Category Archives: International Journal of Quantum Chemistry

Strong‐field coherent control of the proton momentum distribution arising from the n$$ n $$‐photon (n=1,2,3$$ n=1,2,3 $$) field‐dressed adiabatic potentials of H2+$$ {}_2^{+} $$

Posted on 31 August 2023 by nMohammad Noh Daudn

Proton distributions in dissociative-ionization of 2+$$ {}_2^{+} $$ are controlled by manipulating parameters of the strong field laser pulse to yield the desired distributions we want to aim for. The captured images of the distributions have advanced our knowledge of controlling a chemical reaction in more systematic ways. In this study, I have successfully controlled the proton distributions to move preferentially in one direction namely to the right side of H-H⁺ molecule using a specific laser parameter.

Abstract

A systematic directionality coherent control of total proton momentum distributions in the dissociative-ionization of H2+$$ {}_2^{+} $$ subjected to a strong field of six-cycle laser pulses in a full range of carrier-envelope phase ϑ$$ \vartheta $$ is studied by solving a non-Born-Oppenheimer time-dependent Schrödinger equation numerically. The trend of distributions involves insightful investigation into the spatial-temporal overlap between nuclear wave packets evolving on the coupled field-dressed electronic potentials of H2+$$ {}_2^{+} $$ associated with the n$$ n $$-photon potential crossings. This leads to new quantum images for the nonlinear nonperturbative interaction of H2+$$ {}_2^{+} $$ with a strong field. It turns out that the symmetry of the ϑ$$ \vartheta $$-dependent momentum distribution begins to break after undergoing interaction with one-photon field-dressed potentials. At this point, the most probable proton momentum distribution tends to move in a forward direction indicating also that the three-photon field-dressed potentials strongly govern the dissociative-ionization pathway.

Phase‐space relative Rényi entropy in density functional theory

Posted on 28 August 2023 by nÁgnes Nagyn

The phase-space relative Rényi entropy is introduced using the information theoretical and thermodynamic view of density functional theory. In the special case of constant inverse temperature the phase-space relative Rényi entropy is a sum of the position-space relative Rényi entropy and a term arising from the momentum space. This quantity can be considered as a measure of similarity. It includes more information than the position-space measures, it also incorporates momentum-space knowledge.

Abstract

The phase-space relative Rényi entropy is introduced using the information theoretical and thermodynamic view of density functional theory. In the special case of constant inverse temperature the phase-space relative Rényi entropy is a sum of the position-space relative Rényi entropy and a term arising from the momentum space. This quantity can be considered as a measure of similarity. It includes more information than the position-space measures, since it also incorporates momentum-space knowledge.

Revisiting the structure and dynamics of hydrated Cd2+ in aqueous solutions: Insights from the RI‐SCS‐MP2/MM molecular dynamics simulation

Posted on 28 August 2023 by nNiko Prasetyo, nAlberto Krishna Ksatria Winning Kusuma, nLa Ode Muhammad Iqbaln

The MP2 QM/MM MD simulation revealed that Cd²⁺ is coordinated with mostly six water molecules in the first hydration shell with numerous ligand exchange events during the simulation time of 200 ps.

Abstract

The spin component scale MP2/molecular mechanics molecular dynamics simulation investigated the hydration shell formation and hydrated Cd²⁺ dynamics in the water environment. At the first hydration shell, six water molecules with 2.27 Å for the average distance between water and Cd²⁺. Dynamical properties were analyzed by computing the water molecule's mean residence time (MRT) in its first and second hydration shells. The MRT of each shell was determined to be 31.8 and 1.92 ps, suggesting the strong influence of Cd²⁺ in the first hydration shell. The second shell was labile, with an average number of water molecules being 18. Despite the strong interaction between Cd²⁺ and water molecules in the first shell, the influence of ions in the second hydration shell remained weak.

Bond dissociation energies of the fifth‐row elements (InI): A quantum theoretical benchmark study

Posted on 28 August 2023 by nIsmail Badran, nKotaybah Hashlamoun, nNashaat N. Nassarn

Compounds containing fifth-row elements, such as In, Sn, Sb, Te, and I, present a challenge to computational chemistry. The BDE of these compounds were calculated using ab-initio methods, including some popular DFT functionals, as well as MP2 and CCSD(T). The top-performing functionals were MN12SX, MN15L, B3P86, and M062X.

