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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.

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 N 2 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., (© 2022 The Authors. FEBS Letters published by John Wiley & Sons Ltd on behalf of Federation of European Biochemical Societies.)

In this study, the B3LYP hybrid density functional theory was used to investigate the electromechanical characteristics of C 70 fullerene with and without point charges to model the effect of the surface of the gate electrode in a C 70 single-electron transistor (SET). To understand electron tunneling through C 70 fullerene species in a single-C 70 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 C 70 and both the highest occupied molecular orbitals (HOMOs) and the LUMO of the C 70 anion suggest that electron tunneling of pristine C 70 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 C 70 by a single-electron addition, in which the maximum change for the distance between two carbon sites of C 70 is 0.02 Å.

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 ▽ 2 ρ(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., (Copyright © 2018 John Wiley & Sons, Ltd.)

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 As X (X = Al or Ga) and X As defects always induce metallicity of GaAs/AlAs superlattice, and Ga Al and Al Ga 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.

Ice XV is the hydrogen-ordered form of the ice VI phase whose structure was predicted to be Cc and ferroelectric using periodic DFT approaches. However, neutron diffraction and Raman spectroscopy data show the structure to have P1̅ symmetry and to be antiferroelectric. Recent work1 using fragment-based MP2 and CCSD(T) approaches predicts the experimental structure as the ground state. We have reconsidered this problem using fully periodic MP2 and RPA approaches and find that the ferroelectric Cc structure is the lowest energy configuration. However, ubiquitously employed tinfoil boundary conditions stabilize polar structures. We suggest that ferroelectric Cc crystals can grow within a paraelectric ice VI matrix but may become unstable once a fraction of the matrix has become hydrogen-ordered. The reduction in dielectric constant causes P1̅ and other structures with small polarization to become favored, providing a possible resolution between observation and theoretical predictions.