Category Archives: International Journal of Quantum Chemistry

State‐selected photo‐recombination cross sections of H‐like ions in the KLL resonant energy range

Posted on 13 September 2023 by nK Ma, nY Chun

The total and partial cross sections of PR are calculated for the H-like ions with electron energies covering KLL resonant region. The results show that the shape of the partial PR cross sections strongly depends on the recombined final state, where the partial cross-section shape exhibits obvious asymmetry. Moreover, the eigenphase was provided for each PR channel as an important scattering parameter, which can be used to study the time delay of the scattering process.

Abstract

We theoretically study the state-selected photo-recombination process of highly charged ions using the close-coupling approximation and the full relativistic Dirac R-matrix method combined with the Dirac Atomic R-matrix Codes (DARC). Focusing on the interference between the direct and indirect processes and the relativistic effects on the spin-orbit splitting, we calculate the total and partial photo-recombination cross sections of the H-like Ne9+$$ {}^{9+} $$, Cl16+$$ {}^{16+} $$, Fe25+$$ {}^{25+} $$, and Kr35+$$ {}^{35+} $$ ions. The energies of the incident electrons are considered as in the KLL$$ KLL $$ resonant regions, in which the initial state is the 1s$$ 1s $$ ground state of the H-like ions and the recombined states includes the ground state (1s2)1S0$$ {\left(1{s}^2\right)}^1{S}_0 $$ and six lower excited states (1s2s)1S0,3S1$$ {(1s2s)}^1{S}_0{,}^3{S}_1 $$, and (1s2p)3P0,1,2,1P1$$ {(1s2p)}^3{P}_{0,1,2},{\kern0.3em }^1{P}_1 $$ of the He-like ions. We utilize the multi-configuration Dirac-Fock method to calculate the target state wavefunctions, transition energies, and transition probabilities of both the one-electron one-photon (OEOP) and two-electron one-photon (TEOP) transitions from the resonant captured states to the recombined states. By analyzing the calculated atomic data, we identify all resonant peaks in each partial photo-recombination process, and our results agree well with the available results in literature. Our study reveals a significant interference effect in the photo-recombination cross sections, especially in the partial cross sections. Moreover, we present the eigenphase as a function of the electron energy for each partial photo-recombination channel.

Verbenone‐based push–pull chromophores with giant first hyperpolarizabilities: A new structure–property correlation study

Posted on 9 September 2023 by nHejing Sunn

Novel chromophores Ch1–8 based verbenone bridge were designed and systematically investigated using the BLA theory, two states model and SOS model. Chromophores Ch1–Ch8 exhibited distinct features in two-dimensional second order NLO responses, and the strong electro-optical Pockels effect and optical rectification responses.

Abstract

Novel chromophores Ch1–8 based verbenone bridge with various strong donors and acceptors were designed for applications in nonlinear optics, and the nonlinear optical (NLO) properties of those verbenone-type chromophores were systematically investigated using the bond length alteration (BLA) theory, two states model (TSM) and sum-over-states (SOS) model. The results show that several verbenone-based chromophores possess remarkably large molecular second-order hyperpolarizabilities, which is due to its electron distribution close to the cyanine limit, the appropriate strength of acceptor, rather large change in dipole moment and low excitation energy. Computed hyperpolarizability (β _tot ) of Ch6 also approach an outstanding 2922 × 10⁻³⁰ esu in TFE. The hyperpolarizability density analyses and two states model (TSM) were carried out to make a further insight into the origination of molecular nonlinearity of this unique system, suggesting that tuning structure of acceptor and polarity of the medium have great influence on the second-order nonlinear optical properties. More importantly, chromophores Ch1–Ch8 exhibited distinct features in two-dimensional second order NLO responses, and the strong electro-optical Pockels effect and optical rectification responses. The excellent electronic sum frequency generations (SFG) and difference frequency generations (DFG) effect are observed in these verbenone-type chromophores. These chromophores have a possibility to be appealing second-order nonlinear optical (NLO) materials, data storage materials and DSSCs materials from the standpoint of large β values, high LHE, and excellent two-dimensional second order NLO responses.

