 . In this study, we systematically calculated energy band structure, optical properties and charge transfer of the g-C 3 N 4 /Bi 2 MoO 6 (010) and g-C 3 N 4 /Bi 2 WO 6 (010) heterostructures using the hybrid density functional theory approach. The results show that the charge transfer at the interface of the heterostructures induces a built-in potential, which benefits the separation of photogenerated charge carriers. The g-C 3 N 4 /Bi 2 MoO 6 (010) heterostructure with more negative adhesion energy (−1.10 eVA −2 ) is predicted to have a better adsorptive ability and can form more easily compared to the g-C 3 N 4 /Bi 2 WO 6 (010) interface (−1.16 eVA −2 ). Therefore, our results show that the g-C 3 N 4 interaction with Bi 2 MoO 6 is stronger than Bi 2 WO 6 , which is also verified by the smaller vertical separation (3.25 Å) between Bi 2 MoO 6 and g-C 3 N 4 compared to the g-C 3 N 4 /Bi 2 WO 6 (010) interface (3.36 Å). The optical absorption verifies that these proposed Z-scheme heterostructures are excellent visible light harvesting semiconductor photocatalyst materials. This enhancement is ascribed to the role of g-C 3 N 4 monolayer as an electron acceptor and the direct Z-scheme charge carrier transfer at the interface of the heterostructures. This work is useful for designing new types of Z-scheme photocatalyst and offers new insight into Z-scheme charge transfer mechanism for applications in the field of solar energy conversion. [ABSTRACT FROM AUTHOR]

The application of first-principles calculations holds promise for greatly improving our understanding of semiconductor superlattices. Developing a procedure to accurately predict band gaps using hybrid density functional theory lays the groundwork for future studies investigating more nuanced properties of these structures. Our approach allows a priori prediction of the properties of SLS structures using only the band gaps of the constituent materials. Furthermore, it should enable direct investigation of the effects of interface structure, e.g., intermixing or ordering at the interface, on SLS properties. In this paper, we present band gap data for various InAs/GaSb type-II superlattice structures calculated using the generalized Kohn-Sham formulation of density functional theory. A PBE0-type hybrid functional was used, and the portion of the exact exchange was tuned to fit the band gaps of the binary compounds InAs and GaSb with the best agreement to bulk experimental values obtained with 18% of the exact exchange. The heterostructures considered in this study are 6 monolayer (ML) InAs/6 ML GaSb, 8 ML InAs/8 ML GaSb and 10 ML InAs/10 ML GaSb with deviations from the experimental band gaps ranging from 3% to 11%. [ABSTRACT FROM AUTHOR]

Zinc oxide (ZnO) is considered in general as a promising material for solar water splitting. Its wurtzite-structured bulk samples, however, can be considered as active for photocatalytic applications only under UV irradiation, where they possess ∼1% efficiency of sunlight energy conversion due to their wide band gap (3.4 eV). Although pristine ZnO nanowires (NWs) possess noticeably narrower band gaps than the bulk, the tendency of band gap reduction with increasing NW diameter is insufficient, and further modification is required. We have contributed to filling this gap by performing a series of ab initio calculations on ZnO NWs of different diameters ( dNW), which are mono-doped by metal (Ag) and non-metal atoms (C, N) or contain oxygen vacancies with varied concentration (∼3 vs. ∼6%). To reproduce qualitatively the energies of one-electron states of nanowires in our calculations, the hybrid DFT + HF Hamiltonian has been used, based on the PBE0 exchange-correlation functional. We have analyzed changes in the electronic structure induced in a few defect composition scenarios, showing that, for specific concentrations and locations of the dopants, the optical absorption peak of doped ZnO can be shifted to the visible light range with promising efficiency. In agreement with experimental observation, the most significant results have been achieved for carbon-doped ZnO nanowires. They possess the highest photocatalytic suitability, since the band gap is reduced in this case down to 2.1-2.2 eV (for nanowire diameters of 2.9-3.5 nm), which corresponds to optimal 15-17% efficiency of solar energy conversion. [ABSTRACT FROM AUTHOR]

