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Crystal growth, Hirshfeld surface analysis, DFT study and third order NLO studies of Thiourea 4 dimethyl aminobenzaldehyde
摘要： In this work we investigate the crystal growth and the characterization of Thiourea 4 dimethyl aminobenzaldehyde (TDA) crystal. The Molecular geometry shows good agreement with Experimental and Theoretical (HF and DFT) bond lengths and bond angles. From X-ray diffraction studies it shows that the structure belongs to monoclinic structure and experimental, refinement data also discussed. Hirshfeld surface analysis used to clarify the intermolecular interactions in a visual manner. Vibrational assignments of TDA crystal is discussed by FT-IR and FT-Raman spectroscopic studies. The assignments are compared with Density Functional Theory calculation and it shows good agreement with experimental data. The Frontier molecular orbital energy gap is found by TD-DFT method with HOMO-LUMO calculation. The Third order NLO studies for TDA organic crystal is done by Z-scan technique and Optical parameters like Non linear and Linear refractive index are calculated.
关键词： Z-scan Technique,DFT,Hirshfeld surface analysis,X-Ray diffraction,Molecular Geometry.
更新于2025-09-10 09:29:36
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Spectroscopic Investigation (FT-IR, FT-Raman, NMR and UV-Vis),Conformational Stability, NBO and Thermodynamic Analysis of 1-(2-Methoxyphenyl) Piperazine and 1-(2-Chlorophenyl) Piperazine by DFT Approach
摘要： The Vibrational and electronic properties of phenyl substituted compounds 1-(2-methoxyphenyl)piperazine and 1-(2-chlorophenyl)piperazine have been investigated by FT-IR, FT-Raman, NMR and UV-Vis spectral measurements. Density functional theory (DFT) method, using B3LYP functional, with 6-311++G (d,p) basis set, has been performed for assigning vibrational frequencies of the title compounds, which also helps to derive useful information about the structure of the chosen compounds. A detailed interpretation of the Infrared and Raman spectra of the two molecules were reported based on potential energy distribution (PED). 13C and 1H NMR chemical shifts of the molecules were calculated using the gauge independent atomic orbital (GIAO) method. These studies satisfactorily agree the experimental data. Charge density distribution and site of chemical reactivity of the molecule have been studied by mapping electron density isosurface with molecular electrostatic potential (MEP). Stability of the molecules arising from hyperconjugative interactions, charge delocalization have been analyzed using natural bond orbital (NBO) analysis. The compounds have similar HOMO (Highest Occupied Molecular Orbitals) - LUMO (Lowest Unoccupied Molecular Orbitals) gap due to similarity in their structures. The compounds show (π→ π*) transitions in the UV- Visible range.
关键词： NMR,1-(2-methoxyphenyl)piperazine,Natural bond orbitals,DFT,1-(2-chlorophenyl)piperazine,HOMO-LUMO
更新于2025-09-10 09:29:36
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Effects of conjugation on the properties of alkynylcarbazole compounds: experimental and theoretical study
摘要： Four novel dyes containing alkynylcarbazole, namely, 2-((9H -carbazol-3-yl)ethynyl)-9-ethyl-9H -carbazole, 3,6-bis((9-ethyl-9H -carbazol-2-yl)ethynyl)-9H -carbazole, 3-(phenylethynyl)-9H -carbazole and 3,6-bis(phenylethynyl)-9H -carbazole, were synthesized on the basis of single and double substitutes by following the Sonogashira coupling method. The synthesized dyes were then assessed as novel photosensitizers in visible-light photopolymerization to evaluate the effects of conjugation on the properties of aromatic compounds. A comparison between UV–vis and TD/DFT electron transition spectra shows that λmax in theoretical ultraviolet spectra matched well with the experimental spectra; every conjugated alkynylcarbazole dye exhibits a wide absorption band in the range of 300–400 mm. Moreover, conjugation enhancement by switching carbazoleacetylene moieties caused a red shift in the absorption bands. The theoretical study showed that the maxima λ of these molecules ranged from ～330 to 370 mm, corresponding to π→π ? and n→π ? electron transitions. Fluorescence spectroscopic data show that the strongest emission peaks exhibit a red shift because of the addition of conjugated acetylene groups. A combination of alkynyl dyes and iodonium under a halogen lamp atmosphere by visible-light photopolymerization displayed a positive response to the cationic polymerization of bisphenol-A epoxy resin A and free-radical polymerization of tripropylene glycol diacrylate.
