Density Functional Theory Approach Research Articles

Exploration of nonlinear optical enhancement in acceptor-π-donor indacenodithiophene based derivatives via structural variations: a DFT approach.

Herein, a series of indacenodithiophene-based derivatives (TNPD1-TNPD6) were designed having D-π-A architecture via end capped acceptor modulation of a reference molecule (TNPR) to investigate nonlinear optical (NLO) behavior. Quantum chemical calculations were accomplished to examine electronic, structural and optical properties utilizing a density functional theory (DFT) approach at M06 functional with 6-311G(d,p) basis set. For this, natural bond orbitals (NBOs), density of states (DOS), frontier molecular orbitals (FMOs), transition density matrix (TDM) and non-linear optical (NLO) analyses were performed for TNPR and TNPD1-TNPD6. The structural modifications revealed a significant electronic contribution in tuning the HOMOs and LUMOs of the derivatives with lowered energy gaps and wider absorption spectra. FMOs findings revealed that compound TNPD5 was found with the lowest energy gap (1.692 eV) and with the highest softness (0.591 eV-1) among the derivatives. Furthermore, a UV-Vis study also disclosed that maximum absorption (λmax = 852.242 nm) was exhibited by TNPD5 in chloroform solvent. All the derivatives exhibited significant NLO results; in particular, TNPD5 showed the highest first hyper-polarizability (βtot = 4.653 × 10-27 esu) and second hyper-polarizability (γtot = 9.472 × 10-32 esu). These DFT findings revealed that the end-capped substituents play a key role in enhancing the NLO response of these push-pull chromophores and the studied derivatives can be utilized as efficient NLO materials.

End group modulation of A-D-A type small donor molecules for DTP based organic photovoltaic solar cells: a DFT approach.

Here, five new acceptor-donor-acceptor (A-D-A) type small donor molecules C1-C5, have been designed based on the central D unit, dithieno[3,2-b:2',3'-d]pyrrole (DTP). Besides, five different A units, viz. 1,1-dicyano-methylene-5,6-dimethyl-3-indanone, 1,1-dicyano-methylene-5,6-difluoro-3-indanone, 1,1-dicyano-methylene-5,6-dichloro-3-indanone, 1,1-dicyano-methylene-5-nitro-3-indanone, and 1,1-dicyano-methylene-5,6-diamino-3-indanone are selected for these designed compounds C1-C5, respectively. Density functional theory (DFT) and time-dependent density functional theory (TD-DFT) methods have been employed to study the influence of different A units on the geometric, electronic, optical, charge transport and photovoltaic properties of the designed donor molecules. The results reveal that the performance of the designed donor molecules have been improved on attachment of the strong electron withdrawing A units. The observed reorganization energy (λ) values infer the electron donating nature of the designed compounds. Moreover, the absorption properties of the designed compounds manifest that compound C4 possesses the high values of maximum wavelength (λmax) in both gas and solvent phases. The properties of the D/A blends reveal that all designed blends C1-C5/C60-CN, have the capacity to promote charge carrier separation at the D/A interface. Further, the photovoltaic performance of the D/A complexes also reveal that complex C4/C60-CN, with a theoretical PCE of 18%, can be considered as the most promising candidate for application in OSCs.

The influence of Holmium substitution on the magnetic and mechanical properties of Nd2Fe14B: a first principle study

In this study, the ab initio density functional theory (DFT) approach is used to investigate the effect of Holmium (Ho) on the magnetic and mechanical properties of Nd2Fe14B magnets. Neodymium-based permanent magnets (Nd2Fe14B) are the potential permanent magnets to be used in various applications such as wind turbines and electric vehicles. These magnets possess high magnetic field strength and resistance to demagnetization. However, they suffer from low operating temperatures below 585 K. Substitution of Nd with Ho enhances the magnetic strength of the Nd2Fe14B permanent magnet. NdHoFe14B magnets are found to be thermodynamically stable due to negative heats of formation, which is in good agreement with the calculated density of states. Partial substitution of Nd with Ho improves the stability and the magnetic strength of Nd2Fe14B permanent magnets. The findings will provide insight into the future development of permanent magnetic compounds with good magnetic strength.

