Lee-Yang-Parr Research Articles

Structural modification of V1274 moiety to red-shift its light absorption for optical and photovoltaic properties: A DFT molecular insight

In this study, we propose a theoretical strategy to enrich the electronic populations at V1274 core to develop new hole-transporting insulators (1–7) to red shift its maximum absorption (λmax). All calculations are performed using Coulomb Attenuated Method- Becke three parameter Lee–Yang-Parr (CAM-B3LYP) method at the Density Functional Theory (DFT) level. The photovoltaic results vary across different parameters as Open Circuit Voltage (Voc) ranges from 0.87 to 0.98 V, Fill factor (FF) ranges from 0.190 to 0.863, Short Circuit (Jsc) ranges from 26.10 to 48.38 mA/cm2, and Maximum Power (Pmax) ranges from −9.38 to 31.85 W. The λmax varies from 372 to 658 nm. This enhanced absorption capability by the push-pull effect indicates their effectiveness of the chromophores in absorbing light in that specific wavelength range. The significant new density of states (DOS) after adsorbing the designed chromophores onto the TiO2 cluster indicates potential changes in the electronic structure and properties of the material. The significant shift of λmax towards the near-infrared region after nitrogen replacement is important because it indicates improved light absorption in that range, which could enhance its suitability for applications such as near-infrared photodetection or solar energy harvesting.

Elucidating the crystal structures of heteronuclear salen complexes CuL-CdX2 with experimental and computational methods

Two novel heteronuclear salen-type complexes, CuL1-CdCl2 and CuL2-CdI2, have been successfully synthesized and characterized. The characterization processes utilized single-crystal X-ray diffraction, elemental, and FT-IR analysis, revealing the structural properties of the complexes. In both complexes, the Cu(II) ion exhibited an approximate square planar geometry (CuN2O2), where the deprotonated phenoxide-type ligand L2− coordinated to form N2O2. Conversely, For CuL1-CdCl2, the Cd(II) ion displayed a trigonal prismatic geometry, surrounded by two chlorine atoms and four oxygen atoms. Intermolecular and intramolecular interactions within the complex were facilitated by CH···Cl, CH···N, and CH···O hydrogen bondings. For CuL2-CdCl2, the Cd(II) ion displayed a trigonal prismatic geometry, surrounded by two iodine atoms and four oxygen atoms. Intermolecular interactions within the complex were facilitated by weak CH···I hydrogen bonding, while the overall stability of the framework was ensured through weak π···π stacking interactions. According to the Hirshfeld surface analysis results, the H···H contacts constitute a large part of the total surface area for both complexes; this highlights the importance of hydrogen bond interactions in stabilizing the crystal arrangement. The theoretical analysis of the complexes was executed by using Becke's three-parameter hybrid functional for the exchange component and the Lee-Yang-Parr (LYP) correlation function with the LanL2DZ basis set to achieve the optimized geometrical parameters. The results showed that experimental and theoretical calculations were in agreement.

Impact of the Position of the Hydroxyl Group in Monohydroxy Chalcones with 2-Hydroxypropyl-β-Cyclodextrin on Their Spectral, Biological, and Theoretical Properties

3-Hydroxychalcone (3HOCH) and 4-hydroxychalcone (4HOCH) compounds were synthesized from the reaction between acetophenone and either 3-hydroxybenzaldehyde or 4-hydroxy benzaldehyde, using KOH as a catalyst. Then the synthesized compounds were further reacted with two cyclodextrins (CDs) (2-hydroxypropyl-β-cyclodextrin and β-cyclodextrin), by a co-precipitation method to investigate their spectral (absorption, fluorescence, and Fourier transform infrared), biological, and theoretical properties. Two absorption maximums appeared at 307 and 253 nm for 3HOCH and 346 and 254 nm for 4HOCH in aqueous solution by absorption spectrophotometry. In the excited state, dual emission was observed at 362 nm and 426 nm for 3HOCH and 360 nm and 486 nm for 4HOCH in the same medium of H2O by fluorescence spectrophotometry. The apparent changes in the absorption and emission spectra were the result of the inclusion complex with a 1:1 molar stoichiometric ratio. The interaction of 3HOCH, 4HOCH, and the CDs in the solid state was characterized by Fourier-transform infrared spectroscopy (FTIR), powder X-ray diffraction patterns (PXRD), scanning electron microscopy (SEM), antioxidant and antibacterial studies concerning the position of the hydroxyl (-OH) group at the m- or p-positions in chalcone. The optimized highest occupied molecular orbital (HOMO) diagram, lowest unoccupied molecular orbital (LUMO) diagram and molecular electrostatic potential (MEP) map for the isolated molecules and their inclusion complexes were done by Becke’s three-parameter (B3) hybrid functional method using the Lee-Yang-Parr (LYP) correlation levels of density functional theory (DFT) method with 3-21 G basis set.

