Journal of Theoretical and Computational Chemistry

In the current study, the NO adsorption on the Si(100) surface was investigated by DFT including van der Waals forces (vdW). Stable molecular and dissociative configurations were found and compared to previous studies. Furthermore, additional states were investigated where NO adsorbs across dimers. The transformation of NO from molecular adsorbate into a dissociated adsorbate migrated into the subsurface was investigated by nudged elastic band. Several pathways were explored, either multi-staged, or direct from molecular into subsurface migrated configurations, both including and excluding vdW forces. The energy barriers of the single steps of multi-staged pathways never exceed 0.15eV and are, in general, smaller when NO is adsorbed across dimers rather than bridged on a single dimer and when including vdW. Furthermore, the oxygen-bridged configurations are kinetically more accessible than the nitrogen-bridged ones.

Density functional theory (DFT) calculations were used to investigate the gas phase reaction of U${}^{+}$ with COS to produce US${}^{+}+$CO and UO${}^{+}+$CS. It is shown that the two reactions are exothermic and the formation of UO${}^{+}+$CS has the lower energy barrier which agrees with the experimental result that UO${}^{+}$ is the main product. The reaction mechanisms and the potential energy profiles (CPEPs) considering different spin states were presented in detail. Diverse analyses including atoms in molecules, natural bond orbital were used to study the bonding properties of all the involved species.

Adsorption and interaction mechanisms of fullerene-based complex systems for possible drug delivery vehicles have been at the center of increasing attention. In the scope of this work, the interaction mechanism between an important antiviral drug favipiravir and silicon-doped/undoped C60 fullerenes have been investigated using density functional theory (DFT). Calculations were carried out in both gas phase and water media to see the possible solvent effects. The effect of adsorption of the favipiravir on the SiC59 fullerene system and the nature of interaction were examined by analyzing the band shifts in the carbonyl stretching vibrations and natural bond orbital (NBO) properties of the examined complexes. Some important structural and electronic properties were reported and discussed as well. It was observed that doping the C60 fullerene nanocages with silicon atom enhanced the adsorption mechanism and calculations performed in water media gave rise to more stable complexes for silicon-doped systems compared to the results obtained for the gas phase. Results and parameters found in the present search reveal further insights into the drug delivery systems.

A density functional theory (DFT) based multi-step simulation method is used to characterize the detailed molecular structure and inter/intra- molecular interactions of two benchmark liquid crystals (LC) 5CB, 8CB and a novel tri-biphenyl ring bent core LC material. The method uses hybrid DFT at the B3LYP/6-31G* level to obtain molecular structure and Raman data. These results are fed to a crystal packing simulation to find possible crystal structures. A pico-second quantum mechanics/molecular mechanics (QM/MM) simulation model is built for the selected structures with lower overall energy as well as optimal density. The stabilized crystal structures are then extended into a super cell, heated and simulated using a mixed force field and nano-second molecular dynamics (MD). The described simulation process sequence provides predictions of molecular Raman spectrum, LC density, isotropic depolarization ratio, ratio of differential polarizability, order parameters, molecular structures, and rotating Raman spectrum of the different mesophases. The Raman spectra, order parameters and depolarization ratios all agree well with existing experimental and previous simulation results. The study of the novel tri-biphenyl ring bent core LC system shows that the ratio of differential polarizability depends on intra-molecular interactions. The findings presented in this manuscript contribute to the on-going efforts to establish links between LC molecular structures and their properties, including optical behavior.

Two-dimensional optical catalysis materials have a wonderful potential application. Here, a new two-dimensional material consisting of the supported single-atom Au on a graphite carbon nitride (g-C₃N${}_4)$ single layer has been designed and its electronic and optical properties have been characterized by density functional calculations. The bandgap of 1.82eV calculated by the hybrid functional HSE06 shows that the Au/g-C₃N₄ is an indirect semiconductor, and the electron can easily be excited from the single-atom Au to the bottom of the conduction band. This material therefore has relatively strong optical properties in the visible region. Moreover, the process of Au insertion into the cavity of g-C₃N₄ single layer is energy-favorable. This work may provide insights and a new avenue for fabricating supported Au catalysts with high stability.

