This paper reports the comparison of experimental photoionisation spectra of deuterated ammonia (ND 3 ), previously recorded by ( 1 + 1 ′ ) two-photon excitation via the B state ( v 2 ′ = 5 , 6 ) [S. Kuijpers, P. Kalaitzis, E. Sakkoula, S. van de Meerakker, T. Softley and D. Parker, J. Phys. Chem. 128, 10993–11004 (2024).], with multichannel quantum defect theory (MQDT) simulations. The spectra show a dense Rydberg structure which is analysed in terms of over 20 different Rydberg series in each case. New experimental spectra, recorded via the B-state v 2 ′ = 7 intermediate, and a 2 + 1 ′ photoionisation spectrum recorded via v 2 ′ = 5 are also reported here, and MQDT simulations are presented. Using the same quantum defect parameters, the rotationally resolved photoelectron spectra (PES) with 1 + 1 ′ excitation via v 2 ′ = 6 reported in Reference S. Kuijpers et al. are also simulated with MQDT, and show a satisfying level of agreement with experiment. The calculations provide a verification of qualitative arguments about the relative propensity for autoionizing into a range of available open channels, and also an explanation for the differences between PES measured at a resonant wavelength (on a peak in the photoionisation spectrum) as opposed to those recorded off-resonance.

Sulphur hexafluoride (SF6) is in urgent need of efficient degradation methods due to its widespread use in high-voltage electrical equipment and strict emission regulations. This study proposes a novel TiO2 /SiC catalyst synthesised via the sol–gel method for thermocatalytic SF6 conversion. Experimental evaluations revealed that TiO2/SiC achieves complete decomposition of 4% SF6 in a mixed gas (initial pressure: 0.14 MPa, temperature: 700°C) within 9 h, exhibiting a catalytic efficiency 3.73 times higher than pure TiO2. Key degradation products, including SOF4, SO2F2, SOF2, SO2, CF4, and CO2, were identified via GC-MS, with SO2 and SO2F2 as dominant sulphur-containing species. Density Functional Theory (DFT) simulations elucidated the catalytic mechanism: TiO2 facilitates charge transfer between Ti/O atoms and SF6, reducing the activation energy of the initial defluorination step. This energy reduction destabilises S–F bonds, accelerating SF6 breakdown into low-fluorine intermediates, which further oxidise to stable products. The SiC support enhances thermal stability by preventing TiO2 aggregation. TiO2/SiC combines superior efficiency, stability, and simpler synthesis, offering a practical solution for industrial SF6 waste treatment. This work bridges experimental and computational insights, advancing the design of high-performance catalysts for greenhouse gas mitigation. A novel and efficient catalyst, TiO2/SiC was successfully synthetised for the thermocatalytic conversion of SF6 waste gas by the sol–gel method. In addition, the catalytic defluorination mechanism was investigated via the density functional theory and transition state theory.

The goal of this study is to determine, by means of quantum-chemical computations at the M06-2X/aug-cc-pVDZ level of theory, the effects on the energy order, geometry and molecular electrostatic potential changes of the tautomers of canonical bases of DNA and RNA (A, C, G, T and U) upon the {C=C → B(H2)B} substitution, where B(H2)B is the central fragment of diborane(6), leading to the boronated bases Ab, Cb, Gb, Tb and Ub, respectively.

Utilizing first-principles calculations grounded in density functional theory, an exploration of the adsorption characteristics and optical attributes of methane gas on Pt/VO 2 surfaces was undertaken. Initially, the adsorption capacity of methane on a pristine VO 2 surface was scrutinised, revealing that methane exhibits a certain level of physical adsorption on this surface. Subsequently, platinum atoms were introduced onto the clean surface to identify optimal active sites. Based on the most stable platinum/VO 2 substrate, methane gas was adsorbed onto the substrate surface, and the enhancement of adsorption performance due to platinum loading was assessed. Results indicated a significant increase in methane's adsorption energy on the surface post-platinum loading. Detailed electronic structure analysis confirmed that methane's adsorption on the Pt/VO 2 surface is chemical in nature. Furthermore, systematic investigations into the optical properties of various configurations revealed a specific order of light sensitivity in the visible region:VO 2 +Pt+CH 4 > VO 2 +Pt> VO 2 +CH 4 >VO 2 . These findings offer valuable theoretical insights for advancing gas optical sensors.

The structure of a planar double layer system containing both positively charged and negatively charged dimer ions is explored using Monte Carlo simulation in the canonical ensemble. The dimer ions are immersed in a structureless solvent mimicked by a dielectric continuum adjacent to a charged electrode. The dimer cations and dimer anions consist of two equally sized hard spheres fused together; in each dimer, one sphere is charged, while the other is neutral. For a bulk concentration of 1 mol/dm 3 and symmetric dimer valencies of 1:1, singlet distribution functions and the average orientation of the dimers perpendicular to the electrode are obtained for both positive and negative electrode surface charges. At the same fusion levels for both species of dimers, more structure is observed when the fusion level is low rather than when this level is high. Additionally, the coion and counterion profiles tend to be inverted when the electrode surface charge is reversed.