Molecular engineering of inorganic halide perovskites and HTMs for photovoltaic applications

Posted on 8 September 2023 by nFaezeh Pakravesh, nMohammad Izadyarn

Theoretical analysis of V-J behavior demonstrated that the highest V_OC and J_SC related to LiPbF₃ and KSnCl_3, respectively.

Abstract

A comprehensive study was performed for the design of ABX₃ perovskites, (A = Li, K, Na, B = Ge, Sn, Pb, X = F, Cl, Br, I) and organic hole transfer materials, HTMs (Fu-2a, Fu-2b, Fu-2c, and Dm-Q) for efficient perovskite solar cells (PSCs) through quantum chemistry calculations. Photovoltaic characteristics of the investigated perovskites are strongly affected by the halide anions. The results reveal that reducing the exciton binding energy of perovskites enhances the rate of the formation/dissociation of holes and electrons so F-based perovskites are superior from this viewpoint. Additionally, the electron and hole injection processes are more favorable in the case of the F-based perovskites in comparison with other studied perovskites. Moreover, spectroscopic properties of the perovskites demonstrate that KSnCl₃, NaSnCl₃, and F-based perovskites exhibit a greater ability of the light-harvesting and incident photon to current conversion efficiency. Ultimately, based on diverse analyses, F-based perovskites, KSnCl₃ and NaSnCl₃ are the preferred candidates to be applied in the PSCs due to an excellent incident photon to current conversion efficiency, light-harvesting efficiency, short circuit current, and solar cell final efficiency.

The performance of hybrid and F12∗$$ {}^{\ast } $$/F12c explicitly correlated coupled cluster methods for use in anharmonic vibrational frequency computations

Posted on 8 September 2023 by nAlexandria G. Watrous, nBrent R. Westbrook, nRyan C. Fortenberryn

The three components of the Taylor series approximation are computed via the F12-TcCR+$$ + $$DZ approach with the harmonics from F12-TcCR while the cubic and quartic terms are computed with F12-DZ. This method produces accurate results with relatively low computational cost.

Abstract

A hybrid quartic force field approach produces the same accuracies as non-hybrid methods but for less than one quarter of the computational time. This method utilizes explicitly correlated coupled cluster theory at the singles and doubles level inclusive of perturbative triples (CCSD(T)-F12b) in conjunction with a triple-ζ$$ \zeta $$ basis set, core electron correlation, and scalar relativity for the harmonic terms and CCSD(T)-F12b with a valence double-ζ$$ \zeta $$ basis set for the cubic and quartic terms. There is no sacrifice in the prediction of fundamental anharmonic vibrational frequencies or vibrationally-averaged rotational constants as compared to experiment, but the time saved is notable. Other hybrid methods are examined involving different sizes of basis sets and composite terms included or excluded. Not one is more accurate; only one is faster. F12∗$$ {}^{\ast } $$ (also called F12c) is tested as well, but it has an increase in computational time for no increase in accuracy. As such, this work reports a hybrid and composite approach (F12-TcCR+DZ) in the computation of rovibrational spectral data which can be applied to the observation of novel molecules in the gas phase in the laboratory and potentially even in astrophysical environments.

Electronic properties, quantum capacitance and photocatalyst for water splitting of Sc2CO2 MXene under uniaxial strain

Posted on 8 September 2023 by

Uniaxial strain can effectively modulate photocatalytic capacity for overall water splitting. Sc₂CO₂ under strains within appropriate pH scope are potential photocatalyst for water redox reaction. Sc₂CO₂ under tensile strain is potential cathode materials. Wide voltage keeps the electrode type of materials under strain. Sc₂C with mixed termination is further explored.