Lubricating additives can improve the lubricant performance of base oil in reducing friction and wear and minimizing loss of energy. It is of great significance to study the relationship between chemical structures and lubrication properties of lubricant additives. This paper reports a quantitative structure–property relationship (QSPR) model of the maximum nonseizure loads ($P_{\mathrm{\text{B}}}$) of 79 lubricant additives by applying artificial neural network (ANN) based on the algorithm of backward propagation of errors. Six molecular descriptors appearing in the multiple linear regression (MLR) model were used as vectors to develop the ANN model. The optimal condition of ANN with network structure of [6-4-1] was obtained by adjusting various parameters by trial-and-error. The root-mean-square (rms) errors from ANN model are $52.9N$ ($R=0.965$) for the training set and $61.4N$ ($R=0.940$) for the test set, which are superior to the MLR results of $98.5N$ ($R=0.873$) for the training set and $95.6N$ ($R=0.866$) for the test set. Compared to the existing model for $P_{\mathrm{\text{B}}}$, our model has better statistical quality. The results indicate that our ANN model can be applied to predict the $P_{\mathrm{\text{B}}}$ values for lubricant additives.

In this paper, some geometrical models such as Kohler, Muggianu, Toop, and Hillert have been used to estimate the molar volume of Au–Bi–Sn ternary systems based on the data of sub-binary systems over a wide temperature range (673–973K). The density of Au–Bi–Sn alloys was calculated from the calculated molar volume and using theoretical equation along three cross-sections $x_{\mathrm{\text{Au}}}$/$x_{\mathrm{\text{Bi}}}=1$/2, 1/1 and 2/1. In addition, the viscosity of Au–Bi–Sn alloys was calculated by using Seetharaman–Sichen equation over a wide temperature range (673–1273K). The density of these alloys show linear dependence on temperature for all investigated compositions, while the molar volumes increase with increasing temperature and Sn compositions. The results show, as a function of temperature, that the increase in concentration of tin influences the viscosity of the Au–Bi–Sn alloys. The calculated values of density of Au–Bi–Sn alloys are compared with the experimental values reported in the literature, and a good agreement was observed.

In this work, we applied a definition of informational energy and informational temperature using 1865 molecules and showed that such definitions can classify molecules with similar chemical properties such as hardness, softness and chemical potential.

Using complete orthogonal ${{ℒ}}^{(p_l^{*})}$-Self-Friction Polynomials (${{ℒ}}^{(p_l^{*})}$-SFPs) introduced by one of the authors, the analytical and power series formulas for SF atomic nuclear attraction integrals over $\chi$-noninteger Slater type orbitals ($\chi$-NISTOs) and $V$-noninteger Coulomb–Yukawa-like potentials ($V$-NICYPs) are presented, where ${\alpha }^{*}$ are the integer (${\alpha }^{*}=\alpha ,-\infty <\alpha \le 2)$ or noninteger (${\alpha }^{*}\ne \alpha ,-\infty <{\alpha }^{*}<3)$ SF quantum numbers and $p_l^{*}=2l+2-{\alpha }^{*}$. As an application, the computer calculations for dependence of the atomic nuclear attraction integrals over $\chi$-NISTOs and $V$-NICYPs functions are presented.

The present work aims at a better and deeper insight into the forces that govern the intramolecular charge transfer (ICT) and photo injection processes in dyes for dye sensitized solar cells (DSSC). The geometry, electronic structure, electron density distribution, and absorption spectra, for a selected donor-$\pi$-acceptor (D-$\pi$-A) dye for DSSC were computed and analyzed at a high level of DFT theory. The coplanar geometry of the studied dye (D1) indicates a strong conjugation which facilitates ICT. NBO analyses reveal that this ICT amounts to 0.8e, which is localized on the acceptor and anchoring groups resulting in a marked total delocalization interaction energy. The origin of this stabilization is two-fold; first the $\pi$-charge transfer (CT) interaction from donor to acceptor orbitals and the hyperconjugative interactions involving Rydberg states. The effect of fluorine substituents, in the $\pi$-spacer, on the quantum efficiency of DSSCs was investigated. Gibb’s free energy values, redox potentials, excited state life time, non-linear optical properties (NLO) and driving forces for D1 and its fluorinated derivatives were computed.