•4-Substituted thiophene and benzoic acid-based azo dyes.•Effect of substituent on DSSC and NLO properties.•DFT and TD-DFT computational analysis for photovoltaic and NLO properties.•With increasing ...donating strength at position 4 of the thiophene ring, enhancement in DSSC efficiency, and NLO activity.
The effect of altering the donating strength of secondary donors at the 4th position of the thiophene ring in a series of dyes labeled AB1 to AB9 is investigated in this study. According to the findings, the orientation of the secondary donor has a considerable impact on molecular planarity, resulting in changes in charge transfer (CT) properties within the thiophene-azo-benzoic acid backbone. The time-dependent density functional theory (TD-DFT) study supports these findings, indicating that the vertical absorption maximum of the dyes increases with the secondary donor's donating strength. From AB1 to AB5, photovoltaic parameters show an increase in DSSC performance. Furthermore, dye@TiO2 cluster experiments suggest the possibility of these dyes interacting with TiO2, resulting in red-shifted absorbance of dye@TiO2 clusters.
Theoretical predictions are confirmed by the synthesis of AB1 to AB4, with initial absorption in dimethylformamide (DMF) and energies of highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) following a similar pattern as observed in density functional theory (DFT) studies. TGA results show that AB1 to AB4 have remarkable thermal stability, enabling their practical application in DSSCs. The efficiencies of the constructed DSSCs varied, with AB4 having the highest (1.90 ± 0.1) and AB1 having the lowest (1.29 ± 0.1). Secondary donors play a critical role in determining molecular characteristics and device performance, according to the theoretical and experimental DSSC results.
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•Pyrrole and bimetallic Ag-Au/Ni/Cu nano clusters forms stable complexes.•Raman modes are enhanced in the fingerprint region upon complexation.•Noncovalent interactions are high in ...Ag4-Ni2–PYR complex.•Change in electric conductivity can aid in sensor based drug detection.
Interaction between biologically active compounds and metal clusters are of immense theoretical and experimental interest due to its wide range of applications including drug delivery. We conducted a comprehensive analysis of the electronic characteristics of pyrrole interacting with metal atoms by combining DFT simulations with a literature review. Adsorption behavior of pyrrole (PYR) functionalized bimetallic clusters (PYR-Agx-My (x = 4/5, y = 2/1 and M = Au/Ni/Cu) is reported in the present study. In Ag4 and Ag5 systems, AgAu-PYR and AgNi-PYR systems have highest interaction energies. Mulliken charges and HOMO-LUMO energy can be utilized to determine the stability of molecule–metal interactions as well as the reactivity of PYR after they have interacted with metals. Study of noncovalent interactions indicates better interaction is between Ag4-Ni2 and PYR. It is found that electrons are localized over the PYR residue in the cluster.
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 (βtot) 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.
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.
Shape effects of nanocrystal catalysts in different reactions have attracted remarkable attention. In the present work, three types of α-Fe
O
oxides with different micromorphologies were rationally ...synthesized via a facile solvothermal method and adopted in deep oxidation of ethane. The physicochemical properties of prepared materials were characterized by XRD, N
sorption, FE-SEM, HR-TEM, FTIR, in situ DRIFTS, XPS, Mössbauer spectroscopy, in situ Raman, electron energy loss spectroscopy, and H
-TPR. Moreover, the formation energy of oxygen vacancy and surface electronic structure on various crystal faces of α-Fe
O
were explored by DFT calculations. It is shown that nanosphere-like α-Fe
O
exhibits much higher ethane destruction activity and reaction stability than nanocube-like α-Fe
O
and nanorod-like α-Fe
O
due to larger amounts of oxygen vacancies and lattice defects, which greatly enhance the concentration of reactive oxygen species, oxygen transfer speed, and material redox property. In addition to this, DFT results reveal that nanosphere-like α-Fe
O
has the lowest formation energy of oxygen vacancy on the (110) facet ( E
(110) = 1.97 eV) and the strongest adsorption energy for ethane (-0.26 eV) and O
(-1.58 eV), which can accelerate the ethane oxidation process. This study has deepened the understanding of the face-dependent activities of α-Fe
O
in alkane destruction.