The mechanism for aquation of dihalotetraaquachromium(III) complexes ( trans -[Cr(H 2 O) 4 TX] + , where X or T = Cl, Br, or I), including a common component of many nutritional supplements (X, T = Cl) has been investigated using density functional theory. A number of mechanistic pathways were explored including associative interchange (I a ), and dissociative (D) mechanisms. The overall activation enthalpy for the D pathway of the dichloro ( trans -[Cr (H 2 O) 4 Cl 2 ]) system calculated at the PBE0/cc-pVDZ level, with inclusion of an explicit outer sphere water molecule and in aqueous solution (PCM), is in excellent agreement with the experimental result. The results provide a detailed understanding of the mechanism for the hydrolysis of trans -Cr(III) complexes, which could be useful in understanding the speciation of Cr(III) complexes in physiological environments. [ABSTRACT FROM AUTHOR]

An in silico analysis is performed to check the hydrogen storage potential of (HF) m ( m = 1–8) and (H 2 O) n ( n = 1–10) clusters. Each HF unit in (HF) m cluster can bind three H 2 molecules whereas each H 2 O unit in (H 2 O) n can adsorb one hydrogen molecule (excluding H 2 O and (H 2 O) 2 ). It is found that conceptual density functional theory based reactivity descriptors can explain the stability of molecular hydrogen adsorbed (HF) m ( m = 1–8) and (H 2 O) n ( n = 1–10) clusters. The nature of interaction between (HF) m /(H 2 O) n cluster and the adsorbed H 2 molecules is studied using electron density based descriptors. Energy decomposition analysis is carried out to assess the type of interaction between the molecular clusters and adsorbed hydrogen molecules. Ab initio molecular dynamics (AIMD) simulation is also carried out using an atom centered density matrix propagation (ADMP) technique to predict the kinetic stability of hydrogen adsorbed (HF) m and (H 2 O) n analogues in a one picosecond time scale. [ABSTRACT FROM AUTHOR]

The mechanism for the substitution reactions of halopentaaquachromium(III) complexes in the series, [CrX(H 2 O) 5 ] 2+ , where X = F − , Cl − , Br − , or I − have been investigated using density functional theory. Several different mechanistic pathways were explored including associative interchange ( I a ), dissociative ( D ) and the associatively activated dissociation mechanisms ( D a ). The lowest overall activation enthalpy (ΔH ‡ ) obtained for the fluoride system is for the I a pathway, with immediate proton abstraction leading to the formation of HF and the conjugate base. For the chloride, bromide and iodide systems the D a pathway has the lowest ΔH ‡ values. Activation enthalpies determined at the PBE0/cc-pVDZ level, in aqueous solution (PCM), are in excellent agreement with the experimental results (MAD is 1.0 kJ mol −1 ). Reaction profiles were analyzed in terms of activation volumes to explain the observed trends. [ABSTRACT FROM AUTHOR]

Abstract: A comprehensive first-principle investigation, based on hybrid density functional theory, produces strong evidence that the Cu2O band-edges do satisfy the requirements of the H+/H2 and O2/H2O redox levels, demonstrating that it has enough driving force for photocatalytic overall water splitting. The calculated band gap of Cu2O is 2.184eV, which is consistent with the experimental value of 2.17eV. The highly dispersive s–s hybrid states at the conduction band bottom result in a small effective mass of the electron, which is favorable to carrier separation and the carrier transfer to surface, and thus facilitate the reduction of H+ to H2. The strong optical absorption of Cu2O is beneficial to overall water splitting under visible light irradiation. Possible reasons for no observation of H2 in some experiments are also discussed. The results address the ongoing controversy associated with photocatalytic overall water splitting of Cu2O. [Copyright &y& Elsevier]

