Herein, we comprehensively investigated the structural, electronic, optical, and photocatalytic properties of van der Waals heterostructure (vdWHs) MASnBr3/MoS2 (MA: CH3NH3). Monolayer MASnBr3 exhibits dynamical stability, as confirmed by phonon spectrum analysis, but suffers from a wide direct bandgap (2.72 eV at the HSE06-SOC (Heyd-Scuseria-Ernzerhof 2006 – Spin Orbit Coupling) level), limiting its photovoltaic efficiency. The formation of heterostructure with MoS2 results in type-II band alignment that facilitates efficient carrier separation, with HSE06-SOC band gaps of 1.89 eV (for AA-configuration) and 1.36 eV (for AB-configuration), aligning optimally with the solar spectrum, while strain engineering further tunes the band gap, extending light absorption into the near-infrared region. The heterostructure exhibits remarkable optoelectronic performance, including a high optical absorption coefficient (8 × 105 cm−1) and a Spectroscopic Limited Maximum Efficiency (SLME) of up to 30 %, exceeding that of conventional lead-based perovskites and monolayer MASnBr3. Favorable valence and conduction band offsets (VBO = 0.48 eV, CBO = 1.6 eV) ensure rapid electron-hole separation, while robust mechanical stability (Young’s modulus ≈ 80 N·m−1) underscores practical viability. These attributes, combined with its potential for photocatalytic hydrogen evolution, position the vdWHs MASnBr3/MoS2 as a promising candidate for sustainable photovoltaics and photocatalysis, offering tunable optoelectronic properties with robust structural stability.

The electron localization function (ELF) measures electron localization in matter and provides insights into bonds in materials and molecules. This study examines the relationship between ELF and binding energy in bimolecular systems, focusing on van der Waals (vdW) interactions such as Keesom, Debye, and London dispersion forces. These interactions play significant roles in crystalline molecular materials. This work addresses the challenge of accurately calculating binding energies in molecular materials and supramolecular synthons by exploring their correlation with ELF. We use density functional theory and have evaluated seven exchange-correlation functionals to identify which functional provides the most accurate binding energies in comparison to values obtained with coupled cluster. The findings revealed that rev-vdW-DF2 offers high precision, whereas Perdew–Burke–Ernzerhof-D3(BJ) is computationally efficient. These functionals were utilized to demonstrate how ELF can be employed to accurately determine binding energies. By analyzing the ELF and its correlation with binding energies in 95 bimolecular systems held together with physical bindings ranging from weak to strong interactions, we demonstrate a strong linear correlation, with a coefficient of determination (R2) reaching 0.960. These findings suggest that ELF can effectively differentiate between weak and strong vdW interactions, providing a reliable quantitative metric for evaluating interaction strengths. The results indicate that ELF can be used as method to determine the strength of intermolecular interactions, with potential applications in materials science. Especially as a method for analyzing and predicting molecular interaction strengths within molecular materials and supramolecular synthons. This work opens up the possibility to derive all directional physical binding energies of molecular materials within the unit cell directly from the ELF, which has the potential to simplify practical calculations. Furthermore, the study revealed a possible systematic error for current xc-functionals in describing systems with two neighboring O–H⋯O hydrogen bonds between interacting molecules.

Core-level and tunnelling spectroscopies applied to noble gas endofullerenes offer complementary insights into electron transfer rates, addressing both intramolecular and extramolecular processes. Elastic and inelastic tunnelling spectroscopy of empty C₆₀ and Kr@C₆₀ on Pb/Cu(111) each show that the encapsulated atom is essentially invisible to scanning probes. We interpret the lineshape of the lowest unoccupied molecular orbital (LUMO) of Pb-adsorbed (endo)fullerenes in tunnelling spectra as a signature of the dynamic Jahn–Teller (DJ–T) effect. This effect persists in electronically decoupled second-layer molecules, which also display distinct vibronic progressions in on-resonance tunnelling. DFT calculations reproduce the LUMO alignment and low density of states at the Fermi level seen in experimental tunnelling spectra for (endo)fullerenes on Pb, and, in line with submolecular resolution STM images, also predict that an atom-down orientation of the fullerene cage is energetically most favourable (although other adsorption geometries differ only by tens of meV at most). In contrast to the tunnelling data, core-level-focussed techniques – namely, photoemission, X-ray absorption, and resonant Auger–Meitner electron spectroscopy – of Ar@C₆₀/Pb(111) indicate that the encapsulated atom is heavily coupled to the molecular environment, with both a clear influence of substrate screening on the core-level lineshape and the absence of spectator signal in decay spectra.

