The first-order relativistic corrections to the non-relativistic energies of hydrogen-like atom embedded in plasma screening environments are calculated in the framework of direct perturbation theory by using the generalized pseudospectral method. The standard Debye-Hückel potential, exponential cosine screened Coulomb potential, and Hulthén potential are employed to model different screening conditions and their effects on the eigenenergies of hydrogen-like atoms are investigated. The relativistic corrections which include the relativistic mass correction, Darwin term, and the spin-orbit coupling term for both the ground and excited states are reported as functions of screening parameters. Comparison with previous theoretical predictions shows that both the relativistic mass correction and spin-orbit coupling obtained in this work are in good agreement with previous estimations, while significant discrepancy and even opposite trend is found for the Darwin term. The overall relativistic-corrected system energies predicted in this work, however, are in good agreement with the fully relativistic calculations available in the literature. We finally present the scaling law of the first-order relativistic corrections and discuss the validity of the direct perturbation theory with respect to both the nuclear charge and the screening parameter.

The presence of long abandoned, hexagonal omega (ω) phase in steel samples is recently gaining momentum on account of accurate transmission electron microscopy (TEM) measurements. The formation and stabilization of this metastable phase down to room temperature is attributed to the combined effect of factors such as accelerated cooling, special atomic constraints at twin boundaries, and the enrichment of solute elements such as Al, Mn, Si, C, and Cr in the nanometer sized regimes. Here, we present a density functional theory (DFT) study of the effect of the above alloying elements in ω-Fe and confirm the predictions using high resolution TEM observations of the structure of an experimental steel at high magnifications. It is found that the FM and ++- spin states are the most stable for a primitive cell of ω-Fe. The density of states calculations show that the d band occupancy of ω-Fe is changing in presence of the alloying elements, and this in turn will affect the cohesive energy. Further, the dynamical stability analysis from phonon band structure reveals that only ω-Fe with substitutional C exhibits thermodynamic stability. This is in line with experimental indications that the stabilization of ω-phase in ferritic/martensitic steels occurs due to the presence of special symmetry constraints at grain boundaries

The time-dependent density functional theory (TD-DFT) was used to calculate the vibronic absorption spectrum of berberine (BER) in an aqueous solution. The best agreement with the experimental spectrum gives the O3LYP functional. Functionals with long-range correction showed poor agreement with experiment. The molecular orbitals of BER involved in the electronic transition during light absorption in the visible spectral region have been obtained. The dipole moments and atomic charges of the ground and excited states of the BER molecule have been calculated. Maps of BER electron density and electrostatic potential have been drawn. A significant photoinduced electron transfer from the outer di-oxygen five-membered heterocycle to the center of the BER chromophore has been found. According to our calculations, vibronic coupling and Boltzmann distribution play a significant role in the absorption spectrum of BER.

Local correlation methods rely on the assumption that electronic correlation is nearsighted. In this work, we develop a method to alleviate this assumption. The first step is to approximately decompose the electron correlation to the nearsighted and farsighted components based on the wavelength decomposition of electron correlation by Langreth and Perdew. The nearsighted component is then calculated using the recently developed embedded cluster density approximation (ECDA) which is a local correlation method formulated in the context of density functional theory. The farsighted component is calculated based on the system’s Kohn-Sham orbitals. The accuracy of this new method depends on the quality of the decomposition. We examined the method’s accuracy by patching the random phase approximation (RPA) correlation energy in a H₂₄ chain in which the electron correlation is highly nonlocal. This new method predicts bond stretching energies, RPA correlation potential, and Kohn-Sham eigenvalues in good agreement with the benchmarks. Our results demonstrate the importance of including the farsighted part of electron correlation for studying systems having nonlocal correlations.

Aiming at improving the visible-light photocatalytic activities of TiO2(101) surface (TiOS) we make an in-dept study on the TiOS doped with 4d transition metal (TM) atoms. It is shown that the 4d TM dopings can not only produce new impurity energy bands in the bandgap but also result in the semiconductor-metal phase transition. Consequently, the visible-light absorption is strongly strengthened due to the dopings of Y, Zr, Nb, Mo, and Ag, while it is only weakly improved for Tc, Ru, Rh, Pd, and Cd dopings. The improvement in visible-light absorption can be attributed to the intraband or interband transition of electrons. Moreover, the photocatalytic activities are explored, and we find Y and Ag dopings can effectively enhance the photocatalytic activity of TiOS. Thus the mechanism of improving photocatalytic activity of TiOS has been clearly addressed, which is beneficial to further experimental and theoretical researches on TiO2 photocatalysts.

Photovoltaic properties of the natural dyes of chlorophylls consist of Chl a, Chl b, Chl c2, Chl d, Phe a, Phe y and Mg-Phe a, were studied in the gas phases and water. The extension of the π-conjugated system, the substitution of the central Mg2+ and proper functional groups in the chlorophyll structures can amplify the charge transfer and photovoltaic performance. Chl a shows more favorable dynamics of charge transfer than other studied chlorophylls. Chl d, Phe a, Phe y and Mg-Phe a, have a greater rate of the exciton dissociation in comparison with Chl a, Chl b, and Chl c2 originated from a lower electronic chemical hardness, a lower exciton binding energy, and a bigger electron-hole radius. As a result, better efficiencies of the light-harvesting and energy conversion of the chlorophylls mainly appear in the Soret band. The LHE values of the chlorophylls in water show that solvent favorably affects the ability of light-harvesting of the photosensitizers. Finally, based on the energy conversion efficiency, Chl a, Phe a, and Mg-Phe a, are proposed as the best candidates for using in the dye-sensitized solar cells.