N-Nitrosamine sensing properties of novel penta-silicane nanosheets-a first-principles outlook.

N-Nitrosamine is one of the highly toxic carcinogenic compounds that are found almost in the entire environment. In the present work, novel penta-silicene (penta-Si) and penta-silicane (penta-HSi) are utilised to sense the N-nitrosamine in the air environment. Initially, structural firmness of penta-Si and penta-HSi is confirmed using cohesive energy. Subsequently, the electronic properties of penta-Si and penta-HSi are discussed with the aid of electronic band structure and projected density of states (PDOS) maps. The calculated band gap of penta-Si and penta-HSi is 0.251eV and 3.117eV, correspondingly. Mainly, the adsorption property of N-nitrosamine on the penta-Si and penta-HSi is studied based on adsorption energy, Mulliken population analysis along with relative energy gap changes. The computed adsorption energy range is in physisorption (- 0.101 to - 0.619eV), which recommends that the proposed penta-Si and penta-HSi can be employed as a promising sensor to detect the N-nitrosamine in the air environment. The structural, electronic and adsorption behaviour of N-nitrosamine on penta-Si and penta-HSi are studied based onthe density functional theory (DFT) approach. The hybrid generalized gradient approximation (GGA) with Becke's three-parameter (B3) + Lee-Yang-Parr (LYP) exchange correlation functional is used to optimise the base material. All calculations in the present work are carried out in Quantum-ATK-Atomistic Simulation Software.

Study the Electronic and Spectroscopic Characteristics of p-n Heterojunction Hybrid (Sn10O16/C24O6) via Density Functional Theory (DFT)

The electronic characteristics, including the density of state and bond length, in addition to the spectroscopic properties such as IR spectrum and Raman scattering, as a function of the frequency of Sn10O16, C24O6, and hybrid junction (Sn10O16/C24O6) were studied. The methodology uses DFT for all electron levels with the hybrid function B3-LYP (Becke level, 3-parameters, Lee–Yang-Parr), with 6-311G (p,d) basis set, and Stuttgart/Dresden (SDD) basis set, using Gaussian 09 theoretical calculations. The geometrical structures were calculated by Gaussian view 05 as a supplementary program. The band gap was calculated and compared to the measured values. The density of state of the hybrid junction (Sn10O16/C24O6) increased because of the increased number of degeneracy states. Theoretical values of bonds for C=C, C=O, and Sn-O are equal to 1.33, 1.20 and 2.27 Å respectively, these bonds values are in good agreement with experimental values of bond length of 1.34 for the C=C bond, 1.23 for the C=O bond, and 2.3 for the Sn-O bond. . The spectroscopic properties, such as IR spectra have shown a peak which is comparable to longitudinal modes of GO and tin dioxide SnO2 at (1582 and 690) cm-1, respectively.