Abstract

The bond dissociation energies (BDE) of most main-group elements have been accurately measured. However, the BDE values for heavy elements, particularly those from the fifth period (InI), are still missing or poorly validated. This study aims to identify the most accurate computational methods for calculating BDE values of compounds containing fifth-row elements, including In, Sn, Sb, Te, and I, with a focus on readily accessible methods in software packages. The investigation involved a benchmark study using density functional theory (DFT), in addition to the 2nd order Møller–Plesset perturbation theory (MP2) and the coupled cluster with single, double, and perturbative triple excitations CCSD(T). The DFT functionals used in the study include APFD, B3LYP, B3LYP-D3, B3P86, B97-D3, BHandH, HSEH1PBE, M06-2X, MN12-SX, MN15-L, and TPSSH. The functionals were carefully selected to cover some popular functionals as well as to cover all levels of the Jacob's ladder of DFT accuracy. The computed BDE values were compared with experimental values, and the results were filtered to remove any possible outliers. The statistical errors (MAPE, RMSE, and Pearson's) were then calculated and used to assess the performance of the methods.

Study on the microscopic mechanism of adsorption and diffusion of hydrocarbon oil drops on coal surface using molecular dynamics simulations

Posted on 26 August 2023 by nDan Zhao, nXiaoqing Liun

Spreading characteristics of hydrocarbon oil drops on coal surfaces.

Abstract

Flotation of fine coal particles usually uses oil collectors, but the micromechanisms need to be more refined due to the complex structure and abundant functional groups on the surface of coal bodies. The adsorption spreading behavior and interfacial properties of nonpolar oil drops on flat low-order coal (LOC) and high-order coal (HOC) surfaces were investigated in depth using molecular dynamics (MD) simulations, while the effects of different functional groups on LOC surfaces were also considered. The results showed that the contact angle, contact area and interaction energy of oil drops adsorbed on the LOC and HOC surfaces at simulated equilibrium in aqueous environment were 77.68°, 621.49 Ų, −140.94 kcal/mol; 53.98°, 962.14 Ų, and −195.13 kcal/mol, respectively. The smaller the equilibrium contact angle between the oil drops and the surface, the larger the contact area and the larger the absolute value of the interaction energy, the better the spreading effect of the oil drops and the easier the surface is to flotation. Compared with the HOC surface, the oil drops could not displace the water molecules on the LOC surface better and spread poorly on its surface, and the migration rate was higher. This was caused by the abundant functional groups on the surface of LOC. The type of functional group significantly affects the interaction of nonpolar oil drops with hydrophilic surfaces, with the order of adsorption strength being CH₃ > COCH₃ > OH > COOH. The formation of a dense hydrated film of oil drops on the COOH surface was an important reason for the difficulty of flotation on the LOC surface. MD elucidated the mechanism of action of nonpolar oil collectors on LOC and HOC surfaces, which is a guide for efficient flotation on LOC surfaces.

Szeged index of hollow hexagons

Posted on 26 August 2023 by nCarolina Lopera, nRoberto Cruzn

We compute the values of Szeged index of hollow hexagons using the cut method. Hollow hexagons are primitive coronoid systems with exactly six angularly annelated hexagons. The cut method is used to compute the value of the index in terms of the Szeged index of weighted quotient graphs with respect to a c-partition of the edge set.

Abstract

The Szeged index of a connected graph G$$ G $$ (Sz(G)$$ Sz(G) $$) is a well known distance based topological index. A primitive coronoid system is a coronoid system formed by a single chain in a macro-cyclic arrangement consisting of linearly and angularly annelated hexagons. The angular hexagons are called corners. A hollow hexagon is a primitive coronoid system with exactly six corners. In this paper we calculate the values of Szeged index of hollow hexagons using the cut method.

Predicting the multiple parameters of organic acceptors through machine learning using RDkit descriptors: An easy and fast pipeline

Posted on 25 August 2023 by

Machine learning analysis is used for predicting the multiple parameters of organic acceptors using RDkit descriptors. The developed methodology can help to predict the efficient acceptors in a short time and less computational cost.

Abstract

Machine learning (ML) analysis has gained huge importance among researchers for predicting multiple parameters and designing efficient donor and acceptor materials without experimentation. Data are collected from literature and subsequently used for predicting impactful properties of organic solar cells such as power conversion efficiency (PCE) and energy levels (HOMO/LUMO). Importantly, out of various tested models, hist gradient boosting (HGB) and the light gradient boosting (LGBM) regression models revealed better predictive capabilities. To achieve the prediction effectively, the selected (best) ML regression models are further tuned. For the prediction of PCE (test set), the LGBM shows the coefficient of determination (R ²) value of 0.787, which is higher than HGB (R ² = 0.680). For the prediction of HOMO (test set), the LGBM shows R ² value of 0.566, which is higher than HGB (R ² = 0.563). However, for the prediction of LUMO (test set), the LGBM shows R ² value of 0.605, which is lower than HGB (R ² = 0.606). Among the three predicted properties, prediction ability is higher for PCE. These models help to predict the efficient acceptors in a short time and less computational cost.