Hexagonal chains are a special class of catacondensed benzenoid system and phenylene chains are a class of polycyclic aromatic compounds. Recently, A family of Sombor indices was introduced by Gutman in the chemical graph theory. It had been examined that these indices may be successfully applied on modeling thermodynamic properties of compounds. In this paper, we study the expected values of the Sombor indices in random hexagonal chains, phenylene chains, and consider the Sombor indices of some chemical graphs such as graphene, coronoid systems and carbon nanocones.

Energetic compounds containing long nitrogen chain, have been a research hotspot. Fused heterocycles are stable due to their aromatic systems. The compound obtained by combining long nitrogen chain and fused ring can not only retain good energetic property, but also ensure better stability. This work designed eight fused heterocycle-based energetic compounds, 3H-tetrazolo[1,5-d]tetrazole (1) and its derivatives (2-8), containing a nitrogen chain with seven nitrogen atoms. The HOF, thermal stability, and energetic properties of these compounds were studied by using the DFT method. The results show that the introduction of -NO2, -N3, -NF2, -ONO2, -NHNO2 groups increased the density, HOF, detonation velocity, and detonation pressure greatly. The densities of 3, 5, 7, and 8 fall within the range designated for high-energy-density materials. The calculated detonation velocity of the compounds 3 and 8 are up to 9.86 km s-1 and 9.78 km s-1, which are superior to that of CL-20. The kinetic study of the thermal decomposition mechanism indicates that the N-R bonds maybe not the weakest bonds of these compounds. The tetrazole ring opening of the heterocycle-based energetic compounds, followed by N2 elimination is predicted to be the primary decomposition channel, whether or not they have substituent groups.

We report implementation of a hierarchical equations of motion (HEOM) module within the open-source Libra software. It includes the standard and scaled HEOM algorithms for computing the dynamics of open quantum systems interacting with a harmonic bath. The module allows computing evolution of the reduced density matrix as well as spectral lineshapes. The truncation, filtering, and “update list” schemes as well as OpenMP parallelization allow for further computational saving. The package is written in a mix of C++ and Python languages, delivering the best compromise between user friendliness and efficiency. The Python layer of the package takes advantage of standard Python libraries, such as h5py which allows efficient storage and retrieval of the generated results. The package can be seamlessly used within Jupyter notebooks; its careful design shall provide the maximal convenience and intuitiveness to its users.

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.

Density functional theory (DFT) was used to calculate the most stable structures of Gen (n=2-5) clusters as well as the adsorption energies of Gen (n=2-5) clusters after adsorbing single water molecule. The calculation of the reaction paths between Gen (n=2-5) and single water molecule shows that water molecule can react with Gen (n=2-5) clusters to dissociate to produce hydrogen, and O atoms mix with the clusters to generate GenO (n=2-5). According to the energy change of the reactions, the Ge2 cluster is the most efficient among Gen (n=2-5) clusters reacting with single water molecule. The NPA and DOS respectively proved that the Ge atoms in the product don’t reach the highest valence, and it was jointly predicted that GenO (n=2-5) might continue to react with more water molecules. Our findings contribute to better knowledge of Ge’s chemical reactivity, which could aid in the development of effective Ge-based catalysts and hydrogen-production methods.

The MERCURY consortium, established in 2000, has contributed greatly to the scientific development of faculty and undergraduates. The MERCURY faculty peer review publication rate from 2001-2019 of 1.7 papers/faculty/year is 3.4 times the rate of physical science faculty at primarily undergraduate institutions. We have worked with over 1000 students on research projects since 2001, and 75% of our undergraduate research students have been underrepresented in chemistry, either female or students of color. Approximately half of our alumni attend graduate school for the purpose of obtaining advanced degrees in STEM fields and 2/3 are female and/or students of color. We have had more than 1600 attendees at the 18 MERCURY conferences, including 111 invited speakers, 61 of whom have been female and/or faculty of color. In this paper the research accomplishments, transformational outcomes, and scientific productivity of the MERCURY faculty are highlighted.

The present work is intended to bring to the forefront a relatively less explored area of N-Heterocyclic Carbene (NHC) catalyzed alkyne hydro- thiolation and selenation reactions. The present work can be regarded as the first ever computational investigation on the catalytic activity of the NHC catalyzed hydro- thiolation and selenation reactions by exploring the reaction mechanism. Reaction mechanism involves chalcogenol activation followed by alkyne insertion and the second step is found to be the rate determining step. A comparison with the reported uncatalyzed gas phase reaction showed that a simple imidazol-2-ylidene catalyst can lower the free energy barrier by 19.62 and 14.63 kcal/mol respectively for acetylene hydro- thiolation and selenation reaction. All the employed NHCs are proved to be better catalyst for both hydrothiolation and hydroselenation. Effects of factors such as changing the heterocycle, increasing the conjugation, ring expansion and electronic/steric substitution were also investigated. Effect of solvent polarity on the reaction energetics and selectivity has also been analyzed employing THF, DMSO and MeOH as the solvents.