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•The (Ce1-xLax)2Fe14B structures became unstable in the La-doped process.•Total and atomic magnetic moments increased with higher La doping.•The MAE calculated with DFT + U varied ...non-monotonically with La concentration.•The optimal magnetic performance occurred within the range of x = 0.25 to 0.375.•Predicted and discussed the DOS of (Ce1-xLax)2Fe14B calculated using two methods.
We investigated different amounts of La doping on the magnetic characterizations of the (Ce1-xLax)2Fe14B (x = 0, 0.125, 0.25, 0.375, 0.5, 0.625, 0.75, 0.875, 1) structures using standard density functional theory (DFT) and DFT plus U (DFT + U) methods. Substitutions of Ce atoms by La atoms increased the magnetic moment of Fe atoms. The absolute values of the magnetocrystalline anisotropy energy (MAE) calculated by standard DFT method gradually decreased with increasing amounts of La doping, while the MAE using DFT + U method exhibited non-monotonic dependence on La concentration. The optimal magnetic performance occurred within the range of x = 0.25 to 0.375. The DOS showed that the rare earth atomic magnetic moments were in the opposite direction to the magnetic moments of the Fe atoms, and the f-orbital electronic states of Ce atoms predicted by DFT + U method were generally larger than that predicted by standard DFT method.
In this paper we present the implementation and benchmarking of a Time Dependent Density Functional Theory approach in conjunction with Double Hybrid (DH) functionals. We focused on the analysis of ...their performance for through space charge‐transfer (CT) excitations which are well known to be very problematic for commonly used functionals, such as global hybrids.Two different families of functionals were compared, each of them containing pure, hybrid and double‐hybrid functionals.The results obtained show that, beside the robustness of the implementation, these functionals provide results with an accuracy comparable to that of adjusted range‐separated functionals, with the relevant difference that for DHs no parameter is tuned on specific compounds thus making them more appealing for a general use. Furthermore, the algorithm described and implemented is characterized by the same computational cost scaling as that of the ground state algorithm employed for MP2 and double hybrids.
A new implementation of a time dependent density functional theory approach in conjunction with double hybrid functionals is presented together with benchmarks on through space charge‐transfer excitations. The algorithm implemented has the same computational cost scaling as that of the ground state algorithm employed for MP2 and double hybrid DFAs. The results obtained show, beside the robustness of the implementation, that double hybrid functionals are competitive with functionals tuned on excited state properties.
Nitrogen constitutes a significant defect in silicon (Si) as it can affect its mechanical properties. Substitutional nitrogen defects can be created from interstitial nitrogen defects during cooling ...of the crystal. In turn, the substitutional nitrogen atoms can form micro-defects in Si, most important of which are the interstitial oxygen atoms since they have an impact on a device’s characteristics. In the present paper, we study the structure of the defect clusters in Si consisting of substitutional nitrogen and interstitial oxygen atoms. We find that the most stable structure is the one containing two interstitial oxygen atoms, while the presence of these interstitials results to narrow-gap semiconductors.
•The most stable structure of nitrogen and interstitial oxygen defects in silicon is the one containing two interstitial oxygen atoms.•The existence of such oxygen interstitials results in narrow-gap semiconductors.•The existence of substitutional nitrogen atoms in silicon does not affect the bond lengths between consecutive silicon atoms.
The effective adsorption and treatment of toxic gases have attracted great attention amongst researchers, particularly the use of new two-dimensional materials for achieving the adsorption of toxic ...gases. We applied the density functional theory to investigate the stability, geometric structural, electrical, and magnetic properties of NH3 molecules adsorbed on pristine, F-vacancy defected, and transition-metals (V, Cr, Mn, Y, Nb, and Mo) doped Zr2CF2. The charge transfer and adsorption energy of the original substrate were low, indicating that the interaction between NH3 and Zr2CF2 was primarily physical adsorption. After introducing F-vacancy and TM-doping, the adsorption stability was enhanced, with the large charge transfer and high adsorption energies indicating that the adsorption of NH3 transitioned to chemisorption. Electronic density of state diagrams suggested that the enhanced interaction was mainly caused by the hybridization of the d orbitals of dopants and p orbitals of the adsorbed NH3 molecules. The adsorption energy of NH3 molecules on Y-doped Zr2CF2 was the highest at a value of −1.425eV, and the material was also explored as an adsorbent for NH3 gas. After adsorbing six NH3 molecules, the Y-doped substrate had an average adsorption energy of −1.350eV and still maintained a good thermal stability at a temperature of 300 K. These results can provide insights into the development of sensors and adsorbents based on MXenes.
