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 ab initio molecular dynamics simulations are performed to study the atomic structures of Co92-xBxTa8 (x = 30, 32.5, 35, 37.5, at.%) glassy alloys. The result shows that the local packing of B-centered clusters is more efficient than that for Co- and Ta-centered clusters. It is also found that B-centered clusters are the primary structure-forming clusters. The Kasper polyhedra with a Voronoi index of <0 3 6 0> and <0 2 8 0> are dominant in B-centered clusters. Specially, the <0 3 6 0> clusters can form a robust network structure, which plays a key role in mechanical properties. Such a network structure has a higher activation barrier for structural rearrangement and a better resist to plastic flow. Thus, the increase in the fraction of <0 3 6 0> with B content would result in an increase in yield strength as well as a sharp decrease in compression plasticity.

Conjugated open ended cones in which the configured pentagons are consistent, lies in the circle of Fries Kekule structure [8]. This non-adjacent tightest configuration of pentagons as shown in the Fig. 1 is consistent with a Fries Kekule structure and thus provides the most stable cone. In the study, various topological indices of the same structure in regard of physico-concoction resources and bioactivity of substance mixtures are studied which further helps to study the behavior of chemical compounds. In this regard, Zagreb indices M_1^* (G) and M_2^* (G) of a molecular graph G are used to evaluate the complexity in chemical systems and biological organisms. In this manuscript, we consider two complex families of stable carbon nanocones and compute their ECI, TEI and eccentricity-based Zagreb indices.

Assessment of DFT methods through analysis of the Renner-Teller Effect (RTE) in the X2Π state of the NCO radical was completed. Our results suggest that the amount of exact exchange at long range is important for an accurate description of the RTE in NCO. DFT functionals from the B3LYP, PBE, TPSS, M06, and M11 families with standard Correlation Consistent, 6-311G split valence family, as well as Sadlej, and Sapporo polarized triple-ζ basis sets were assessed. Our Renner coefficients are compared with previously published theoretical and experimental results to characterize the overall accuracy of various functional/basis set combinations in determining the RTE splitting in the Π (bending) modes of NCO(X2Π). We suggest that this method of analysis can be extended to other systems, serve as an accuracy metric when selecting a functional, and provide a means to create training sets for machine learning in computational molecular physics applications.

Electrochemotherapy is an effective strategy for the treatment of solid tumors by exposing tumor cells to electric fields to enhance the bioactivity of non-permeable or low permeable anticancer drugs, such as cisplatin. To understand the improved efficiency of cisplatin in electrochemotherapy, the effects of oriented external electric fields (OEEFs) on the geometric structures and relevant electronic properties of cisplatin have been systemically investigated by density functional theory (DFT) computations in this work. Our results reveal that the presence of positive OEEFs on cisplatin can not only weaken its Pt-Cl bonds, but also enhance the intramolecular charge transfer in it, which effectively accelerates the critical hydrolysis step involved in the mechanism of its biological activity. Moreover, the positive OEEFs can facilitate the attack of the singly aquated cis-[Pt(NH3)2(H2O)Cl]+ on DNA, and enlarge the dipole moments and water solubility of cisplatin and its aquated product. Consequently, this work provides a deeper insight into the higher efficacy of electrochemotherapy than traditional chemotherapy from a molecular point of view.

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.

Introduction of a heterocyclic ring and an amino-ethyl-amino group to D-A type photosensitive dyes can modulate the lifetime of the charge separation generated in the D-A dyes as well as their electronic and UV-Vis absorption properties. Here we performed DFT and TDDFT calculations to study eleven derivatives of a triphenylamine-pyrimidine, MTPA-Pyc, in order to improve the performance of MTPA-Pyc as solar cell sensitizers. Five heterocyclic rings and an amino-ethyl-amino group were introduced on the styryl moiety of MTPA-Pyc. The results show that introduction of heterocyclic rings generally causes an absorption red-shift, but absorption intensity is reduced due to the increase of dihedral angle between the donor and acceptor. Further introduction of an amino-ethyl-amino group to these dyes with a heterocyclic ring modification disrupts the conjugation between donor and acceptor, which does not benefit the absorption but may have potential to increase the lifetime of charge separation of the dyes. This work identified two out of eleven dyes that have the best potential for solar cell applications.

Quantum chemical calculations are applied to study the complexes between X2TO (X=H, F, Cl, Br, CH3; T=C, Si, Ge, Sn) and CO2. The carbon atom of CO2 as a Lewis acid participates in the O•••C carbon bond, whereas its oxygen atom as a base engages in the O•••T tetrel bond with X2TO. Most of complexes are stabilized by a combination of both O•••C and O•••T interactions. The interaction energies are dependent on the nature of T and X atoms/groups. Both the electron-withdrawing halogen group and the electron-donating methyl group increase the interaction energy, up to 51 kJ/mol in F2SiO•••CO2. One F2SiO molecule can bind with different number of CO2 molecules from one to four; as the number of CO2 increases, the average interaction energy for each CO2 is decreased but it can contribute at least 27 kJ/mol stabilization energy. Therefore, silicon-containing molecules are good absorbents for CO2.

