As a continuation of Part I, dedicated to the ground state of He-like and Li-like isoelectronic sequences for nuclear charges $Z \leq 20$, and Part II, dedicated to two excited states of He-like sequence, two ultra-compact wave functions in the form of generalized Guevara-Harris-Turbiner functions are constructed for Li-like sequence. They describe accurately the domain of applicability of the Quantum Mechanics of Coulomb Charges (QMCC) for energies (2-3 significant digits (s.d.)) of the spin-quartet state $1^40^+$ of Li-like ions (in static approximation with point-like, infinitely heavy nuclei). Variational parameters are fitted in $Z$ by 2nd degree polynomials. The most accurate ultra-compact function leads to the absolute accuracy $\sim 10^{-3}$\,a.u. for energy, and $\sim 10^{-4}$ for the normalized electron-nuclear cusp parameter for $Z \leq 20$. Critical charge $Z=Z_B$, where the ultra-compact trial function for the $1^40^+$ state looses its square-integrability, is estimated, $Z_B(1^4\,0^+) \sim 1.26 - 1.30$. As a complement to Part I, square integrability for the compact functions constructed for the {\it ground, spin-doublet state} $1^2\,0^+$ of the Li-like sequence is discussed. The critical charge, for which these functions stop to be normalizable, is estimated as $Z_B( 1^2\,0^+) = 1.62 - 1.65$. It implies that at $Z=2$ - the negative helium ion He$^-$ - both states $1^2\,0^+$ and $1^4\,0^+$ exist as states embedded to continuum.

This work presents a thoroughgoing theoretical study on the OH-initiated combustion chemical kinetics and atmospheric degradation of C4F9N by employing high-level quantum chemical methods and RRKM/master-equation theory. All the stationary points on potential energy surface were cautiously investigated at B3LYP/6-311++G(d,p) level for geometry optimizations, and thereby their single-point energies were refined by applying CCSD(T)/6-311++G(d,p) method. Based on quantum calculations, kinetics and branching ratios for the major channels were predicted within 300-3000 K and 0.01-100 atm by solving the RRKM/master-equations. The addition of OH to C4F9N generating M1 dominates the overall kinetics at low temperatures. Subsequently, its two β-scission channels of C-C bonds forming CF3CF2N=CF(OH)+CF3 (P8) and CF2=NCF(OH)CF3+CF3 (P9) become competitive and play a lead role in whole C4F9N+OH system at the corresponding high temperatures and elevated pressures. The formation of CF3 radical prompts two routes to potentially have the significant contribution to flame inhibition in actual applications. Additionally, the complex degradation pathways of C4F9N were also looked into by successively reacting with various oxides, including OH, O2, NO, HO2, to finally generate the removal products CF3CF2N(OOH)CF(OH)CF3 (Pd2), CF3CFO (Pd3-2), and CF3CF2NO (Pd4). The atmospheric lifetime of C4F9N is evaluated as 72 years regarding to one step addition between C4F9N and OH radical.

Attachment of one electron to 1,2-diBeX-benzene and 1,2-diZnX-benzene derivatives leads to the formation of stronger Be-Be and Zn-Zn interaction. This is reflected in the dramatic shortening of the Be-Be and Zn-Zn distance. The formation of these 2-center-1-electron bonds have also been confirmed by topological survey of electron density using quantum theory of atoms in molecules and electron localization function. The formation of these bonds is expected to render stability to these radical anions. These radical anions are stable towards electron detachment and computed bond dissociation energy values are also significant.

Through the comprehensive analysis of ab initio and experimental results of a large number of diatomic systems, the systematic deviation of ab initio method in vibrational energies prediction caused by physical/mathematical simplification is located. A joint ab initio and machine learning method based on information across molecules is proposed to deal with the problem. Starting from an ab initio model, and then systematically modifying it through machine learning, the vibrational energies prediction of many diatomic systems (SiC, HBr, NO, PC, N2, SiO, O2, ClF, etc.) have been improved, and significantly surpassed the more complex ab initio model. In addition to the improvement of accuracy, the new method also greatly reduces the computational expense, and is applicable for the systems without experimental data.