When investigating charged defects in semiconductors or insulators, the traditional method to render them charged is by adding/removing electrons to/from the supercell. However, this method can be problematic due to the necessity to include an artificial jellium counter-charge. Herein, we investigate an alternative approach to charging – using explicit compensating donors/acceptors, in the form of substitutional atoms with suitable valence. This method yields pairs of charged defects in neutral supercells, thereby eliminating the need for jellium altogether. We test the method for a collection of model systems consisting of charge-compensated point defects in diamond (NV/SiV-centers, substitutional nitrogen/phosphorous/oxygen/sulfur donors, and substitutional boron/beryllium acceptors). We report the resulting charges, local geometries, spin densities, Kohn-Sham energy levels, and electronic transition energies for selected defect pairs and compare them with those for the individual defects in charged supercells. We find that charging by explicit donors/acceptors works well if properly designed but interpretation of the results can be challenging. We advocate for the cautious use of this approach to complement traditional charge correction schemes and to analyze the charge-compensation mechanisms occurring in actuality.

Crystalline thermoelectric materials, especially SnSe crystals, have emerged as promising candidates for power generation and electronic cooling. In this study, significant enhancement in ZT is achieved through the combined effects of lattice distortions and band convergence in multiple electronic valence bands. Density functional theory (DFT) calculations demonstrate that cation vacancies together with Pb substitutional doping promote the band convergence and increase the density of states (DOS) near the Fermi surface of SnSe, leading to a notable increase in the Seebeck coefficient (S). The complex defects formed by Sn vacancies and Pb doping not only boost the Seebeck coefficient but also optimize carrier concentration (nH) and enhance electrical conductivity (σ), resulting in a higher power factor (PF). Furthermore, the localized lattice distortions induced by these defects increase phonon scattering, significantly reducing lattice thermal conductivity (κlat) to as low as 0.29 W m−1 K−1at 773 K in Sn0.92Pb0.03Se. Consequently, these synergistic effects on phonon and electron transport contribute to a high ZT of 1.8. This study provides a framework for rational design of high-performance thermoelectric materials based on first-principles insights and experimental validation.

Zn anodes in aqueous rechargeable zinc batteries (AZBs) are plagued by irreversibility issues stemming from dendrite growth, hydrogen evolution, and corrosion. The design of separator offers a promising approach to enhance the reversibility of Zn anodes, but a universal strategy for rational separator design remains elusive. In this study, we propose a comprehensive design principle that takes into account the selective binding with Zn²⁺, H+ and H₂O, and further suggest that separators should ideally exhibit strong binding strength with H⁺ and H₂O but weak with Zn²⁺. We explore four typical scenarios based on varying binding strengths and identify polyethersulfone (PES) as a highly promising separator through screening of various commercial separators. Both experiment and theoretical calculations reveal that PES effectively regulates the transfer of Zn²⁺, H⁺ and H₂O, thereby concurrently suppressing dendrite growth, hydrogen evolution, and corrosion. As a result, the Zn‖Zn symmetric battery can operate for over 4000 h at 1 mA cm⁻² and 1 mA h cm⁻². Furthermore, the full battery can deliver an impressive lifespan of over 6400 cycles at 3 A g⁻¹. This work not only introduces a new separator for high-performance AZBs but also provides guiding principles for functional separator design.