New insights into band inversion and topological phase of TiNI monolayer.

Two-dimensional (2D) topological insulators (TIs) hold great promise for future quantum information technologies. Among the 2D-TIs, the TiNI monolayer has recently been proposed as an ideal material for achieving the quantum spin Hall effect at room temperature. Theoretical predictions suggest a sizable bandgap due to the spin-orbit coupling (SOC) of the electrons at and near the Fermi level with a nontrivial 2 topology of the electronic states, which is robust under external strain. However, our detailed first-principles calculations reveal that, in contrast to these predictions, the TiNI monolayer has a trivial bandgap in the equilibrium state with no band inversion, despite SOC opening the bandgap. Moreover, we show that electron correlation effects significantly impact the topological and structural stabilities of the system under external strains. We employed a range of density functional theory (DFT) approaches, including HSE06, PBE0, TB-mBJ, and GGA+U, to comprehensively investigate the nontrivial topological properties of this monolayer. Our results demonstrate that using general-purpose functionals such as PBE-GGA for studying TIs can lead to false predictions, potentially misleading experimentalists in their efforts to discover new TIs.

SYNTHESIS, SPECTRAL CHARACTERIZATION, DFT AND DOCKING STUDIES OF 5-(4-CHLOROPHENYL)-3-(COUMARIN-3-YL)-1H-PYRAZOLE AND 5-(4-CHLOROPHENYL)-3-(COUMARIN-3-YL)ISOXAZOLE

Five membered hetrocyclic moieties have been proven to possess strong biological activities. The compounds5-(4-chlorophenyl)-3-(coumarin-3-yl)-1H-pyrazoleand 5-(4-chlorophenyl)-3-(coumarin-3-yl)isoxazole were synthesized and characterized by IR,1H and 13C NMR, and high-resolution mass spectrometry.The structural optimization and the interpretation of theoretical vibrational spectra is made by the Gaussian 09 software and the B3LYP/6-31G density functional theory (DFT) approach. Bond lengths, bond angles have all been studied. The Mulliken population analysis on atomic charges is performed. The thermodynamic stability in the ground state and reactivity of the compounds in the excited state are explained by the HOMO–LUMO energy gap. The molecular docking study is carried out usingPyRx. The anti-oxidant activities of the derivatives were determined by DPPH scavenging assay. The synthesized compound showed remarkable antioxidant activity. The newly synthesized compound were tested for their anticancer activity against HeLa cell line in vitro by MTT assay method.

Impacts of external fields on aromaticity and acidity of benzoic acid: a density functional theory, conceptual density functional theory and information-theoretic approach study.

The impact of external fields on the molecular structure and reactivity properties has been of considerable interest in the recent literature. Benzoic acid as one of the most widely used compounds in medicinal and materials sciences is known for its dual propensity in aromaticity and acidity. In this work, we systematically investigate the impact of a uniform external electric field on these properties. We apply density functional theory, conceptual density functional theory, and an information-theoretic approach to appreciate the change pattern of aromaticity and acidity properties in external fields with different strengths. Our results show that they possess different change patterns under external fields, which can be satisfactorily rationalized by variations in reactivity descriptors and partial charges. The surprising yet novel results from this study should enrich the body of our knowledge about the impact of external fields for different kinds of electronic properties and provide guidance and foundation for future studies of this phenomenon in other molecular systems.

Synthesis, DFT and antioxidant studies of 2-(alkylamino)-4-(naphth-2-yl) thiazole

2-(Alkylamino)-4-(naphth-2-yl)thiazoles have been synthesised from 2-bromoacetyl naphthalene and characterized by UV, IR, and 1H NMR. The geometry of the molecules is optimised using the Gaussian 09 software programme and the B3LYP/6-31G density functional theory (DFT) approach. The bond lengths, bond angles, and dihedral angles of 2- (alkyamino)-4-(naphth-2-yl)thiazoles have been studied. Vibrational bands to distinct structural groups and their relevance have been predicted using vibrational spectra analysis and shown to be reliable when compared to experimental data and with literature observations. Atomic charges have been estimated using the Mulliken population analysis. The charge transfer within the molecule is confirmed by the computed energy gap between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO). The molecular docking study has been carried out.