The optical properties, electronic charge density, electronic structure of the new layered selenides materials, BaGdCuSe3, CsUCuSe3, CsZrCuSe3, and CsGdZnSe3 compounds have been calculated by using the full potential and linear augmented plane wave (FP-LAPW) methods as applied in the WIEN2k package, which is based on the density functional theory. The ALnMSe3 compound’s structure of these was (A= Cs, Ba; Ln = Zr, Gd, U; M= Cu, Zn) is composed of ] (n = 1, 2) layers, which might be separated by A atoms. It is to be observed that there is strong hybridization has been observed between the s, p, and d states of Zr, Gd, and Cu atoms. As the charge density contour, around the gadolinium atom, the charge density contours are completely circular, but the Gadolinium “Gd” atom shows an ionic nature. To calculate the refractive index, we used Kramer’s Kronig correlations with the imaginary part. The decrease in the refractive index is due to the lack of probability for direct excitation of the electrons, resulting in a loss of energy. The value of the static refractive index for all reference compounds is about 1.75 ~ 2.25.

Metadynamics simulation has been used to describe the conformational energy landscapes of several helical quinoline oligoamides bearing β-pinene-derived pyridine at either the C or N terminus. Based on the experimental results, helix-sense preference for four types of foldamers with the chiral terminal group has been verified. To compare to the key factors of inducing handedness to helical-sense preference, a terminal group with three hydrogen bond sites is designed and corresponding foldamers are built. The calculated results show the delocalization effect and steric hindrance mainly responsible for a particular helix-sense preference for the investigated foldamers. The more hydrogen bonds between the terminal group and oligoamide units are formed, the more stable foldamers are.

Detailed theoretical investigations on their structural and electronic properties of two-dimensional (2D) monofluorinating phenethylammonium perovskite are required to deeply understand the origin of the crystal structural and optoelectronic differences caused by organic spacers. Herein, formation energy, non-covalent interaction, band structure, exciton binding energy, carrier mobility and optical absorption spectra of 2D monofluorinating phenethylammonium lead iodide perovskite were calculated using density functional theory. Results show that steric effect leads to the orientational disorder of spacers in ortho-fluorinating phenethylammonium perovskite and weak interaction leads to the herringbone configuration of spacers in meta-fluorinating phenethylammonium perovskite. Exciton binding energy significantly influences the short circuit current density (JSC) of fluorophenethylammonium-based 2D perovskites, which can well explain the experimental trends of JSC. Formation energy analysis of perovskites with the same chemical components but different crystal structures and exciton binding energy calculation can be additional strategies in high-throughput screening for high-performance 2D perovskites.

A first principle investigation of structural, mechanical, thermodynamical, electronic and thermoelectric properties of PdTiZ (Z = Ge and Pb) was carried out using plane wave pseudopotential (PP-PW) method. The exchange-correlation was considered with the generalized gradient approximation of Perdew-Burke-Ernzerhof (PBE-GGA). The energy band structure of the sample material exhibited semiconducting energy band structure with indirect energy band gaps of 0.66 eV and 0.387 eV in PdTiGe and PdTiPb respectively with density of states being mainly dominated by the p state of Z and d states of Ti atom around the vicinity of the Fermi energy level. The sample compounds were found to be mechanically stable in their non-magnetic cubic phase. PdTiGe was found to be harder and stiffer than PdTiPb. The positive phonon modes of the compounds predicted their dynamical stabilities. Thermodynamic study revealed that pressure has a negative effect on heat capacity whereas Debye temperature increases with enhanced pressure in both the sample compounds. The thermoelectric properties of the sample compounds predicted that p-type nature of the sample compounds possess better thermoelectric performance. The room temperature Seebeck coefficient values are found to be 98.73 µV/K and 94.82 µV/K for PdTiGe and PdTiPb, respectively, whereas they reflected the S values of 245.73 µV/K and 218.77 µV/K at 1200 K at n = 1021 cm-3. The lowest value of lattice thermal conductivity (K_L) of 2.28 W/m-K and 0.98 W/m-K was observed for PdTiGe and PdTiPb respectively. The optimum dimensionless figure of merit of 0.66 (1200 K) and 0.64 (1000 K) were found for p-type PdTiGe and PdTiPb, respectively at optimum carrier concentration.