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•The adsorption of NH3 on perfect Zr2CF2 was physical adsorption.•The introduction of F-vacancy enhanced the adsorption stability of NH3 molecule.•The doping of transition-metal (V, Cr, Mn, Y, Nb, Mo) significantly improved the sensitivity of Zr2CF2 to NH3 gas.•Y-doped Zr2CF2 can be used as effective adsorbent to NH3 gas.
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•Bi2WO6 with gradient oxygen vacancies for highly photocatalytic activity.•The role of oxygen vacancy was investigated and illustrated in detail.•In situ DRIFTS combined DFT ...calculations reveal the reaction process and mechanism.
We successfully synthesized the Bi2WO6 (BWO) with gradient concentration of oxygen vacancies and exhibited the excellent photocatalytic NO oxidation activity. And the oxygen vacancy introduced in photocatalyst is a popular method to enhance the photocatalytic performance. The formation of oxygen vacancy defects in BWO is responsible for the tuning band structure and modifying surface chemical state to improve carriers separation efficiency, enlarge visible light absorption range and facilitate reactant activation, which is unambiguously verified by the UV–vis DRS, XPS, EPR and DFT calculations. Moreover, the role of surface oxygen vacancy defects and reaction mechanism of photocatalytic NO oxidation were discussed in detail by combing the in situ DRIFT and theoretical calculations. This work could be broadly used to the design and synthesize high efficient photocatalysts and pave a way to understand the reaction mechanism of NO oxidization.
Double perovskite oxides (DPOs) having 3d-5d electrons provide an optimal field to investigate the entanglement between spin–orbit coupling and electron correlation, displaying unusual physical ...phenomena. Here, we predicted a large magnetic anisotropy energy (MAE) constant of 1.7 × 108 erg/cm3 in a pristine ferrimagnetic (FiM) Y2NiIrO6 DPO with the magnetic easy axis of the monoclinic b-axis. The estimated Curie temperature (TC) of 198 K using the Heisenberg model agrees well with the experimentally observed value of 192 K. Antiferromagnetic coupling between Ni and Ir ions is confirmed, which supports the FiM as a ground state of the system. Furthermore, it is found that the motif displays a Mott-insulating nature because of the exceptional Jeff=12 state of Ir+4 with an effective magnetic moment (meff.) of ∼2.19μB/u.c. (per unit cell), where Ni/Ir ion contains 1.68/−0.49μB. Upon substitution of Ce at Y-site (Ce@Y), few states grow at the Fermi level which belongs to Ir 5d orbitals and meff. enhanced to 3.13 μB/u.c., while FiM survives as a ground state. Along with this, Ni moment remains unchanged, while it substantially reduces to −0.10μB for Ir ion which leads to be in a ＋ 3 (5d6) state with S = 0 and almost persists in the paramagnetic phase. Due to the larger atomic radii of Ce than that of Y, the Ce@Y-doped motif exhibits a large structural distortion as compared to the pristine one, which increases the MAE and TC values simultaneously. Furthermore, calculated enthalpies of formation, distinct elastic constants, and phonon dispersion spectrums ensure the thermodynamic, mechanical, and dynamical stability of the pristine as well as the Ce@Y-doped system, respectively.
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•Strong antiferromagnetic interactions between Ni and Ir results in a ferrimagnetic (FiM) state.•The 010 (b-axis) is the easy magnetic axis with a large anisotropy constant (K) of 1.78 × 108 erg/cm3.•Pristine structure displays a Mott-insulating phase due to unusual Jeff=12 state of Ir＋4 ion.•Strikingly, a Mott-insulating-to-metallic state is established in the Ce-doped motif.•A significant enhancement in K value and Curie temperature is predicted for Ce-doped system.
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