On the example of forty ion pairs, the study demonstrates how the core-level binding energy values can be calculated and used to plot theoretical spectra at a low computational cost using density functional theory methods. Three approaches for obtaining the binding energy values are based on delta Kohn–Sham (ΔKS) calculations, 1s Kohn–Sham orbital energies, and atomic charges. The ΔKS results show a good agreement between the available experimental X-ray photoelectron data. 1s Kohn–Sham orbital energies and atomic charges also correlate with the ΔKS results.

Carbon nanotubes (CNTs) have excellent catalytic activity in liquid phase reaction, especially in aerobic oxidation of cumene. In previous work, the conversion of cumene was 41.8% and the selectivity of cumene hydroperoxide was 71.5%, which was catalyzed by CNTs. But a small amount of impurity Zn2+ totally blocked up the aerobic oxidation of cumene that catalyzed by CNTs, which is an unexpected discovery. By analyzing the catalytic mechanism of CNTs, the inhibition effect of Zn2+ is locked on the abstraction of H atom from cumene. The inhibition of Zn2+ is confirmed in two effects by density functional theory (DFT) calculations. Firstly, due to the strongly coordination of active oxygen species (ROS) by Zn2+, the energy barrier of initial reaction increases to 1.90 eV, which is nearly 4 times higher than that of the only ROS promoted-process. Secondly, the interaction of Zn2+ and RO· or ROO· to inhibits the chain propagation reaction of free radicals. This work precisely demonstrates that the inhibition effect of Zn2+ on initial reaction of cumene. The most significant thing is that the effect of metallic heteroatoms is not negligible in organic oxidation reaction.

Isoprene (2-methyl-1, 3-butadiene (C5H8)) is one of the most prominent and abundant non-methane hydrocarbon existing in the lower level of the troposphere. In this work, possible reaction mechanism of chlorine (Cl) radical initiated isoprene and its subsequent reactions are investigated using quantum chemical methods. The calculated thermodynamic result shows that the reaction of isoprene with the Cl radical at the terminal C=C bond position plays an important role to predict the end products. The calculated rate coefficient for the reaction between isoprene and Cl radicals (Cl addition at C1, C3, C4 and C5 positions) is found to be 4.89⨯10-11, 6.91⨯10-10, 1.63⨯10-10 and 8.12⨯10-10 cm3/molecule/sec at 298K. The branching ratio and atmospheric lifetime have been calculated from the reaction rate coefficient values of isoprene+Cl. The reaction force analysis predicts Cl radical addition at the terminal C=C bond position plays a dominant role by structural rearrangement. The kinetic and thermodynamic results reveal that the electrophilic addition of Cl radical to the terminal carbon atom plays the dominant role in the marine boundary. Further, the subsequent reaction of Cl-isoprene adduct radical helps for the development of ozone layer during daytime.

A Majorana fermion is the single fermionic particle that is its own antiparticle. Its dynamics is determined by the Majorana equation, where the spinor field is by definition equal to its charge-conjugate field. In this paper, we investigated Shannon’s entropy of linear Majorana fermions to understand how this quantity is modified due to an external potential of the linear type linear. Subsequently, we turn our attention to the construction of an ensemble of these Majorana particles to study the thermodynamic properties of the model. Finally, we show how Shannon’s entropy and thermodynamic properties are modified under the linear potential action. KEYWORDS: Majorana Fermions; Thermodynamic properties; Shannon’s Entropy.

This work investigates possible improvements in the accuracy of semiempirical quantum chemistry (SQC) methods for the prediction of standard enthalpy of formation (Δ_f H^o) through the use of artificial neural network (ANN) with molecular descriptors. A total number of 142 organic compounds with enough structural diversity has been considered in the training set. Standard enthalpy of formation for the selected compounds at the semiempirical PM3 and PM6 quantum chemistry methods is collected from literature, and is calculated by using semiempirical PM7 method in this work. The multiple stepwise regression is first employed to screen effective molecular descriptors, which are highly correlated with the error terms of the standard enthalpy of formation compared with experimental values. The obtained 7 effective molecular descriptors are then used as input set to establish three 7-11-1 neural network-based correction models to improve the accuracy of SQC methods. By using the developed correction models, the mean absolute errors (MAE) for Δ_f H^oof PM3, PM6, and PM7 methods are reduced from 22.36, 18.60, 17.27to 9.86, 9.83, 8.95, respectively in kJ/mol. Meanwhile, the results of the test set show that the neural network does not have the problem of over-fitting. Detailed analysis of the 7 effective molecular descriptors indicates that the major source to the correction models is from the electron withdrawing effect. The developed ANN models for the three selected SQC methods provide an efficient method for the quick and accurate prediction of thermodynamic properties.