Based on the Crystal structure Analysis by Particle Swarm Optimization (CALYPSO) searching method and density functional theory (DFT), theoretical studies about structures, electronic and thermodynamic properties have been investigated systematically at the TPSSh/6-311+G(d) level for NiB2n0/- (n=7-11) clusters. Results found that the lowest energy structures possess a Ni atom-centered double ring tubular boron structures, NiB180/- except. Relative stabilities were analyzed via computing their vertical ionization potentials (VIP), vertical electronic affinity (VEA), adiabatic electronic affinity (AEA), HOMO-LUMO gaps and hardness. The infrared spectra, Raman spectra and photoelectron spectra were computationally simulated to facilitate their experimental characterizations. At last, aromatic properties (Nucleus independent chemical shift) and thermodynamic properties (enthalpy and entropy) with temperature were discussed in detailed for studied systems.

In order to study the properties of new energetic compounds formed by introducing nitroazoles into 2,4,6-trinitrobezene, the density, heat of formation and detonation properties of 36 nitro-1-(2,4,6-trinitrobenzene)-1H-azoles energetic compounds are studied by density functional theory, and their stability and melting point are predicted. The results show that most of target compounds have good detonation properties and stability. And it is found that nitro-1-(2,4,6-Trinitrophenyl)-1H-pyrrole compounds and nitro-1-(2,4,6-trinitropenyl)-1H-Imidazole compounds have good thermal stability, and their weakest bond is C-NO2 bond, the bond dissociation energy of the weakest bond is 222 kJ mol-1-238 kJ mol-1 and close to TNT (235 kJ mol-1). The weakest bond of the other compounds may be the C-NO2 bond or the N-N bond, and the strength of the N-N bond is related to the nitro group on azole ring.

Histidine (an imidazole-based amino acid) is a promising building block for short aromatic peptides containing a proton donor/acceptor moiety. Previous studies have shown that polyalanine helical peptides substituted at regular intervals with histidine residues exhibit both structural stability as well as high proton affinity and high conductivity. Here, we present first-principle calculations of non-aqueous histidine-containing 310-,  and -helices and show that they are able to form hydrogen-bonded networks mimicking proton wires that have the ability to shuttle protons via the Grotthuss shuttling mechanism. The formation of these wires enhances the stability of the helices, and our structural characterizations confirm that the secondary structures are conserved despite distortions of the backbones. In all cases, the helices exhibit high proton affinity and proton transfer barriers on the order of 1~4 kcal/mol. Zero-point energy calculations suggest that for these systems, ground state vibrational energy can provide enough energy to cross the proton transport energy barrier. Additionally, ab initio molecular dynamics results suggests that the protons are transported unidirectionally through the wire at a rate of approximately 2 Å every 20 fs. These results demonstrate that efficient deprotonation-controlled proton wires can be formed using non-aqueous histidine-containing helical peptides.

Graphene quantum dots (GQDs) are known for their low toxicity, strong fluorescence, high surface area, large solubility and tunable band gaps. However, the change in their properties depends on the preparation processes of GQDs. Thus, certain types of preparation lead to certain defects, such as surface defect, edge defects, Stone-Wales defect. These structural defects are responsible for hindering GQDs to possess their regular shape that affects the morphological properties of GQDs. Thus, the optical and electrical properties get affected. The GQDs, which are synthesized via acidic methods are generally more vulnerable to defects compared to those synthesized using eco-friendly methods. Thereby, the aim of this review is to discuss the causes of structural defects. Moreover, it focuses on how they affect the properties of GQDs and to what extent they affect them. The processes of regulating defects have been elucidated so that more efficient applications can be designed using GQDs with controlled amounts of defects.