The stabilities and electronic structures of the bulk and several low‐index surfaces of β‐TaON were studied quantum‐chemically at semi‐empirical and hybrid density‐functional level. Excitation spectra of the bulk and surfaces were calculated by using an iterative CIS approach (MSINDO‐CIS). The calculated structure parameters, atomic positions and band gaps for the bulk are compared with experimental data. For comparison we also studied a hypothetical configuration of TaON where the anion ordering is changed. The O/N distribution has a significant effect on the optical spectra and may effect the photocatalytic efficiency of the material. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) Part of Focus Issue on “Functional Oxides” (Eds.: T. Frauenheim, J. M. Knaup, P. Broqvist, S. Ramanathan) The authors have studied the surface stability and electronic structure of TaON low‐index surfaces with two possible anion configurations at hybrid DFT‐level. Additionally, they performed MSINDO‐CIS calculations and present optical spectra for the bulk and surfaces. [ABSTRACT FROM AUTHOR]

A systematic study of a Li atom and four types of SiGe (6,6) nanotubes (NTs) of length ~20 Å has been performed to explore SiGeNTs' viability as anode material in Li-ion batteries. For all structures, full geometry and spin optimizations were performed without any symmetry constraints. We used the hybrid functional B3LYP and an all electron 6-311G**//3-21G* basis set implemented in GAUSSIAN 09 suite of software. All possible internal and external adsorption sites were considered, and it was found that some tubes deformed as a result of the Jahn-Teller effect. Out of all four types, type III NTs were found to retain the tubular shape for most cases of adsorption. Our calculations predict that SiGeNTs attract Li atom on top of Si, on top of Ge, and on top of hollow sites with adsorption energies ranging from 0.888 to 1.657 eV. Most probable sites for external and internal adsorptions were quasi on top of Ge site and quasi hollow site, respectively. After adsorption of the Li atom, Jahn-Teller active orbitals of the systems vanished from the frontier orbital region, indicating that more Li atoms can be adsorbed while keeping the desired tubular shape. In general, the difference between the highest occupied molecular orbital (HOMO) energy level and the lowest unoccupied molecular orbital (LUMO) energy level decreased with respect to the bare SiGeNT values. The decreased HOMO-LUMO gaps vary between 0.685 and 0.930 eV. Charge population analysis indicated that charge generally accumulated around the nearest neighbor atoms to the Li atom. We conclude that with the careful placement of Li atoms, SiGeNTs can be very successful as anode material in Li-ion battery technology. [ABSTRACT FROM AUTHOR]

Abstract: The roles of oxygen vacancies on the electronic and magnetic properties of Ni doped In2O3 have been studied by first-principles calculations based on hybrid functional theory. Our results predict that the Ni-doped In2O3 system displays a ferromagnetic semiconducting character. However, the presence of oxygen vacancies results in antiferromagnetic coupling between the neighboring Ni pair bridged by an oxygen vacancy. The antiferromagnetic coupling is found to arise from the predominant role of superexchange due to the strong Ni 3d–O 2p hybridization. Consequently, the oxygen vacancies play a key role in the lower saturation magnetization of Ni:In2O3 polycrystalline sample, as observed in experiments. [Copyright &y& Elsevier]

Ab initio calculations have been performed to study the electronic and geometric structure properties of zigzag silicon nanotubes. Full geometry and spin optimizations have been performed without any symmetry constraints with an all electron 3-21G* basis set and the B3LYP hybrid functional. The largest zigzag SiNT studied here, (12, 0), has a binding energy per atom of 3.584 eV. Atomic hydrogen and oxygen adsorptions on (9, 0) and (10, 0) nanotubes have also been studied by optimizing the distances of the adatoms from both inside and outside the tube. The adatom is initially placed in four adsorption sites-parallel bridge (PB), zigzag bridge (ZB), hollow, and on-top site. The on-top site is the most preferred site for hydrogen atom adsorbed on (9, 0), with an adsorption energy of 3.0 eV and an optimized distance of 1.49 Å from the adatom to the nearest silicon atom. For oxygen adsorption on (9, 0), the most preferred site is the ZB site, with an adsorption energy of 5.987 eV and an optimized distance of 1.72 Å. For atomic hydrogen adsorption on (10, 0), the most preferred site is also the on-top site with an adsorption energy of 3.174 eV and an optimized distance of 1.49 Å. For adsorption of atomic oxygen on (10, 0), the most preferred site is PB site, with an adsorption energy of 6.306 eV and an optimized distance of 1.71 Å. The HOMO-LUMO gaps of (9, 0) after adsorptions of hydrogen and oxygen atoms decrease while the HOMO-LUMO gaps of (10, 0) increase after adsorption of hydrogen and oxygen. [ABSTRACT FROM AUTHOR]