Impact of Solvent Polarity on the molecular properties of Dimetridazole

Recently molecular activity of dimetridazole (DMZ) gained interested due to medical applications. In this study, a computational investigation of the solvent impact on solvation free energy, dipole moments, polarizability, hyper-polarizability and characteristic atomic properties; hardness and softness quality, chemical potential, electronegativity and electrophilicity have been accounted for DMZ. All forms of the calculation for both gas phase and solution phase used Becke 3-Parameter of Lee-Yang parr (B3LYP) theory with a 631++G basis set. Using the Solvation Model on Density (SMD), the effect of solvent polarity on solvation free energy, dipole moment, polarizability, hyper-polarizability and molecular properties were measured. The dipole moment of the DMZ was lower value in a gas phase comparative with solution phase. Furthermore, the electronegativity and chemical potential were increased from non-polar to polar solvents, while electrophilicity index was decreased. However, in case of chemical hardness & softness, the opposite relationship has been found. The results of this study contribute to an understanding of the molecular activity of DMZ, and stimulate its activity in solution phase. Keywords: Dimetrizole, Solvation model, Dipole moment, Solvent-free energy, Molecule polarizability.

Density functional study of atoms spatially confined inside a hard sphere

AbstractAn atom placed inside a cavity of finite dimension offers many interesting features, and thus has been a topic of great current activity. This work proposes a density functional approach to pursue both ground and excited states of a multi‐electron atom under a spherically impenetrable enclosure. The radial Kohn‐Sham (KS) equation has been solved by invoking a physically motivated work‐function‐based exchange potential, which offers near‐Hartree‐Fock‐quality results. Accurate numerical eigenfunctions and eigenvalues are obtained through a generalized pseudospectral method (GPS) fulfilling the Dirichlet boundary condition. Two correlation functionals, viz., (i) simple, parametrized local Wigner‐type, and (ii) gradient‐ and Laplacian‐dependent non‐local Lee‐Yang‐Parr (LYP) functionals are adopted to analyze the electron correlation effects. Preliminary exploratory results are offered for ground states of He‐isoelectronic series (Z = 2 − 4), as well as Li and Be atom. Several low‐lying singly excited states of He atom are also reported. These are compared with available literature results–which offers excellent agreement. Radial densities as well as expectation values are also provided. The performance of correlation energy functionals are discussed critically. In essence, this presents a simple, accurate scheme for studying atomic systems inside a hard spherical box within the rubric of KS density functional theory.

Molecular multibond dissociation with small complete active space augmented by correlation density functionals.

Molecular multibond dissociation displays a variety of electron correlation effects posing a challenge for theoretical description. We propose a CASΠ(M)DFT approach, which includes these effects in an efficient way by combining the complete active space self-consistent field method with density functional theory (DFT). Within CASΠ(M)DFT, a small complete active space (CAS) accounts for the long-range intrabond and middle-range interbond nondynamic correlation in the stretched bonds. The common short-range dynamic correlation is calculated with the Lee-Yang-Parr (LYP) correlation DFT functional corrected for the suppression of dynamic correlation with nondynamic correlation. The remaining middle-range interbond dynamic correlation is evaluated with the modified LYP functional of the bond densities. As a result, CASΠ(M)DFT potential energy curves (PECs) calculated in the relatively small triple-zeta basis closely reproduce the benchmark complete basis set PECs for the following prototype multibonded molecules: N2, CO, H2O, and C2.

Density functional theory based probe of the affinity interaction of saccharide ligands with extra-cellular sialic acid residues

Changes in glycosylation pattern leads to malignant transformations among the cells. In combination with upregulated actions of sialyltransferases, it ultimately leads to differential expression of sialic acid (SA) at cell surface. Given its negative charge and localization to extracellular domain, SA has been exploited for the development of targeted theranostics using approaches, such as, cationization and appending recognition saccharides on carrier surface. In this study, we have performed quantum mechanical calculations based on density functional theory (DFT) to study the interaction of saccharides with extracellular SA. Gradient-corrected DFT with the three parameter function (B3) was utilized for the calculation of Lee–Yang–Parr (LYP) correlation function. Atomic charge, vibrational frequencies and energy of the optimized structures were calculated through B3LYP. Our calculations demonstrate a stronger galactose–sialic acid interaction at tumour-relevant low pH and hyperthermic condition. These results support the application of pH responsive delivery vehicles and targeted hyperthermic chemotherapy for eradicating solid tumour deposits. These studies, conducted a priori, can guide the formulation scientists over appropriate choice of ligands and their applications in the design of ‘smart’ theranostic tools.