The effect of the presence of a deuterium (D) or tritium (T) isotope bonded to the alpha carbon of glycine is determined without the need to apply external forces e.g. electric fields or using normal mode analysis. Isotopic effects were accounted for using the mass-dependent diagonal Born-Oppenheimer energy correction (DBOC) at the CCSD level of theory. We calculated the stress tensor trajectories of the dominant C-N bond within next generation quantum theory of atoms in molecules (NG-QTAIM). S-character chirality was discovered using the stress tensor trajectories, instead of the Cahn–Ingold–Prelog (CIP) rules, for ordinary glycine. The S-character chirality was preserved after the substitution of the H on the alpha carbon for a D isotope but transformed to R-character chirality after replacement with the T isotope. This reversal of the chirality depending on the presence of a single D or T isotope bound to the alpha carbon adds to the debate on the nature of the extraterrestrial origins of chirality in simple amino acids. We demonstrate that NG-QTAIM is a promising tool for understanding isotopic induced electronic charge density changes, useful in analysis of infrared (IR) or circular dichroism (CD) spectra explaining changes in mode couplings and bands intensities or sign.

In order to elucidate the temperature-dependent valence state of Ce ion and the occupation number of Ce 4f electrons in cerium mononitride (CeN), we perform an ab initio calculation on CeN by using a many-body scheme combing density functional theory (DFT) with dynamical mean field theory (DMFT), taking into account the spin-orbit coupling (SOC) interaction and on-site Coulomb repulsion between Ce 4f electrons. Results demonstrate that Ce 4f j=5/2 and j=7/2 manifolds undergo insulating-metallic transition with the increasing of temperature. Ce 4f-conduction electrons hybridization, f-f correlation, SOC interaction and final state effects yield a complicated spectrum function in CeN. Ce 4f atomic configuration transition and hybridization might be responsible for the temperature-dependent occupancy number of Ce 4f electrons and the mixed-valence state in CeN. A fact that localization of Ce 4f electrons, i.e., 4f1 configuration or Ce3+ valence, increases with the increasing of temperature could account for the experimentally observed lattice constant versus temperature data. Finally, the so-called quasiparticle band structure is also discussed for comparison with experimental angle-resolved photoemission spectrum (ARPES).

The noncovalent interactions between a redox-active molecule, phenyl-substituted dithiafulvene (Ph-DTF), and ten commonly encountered nitroaromatic compounds (NACs) were systematically investigated by means of density functional theory (DFT) calculations and ab initio molecular dynamics (AIMD) simulations. Our modeling studies examined their 1:1 complexes in terms of equilibrium geometries, frontier molecular orbitals (FMOs), nature of noncovalent forces, intermolecular charge transfer (ICT), interaction energies and related energy decomposition analysis. The computational results indicate that Ph-DTF can form thermodynamically stable supramolecular complexes with trinitro-substituted benzenes (e.g., 2,4,6-trinisuchtrotoluene and picric acid), but its interactions with mono- and dinitrobenzenes do not exhibit such stability. The selective binding properties are further corroborated by AIMD simulations. Overall, this computational work establishes a comprehensive understanding of the nature of noncovalent interactions of Ph-DTF with various NACs, and the results can be used as theoretical guidance for the rational design of selective receptors and/or chemosensors for certain NACs that are of great concern in current industrial applications and environmental control.

This article corrects the paper Int. J. Quantum. Chem. 120 e26221 (2020) by P. R. Surjan

Interference patterns in the scattering of positrons and electrons by diatomic homonuclear molecules are ab initio calculated. Our results are compared to model potential calculations with incident particles in twisted and plane wave states. All calculations are obtained in the first Born approximation framework. The comparison of the elastic differential cross sections shows how an ab initio description of the electronic molecular structure influence the interference minima structure. The origin of such patterns are also discussed.

The Fourier transform of Cartesian Gaussian functions product is presented in the light of positron scattering. The calculation of this class of integrals is crucial in order to obtain the scattering amplitude in the first Born approximation framework for an _ab initio_ method recently proposed. A general solution to the scattering amplitude is given to a molecular target with no restriction due to symmetry. Moreover, symmetry relations are presented with the purpose of identifying terms that do not contribute to the calculation for the molecules in the D∞h point group optimizing the computational effort. KEYWORDS — Positron and electron scattering, Fourier transform of the Gaussian product theorem, McMurchie-Davidson procedure, Obara-Saika procedure, linear molecules .