A wide-range semiclassical self-consistent average atom model

The discovery of material properties at extremes, which are essential for high energy density physics development, requires the most advanced experimental facilities, theories, and computations. Nowadays, it is possible to model properties of matter in such conditions using the state-of-the-art density functional theory (DFT) or path-integral Monte Carlo approaches with remarkable precision. However, fundamental and computational limitations of these methods impede their practical usage, while wide-range thermodynamic and transport models of plasma are required. As a consequence, an average atom (AA) framework is still relevant today and has been attracting more and more attention lately. The self-consistent field and electron density in an atomic cell is usually obtained using the Thomas–Fermi (TF), Hartree–Fock, Kohn–Sham approaches, or their extensions. In this study, we present the AA model, where semiclassical wave functions are used for bound states, while free electrons are approximated by the TF model with a thermodynamically consistent energy boundary. The model is compared in various regions of temperatures and pressures with the reference data: the Saha model for rarefied plasma, DFT for warm dense matter, and experimental shock Hugoniot data. It is demonstrated that a single AA model may provide a reasonable agreement with the established techniques at low computational cost and with stable convergence of the self-consistent field.

Combined experimental and DFT approach to BiNbO4 polymorphs.

Here we present a detailed ab initio study of two experimentally synthesized bismuth niobate BiNbO4 (BNO) polymorphs within the framework of density functional theory (DFT). We synthesized orthorhombic α-BNO and triclinic β-BNO using a solid-state reaction technique. The underlying Pnna and P1̄ crystal symmetries along with their respective phase purity have been confirmed from Rietveld refinement of the powdered X-ray diffraction measurements in combination with generalized gradient approximation of Perdew-Burke-Ernzerhof (GGA-PBE) based DFT simulations. The scanning electron micrographs revealed average grain sizes to be 500 nm and 1 μm for α-BNO and β-BNO respectively. The energy-dispersive X-ray spectroscopy identified the Bi, Nb, and O with proper stoichiometry. The phase purity of the as-synthesized samples was further confirmed by comparing the local density approximation (LDA) norm-conserving pseudo-potential based DFT-simulated Raman peaks with that of experimentally measured ones. The relevant bond vibrations detected in Fourier transform infrared spectroscopy were matched with GGA-PBE derived phonon density of states simulation for both polymorphs. The structural stability and the charge dynamics of the polymorphs were verified from elastic stress and born charge tensor simulations respectively. The dynamical stability of the α-BNO was confirmed from phonon band structure simulation using density functional perturbation theory with Heyd-Scuseria-Ernzerhof (HSE06) hybrid functional. The electronic band gaps of 3.08 and 3.36 eV for α-BNO and β-BNO measured from UV-Vis diffuse reflectance measurements were matched with the sophisticated HSE06 band structure simulation by adjusting the Hartree-Fock exchange parameter. Both GGA-PBE and HSE06 functional were used to simulate complex dielectric function and its derivatives with the help of Fermi's golden rule to define the optical properties in the linear regime. All these may have provided a rigorous theoretical analysis for the experimentally synthesized α-BNO and β-BNO polymorphs.

Electronic properties and carrier mobilities of nanocarbons formed by non-benzoidal building blocks.