Highlights: [•] Improvement of B3LYP. [•] Parameterization optimization. [•] Organic reaction mechanism. [•] Enthalpy of formation. [Copyright &y& Elsevier]

We present a systematic study of the electronic, geometric, and magnetic properties of the actinide dioxides, UO2, PuO2, AmO2, U0.5Pu0.5O2, U0.5Am0.5O2 and Pu0.5Am0.5O2. For UO2, PuO2 and AmO2, both density functional and hybrid density functional theory (DFT and HDFT) have been used. The fractions of exact Hartree-Fock (HF) exchange chosen were 25% and 40% for the hybrid density functional. For U0.5Pu0.5O2, U0.5Am0.5O2 and Pu0.5Am0.5O2, only HDFT with 40% exact HF exchange was used. Each compound has been studied at the nonmagnetic, ferromagnetic and anti-ferromagnetic configurations, with and without spin-orbit coupling (SOC). The lattice parameters, magnetic structures, bulk moduli, band gaps and density of states have been computed and compared to available experimental data and other theoretical results. Pure DFT fails to provide a satisfactory qualitative description of the electronic and magnetic structures of the actinide dioxides. On the other hand, HDFT performs very well in the prediction and description of the properties of the actinide dioxides. Our total energy calculations clearly indicate that the ground-state structures are anti-ferromagnetic for all actinide dioxides considered here. The lattice constants and the band gaps expand with an increase of HF exchange in HDFT. The influence of SOC is found to be significant. [ABSTRACT FROM AUTHOR]

A systematic study of silicon carbide nanocones of different disclination angles and different tip geometries using the finite cluster approximation is presented. The geometries of the nanocones have been spin optimized using the hybrid functional B3LYP (Becke's three-parameter exchange functional and the Lee-Yang-Parr correlation functional) and the all electron 3-21G* basis set. The study indicates that the binding energy per atom or the cohesive energy of the nanocones depends not only on the size of the nanocones but also on the disclination angle of the nanocones. The study also shows that the electronic properties of nanocones depend on disclination angles, size of the nanocone clusters, and the structure of edge of the nanocones. A study of binding energies, natural bond orbital (NBO) charge, density of states, and the gap between highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) has been performed for all nanocones from disclination angles of 60° to 300°. [ABSTRACT FROM AUTHOR]

Quantum mechanical calculations (AM1, PM3, ab initio HF/3-21G, DFT(B3LYP/6-31G*) and MP2//(B3LYP/6-31G*) have been used to study the inverse-demand synchronous concerted Diels-Alder reactions between dimethyl-1,2,4,5-tetrazine-3,6-dicarboxylate (diene) and a variety of dienophiles (ethylene, cyclopentadiene, 1-hexene, cyclohexene). All the molecular structures (reactants, transition states, intermediates and adducts) were optimized using the semi-empirical AM1 method. The calculated energies and volumes showed that the cycloaddition reaction followed a mechanism involving the formation of an intermediate, elimination of N, and a 1,3-hydrogen shift adduct. The reaction energies of the systems were obtained by using semi-empirical AM1 calculations and showed good agreement with the experimental data. In contrast, calculations of the reaction energies using PM3, HF/3-21G, DFT (B3LYP/6-31G*) and MP2//(B3LYP/6-31G* were in poor agreement with the experimental data. Compared to the experimental data, the activation energies were overestimated using AM1, PM3 and HF/3-21G, while they were underestimated using DFT (B3LYP/6-31G*) and MP2//(B3LYP/6-31G*). [ABSTRACT FROM AUTHOR]