This study presents a theoretical simulation of the interactions between XCN molecules (X = F, Cl, Br, and I) and phosphine amine (PA) based on ab initio calculations. Our results revealed the formation of three optimised structures, denoted as Structure-A to Structure-C. The Structures-A and C are stabilized through halogen bonding(XB) interactions of the types N···X and P···X, respectively, while structure–B corresponds to a dual, Pnictogen-Tetrel (PnB–TB) complex involving N···P and P···C interactions. The computed interaction energies established the following stability order: Structure-A > Structure-C > Structure-B. Natural Bond Orbital (NBO) analysis demonstrated that two orbital interactions, lp(N) → BD*(P–N) and lp(P) → BD*(C–N), play a critical role in stabilising the complexes of structure–B. These findings are fully consistent with the results obtained from Noncovalent Interaction (NCI) analysis, whereas the Atoms-in-Molecules (AIM) analysis did not provide satisfactory results for these systems. To achieve a deeper understanding of the properties of the resulting complexes, a series of complementary analyses were performed. These included molecular electrostatic potential (MEP), geometry optimisation, spectroscopy, interaction energy (ΔIE) calculations, Natural Bond Orbital (NBO) analysis, Atoms-in-Molecules (AIM) analysis, Noncovalent Interaction (NCI) index analysis, and Energy Decomposition Analysis (EDA).

Ultrafast nonradiative decay in photoexcited molecules is governed by a delicate interplay of vibrational motions and intramolecular interactions. Substituted phenols offer a valuable model for understanding how structural modifications, such as hydrogen bonding and out-of-plane distortions, influence excited-state relaxation. Here, we investigate the excited-state dynamics of ortho-fluorophenol using on-the-fly nonadiabatic surface hopping simulations with Zhu–Nakamura transition probabilities at the CASSCF(12,9)/6-311++G** level. We performed two sets of simulations: one initiating at ππ* (S1) state, and another at πσ* (S2) state. From the S1 state, no trajectories relaxed within 100 fs, consistent with nanosecond-scale tunnelling seen in experiment. In contrast, 44% of S2-initiated trajectories underwent internal conversion to S1 within 100 fs. Among these, 27% led to rapid O–H dissociation (< 20 fs), while 17% decayed via a non-dissociative route involving ‘butterfly’ vibrations, low-frequency out-of-plane motions of the C–F, C–OH, or C–H groups that preserve the hydrogen bond. Only 8% reached the ground state in this time window. Notably, C–F dissociation was not observed in any case. These findings highlight the role of vibrational mode coupling in directing energy flow between dissociative and non-dissociative pathways. They underscore how hydrogen bonding and substituent geometry can modulate relaxation behaviour in photoresponsive molecular systems.

An efficient and accurate approach inc2-db-B0 for applying high level ab initio correlation methods CCSD(T) and CCSD(T)-F12 to large molecular clusters is proposed. It exploits the locality of the electron correlation and only requires the incremental expansion of the correlation energy up to second order, thus significantly increasing the calculation speed. Calibration calculations for water clusters with up to 20 molecules yield errors in total CCSD(T) energies of about 0.15 kcal/mol per molecule. The approach is further examined for three systems: (H 2 O) 17 , (CH 3 CN) 6 and ( CH 2 = CH 2 ) 13 . All have isomers very close in energy and their polarised triple-zeta basis set CCSD(T) calculations involve between 1200 and 2400 basis functions. The reported inc2-db-B0 calculations are feasible for ordinary hardware and provide relative energies with errors of less than 0.15 kcal/mol in comparison to the standard implementation, whereas the computational cost is reduced by more than 100 times. When comparing the results of selected modern density functional theory (DFT) approaches to the ab initio reference data presented here, we observe that the accuracy of DFT is still somewhat unpredictable for the small energy differences between the cluster isomers.

The surfactants SDBS, OA-12, and APG1214 were utilised to establish a lignite coal-binary surfactant-water system through molecular dynamics. This investigation focused on the charge density and frontier orbital distribution of single molecules, as well as the effect of binary surfactants on lignite wetting. The results showed that the distinct hydrophilic structures exhibit markedly divergent electronic potential energy distributions. Among the selected surfactants, APG1214 exhibited the most significant energy band gap (5.713 eV), demonstrating superior adsorption stability and interfacial wetting properties. All interaction energies were negative, confirming the spontaneous tendency of the adsorption process. The directional arrangement of the surfactant molecules from the initial configuration to the equilibrium state significantly reduced the interfacial formation energy, increased the intermolecular force, and promoted the adsorption of water molecules onto the coal surface. Relative concentration and mean square displacement analyses revealed that the APG1214-OA-12 binary surfactant exhibited the best wettability performance on lignite. These results can provide valuable references for researching and developing new surfactants.

A comparative computational study of model HCN … HCN … XF and HNC … HNC … XF (XF = HF, LiF, BeF2, BF3, ClF, PH2F, SF2 and SiH3F) trimers was undertaken to (i) examine the variation of the relative energetic stability/properties of the hydrogen-bonded HCN … HCN (HNC … HNC) dimer subunits when the Lewis acid XF is attached via various noncovalent interactions, and (ii) examine the variation of the relative energetic stability/properties of the HCN … XF (HNC … XF) dimer subunit when HCN (HNC) is attached via a hydrogen bond to form the corresponding trimers. This study allowed us to assess and compare the cooperative effects of various noncovalent interactions in these trimers, with nonadditive energies providing an energetic measure of cooperativity. The properties computed for the dimer subunits and the trimers include interaction energies, intermolecular separations, bond length changes, vibrational frequencies and their infrared intensity changes on complexation.