Exotic 1D and 2D carbon nanostructures have been grown in the laboratory in the last few years by means of surface-assisted chemical routes. In these processes, the strategical choice of a molecular precursor plays a dominant role in the determination of the synthesized nanocarbon. Further variations of these techniques are able to produce non-benzoidal carbon quantum-dots (QDs). Considering this experimental scenario as motivation, we propose a series of nanoribbon systems based on concatenating recently synthesized carbon QDs containing pentagonal, hexagonal, and heptagonal rings. We use density functional theory (DFT) simulations to reveal their properties can range from metallic to semiconducting depending on the concatenation hierarchy used to form the nanoribbons. This DFT implementation is based on a LCAO approach to describe valence wavefunctions and most of the simulations employ the PBE-GGA functional. Since this functional is known to underestimate band gaps, we also use the B3LYP functional in a plane-wave DFT approach for a selected case for comparison purposes. These systems show a different gap versus width relationship compared to conventional graphene nanoribbons setups and a particular set of carrier mobility values. We further discuss the interplay between the QD's frontier states and the electronic properties of the nanoribbons in light of their structural details.

Free-atom-like d states beyond the dilute limit of single-atom alloys.

Through a data-mining and high-throughput density functional theory approach, we identify a diverse range of metallic compounds that are predicted to have transition metals with "free-atom-like" d states that are highly localized in terms of their energetic distribution. Design principles that favor the formation of localized d states are uncovered, among which we note that site isolation is often necessary but that the dilute limit, as in most single-atom alloys, is not a pre-requisite. Additionally, the majority of localized d state transition metals identified from the computational screening study exhibit partial anionic character due to charge transfer from neighboring metal species. Using CO as a representative probe molecule, we show that localized d states for Rh, Ir, Pd, and Pt tend to reduce the binding strength of CO compared to their pure elemental analogues, whereas this does not occur as consistently for the Cu binding sites. These trends are rationalized through the d-band model, which suggests that the significantly reduced d-band width results in an increased orthogonalization energy penalty upon CO chemisorption. With the multitude of inorganic solids that are predicted to have highly localized d states, the results of the screening study are likely to result in new avenues for heterogeneous catalyst design from an electronic structure perspective.

ESIPT-induced spin-orbit coupling enhancement leads to tautomer fluorescence quenching of the 10-HHBF molecule.

We present novel insights into the interplay between excited state intramolecular proton transfer (ESIPT) and spin-orbit coupling (SOC) in the 10-hydroxy-11H-benzo[b]fluoren-11-one (10-HHBF) molecule, utilizing the time-dependent density functional theory approach and femtosecond transient absorption spectroscopy. Our discoveries entail a reassessment of the luminescence mechanism for 10-HHBF, characterizing it as an ESIPT fluorophore. Additionally, we demonstrate that the molecule undergoes intersystem crossing (ISC) following proton transfer, which quenches the fluorescence of the proton-transferred state, thus resulting in the absence of dual emission and a limited spectral range of fluorescence. Furthermore, our investigation reveals that 10-HHBF displays an SOC enhancement feature induced by ESIPT, which facilitates the ISC process. This trait serves as a barrier to the application of 10-HHBF in single-molecule white light emitters (SMWLEs). Our findings underscore the notable influence of the ESIPT-induced spin-orbit interaction enhancement on luminescent properties, which necessitates consideration in the design of SMWLEs.

Noncovalently bound excited-state dimers: a perspective on current time-dependent density functional theory approaches applied to aromatic excimer models

We assess most recent TD-DFT methods on excimers and highlight shortcomings of current strategies to treat dispersion in excited states.

Density Functional Theory Approach to Evaluate the Structure Of Modified Titania/Graphene Composite and Photooxidation Products of 9-(N,N-Dimethylaminomethyl) Anthracene System

The current work reports the modification of graphene/titania composite by metal and non-metal to improve the photocatalytic activity in visible region. The M-RGO-TiO2-N system was prepared by Hummer’s method followed by hydrothermal technique. On reaction, tertiary amine appended anthracene and its phenyl derivative yielded anthraquinone as the major product with almost 90% yield. Photo-oxidation of phenyl protected derivative of 9-NN-dimethyalaminomethyl anthracene yielded a very stable intermediate, 9-hydroxy 9-phenyl anthrone over a short span of time. All the products were separated by silica column chromatography using 70:30 hexane/DCM as the mobile phase. The separated compounds were characterized by 1HNMR. Theoretical investigations on the structure of the catalytic system and photo oxidation products of anthracene compounds were studied in detail by using Density functional theory calculations. Significant reduction in band gap of titania was observed from 2.84 eV to 1.84 eV after the modification of titania/graphene heterojunction with metal ions. The geometry optimized structures and energy calculations unmistakably confirmed various interactions of titania and graphene via metal ion and feasibility of the photo oxidation reaction, respectively.