关键词： photopolymerization,Synthesis,alkynylcarbazole,photosensitizers,DFT calculations
更新于2025-09-10 09:29:36
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Intermediate States Directed Chiral Transfer on a Silver Surface
摘要： Chiral synthesis on surfaces has acquired tremendous interests. We herein report a novel approach of two-dimensional chiral transfer directed by metal-organic intermediate states on a silver surface. With initial deposition at low temperature, the achiral 4,4'-dihydroxybiphenyl molecules self-assemble into large scale two-dimensional networks with four-fold symmetry via intermolecular hydrogen bonding. Fine controlled annealing, however, leads to the formation of tetramer-like chiral metal-organic hybrids, which self-organize into enantiomeric islands on the Ag(100) surface. Subsequent ortho C-C couplings of the reactants lead to dimer products. Of great importance, the chirality expressions of the dimer products are observed to be transferred directly from that of the tetramer intermediate states. The detailed reaction pathways are rationalized by DFT calculations and synchrotron-based XPS experiments, demonstrating the mechanisms of the chiral transfer.
关键词： metal-organic intermediate states,4,4'-dihydroxybiphenyl,DFT calculations,chiral synthesis,synchrotron-based XPS,silver surface,chiral transfer
更新于2025-09-10 09:29:36
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Half-Metallic Ferromagnetism Character in Cr-Doped CaS Diluted Magnetic Insulator and Semiconductor: an Ab Initio Study
摘要： The overall aim of this study is to investigate theoretically the structural, electronic, and magnetic properties of calcium sulfide (CaS) doped with chromium (Cr) impurity, in order to conduct a new search dilute magnetic semiconductors (DMS) suitable for different applications in electronics and spintronics. For measuring, the physical property of this compound is implemented using the first principles approach employed in WIEN2K code. The structural characteristics are optimized using the Generalized Gradient Approximation established by Perdew-Burk-Ernzerhof (PBE-GGA). We calculate and minimize the total energy of the three ternary compounds (Ca0.75Cr0.25S, Ca0.50Cr0.50S, and Ca0.25Cr0.75S) in the paramagnetic (PM), ferromagnetic (FM), and antiferromagnetic (AFM) phase. We find all compounds stable in (FM) structure, whereas the modified Becke and Johnson local density approximation (mBJ-LDA) functional has been employed to evaluate the electronic and magnetic properties. Based on our findings, indicate that this system revealed a half-metallic ferromagnetic behavior with half-metallic gap (HM) and 100% spin-polarized at the fermi level for all chromium (Cr) concentrations. This advantageous set of properties is due to the half-metallic behavior, where the majority spin and minority spin exhibit metallic and semiconducting behaviors respectively. The chromium atom is the most important source of the total magnetic moment in these compounds (4 μβ) by comparison with magnetic moments produced by Ca and S atoms, which have minor contribution. Finally, our prediction results require an experimental confirmation in the future.
关键词： Diluted magnetic insulators (DMI),Spintronics,CaS,HM ferromagnetism,Density functional theory (DFT)
更新于2025-09-10 09:29:36
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Pd-doped MoS2 monolayer: A promising candidate for DGA in transformer oil based on DFT method
摘要： Density functional theory (DFT) method was carried out to simulate the adsorption of three dissolved gases on Pd-doped MOS2 (Pd-MoS2) monolayer. We initially studied the possible structures of Pd-MoS2 monolayer and found that the Pd dopant preferred to be adsorbed onto the surface by TMo site. The adsorption and desorption performance, along with the sensing principle of Pd-MoS2 towards three typical gases, including H2, CH4 and C2H2, were analyzed. These analysis indicated that Pd-MoS2 could be a satis?ed material for C2H2 and H2 sensing at speci?c condition; while it is unsuitable for detection of CH4 due to the weak interaction and extremely short recovery time. All these give a ?rst insight into the application of Pd-MoS2 for DGA, evaluating the working operation of the transformer through sensitive detection of H2 and C2H2. We are hopeful that this work would support informative knowledge for experimentalists to realize the potential of Pd-MoS2 in the ?eld of electrical engineering in the near future.