The three lowest spin states (S=0,1,2) of twelve representative Na13+ isomers have been studied using both, KS-DFT via three hybrid density functionals, and benchmark multireference CASSCF and CASPT2 methods with a couple of Dunning’s correlation consistent basis sets. CASSCF(12,12) geometry optimizations were carried out. Since 12 electrons in 12 active orbitals span the chemically-significant complete valence space, the results of the present study provide benchmarks for Na13+. The CASPT2(12,12)/cc-pVTZ* lowest energy structures are three nearly degenerate singlets (S=0): an isomer formed from two pentagonal bipyramids fused together (PBPb), a capped centered-squared antiprism [CSAP-(1,3)] and an optimum tetrahedral OPTET(II) structure, the last two lying 0.88 and 1.63 kcal/mol above the first, respectively. The lowest triplet (S=1) and quintet (S=2) states lie 4.33 and 3.77 kcal/mol above the singlet global minimum, respectively. The latter is a deformed icosahedron while the former is a CSAP-(1,3). The flatness of the potential energy surface of this cluster suggests a rather strong dynamical character at finite temperature. Prediction of the lowest energy structures and electronic properties is crucially sensitive both to non-dynamical and dynamical electron correlation treatment. The CASPT2 vertical ionization energy is 3.66 eV, in excellent agreement with the $3.6 \pm 0.1$ eV experimental figure. All the isomers are found to have a strong multireference character, thus making Kohn-Sham density functional theory fundamentally inappropriate for these systems. Only large multiconfigurational complete active space self-consistent field (CASSCF) wavefunctions provide a reliable zeroth-order description; then the dynamic correlation effects must be properly taken into account for a truly accurate account of the structural and energetic features of alkali-metal clusters.

Abstract: In the present work, the geometric structures, the frontier molecular orbitals and the enthalpy of formation (HOF) of thirty six 1, 2, 4, 5-tetrazine derivatives (FTT) were systematically studied by using the B3LYP/6-311+G* method of density functional theory. Meanwhile, we also predicted the stability, detonation properties and thermodynamic properties of all FTT compounds. Results showed that all compounds have superior enthalpy of formation far exceeding that of common explosives RDX and HMX, ranging from 859kJ·mol-1-1532kJ·mol-1. In addition, the detonation performance (Q = 1426cal·g-1 -1804cal·g-1; P = 29.54GPa - 41.84GPa; D = 8.02km·s-1 - 9.53km·s-1), which is superior to TATB and TNT. It is also concluded that the introduction of coordination oxygen on the tetrazine ring can improve the HOF, density and detonation performance of the title compound, and -NH-NH- bridge and -NHNO2 group are also the perfect combination to increase these values. In view of stability, because of the fascinating performance of D3 (ρ =1.89g·cm-3; D = 9.38km·s-1; P = 40.13GPa)，E3(ρ = 1.87g·cm-3; D = 9.19km·s-1; P = 38.35GPa), F1 (ρ = 1.87g·cm-3; D = 9.42km·s-1; P = 40.23GPa) and F3 (ρ= 1.92g·cm-3; D = 9.53km·s-1; P = 41.84GPa), makes them very attractive to be chosen as HEDMs.

An extended computational approach has been utilized to explore the reactions of acids with carbonyl oxide, also known as Criegee intermediate (CI). The reactions were explored inside water cluster containing 50 water molecules. All possibilities of product formation were considered. Among the considered acids, the rate of 1,4-insertion follows the order - HCOO < HCl < HNO3. The most stable products of the reactions between the considered acids and CI have been identified.

The mechanisms of Cp*Rh(OAc)2-catalyzed coupling reaction of N-methoxybenzamide with alkyl-terminated enyne have been investigated by density functional theory (DFT) calculations. With the addition of NaOAc and changing solvent, the product transforms from lactam P1 in reaction A to iminolactone P2 in reaction B, due to the formed stable OAc- coordinated intermediate. The electronic effect and steric effect account for the observed regioselectivity in reaction B collectively.