Mukherjee's type of multireference coupled-cluster (MkMRCC), approximate spin-projected spin-unrestricted CC (APUCC), and AP spin-unrestricted Brueckner's (APUBD) methods were applied to didehydronated ethylene, allyl cation, cis-butadiene, and naphthalene. The focus is on descriptions of magnetic properties for these diradical species such as S-T gaps and diradical characters. Several types of orbital sets were examined as reference orbitals for MkMRCC calculations, and it was found that the change of orbital sets do not give significant impacts on computational results for these species. Comparison of MkMRCC results with APUCC and APUBD results show that these two types of methods yield similar results. These results show that the quantum spin corrected UCC and UBD methods can effectively account for both nondynamical and dynamical correlation effects that are covered by the MkMRCC methods. It was also shown that appropriately parameterized hybrid density functional theory (DFT) with AP corrections (APUDFT) calculations yielded very accurate data that qualitatively agree with those of MRCC and APUBD methods. This hierarchy of methods, MRCC, APUCC, and APUDFT, is expected to constitute a series of standard ab initio approaches towards radical systems, among which we could choose one of them, depending on the size of the systems and the required accuracy. [ABSTRACT FROM AUTHOR]

Abstract: We calculate defect levels of dangling bonds in germanium using hybrid density functionals. To validate our approach, we first consider the dangling bond in silicon finding two well-separated defect levels, in excellent correspondence with their experimental location. Application of our scheme to the dangling bond in germanium then yields two very close defect levels lying just above the valence band, consistent with the location of the experimentally determined charge neutrality level. The small correlation energy and the proximity to the valence band edge provide an explanation for the absence of clear defect signatures in electrical and electron spin resonance experiments. [Copyright &y& Elsevier]

The mechanism for the oxidation of catechol by catechol oxidase has been studied using B3LYP hybrid density functional theory. On the basis of the X-ray structure of the enzyme, the molecular system investigated includes the first-shell protein ligands of the two metal centers as well as the second-shell ligand Cys92. The cycle starts out with the oxidized, open-shell singlet complex with oxidation states Cu2(II,II) with a μ-η2:η2 bridging peroxide, as suggested experimentally, which is obtained from the oxidation of Cu2(I,I) by dioxygen. The substrate of each half-reaction is a catechol molecule approaching the dicopper complex: the first half-reaction involves Cu(I) oxidation by peroxide and the second one Cu(II) reduction. The quantitative potential energy profile of the reaction is discussed in connection with experimental data. Since no protons leave or enter the active site during the catalytic cycle, no external base is required. Unlike the previous density functional theory study, the dicopper complex has a charge of +2. [ABSTRACT FROM AUTHOR]

Abstract: Hybrid density functional calculations are performed on a series of 21 new quinoxaline derivatives, which would likely exhibit important biological activities. Optimized geometries, harmonic vibrational frequencies, and 1H chemical shifts are reported and compared with experimental data when available. In addition, melting points of 75 derivatives are predicted resorting to the Quantitative Structure–Property Relationship (QSPR) Theory, doing the variable selection by means of the Replacement Method and using 875 theoretical descriptors obtained from Dragon 5 software. The best relationship found has seven descriptors with R =0.8818 and R l−10%−o =0.7705. [Copyright &y& Elsevier]

Recently, the synthesis and the NMR characterization of a series of eight alloxan-based thiosemicarbazones and semicarbazones were reported. These compounds exhibit a strongly hydrogenbonded hydrazinic proton that is a part of a characteristic six-membered ring. This proton is highly deshielded and resonates far downfield in the proton NMR spectra. In this report, mPW1PW91/6-31+G(d,p) calculations have been used to investigate the structure and other molecular properties of this series of eight compounds. The relationship between the 1H and 13C NMR chemical shifts and various geometric parameters was investigated, and linear relationships for proton peaks that are involved in hydrogen-bond interactions were found. [ABSTRACT FROM AUTHOR]