关键词： DGA,Transformer oil,DFT,Pd-MoS2 monolayer
更新于2025-09-10 09:29:36
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Multibeam Digital Array Receiver Using a 16-point Multiplierless DFT Approximation
摘要： An N -element array with receivers subject to an N -point spatial FFT leads to N directionally-orthogonal RF beams. FFTs are fast algorithms for computing an N -point DFT at reduced complexity. The brute-force computation of a DFT requires O(N 2) multiplications while an FFT provides the same computation at O(N log N ) multiplications. The digital chip area and power consumption of the DFT computation are still dominated by the multipliers required by the FFT used. In this paper, an approximation to the 16-point DFT is proposed which maintains mathematical properties close to the ideal 16-point DFT to obtain 16 RF beams by computing an approximate spatial DFT in every clock cycle at significantly lower area and power in the digital realization. The proposed approximation can be implemented using FFT-like fast algorithms that are multiplierless, thereby further reducing the digital chip area and power consumption associated with multiplication in a conventional FFT approach, to zero. A 16-beam beamformer employing a 16-element linear array of patch antennas, direct-conversion receivers and a Xilinx Virtex-6 FPGA based real-time digital back-end clocked at 240 MHz are described as an example realization of 16 complex-valued (IQ) receive-mode RF beams, centered at 2.4 GHz with 120 MHz of bandwidth per beam.
关键词： low-complexity algorithms,spatial DFT,beamforming,Multibeam
更新于2025-09-10 09:29:36
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Computational screening of bulk materials with intrinsic intermediate band
摘要： Intermediate band compounds are promising high-efficiency materials for solar cells. Besides that, they also show unusual properties that make them interesting from a fundamental point of view. In this work, we create a series of filters capable of searching the AFLOW-ICSD materials database for compounds that show intrinsic intermediate bands. We analyse all available binary and ternary compounds, totaling 45,656 entries. The selected materials show at least one narrow band (maximum width of 1 eV) next to the energy gap. After removal of repeated entries and of wide bandgap insulators, we end up with a total of 660 materials that present intermediate bands. From this group, the majority has completely empty or filled intermediate bands or, during new calculations, changed to another state with a different type of intermediate band or no band of this type. Nevertheless, three compounds fulfill all criteria and continue to present a partially filled intermediate band (Bi2Rh2O7, Ca5FeN6, and OsTb6I10), showing potential for solar cells applications.
关键词： Intermediate band,Solar cells,Materials screening,High-throughput screening,DFT calculations
更新于2025-09-10 09:29:36
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Enhanced photocatalytic H2 evolution and phenol degradation over sulfur doped meso/macroporous g-C3N4 spheres with continuous channels
摘要： S-doped meso/macroporous g-C3N4 spheres (SMCN) were successfully synthesized via an in situ novel method utilizing millimeter-scale porous silica spheres as template and thiourea as precursor and S source. Such SMCN possessed millimeter-scale spherical morphology with continuous channels at 20e80 nm in the interior of the spheres, and exhibited increased H2 generation rate (15 times) and phenol degradation rate (5 times) under visible light irradiation compared with that over pristine g-C3N4, mainly due to the enlarged surface area, enhanced mass transfer and improved ef?ciency of charges separation all stemming from the synergetic effects of the S doping and pore creating. Notably, density functional theory (DFT) calculations were employed to further understand the mechanism of the photocatalytic enhancement with regard to the optical absorption property at atomic level. Combined with the ?nite difference time domain (FDTD) simulations aiming at evaluating the effect of the nanoscale pore architecture on the optical absorption ability, it was revealed that not only the S doping but also the meso/macroporous structure resulted in the enhancement of the optical absorption, which was considered to be an essential role for the enhanced photocatalytic performances over SMCN.
关键词： Continuous channels,FDTD simulation,Optical absorption,DFT,S-doping
更新于2025-09-10 09:29:36
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First-Principle Study of Ammonia Decomposition and Nitrogen Incorporation on the GaN Surface in Metal Organic Vapor Phase Epitaxy
摘要： Based on the density functional theory (DFT), we theoretically investigate the growth mechanism of GaN (0001) using the Metal-Organic Vapor-Phase Epitaxy (MOVPE). We first identify the structure of the growing Ga rich GaN (0001) surface, then study the adsorption of NHx (x = 0-3) on such surface. We find that NH2 and NH units spontaneously intervene in the Ga-Ga weak bonds on the Ga-rich GaN (0001) surface. A reaction pathway of decomposition of NH3 on Ga rich surface is revealed. During reaction, N is found to incorporate in the weak Ga-Ga bond and form - Ga - (NH) - Ga - structure. The activation barrier of NH3 is surprisingly small, just 0.63eV. We also explore the decomposition of NH2 to N to form Ga-N network and find the plausible reaction pathway with the energy barrier of 2 eV. Taking into account the chemical potential of an H2 molecule in the gas phase at the growth temperature, we find that this reaction can be overcome. This NH3 decomposition mechanism and the N incorporation on GaN is a new growth mechanism catalyzed by the growing surface.
关键词： NH3 decomposition,DFT,N incorporation,MOVPE,GaN
更新于2025-09-10 09:29:36