Correlation energy, correlated electron density, and exchange-correlation potential in some spherically confined atoms.

We report correlation energies, electron densities, and exchange-correlation potentials obtained from configuration interaction and density functional calculations on spherically confined He, Be, Be2+ , and Ne atoms. The variation of the correlation energy with the confinement radius Rc is relatively small for the He, Be2+ , and Ne systems. Curiously, the Lee-Yang-Parr (LYP) functional works well for weak confinements but fails completely for small Rc . However, in the neutral beryllium atom the CI correlation energy increases markedly with decreasing Rc . This effect is less pronounced at the density-functional theory level. The LYP functional performs very well for the unconfined Be atom, but fails badly for small Rc . The standard exchange-correlation potentials exhibit significant deviation from the "exact" potential obtained by inversion of Kohn-Sham equation. The LYP correlation potential behaves erratically at strong confinements. © 2016 Wiley Periodicals, Inc.

Towards improved local hybrid functionals by calibration of exchange-energy densities.

A new approach for the calibration of (semi-)local and exact exchange-energy densities in the context of local hybrid functionals is reported. The calibration functions are derived from only the electron density and its spatial derivatives, avoiding spatial derivatives of the exact-exchange energy density or other computationally unfavorable contributions. The calibration functions fulfill the seven more important out of nine known exact constraints. It is shown that calibration improves substantially the definition of a non-dynamical correlation energy term for generalized gradient approximation (GGA)-based local hybrids. Moreover, gauge artifacts in the potential-energy curves of noble-gas dimers may be corrected by calibration. The developed calibration functions are then evaluated for a large range of energy-related properties (atomization energies, reaction barriers, ionization potentials, electron affinities, and total atomic energies) of three sets of local hybrids, using a simple one-parameter local-mixing. The functionals are based on (a) local spin-density approximation (LSDA) or (b) Perdew-Burke-Ernzerhof (PBE) exchange and correlation, and on (c) Becke-88 (B88) exchange and Lee-Yang-Parr (LYP) correlation. While the uncalibrated GGA-based functionals usually provide very poor thermochemical data, calibration allows a dramatic improvement, accompanied by only a small deterioration of reaction barriers. In particular, an optimized BLYP-based local-hybrid functional has been found that is a substantial improvement over the underlying global hybrids, as well as over previously reported LSDA-based local hybrids. It is expected that the present calibration approach will pave the way towards new generations of more accurate hyper-GGA functionals based on a local mixing of exchange-energy densities.

Performance of Density Functional Methods. Some Difficult Cases for Small Systems Containing Cu, Ag, or Au

Twenty-six density functional theory (DFT) methods were tested in conjunction with three different effective core potentials (ECPs) and their corresponding valence basis sets, for studying the behavior of DFT methods in small systems containing Cu, Ag, or Au where it is well-known that some functionals fail. The DFT results were compared with those obtained with post Hartree-Fock methods: second-order many-body perturbation theory (MP2), coupled cluster singles-doubles (CCSD), and coupled cluster singles-doubles with perturbative triples, CCSD(T). Calculations were carried for M3 (M = Cu, Ag, Au); M4(-), (M = Cu, Ag) and [H2O-Cu](+2). The comparison of the DFT calculated values with the Post Hartree-Fock values showed that, in general, all generalized gradient approximation (GGA) type functionals fail to describe these systems. The hybrid GGA functionals (H-GGA) showed a better behavior; however, when the Lee-Yang-Parr (LYP) exchange-correlation functional was used, wrong results were obtained. The results with the hybrid meta (HM-GGA) functionals, as in the case of H-GGAs, showed that, to obtain similar results to MP2 or CCSD(T), it is necessary to have a high Hartree-Fock exchange percentage. Spurious results obtained with the H-GGA or HM-GGA methods can be eliminated increasing the Hartree-Fock exchange percentage in the H-GGA or HM-GGA type functionals. Among the different functionals tested, the BB1K and MPWB1K functionals showed the best agreement with the MP2 and CCSD(T) results.