Abstract: Hybrid density functional theory calculations at the B3-LYP/6-31G** level of theory are used to explore the interactions between singly, doubly, and triply charged fullerene cations and ammonia. The calculations illuminate (and generally support) several aspects of the previously-reported experimental results for these systems. Primary adduct formation is exothermic but is hindered by an energetically costly localized distortion of the fullerene cage at the site of addition, as the ‘chosen’ carbon atom shifts from strained sp2 to sp3 coordination. The 50–75kJmol−1 ‘deformation energy’ is substantially larger than the residual strength of the bond between C60 + and NH3. Although the deformation energy rises with increasing fullerene ion charge state, it does so less steeply than does the electrostatic attraction between C60 n+ and NH3, so that the overall bond strength to NH3 is progressively and substantially larger for the di- and tricationic adduct ions. For all charge states, a proton-bound structure is found to be the energetically preferred secondary adduct, but for dicationic and tricationic adducts formation of a secondary adduct is significantly less exothermic than proton transfer. It appears that the failure of C60 + to add measurably to nucleophiles weaker than NH3 arises because such nucleophiles are not able to overcome the required deformation energy to effect bond formation. We find also that, in contrast to a simple electrostatically-driven model of ‘handle’ formation (in which it was proposed that the most strongly bound doubly-derivatized fullerene dications would be those for which the ‘handles’ were most widely separated across the fullerene framework) the lowest-energy double-handled adducts are in fact those for which the remaining resonance stabilization is greatest, with electrostatic considerations apparently taking a back seat on the question of relative stability. Similar considerations appear to apply to the double-handled tricationic adducts. [Copyright &y& Elsevier]

Oxo‐ or hydroxo‐bridged diiron centers are ubiquitous in metalloenzymes such as hemerythrin (Hr), ribonucleotide reductase, methane monooxygenase, and rubrerythrin. In each enzyme the diiron core plays a central role in the highly specific reaction. To elucidate mechanisms of these reactions, many experimental studies have been carried out, and bioinorganic model compounds have also been synthesized for the purpose. In this study electronic structures of diiron centers for Hr model compounds are investigated from the viewpoint of magnetic interactions. To this end, the Hubbard model for the three‐center four‐electron bond is analytically solved to elucidate an important role of electron correlation and the resulting superexchange interaction between localized spins. The hybrid density functional theory (DFT) calculations also are performed for Hr model compounds to provide the natural orbitals and their occupation numbers, which are crucial for computations of several chemical indices, such as effective bond order, information entropy, and unpaired electron density. These indices are useful for characterization and understanding of chemical bonds in FeOFe cores. The calculated effective exchange integrals (Jab) are wholly consistent with the available experiments. The orbital interactions in the FeOFe cores are reconsidered in relation to recent work by other groups. It is found that magnetic interactions are sensitive to the hydrogen bonds in the systems and are related to effective regulation of the activity. Implications of the calculated results are discussed in relation to the nature of chemical bonds in the FeOFe cores of several biological systems. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004 [ABSTRACT FROM AUTHOR]

Hybrid density functional theory with the B3LYP functional has been used to investigate the catalytic mechanism of catechol oxidase. Catechol oxidase belongs to a class of enzymes that has a copper dimer with histidine ligands at the active site. Another member of this class is tyrosinase, which has been studied by similar methods previously. An important advantage for the present study compared to the one for tyrosinase is that X-ray crystal structures exist for catechol oxidase. The most critical step in the mechanism for catechol oxidase is where the peroxide O–O bond is cleaved. In the suggested mechanism this cleavage occurs in concert with a proton transfer from the substrate. Shortly after the transition state is passed there is another proton transfer from the substrate, which completes the formation of a water molecule. An important feature of the mechanism, like the one for tyrosinase, is that no proton transfers to or from residues outside the metal complex are needed. The calculated energetics is in reasonable agreement with experiments. Comparisons are made to other similar enzymes studied previously. [ABSTRACT FROM AUTHOR]

The electronic structure of quasi-one-dimensional halogen-bridged binuclear metal complex Ni2(dta)4I (dta=CH3CS2−) was investigated by hybrid density functional theory. UB3LYP was successfully applied to reproduce averaged-valence spin density wave state. The magnetic interactions between Ni dimers were estimated by calculating effective exchange integrals (Jab) using Ni2(dta)4I dimer and tetramer models. Calculated J values were consistent with that of experimental results. The natural orbital analysis of the broken-symmetry UB3LYP solution were performed to elucidate symmetry-adapted molecular orbitals and their occupation numbers. Several chemical indices such as polyradical character and information entropy were introduced on the basis of the occupation numbers to discuss the bonding character of MMX chain. All these indices supports that Ni2(dta)4I was in the strongly correlating electron system. [Copyright &y& Elsevier]

