The Feynman dispersion correction for MNDO extended to F, Cl, Br and I A small coding error in the development version of EMPIRE led to some inconsistencies in the above article. They are corrected in this erratum.

Exploring the effect of phosphorus doping on the utility of g-C 3 N 4 as an electrode material in Na-ion batteries using DFT method Abstract The suitability of P-doped g-C3N4 for sodium storage was assessed using density functional theory. The electronic structure of P-doped g-C3N4 was calculated and the results indicate that the presence of the P atom causes the band gap of g-C3N4 to narrow. Na adsorption on a P-g-C3N4 sheet was investigated. Projected density of states (PDOS) analysis revealed that pyridinic nitrogen atoms in g-C3N4 play the main role in Na adsorption. High binding energies were calculated for Na storage on g-C3N4, leading to a high voltage range (1–3 V) and a high Na diffusion barrier (2.3 eV). Doping the substrate with more P atoms resulted in lower voltages (below 2.2 V), easier Na diffusion (with a barrier of 1.2 eV), and therefore a material that was better suited than g-C3N4 for use in anodes.

The reaction pathway analysis of phosphoric acid with the active radicals: a new insight of the fire-extinguishing mechanism of ABC dry powder Abstract Dry powder fire-extinguishing agent is one of Halon substitutes due to its superior fire-extinguishing performance, non-toxicity, and environmental friendliness. As one of the most widely used dry powders, ABC dry powder has attracted wide attention. Understanding its reaction mechanism is important to the design of more efficient compound dry powder based on it. When ABC dry powder was applied to the flame, ammonium dihydrogen phosphate (the main fire-extinguishing component of ABC dry powder) would rapidly decompose into phosphoric acid (H3PO4) and ammonia. Therefore, in order to figure out the chemical reaction mechanism of ABC dry powder and active radicals, the main focus of this paper is on the H3PO4. Analysis of the electrostatic potential on van der Waals surface of H3PO4 was carried out. Besides, detailed theoretical investigation has been performed on the mechanism, kinetics, and thermochemistry of the reactions of H3PO4 with H, OH, and CH3 radicals and further decomposition of H3PO4using M06-2X/6-311G(d,p)//CCSD(T)/cc-pVTZ level of theory. Mayer bond order for all intrinsic reaction coordinate points was also calculated. Finally, it is theoretically proved that ABC dry powder extinguishes the fire mainly by chemical inhibition on H and OH radicals. Grapical Abstract .

Ab initio study on the six lowest energy conformers of iso-octane: conformational stability, barriers to internal rotation, natural bond orbital and first-order hyperpolarizability analyses, UV and NMR predictions, spectral temperature sensitivity, and scaled vibrational assignment Abstract In this paper, we present the quantum electronic study of iso-octane, based on MP2 and B3LYP methods using the 6-311++G(d,p) basis set. In addition to conformational stability and internal rotation barriers studies, the delocalization energies associated with the internal charge transfer (ICT) within each of the six lowest energy conformers were evaluated using NBO analysis. With the aim to differentiate even more between these conformers, the energy gap between HOMO and LUMO orbitals, chemical softness, and first-order hyperpolarizability (nonlinear optics property) were evaluated. Similarly, their spectral behavior was investigated at different levels; the ultraviolet (UV) absorption bands were assigned using molecular orbitals data obtained by TD-B3LYP calculations with 6-311++G(d,p) basis set, while carbon 13C NMR and proton 1H signal peaks were assigned using the GIAO-B3LYP/6-311++G(d,p) method. In addition, the normal mode calculations of the most and least stable conformers using a scaled force field in terms of nonredundant local symmetry coordinates were carried out to approach the vibrational spectra temperature dependency.

Theoretical investigation of the structure, detonation properties, and stability of bicyclo[3.2.1]octane derivatives Abstract A series of nitro group and aza nitrogen atom derivatives, based on bicyclo[3.2.1]octane, were designed and studied by theoretical methods. The geometric structure calculations were performed at B3LYP/6-311G(d,p), B3P86/6-311G(d,p), B3LYP/6-31G(d), and B3PW91/6-31G(d,p) levels. The electrostatic potential analysis, heats of formation, densities, heats of sublimation, detonation performances, bond dissociation energies (BDEs), and impact sensitivities of the designed compounds were calculated by reasonable calculation methods to evaluate their comprehensive properties and establish the relationship between structure and performance. Results show that density and detonation properties always increase with the increasing number of nitro groups and aza nitrogen atoms. BDEs generally decrease with the increasing number of nitro groups. Except for BDEs of A9, B9, and D8, BDEs of all designed compounds are larger than 20 kcal mol–1 and meet the requirement for new high energy density compounds (HEDCs). Two theoretical prediction methods show all the designed compounds have an acceptable impact sensitivity. Detonation velocity and detonation pressure were predicted in the range of 5.24–9.59 km/s and 9.97–43.44 GPa, respectively. Eleven compounds have better detonation properties than HMX, and seven compounds meet the criteria for HEDCs. Taking thermal stability and impact sensitivity into consideration, four compounds (C9, E8, F8, and G7) may be considered as new potential HEDCs, and C9, E8, and F8 may have similar detonation properties to the famous CL-20. Graphical abstract Four new HEDCs with acceptable impact sensitivity (C9, E8 and F8 may have similar detonation properties to the famous CL-20)

Theoretical insights into the hydrogen bonding interaction in the complexation of epinephrine with uracil Abstract The present study is aimed at probing the hydrogen bonding interaction between epinephrine and uracil by means of density functional theory calculations concerning their complexation’s geometries, interaction energies, and vibrational frequencies. Geometry optimization was carried out giving 19 stable geometries of epinephrine-uracil complex with interaction energies in a range of – 21.51 to – 62.37 kJ mol−1 using the basis set superposition error (BSSE) correction. The analysis of structure and vibration shows that the hydrogen bonding elongates the length of corresponding bond O(N)–H and decreases the symmetric stretching vibrational frequency, which indicates red-shifted H-bonding interactions in all the geometries. Additionally, the analysis with theories of natural bond orbital (NBO), atoms in molecules (AIM), and the reduced density gradient (RDG) of hydrogen bonding properties and characteristics of the 19 geometries suggests that the hydrogen bonding in all the optimized structures of epinephrine-uracil complex is kind of a closed-shell interaction and mainly electrostatic dominant.