Synthesis, crystal studies, antimicrobial activity, and BSA binding studies of metal complexes derived from pyridyl-based hydrazone: Multi-spectroscopic and DFT approach

We describe herein the synthesis of a pyridyl-benzothiazole hydrazone ligand (BP) and its metal complexes (BP1–BP4) incorporating Co(II), Ni(II), Cu(II), and Zn(II) cations. The molecular structures of BP and two of its complexes, BP1 and BP3, have been determined by single-crystal X-ray diffraction analysis. Octahedral complexation of the central metal ion by the NNN donor ligand in a 1:2 stoichiometry has been confirmed by various spectroscopic techniques, that is, IR spectroscopy, NMR spectrometry, and UV/Vis spectrophotometry, and corroborated by electrospray-ionization mass spectrometry and cyclic voltammetry. Diffuse-reflectance spectra revealed the presence of d-d transitions in all of the complexes, except in the case of BP4, which has no unpaired electron. The thermal stabilities of the complexes have been assessed by thermogravimetry and differential thermogravimetry, which revealed stepwise decomposition. Significant differences in the morphologies of the complexes have been discerned by FE-SEM analysis. Hirshfeld surface analysis has revealed the establishment of N⋅⋅⋅H, H⋅⋅⋅H, and C⋅⋅⋅H noncovalent interactions. Density functional theory (DFT)-based calculations have been applied to investigate the chemical reactivities and optimized structures of BP and BP1–BP4. A 1,3-proton shift in BP was confirmed and the HOMO-LUMO energy gap was assessed through DFT-based methods. Photophysical studies have revealed a large Stokes shift for BP, which is reduced upon complexation with metal ions. In vitro anti-microbial screening of the prepared compounds has been performed against four bacterial strains (Bacillus cereus, Staphylococcus aureus, Escherichia coli, and Xanthomonas campestris) and two fungal strains (Candida albicans and Fusarium oxysporum), which revealed most potent inhibition of bacterial and fungal growth, with minimum inhibitory concentrations of 128 and 256 μg/mL, by BP1 and BP3, respectively. BP1 exhibits broad-spectrum anti-bacterial activity exceeding that of the standard drug chloramphenicol. Spectroscopic methods have been utilized to explore the interaction between BP1 and bovine serum albumin (BSA). A hypsochromic shift in fluorescence intensity and a hyperchromic shift in the absorption band of BSA with different concentrations of BP1 have yielded significant binding information. BSA binding studies have revealed a negative value of Gibbs free energy, confirming the spontaneity of BSA–BP1 complex formation.

Metal clusters/modified graphene composites with enhanced CO adsorption: a density functional theory approach

Metal clusters/modified graphene composites with enhanced CO adsorption: a density functional theory approach

Electronic and Magnetic Properties of K2Mn3S4

Many opto-electronic and energy efficient devices depend on semiconductors’ direct as well as indirect band gap. Using spin-polarized density functional theory approach, we calculate the electronic structure and magnetic properties of K2Mn3S4. We found that this system has a ferrimagnetic ground state with a saturated magnetic moment of 10μB per unit cell. This was mostly caused by the antiferromagnetic interaction between the Mn (I) and Mn (II) atoms, with individual magnetic moment of 4.2 μB and 4.1 μB, respectively. More significantly, from the density of states and band structure calculations, K2Mn3S4 is noted as a semiconductor with an indirect band gap of 1.1 eV between the top of the valence band of spin up channel and bottom of the conduction bands of spin down channel, indicating the material as a promising candidate for photovoltaic and opto-electronic devices.