Hybrid density functional theory (B3-LYP and B3-PW91) and counterpoise-corrected ab initio (MP2) calculations have been performed for the adducts of the main-group metal ions Na+, Mg+, Al+, K+, and Ca+ with the phenyl radical C6H5. While the calculated bond dissociation energies (BDEs) and complexation geometries of the alkali metal ion adducts do not differ substantially from those determined for the analogous M+/benzene π-complexes, the alkaline earth ions exhibit a strong preference for σ-bond formation at the bare C atom of the phenyl ring, with calculated BDEs exceeding those determined for benzene complexation by approximately 80 and 150 kJ mol−1 for Mg+ and Ca+, respectively. This σ-coordination is only feasible when the unpaired spins on the reactant Mg+ (or Ca+) and C6H5 radicals are opposed, thereby leading to a closed-shell (singlet state) adduct ion. When the unpaired spins are aligned, the triplet-state adduct thus produced adopts π-complex minimum energy geometry with a BDE significantly below that of the corresponding M+/benzene complex. Both π- and σ-coordination are also found to be local minima on the AlC6H5+ potential energy surface, with the BDE of the Al+/C6H5 σ-complex being approximately 50 kJ mol−1 larger than that of the corresponding π-complex, and about 20 kJ mol−1 above the BDE for Al+/benzene. The overall results of our study show that the phenyl radical exhibits a much greater degree of selectivity between the main-group metal ions represented here than is evident for benzene. The phenyl radical BDEs range from 59.7 (K+) to 264.7 kJ mol−1 (Ca+) according to calculations at the B3-PW91/6-311+G(2df,p) level of theory, which contrasts with the 65.5 (K+) to 147.9 kJ mol−1 (Al+) BDE values determined for benzene at the same level of theory. [Copyright &y& Elsevier]

The HNO isomerization into HON was examined with a variety of density functional theory methods, including the B1LYP, B3LYP, and the MPW1PW91 method coupled to a relatively large 6-311G(2d,2p) basis set. In addition, the CBS-Q, and G2 methods were used to further evaluate the barrier to isomerization, which is believed to occur through a three-center cyclic transition state. The difference in energy between the two isomers is predicted to being around 40–41 kcal mol−1 when any of the methods are applied. [Copyright &y& Elsevier]

The recent discovery of Na 3 LiTi 5 O 12 (NTO), which possesses spinel symmetry (Fd 3 ¯ m , #227) with the 8a site occupied by Na, has enabled investigations into the effect of the 8a-site cation on the physical properties of spinel titanates. Hence, in this study, the optical and photocatalytic properties of NTO were investigated and compared with those of spinel Li 4 Ti 5 O 12 (LTO) and rutile TiO 2. The bandgaps were estimated theoretically using hybrid density functional theory and experimentally using the ultraviolet–visible spectroscopy, and the obtained results were similar for both methods and spinel titanates. The valence- and conduction-band components of the spinel-type titanates were similar to those of other titanium oxides, and both NTO and LTO exhibited photocatalytic activity for sacrificial H 2 evolution from water. However, although they have similar band structures and optical properties, the NTO photocatalytic activity was clearly lower than that of LTO. This can be attributed to the surface roughness and ease of defect formation in the NTO system, which hindered charge separation. These results indicate that the optical properties of spinel-type titanates can be tuned by replacing the cations at the 8a sites. [Display omitted] • The bandgaps of Li 4 Ti 5 O 12 (LTO) and Na 3 LiTi 5 O 12 (NTO) are similar. • The photocatalytic activities of LTO and NTO are different. • NTO is more susceptible to defects than LTO. • This is the first report on the optical properties and catalytic activity of NTO. [ABSTRACT FROM AUTHOR]