Abstract

MXenes have wide applications because of the structural flexibility and compositional diversity. Quantum capacitance, electronic and photocatalytic properties of Sc₂CO₂ monolayer under uniaxial strains are investigated by first-principles calculation. Sc₂CO₂ monolayer can withstand stress up to 13.96 N/M and about 14% tensile uniaxial strain limit. Sc₂CO₂ undergoes a transition from semiconductor to metal at −15% uniaxial strain. Sc₂CO₂ under uniaxial strains are only used for the water reduction at pH = 0. Sc₂CO₂ under uniaxial strains of −10%, −7%, −3%, 0%, and 4% within the appropriate pH scope are potential photocatalysts for water redox reaction. Sc₂CO₂ with −15% uniaxial strain is promising anode material, and Sc₂CO₂ with tensile uniaxial strain is more potential cathode material. Wide voltage improves the top quantum capacitance at negative bias under uniaxial strain and keeps the type of electrode materials. Quantum capacitance of Sc₂C with mixed termination (Sc₂CO_0.59F_1.19(OH)_0.22) under uniaxial strain is explored. The introduction of uniaxial strain and mixed termination has little effect on the electrode type of Sc₂CO₂ MXene.

Calculation of the moscovium ground‐state energy by quantum algorithms

Posted on 8 September 2023 by nV. A. Zaytsev, nM. E. Groshev, nI. A. Maltsev, nA. V. Durova, nV. M. Shabaevn

The possibility of simulating the electronic structure of ions and atoms by quantum algorithms is studied in the example of the moscovium atom. Among all tested approaches, the variational quantum eigensolver with the problem-inspired ansatz and Adam optimizer demonstrated the highest level of scalability while simultaneously providing a high level of accuracy for the ground-state energy.

Abstract

We investigate the possibility to calculate the ground-state energy of the atomic systems on a quantum computer. For this purpose we evaluate the lowest binding energy of the moscovium atom with the use of the iterative phase estimation and variational quantum eigensolver (VQE). The calculations by the VQE are performed with a disentangled unitary coupled cluster ansatz and with various types of hardware-efficient ansatze. The optimization is performed with the use of the Adam and quantum natural gradients procedures. The scalability of the ansatze and optimizers is tested by increasing the size of the basis set and the number of active electrons. The number of gates required for the iterative phase estimation and VQE is also estimated.

Hydrogen diffusion on (100), (111), (110) and (211) gold faces

Posted on 7 September 2023 by nNadezhda V. Dokhlikova, nMaxim V. Grishin, nSergey V. Doroninn

The surface diffusion barriers of H increase in the following Au series: (110) < (111) < (100) < (211). The presence of low-coordinated Au atoms significantly reduces the surface adsorption barrier of H. A U-shaped dependence of the surface diffusion energy of H on the centres of the s- and d-bands of the gold atoms has been revealed.

Abstract

Calculations showed that hydrogen adsorption into subsurface sites is most likely to occur on Au (110) and (211) faces. The presence of low-coordinated Au atoms on significantly reduces the barrier of subsurface adsorption of H. The barriers of H surface diffusion increase in the following Au series: (110) < (111) < (100) < (211). An analysis of the dependence of the surface diffusion barriers on the electronic structure of gold atoms on the respective faces revealed a U-shaped dependence of the centers of the s- and d-bands. This dependence is the result of the filling of the s- and d-bands on different faces of the gold. The results obtained suggest that it is possible to use band centers to determine surface diffusion barriers.

Density functional theory study of the isomerization conversion of the cluster ConMoS (n = 1–5)

Posted on 5 September 2023 by

This study employs density functional theory in conjunction with transition state theory to investigate the isomerization process of the clusters. The analysis predominantly centers on a comprehensive theoretical exploration, encompassing both chemical thermodynamics and dynamic considerations. Additionally, the study predicts the equilibrium constants and spontaneity associated with potential isomerization reactions.

Abstract

To investigate the isomerization transition of cluster Co_nMoS (n = 1–5), we employ density functional theory and transition state theory methods in this study. The cluster is optimized at the B3LYP/def2tzvp quantum chemical level. The results reveal eight isomerization reactions for the clusters Co _n MoS (n = 3, 5). Analyzing the activation energies shows a greater propensity for the isomerization transformation in the forward reaction compared to the reverse reaction. At room temperature, six isomerization transformation processes exhibit rapid conversion to the product configurations. Investigation of the equilibrium constants and application of the Arrhenius formula demonstrate that the cluster isomerization reactions are primarily driven by the forward reactions, with four reactions displaying efficient reactant to product conversion rates. Furthermore, there exists a consistent relationship between the structural complexity of the cluster and the change in entropy value. This study provides theoretical insights into reaction rates and optimization of reaction pathways, facilitating mutual validation and development between experimental and theoretical approaches.