Theoretical study of the electronic structure of mono-bromide of lanthanum molecule including spin-orbit coupling effects Abstract Among the family of lanthanide halides compounds, this work is devoted to the third halogen bromine. The presented lanthanum bromide LaBr molecule has a remarkable scientific interest regarding the other molecules because it presents few experimental studies and only one theoretical study. The theoretical electronic structure of the LaBr molecule is achieved by using the post-Hartree–Fock methods manifested by the complete active space self consistent field (CAS-SCF) method and the multi reference configuration interaction with single and double excitation (MRCI-SD) method. All of these calculations are performed via the quantum chemistry software MOLPRO. We predicted for the first time in the literature, 24 lowest-lying electronic states in the representation 2S+ 1Λ(±) and their corresponding components in the representation Ω(±) when taking into account the spin-orbit coupling (SOC), situated below 22,000 cm− 1. We calculated the spectroscopic constants for both cases (without/with SOC effects) related to the 13 singlet and 11 triplet states and for their components. We drew also in this paper the potential energy curves (PECs in a range of internuclear distance R varying from 2.00 to 4.22 Å. Graphical Abstract Potential energy curves for 13 singlet electronic states of LaBr

Atomic shells according to ionization energies Abstract This article relies only on experimental data rather than getting involved with theories, calculations, approximations, or interpolations. Experimental ionization energies of all atoms in the periodic table are collected and utilized to discover the order of electronic shells. The assumption in this paper is mainly the energy difference between atomic shells. In other words, one should observe an abrupt change in the energy moving from one atomic shell to another. Electronic energies within an atom are either kinetic or potential. Potential energy can be further broken into “electron–nucleus attraction” and “electron–electron repulsion” energies. The ionization energy that holds an electron onto an atom is equal to the balance of electronic energies. Electronic energies should show jumps and drops when moving from one atomic shell to another and ionization energy is the only part of total energy that can be obtained experimentally. Hence, the variations of experimental ionization energies between consecutive electrons were utilized to investigate the order of atomic shells. The variations of ionization energy were drawn versus the electron numbers to find abrupt changes in the energy, which are so-called “peaks”. Then the observed peaks in the graphs were recorded as evidence for the order of atomic shells. The observed order of peaks did not completely match and support the order of atomic shells given by the well-known aufbau (or Madelung) rule. Thus, the observation is reported and a consistent view of the periodic table according to the new order is presented.

Design and photoelectric properties of D-A-π-A carbazole dyes with different π-spacers and acceptors for use in solar cells: a DFT and TD-DFT investigation Abstract Density functional theory (DFT) and time-dependent DFT (TD-DFT) were used to calculate the properties of the carbazole dyes TYZ-1 to TYZ-5, which differed in their π-spacers. The carbazole dyes TYZ-6 and TYZ-7 were then designed; these were based on TYZ-3 (which had 2,2′:5′,2″-terthiophene as its π-spacer) but had more strongly electron-withdrawing second acceptor groups than TYZ-3. All of these dyes except for TYZ-5 presented quasi-planar conformations, and the calculated energies of their highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) molecular orbitals as well as their HOMO-LUMO gaps (Eg) suggest that these dyes are suitable for use as sensitizers. Lengthening the π-spacer and increasing its degree of conjugation were found to cause the absorption spectrum of the dye to redshift and to facilitate hole injection. The Eg values of TYZ-6 and TYZ-7 were calculated to be smaller than that of TYZ-3 due to the weaker electron-withdrawing power of the second acceptor group in TYZ-3, and the dyes TYZ-2, TYZ-3, TYZ-6, and TYZ-7 presented the smallest Eg values. Local electron excitations following UV-vis absorption led to electronic transitions, particularly HOMO to LUMO transitions (> 94.3% of all transitions). The excited states of these dyes were found to have quasi-planar conformations, although their dihedral angles were smaller than those in the corresponding ground states. The Stokes Shifts calculated for the seven dyes (which ranged from 51.9 to 98.1 nm) suggested that self-absorption was unlikely to occur. Overall, the calculations indicated that the dyes TYZ-2, TYZ-3, TYZ-6, and TYZ-7 are promising candidates for use in dye-sensitized solar cells.

Computational insights into the mechanism of formaldehyde detection by luminescent covalent organic framework Abstract Luminescent covalent organic frameworks (COFs) as fluorescent sensor materials provide a distinct advantage over other materials. In this work, we investigated the hydrogen bonding between the luminescent COF Ph-An-COF and formaldehyde in its excited electronic state by using density functional theory and time-dependent density functional theory to determine whether this type of COF can be used for formaldehyde detection. Hydrogen bonding significantly changed the nature of the frontier orbital and the luminescent properties. Our study reveals that the hydrogen bonding was strengthened in the excited state and the fluorescence rate coefficient was significantly reduced, which is not favorable for the luminescence of this type of COF and would lead to a luminescence decrease or quenching phenomenon. Therefore, this type of luminescent COF can be used as a potential chemical sensor to detect formaldehyde. This work provides an insight into the design of luminescence covalent organic frameworks.