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The effects of pressure on the mechanical, electrical structure, and optical characteristics of cubic fluoroperovskite XMgF 3 (X = Al, Ga, In, Tl) are investigated based on the first principles methods. The calculated lattice constants are in good agreement with those in the literature. According to the mechanical properties, all the compounds exhibit ductility and anisotropy, and the inter-atomic binding bonds of these materials are ionic. According to Kleinman's parameter, bond stretching is dominant in XMgF 3 (X = Al, Ga, In, Tl). Among all studied compounds, AlMgF 3 carries the highest machinable index, indicating that it is the most machinable and suitable material for industrial applications. The electronic structures show that AlMgF 3 and InMgF 3 are indirect bandgap semiconductors, while GaMgF 3 and TlMgF 3 are direct bandgap insulators at 0 GPa. The values of band gap for all the compounds decrease with the increasing pressure. X-s and F-p orbital states contribute primarily to the top of the valence band, whereas X-p orbital states dominate the bottom of the conduction band. The overall shape of electron state density under pressure does not change significantly, but its peak widens. The optical properties of XMgF 3 (X = Al, Ga, In, Tl) crystal at zero pressure and high pressures are further investigated. The results indicate that XMgF 3 compounds have outstanding ultraviolet (UV) absorption properties and could be used in UV optical devices. Moreover, the low reflectivity values of XMgF 3 crystals make the compounds potential anti-reflective coating materials. [ABSTRACT FROM AUTHOR]

Donor-π bridge-acceptor (D-π-A) design principle has been widely employed to build functionalized materials with excellent optical properties, whereas its feasibility in electrocatalytic reactions is seldom investigated. We demonstrate the primary study of D-π-A rule in constructing electrocatalysts for oxygen reduction reaction (ORR) purpose by rationally designing three cobalt porphyrins EGZ1–3 with 9H-carbazole, triphenylamine and N,N-diphenyl-[1,1′-biphenyl]-4-amine as the donor substituents, respectively, cobalt porphyrin as the π bridge, and cyanoacrylic acid as the acceptor unit. The electronic properties of the molecules are calculated using the density functional theory and the composite catalysts EGZs/C are characterized by a series of spectroscopic approaches. The electrochemical measurements show that EGZ3/C attains a more positive reduction potential and a greater response current density than EGZ1/C and EGZ2/C, which is possibly due to the optimized electronic structure and the substituent effect. The electron transfer number as well as hydrogen peroxide generation yield values suggest slightly better selectivity of EGZ3/C and EGZ2/C than those of EGZ1/C (i.e., ~ 2.9, ~ 2.9 vs. ~ 2.7 and ~ 54%, ~ 53% vs. ~ 62%, respectively) towards full oxygen reduction. Our result reveals the feasibility of the D-π-A design rule and the importance of molecular electronic state and the substituent feature in constructing ORR electrocatalysts. [Display omitted] • Three donor-π-acceptor cobalt porphyrins are synthesized. • The electronic structure of porphyrins is calculated by density functional theory. • Porphyrin-carbon black composites are studied in oxygen reduction reaction. • The electrocatalyst EGZ3/C attains the best ORR performance. • Both electronic structure and substituents affect the electrocatalytic activity. [ABSTRACT FROM AUTHOR]

[Display omitted] • • EA, VDE and frequencies of RhO n −(n = 1–––2) were determined by experiment and calculations. • • Based on the DFT calculations, the theoretical ADEs, VDEs and simulated PES of anionic RhO n − (n = 1–––4) clusters were obtained. • • The associated molecular orbitals (MOs), natural population analysis (NPA) and bond order analysis have been utilized. The photoelectron spectroscopies of RhO n – (n = 1–2) were obtained via using the photoelectron velocity-map imaging (PE-VMI) approach. The experimental values of the adiabatic detachment energy (ADE) and vertical detachment energy (VDE) for RhO– were reported to be 1.58 ± 0.02 eV. The experimental AED and VDE values of RhO 2 – were reported to be 2.70 ± 0.02 eV and 2.79 ± 0.02 eV, respectively. The vibrational frequencies of RhO– and RhO 2 – measured from photoelectron spectra (PES) were 817(76) cm−1 and 932(55) cm−1, respectively. Based on the density functional theory (DFT), the RhO n –1/0 (n = 1–4) clusters were investigated. The optimized configurations of corresponding ground states and low-lying clusters were discovered. Meanwhile, the simulated photoelectron spectroscopy (PES) of RhO n – (n = 1–4) and the theoretical ADE and VDE values of RhO n – (n = 1–4) clusters were unveiled to assist future experimental studies of Rhodium oxide clusters. Moreover, the associated molecular orbitals (MOs), natural population analysis (NPA) and bond order analysis have been utilized to investigate the chemical bonding in these groups. [ABSTRACT FROM AUTHOR]