Effect of green solvents physical, chemical, biological and bonding nature on 5-acetyl-thiophene-2-carboxylic acid by DFT and TD-DFT approach – An antiviral agent

The density functional theory (DFT) is applied to 5-acetyl-thiophene-2-carboxylic acid (5AT2CA). To determine the optimal structure and different physical, chemical, and biological characteristics, the B3LYP technique and 6–311++G(d,p) basis set are employed. The binding energies and ellipticity are determined using the atoms in molecules theory (AIM). NBO analysis is used to study the exchanges between the contributor and receiver by energies. By utilizing HOMO-LUMO values and important electronic parameters, stability is determined. The molecular electrostatic potential (MEP) and Fukui function from Mulliken charges are used to determine the reactive regions of the molecule. The TD-DFT technique obtains the electronic transition using UV–Vis spectrum with various solvents. NLO studies were carried out on this molecule. Studies of temperature effect on 5AT2CA are done by thermodynamic parameters. Drug-likeness and molecular docking tests are used to evaluate the bioactivity and antiviral properties.

Theoretical study on the free radical scavenging potency and mechanism of natural coumestans: Roles of substituent, noncovalent interaction and solvent

The free radical scavenging potency and mechanisms of seven representative natural coumestans were systematically evaluated using density functional theory (DFT) approach. Thermodynamic feasibility of different mechanisms was assessed by various physio-chemical descriptors involved in the double (2H+/2e‒) radical-trapping processes. Energy diagram and related transition state structures of the reaction between wedelolactone (WEL) and hydroperoxyl radical were constructed to further uncover the radical-trapping details. Results showed that the studied coumestans prefer to scavenge radicals via formal hydrogen atom transfer (fHAT) mechanism in the gas phase and non-polar environment, whereas sequential proton loss electron transfer (SPLET) is favored in polar media. Moreover, the feasibility of second fHAT and SPLET processes was also revealed. Sequential double proton loss double electron transfer (SdPLdET) mechanism represents the preferred pathway in aqueous solution at physiological pH. Our findings highlight the essential role of ortho-dihydroxyl group, noncovalent interaction and solvents on radical-trapping potency. 4′-OH in D-ring was found to be the most favorable site to trap radical for most of the studied coumestans, whereas 3-OH in A-ring for lucernol (LUN).

Modeling the anti-Methicillin-Resistant Staphylococcus aureus (MRSA) Activity of (E)-6-chloro-N2-phenyl-N4-(4-Phenyl-5-(Phenyl Diazinyl)-2λ3, 3 λ2- Thiazol-2-yl)-1, 3, 5-Triazine-2,4- Diamine

To combat the rise of multidrug-resistant microorganisms like methicillin-resistant Staphylococcus aureus (MRSA), new antibiotic classes are required. Hence, experimental and theoretical calculation utilizing density functional theory (DFT) approach and in-silico molecular docking approach have been exploited in this study on the title molecule: (E)-6-chloro-N2-phenyl-N4-(4-phenyl-5-(phenyl diazinyl)-2λ3, 3 λ2- thiazol-2-yl)-1, 3, 5-triazine-2,4- diamine (CPTD) at the B3PW91, ɷB97XD, and PBE0/6-311++G(d, p) level of theory to elucidate its drug like potential against MRSA. Molecular docking analysis was performed on the proposed structure using the following proteins PDB: ID 3T07, 4DKI, 6H50, and 6U3Y and the best binding scores with the ligand were examined to be −9.6 kcal/mol, −7.2 kcal/mol, −6.4 kcal/mol, and −8.6 kcal/mol respectively. However, it’s worth noting that 3T07 and 6U3Y proteins displayed greater binding ability revealing essential amino acids as several active sites were seen adhering efficiently to CPTD. The molecular dynamic simulation corroborated that in the case of protein backbone atoms, it was found that the average RMSD values for complexes of CPTD + 3T07, CPTD + 4DKI, CPTD + 6H5O, and, CPTD + 6U3Y were 2.719 Å, 4.122 Å, 4.021 Å, and 4.619 Å respectively. Thus, it can fervently be stated that the proposed drug substantiates greater antibacterial or inhibitory potential than clindamycin, and hereafter can be developed pharmaceutically to curb MRSA.