Synthesis, Spectroscopy, Theoretical, and Electrochemical Studies of Zn(II), Cd(II), and Hg(II) Azide and Thiocyanate Complexes of a New Symmetric Schiff-Base Ligand

Synthesis of zinc(II)/cadmium(II)/mercury(II) thiocyanate and azide complexes of a new bidentate Schiff-base ligand (L) with general formula of MLX2(M = Zn(II), Cd(II), and Hg(II)) in ethanol solution at room temperature is reported. The ligand and metal complexes were characterized by using ultraviolet-visible (UV-visible), Fourier transform infrared (FT-IR),1H- and13C-NMR spectroscopy and physical characterization, CHN analysis, and molar conductivity.1H- and13C-NMR spectra have been studied in DMSO-d6. The reasonable shifts of FT-IR and NMR spectral signals of the complexes with respect to the free ligand confirm well coordination of Schiff-base ligand and anions in an inner sphere coordination space. The conductivity measurements as well as spectral data indicated that the complexes are nonelectrolyte. Theoretical optimization on the structure of ligand and its complexes was performed at the Becke’s three-parameter hybrid functional (B3) with the nonlocal correlation of Lee-Yang-Parr (LYP) level of theory with double-zeta valence (LANL2DZ) basis set using GAUSSIAN 03 suite of program, and then some theoretical structural parameters such as bond lengths, bond angles, and torsion angles were obtained. Finally, electrochemical behavior of ligand and its complexes was investigated. Cyclic voltammograms of metal complexes showed considerable changes with respect to free ligand.

The investigation of the low magnetic iron ores by EPR and their component FeO by DFT

The results of low magnetic ores investigations by EPR in X-band and their component FeO by DFT are presented in article. The laws in change of the absorption area, values of the g-factor and the intensities in samples depending on concentration FeO are found out. The presence at samples of the paramagnetic ions of the chromium and the manganese brings the features in laws of the absorption. The electronic configuration, equilibrium distance, total energy for FeO has been received in calculations using Hartree–Fock, Becke88 exchange potentials, Lee–Yang–Parr (LYP) correlation potential and combination potential B3-LYP.

Structural and electronic properties of gold microclusters: assessment of the localized Hartree–Fock method

We assess the localized Hartree-Fock (LHF) method for the simulation of the structural and electronic properties of gold microclusters. We compute the minimum-energy geometries, atomization energies, dipole moments, and single-particle spectra for five gold clusters, Au(N), and their anions, Au(N)-, with N < or = 4. Calculations are performed with the LHF functional, with and without the addition of the Lee-Yang-Parr (LYP) correlation, and the results are compared with those obtained from other semilocal and hybrid functionals as well as from Hartree-Fock calculations. The LHF functional yields structural properties of similar quality to the other exchange-only methods, but superior molecular orbital energies are found. The LHF single-particle spectrum is free of the artifacts typical for HF and standard DFT calculations and in good agreement with available experimental reference data. The inclusion of correlation by the LYP functional produces a significant improvement of geometries and energetics, but has only a minor impact on the orbital energies.

Dual‐level direct dynamics studies for the reactions of OH radical with bromine‐substituted ethanes

The dynamic properties of the multichannel hydrogen abstraction reactions of CH(3)CH(2)Br + OH --> products and CH(3)CHBr(2) + OH --> products are studied by dual-level direct dynamics method. For each reaction, three reaction channels, one for alpha-hydrogen abstraction and two for beta-hydrogen abstractions, have been identified. The minimum energy paths (MEPs) of both the reactions are calculated at the Becke's half-and-half (BH&H)-Lee-Yang-Parr (LYP)/6-311G(d, p) level and the energy profiles along the MEPs are further refined with interpolated single-point energies (ISPE) method at the G2M(RCC5)//BH&H-LYP level. There are complexes with energies less than those of the reactants or products located at the entrance or exit channels, which indicates that the reactions may proceed via an indirect mechanism. By canonical variational transition-state theory (CVT) the rate constants are calculated incorporating the small-curvature tunneling (SCT) correction in the temperature range of 220-2000 K. The agreement of the rate constants with available experimental values for two reactions is good in the measured temperature range. The calculated results show that alpha-hydrogen abstraction channel is the major reaction pathway in the lower temperature for two reactions, while the contribution of beta-hydrogen abstraction will increase with the increase in temperature.