Single-atom catalysts (SACs) supported on two-dimensional carbon-based materials offer a sustainable alternative to the Haber-Bosch process for ammonia production via electrocatalytic nitrogen reduction (eNRR). First-principles density functional theory simulations were employed to investigate transition metal-decorated holey graphyne (TM@HGY; TM: Sc, Cu, Mo, Ru) SACs for eNRR. Interaction energy and ab initio molecular dynamics simulations confirm their thermodynamic and thermal stability (300–500 K). Bader charge analysis reveals electron transfer of 0.50–1.53e from TMs to HGY, while density of states and electron localization function analyses indicate metallic conductivity and efficient charge delocalization. N  N bond elongation (1.11–1.19 Å) shows effective N₂ activation over the designed catalysts. Gibbs free energy profiles identify Ru@HGY as the most active catalyst, requiring −0.54 V of applied potential for both alternating and distal pathways. All SACs demonstrate Remarkable suppression of the hydrogen evolution reaction with substantial potential (−0.80 V to −1.26 V), ensuring high selectivity for ammonia production.

In this study, non-equilibrium molecular dynamics (NEMD) simulations with a reactive force field were used to investigate the tribochemical properties of glycerol, with and without water, confined between two ferrous surfaces. The results demonstrated that glycerol significantly reduced friction on α-Fe slabs more effectively than on functionalized amorphous magnetite. A numerical method was introduced to identify the interface region and evaluate the dissociated surface atoms. It was found that the dissociation rate of glycerol molecules increased with applied normal pressure and shear stress. Additionally, the production rate of water molecules from glycerol dissociation was consistently positive for all solutions above 80 % wt. The assumption of linear velocity distribution across the film thickness was validated for all systems studied.

In this work, we investigate the ion pair tetramethylphosphonium cation, [P1,1,1,1]+, and bis(oxalato)borate anion, [BOB]−, as a model system for the study of ionic liquids interacting with both hydroxylated and oxygen terminated α-SiO2 (001) surfaces, using first-principles electronic structure theory. We use a single ionic pair and clusters of ion pairs, in order to have exclusively neutral supercell slab models. We use dispersion-corrected density functional theory (DFT) to ascertain that both the strong physical binding between the ions, dominated by ionic binding, and the weaker physical binding of ions to the different surfaces are correctly described. We have found that the binding of ion pairs is stronger to the hydroxylated α-SiO2 (001) surface compared to the oxygen terminated surface, which is attributed to the formation of H-binding with the oxygen atom(s) of the [BOB]− anion. Through rotation of ionic pair(s), we estimate the surface-ions energy barrier for translational movement and, thus, the strength of H-binding of the ions. At the surface of hydroxylated α-SiO2 (001), we have studied how water molecules form a network of H-binding with the OH groups of the surface and the [BOB]− anion, which offers an explanation for the reduction in the friction of ionic liquids on the inclusion of water. We suggest modeling protocols for simulation of ion pairs on surfaces, which can open up the possibility to use DFT to aid in designing and understanding the physicochemical mechanism of interactions of ionic materials (including ionic liquids) in various technological applications.

We present first-principles results on monolayer (ML) and bulk titanium carbide (TiC) exhibiting dual topological characteristics: a quantum spin Hall insulator state in two-dimensional ML and a type-II Dirac semimetal state in its three-dimensional bulk form. The nontrivial nature of ML TiC is confirmed through the calculation of a Z2 invariant, spin Hall conductivity, and edge states. The edge band structure of ML TiC displays a single pair of gapless edge states at the 𝑀 point. The insulating topological phase in ML TiC is driven by a band inversion around the 𝑀 point involving Ti-𝑑 orbitals, with a nontrivial band gap of 0.47 eV. Our findings also indicate that ML TiC possesses excellent dynamical and thermal stability. Moreover, the bulk, ML hollow sphere arrays, and a 4-nm-thick film of TiC have already been synthesized, suggesting the high feasibility of the experimental synthesizing of ML TiC. On the other hand, we demonstrate that the bulk TiC hosts both a type-II Dirac cone and a topological nodal surface without spin-orbit coupling, protected by a combined symmetry of inversion and time reversal. The presence of spin-orbit coupling removes the nodal surface while preserving the type-II Dirac cone. Surface states connecting bulk Dirac nodes in bulk TiC can be readily observed, making the surface characteristics easily detectable in experiments.