Quotient of quotient graph a novel approach to compute π$$ \pi $$‐conjugated dendrimer and predict its properties

Posted on 4 September 2023 by nD. Antony Xavier, nS Akhila, nEddith Sarah Varghese, nTheertha Nair, nAnnmaria Babyn

Truxene, a polycyclic compound characterized by its unique C3$$ {C}_3 $$ topology and rigid planar structure, has interesting applications in the electronic and optoelectronic field. π$$ \pi $$-conjugated dendrimers have several potential applications in electronic and optoelectronic devices such as organic field-effect transistors, solar cells, and electroluminescent devices. Star-shaped molecules possess well-defined molecular structures as well as superior chemical purity and exhibit properties of strong blue emission. Different distance-based topological indices are computed for gradient star persistent π$$ \pi $$-conjugated dendrimer. This work helps to determine various properties of the dendrimers with truxenes which have application in disparate fields. Also, the graphical presentation may help in the comparative study of various properties and characteristics of the structure. Through linear regression, the photovoltaic, and electrochemical properties are compared with the π$$ \pi $$-conjugated dendrimer parameters and received excellent correlation.

Abstract

The role of dendrimers is getting updated and grabbing immense attention in many fields. Dendrimers are used in a broad spectrum, in specific, it is widely utilized in drug delivery, for targeted carrier and specific action. Also, in drug catalysis, it improves the solubility of poorly soluble drugs and increases the stability of active ingredients within the cores. Many researchers are interested in developing new dendrimers by using various compounds. π$$ \pi $$-conjugated dendrimers via truxenes and thienylethynylene units, are considered a promising material in the field of medicinal chemistry, bio-organic, and environmental sciences. In QSAR/QSPR, the structural analysis of chemical compounds is examined by topological descriptors. In this article, the various distance-based topological indices such as Wiener, Szeged, and Mostar of gradient star-persistent π$$ \pi $$-conjugated dendrimers are determined. Since gradient star-persistent π$$ \pi $$-conjugated dendrimers have odd cycles, the usual cut method is not applicable, therefore we use a new concept, the quotient of quotient graph to determine the numerical expression of various indices. An analysis of linear regression reveals that degree-based topological descriptors predict better physicochemical properties.

Ag‐based bimetallic clusters as catalysts for p‐nitrophenol reduction by glycerol: A DFT investigation

Posted on 1 September 2023 by nAkshita Khandelwal, nDanish Khan, nJyoti Kuntail, nIndrajit Sinhan

DFT calculation of Ni@Ag cluster interacting simultaneously with p-nitrophenol and glycerol molecules.

Abstract

Reducing p-nitrophenol (PNP) to p-aminophenol is an industrially relevant synthesis. Nevertheless, only a few heterogeneous catalysts have been evaluated for the reduction of PNP by glycerol. Appropriate quantum computational studies can screen potential catalysts for this crucial green reaction. The present research investigates the catalytic activities of Pd@Ag and Ni@Ag core-shell nanogeometries toward PNP reduction by glycerol through density functional theory (DFT) calculations. The central atom of a geometry-optimized 13-atom Ag cluster was replaced by Pd and Ni atoms to create the core-shell morphologies. The interaction energies of PNP and glycerol with each of the (metal/bimetallic) clusters were evaluated by DFT calculations to find the best PNP and glycerol molecule orientation with the respective bimetallic cluster. Electrostatic potential surface and natural bond orbital analyses were performed to study the charge distribution and transfer between atomic orbitals. The frequencies of vibrational modes in isolated PNP/glycerol structures were compared to those when these molecules were in the presence of the different metal clusters to infer the effect of the interactions. All performed analyses indicated improved catalytic activity toward PNP reduction by glycerol upon Ni-doping of the Ag₁₃ cluster.