Application of the Sakurai‐Sugiura projection method to core‐excited‐state calculation by time‐dependent density functional theory

The Sakurai-Sugiura projection (SS) method was implemented and numerically assessed for diagonalization of the Hamiltonian in time-dependent density functional theory (TDDFT). Since the SS method can be used to specify the range in which the eigenvalues are computed, it may be an efficient tool for use with eigenvalues in a particular range. In this article, the SS method is applied to core excited calculations for which the eigenvalues are located within a particular range, since the eigenvalues are unique to atomic species in molecules. The numerical assessment of formaldehyde molecule by TDDFT with core-valence Becke's three-parameter exchange (B3) plus Lee-Yang-Parr (LYP) correlation (CV-B3LYP) functional demonstrates that the SS method can be used to selectively obtain highly accurate eigenvalues and eigenvectors. Thus, the SS method is a new and powerful alternative for calculating core-excitation energies without high computation costs.

Extension of the Core-Valence-Rydberg B3LYP Functional to Core-Excited-State Calculations of Third-Row Atoms

A modified core-valence-Rydberg Becke's three-parameter exchange (B3) + Lee-Yang-Parr (LYP) correlation (CVR-B3LYP) functional is proposed in order to calculate core-excitation energies of third-row atoms with reasonable accuracy. The assessment of conventional exchange-correlation functionals shows that the appropriate portions of Hartree-Fock (HF) exchange for core-excited-state calculations depend on shells: 70% and 50% for K-shell and L-shell excitations, respectively. Therefore, the modified CVR-B3LYP functional is designed to use the appropriate portions of HF exchange, 70%, 50%, and 20%, for K-shell, L-shell, and valence regions separately. Time-dependent density functional theory calculations with the modified CVR-B3LYP functional yield both K-shell and L-shell excitation energies with reasonable accuracy. The modified CVR-B3LYP also provides valence-excitation energies and standard enthalpies of formation accurately. Thus, the modified CVR-B3LYP describes all of the K-shell, L-shell, and valence electrons appropriately.

Hybrid exchange-correlation functional for core, valence, and Rydberg excitations: Core-valence-Rydberg B3LYP

The core-valence-Rydberg Becke's three-parameter exchange (B3)+Lee-Yang-Parr (LYP) correlation functional (CVR-B3LYP) is proposed as a means to improve descriptions of Rydberg excitations of core-valence B3LYP (CV-B3LYP). CV-B3LYP describes excitations from both core and occupied valence orbitals to unoccupied valence orbitals with high accuracy but fails to describe those to Rydberg orbitals. CVR-B3LYP, which adopts the appropriate portions of Hartree-Fock exchange for unoccupied valence and Rydberg regions separately, overcomes the disadvantage of CV-B3LYP. Numerical assessment confirms that time-dependent density functional theory calculations with CVR-B3LYP succeed in describing not only core excitations but also Rydberg excitations with reasonable accuracy.

Time-dependent density functional theory (TDDFT) calculations for core-excited states: Assessment of an exchange functional combining the Becke88 and van Leeuwen–Baerends-type functionals

We propose and assess an exchange-correlation functional, BmLBLYP, in order to describe both core and valence excited states with high accuracy in the time-dependent density functional theory (TDDFT) calculations. The BmLBLYP functional is designed to adopt the modified van Leeuwen–Baerends (mLB) and the Becke 88 (B88) exchange functionals, combined with the Lee–Yang–Parr (LYP) correlation functional. The combination of BmLBLYP is based on the analysis that the LB94 functional behaves better for the core excitations than the B88 functional, while the opposite is true for the valence excitations. Numerical assessment confirms the high accuracy and wide applicability of the BmLBLYP functional.