Single atom catalysts with iron ions in the active site, known as FeNC catalysts, show high activity for the oxygen reduction reaction and hence hold promise for access to low cost fuel cells. Due to the amorphous, multi-phase structure of the FeNC catalysts, the iron environment and its electronic structure are poorly understood. While it is widely accepted that the catalytically active site contains an iron ion ligated by several nitrogen donors embedded in a graphene-like plane, the exact structural details such as the presence or nature of axial ligands are unknown. Computational chemistry in combination with Mössbauer spectroscopy can help to unravel the geometric and electronic structures of the active sites. As a first step towards this goal, we present a calibration of computational Mössbauer spectroscopy for FeN4-like environments. The uncertainty of both the isomer shift and the quadrupole splitting prediction is determined, from which trust regions for the Mössbauer parameter predictions of computational FeNC models are derived. We find that TPSSh, B3LYP, and PBE0 perform equally well; the trust regions with B3LYP are 0.13 mm s−1 for the isomer shift and 0.45 mm s−1 for the quadrupole splitting. The calibration data is made publicly available in an interactive notebook that provides predicted Mössbauer parameters with individual uncertainty estimates from computed contact densities and quadrupole splitting values. We show that a differentiation of common FeNC Mössbauer signals by a separate analysis of isomer shift and quadrupole splitting will most likely be insufficient, whereas their simultaneous evaluation will allow the assignment to adequate computational FeNC models.

In thiswork,we have computed and implemented one-body integrals concerning gaussian confinement potentials over gaussian basis functions. Then, we have set an equivalence between gaussian and Hooke atoms and we have observed that, according to singlet and triplet state energies, both systems are equivalent for large confinement depth for a series of even number of electrons n = 2, 4, 6, 8 and 10. Unlike with harmonic potentials, gaussian confinement potentials are dissociative for small enough depth parameter; this feature is crucial in order to model phenomena such as ionization. In this case, in addition to corresponding Taylor series expansions, the first diagonal and sub-diagonal Padé approximant were also obtained, useful to compute the upper and lower limits for the dissociation depth. Hence, this method introduces new advantages compared to others.

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.

We have explored the structural and energetic properties of a series of RMX3–NH3 (M=Si, Ge; X=F, Cl; R=CH3, C6H5) complexes using density functional theory and low-temperature infrared spectroscopy. In the minimum-energy structures, the NH3 binds axially to a halogen, while the organic group resides in equatorial site about the metal. Remarkably, the primary mode of interaction in several of these systems seems to be hydrogen bonding (C-H–N), rather than a tetrel N-M interaction. This is particularly clear for the RMCl3–NH3 complexes, and analyses of the charge distributions of the acid fragment corroborate this assessment. We also identified a set of metastable geometries in which the ammonia binds axial to the organic substituent. Acid fragment charge analysis also provide a clear rationale as to why these configurations are less stable than their R-equatorial counterparts. In matrix-IR experiments, we see clear evidence of the minimum-energy form of CH3SiCl3–NH3, but analogous results for CH3GeCl3–NH3 are less conclusive. Computational scans of the M-N distance potentials for CH3SiCl3–NH3 and CH3GeCl3–NH3, both in the gas phase and bulk dielectric media reveal a great deal of anharmonicity, and a propensity for condensed-phase structural change.

Organometallic sandwich complexes have been attracting tremendous interest for their potential applications in electronics and spintronics. Here, we systematically studied the structures, electronic and magnetic properties of one dimensional (1D) transition metal (TM)-anthracene (Ant) sandwich molecular wires (SMWs), [TM2Ant]∞ and [TM3Ant]∞ (TM=Ti, V, Cr, Mn), based on density functional theory calculations. Our results showed that all the 1D SMWs display normal sandwich configurations with their binding energies closely related to the choice of TM atoms. Excepting 1D [Mn2Ant]∞ and [Fe3Ant]∞ favoring antiferromagnetic ordering, most 1D [TM2Ant]∞ and [TM3Ant]∞ SMWs display robust ferromagnetic feathers. Particularly, 1D [Cr3Ant]∞ SMW is revealed to be ferromagnetic half-metal with large magnetic moment of 28.0µB per unit cell. Further spintransport calculations double proved that 1D [Cr3Ant]∞ SMW are good spintransport molecular devices. Our findings shed light on the properties of 1D Ant based SMWs and propose a new way to design potential electronic and spintronic devices.

Ligand field theory (LFT) calculations of energy levels were performed for the neutral actinide monooxides (AnO) and their singly and doubly ionized cations (AnO+ and AnO2+ by treating the molecular electronic states as Anm+ free-ion energy levels (where An ∈ Th through Lr and m=1, 2, 3, or 4) perturbed by the electric field of O2- or O-. LFT parameters obtained from fits to the energy levels of ThO, ThO+, UO, and UO+ were used to compute molecular energy levels for the lowest energy (maximum Sc, maximum Lc) 5f-core states of An4+, An3+, An2+, and An+ for the majority of the An4+O2-, An3+O-, An3+O2-, An2+O-, An2+O2- , and An+O- electronic configurations. Simple linear relationships enabled predictions of the dissociation energies for AnO, AnO+ and AnO2+ (where An ∈ Bk through Lr) and ionization energies for AnO and AnO+ (where An ∈ Bk through Lr), mainly based on recent accurate experimental data for the ionization energies of An atoms (where An ∈ Fm, Md, No, and Lr) and correlations with the energetics of the atoms and ions.