In this study, the B3LYP hybrid density functional theory was used to investigate the electromechanical characteristics of C70 fullerene with and without point charges to model the effect of the surface of the gate electrode in a C70 single-electron transistor (SET). To understand electron tunneling through C70 fullerene species in a single-C70 transistor, descriptors of geometrical atomic structures and frontier molecular orbitals were analyzed. The findings regarding the node planes of the lowest unoccupied molecular orbitals (LUMOs) of C70 and both the highest occupied molecular orbitals (HOMOs) and the LUMO of the C70 anion suggest that electron tunneling of pristine C70 prolate spheroidal fullerene could be better in the major axis orientation when facing the gate electrode than in the major (longer) axis orientation when facing the Au source and drain electrodes. In addition, we explored the effect on the geometrical atomic structure of C70 by a single-electron addition, in which the maximum change for the distance between two carbon sites of C70 is 0.02 Å. [ABSTRACT FROM AUTHOR]

A single-photon emission (SPE) system based on a solid state is one of the fundamental branches in quantum information and communication technologies. The traditional bulk semiconductors suffered limitations of difficult photon extraction and long radiative lifetime. Two-dimensional (2D) semiconductors with an entire open structure and low dielectric screening can overcome these shortcomings. In this work, we focus on monolayer h -AlN due to its wide band gap and the successful achievement of SPE compared to its bulk counterpart. We systematically investigate the properties of point defects, including vacancies, antisites, and impurities, in monolayer h -AlN by employing hybrid density functional theory calculations. The -1 charged Al vacancy (V Al - ) and +1 charged nitrogen antisite (N Al + ) are predicted to achieve SPE with the zero-phonon lines of 0.77 and 1.40 eV, respectively. Moreover, the charged point-defect complex C Al V N + , which is composed of vacancies and carbon substitutions, also can be used for SPE. Our results extend the avenue for realizing SPE in 2D semiconductors.

We present a benchmark study of binding energies for dioxin‐imprinted polymer complexes. A density functional theory approach was used for screening the polymerization precursors in the rational design of molecularly imprinted polymers (MIPs). Tetrachlorodibenzo‐p‐dioxin (TCDD) was taken as an imprinted molecule. The geometry optimization, natural bond orbital charge, and molecular electrostatic potential of TCDD and acrylamide (AM) were studied at the M062X level and 6‐31G(d,p) belonging to one of the hybrid density functional theories. The results of molecular electrostatic potential and natural bond orbital charge analysis were comparable. Among the studied functional monomers—AM, methacrylic acid (MAA), itaconic acid, and vinyl pyridine—AM was confirmed as the best functional monomer, because the strongest interaction (the maximum number of hydrogen bonds and the lowest binding energy) occurs between TCDD and AM. The stability property was excellent when the ratio of TCDD and AM was 1:4. The polarizable continuum model was used for solvent calculations. Computational results showed that acetonitrile plays an important role in the MIP formation, as it seems to control the size and the shape of the cavity. The atoms in molecule and Becke surface method have also been applied to understand the nature and strength of the hydrogen bonding interactions in complexes. TCDD‐AM complexes were found involving C–O···Cl and N–H···Cl hydrogen bonds. Good correlations have been established between hydrogen bond lengths versus atoms in molecule topological parameter like electron density ρ(r) and its Laplacian ▽2ρ(r) at the bond critical points. On ground of theoretical results, a series of MIPs were synthesized. The MIP prepared using TCDD as the template, the functional monomer (AM), and the cross‐linker (TRIM) in acetonitrile solvent exhibited the highest adsorption capacity for TCDD. The maximum binding capacity of TCDD on the MIP was 3.7 μg/mg. This research work can provide a theoretical reference for the fabrication and characterization of novel TCDD‐MIPs for environmental applications. This research article provides a better understanding of important interactions for the development of molecularly imprinted technology. This work will help to improve the selective detection and remediation of a particular dioxin, in environmental samples. Moreover, the theoretical simulation used in this research article is rapid and reliable for the combinatorial screening of polymer precursors in experimental‐free way to design nano‐porous polymeric material for environmental application. [ABSTRACT FROM AUTHOR]