A quantum chemical prediction on arc interruption capability of the dielectric gases

Posted on 23 August 2023 by nMi Zhang, nHua Hou, nBaoshan Wangn

A priori quantum chemical model based on the electrostatic potential surfaces has been developed to predict the arc interruption capability of the dielectric gases straightforwardly by electronic descriptors. In terms of the rate of rise of the recovery voltage, the structure–activity relationship model is viable for the virtual screening of novel arc-quenching replacement gases for SF₆, which is superior to the routine fluid magneto-hydrodynamic model.

Abstract

The use of sulfur hexafluoride (SF₆) as an electrical insulator and arc-quenching gas in high-voltage equipment raises serious environmental concerns. The search of a replacement gas for SF₆ is hindered by a priori assessment on its interruption performance. The routine fluid or mathematic magneto-hydrodynamic models for arc burning and extinguishing are too complex to be practical for virtual screening. Herein a state-of-the-art quantum chemical model to predict the interruption capability of the dielectric gases straightforwardly has been established in terms of the rate of rise of the recovery voltage (RRRV). On the basis of the molecular electrostatic potentials, five sets of descriptors, including the global statistical parameters vσ2$$ {v\sigma}^2 $$ and Π$$ \Pi $$, the site-specific parameter ΔV _s, the total positive surface area A _s ⁺, augmented with the product of polarizability and dipole moment αμ, were optimized to reveal the inherent mechanisms for interruption and thus a viable structure–activity relationship mode for RRRV has been developed with the correlation coefficient 0.975. Theoretical RRRV relative to SF₆ = 100 for all the known dielectric gases are in good agreement with the experimental data by a mean absolute deviation of 3.6. Accordingly, the perfluorinated cycloalkenes and alkynes, in particular, 1,3,3,3-tetrafluoropropyne, are found to be the promising candidates as the replacement dielectric gases for SF₆.

Study on the sensing characteristics of two‐dimensional material WTe2 to toxic gases HF and Cl2

Posted on 23 August 2023 by

The gas sensing characteristics of monolayer WTe₂ to toxic gases are studied by doping atoms, applying vertical electric field and drawing current–voltage curve, which provides important reference value for the development of gas sensors and the detection and recovery of toxic gases in the future.

Abstract

The adsorption characteristics of gas molecules HF and Cl₂ on monolayer WTe₂ surface are studied by first-principles calculation method. The results show that monolayer WTe₂ is more sensitive to gas molecule Cl₂. The adsorption performance of monolayer WTe2 to gas molecule HF cannot be improved by doping atoms. When the upward vertical electric field is applied, the sensitivity of monolayer WTe₂ to gas molecule Cl₂ is improved, and when the downward vertical electric field is applied, the monolayer WTe₂ shows an obvious desorption trend to gas molecule Cl₂. The vertical electric field cannot significantly enhance the interaction between gas molecule HF and Ag-doped monolayer WTe₂. Our research confirms that monolayer WTe₂ is more sensitive to gas molecule Cl₂ and can be improved or desorbed by the vertical electric field, while that of monolayer WTe₂ for gas molecule HF cannot significantly change. Furthermore, the electrical transport characteristics of monolayer WTe₂ and Cl₂-WTe₂ system are studied to better explain the reason for the higher sensitivity to gas molecule Cl₂. The research results of this paper provide theoretical guidance for the experimental preparation of high sensitivity gas sensor based on two-dimensional transition metal dichalcogenide WTe₂.

Bound state calculations for Hulthén–Hellmann type potential by improved asymptotic iteration method

Posted on 22 August 2023 by nZeynel Yalçınn

Coulomb and Hulthén–Hellmann potential versus r for A = 0.002, B = 2, C = 1, α = 0.001

Abstract

In this study, some nonrelativistic energy eigenvalues of Hulthén–Hellmann type interaction were calculated using the improved asymptotic iteration method (improved AIM) by applying the Greene–Aldrich approach for the inverse square term of the potential. Calculations have also been made for some special cases of the Hulthén–Hellmann potential. It is seen that the results obtained are in excellent agreement with those previously obtained from other methods.