Exploring the structural and electronic properties of Fe-doped gallium clusters: A density functional theory study

Lead-free A2ZrX6 “defect” perovskites hold significant potential for many optoelectronic applications due to their stability and tunable properties. Extending a previous work, we present a first-principles density functional theory (DFT) study, utilizing PBE and HSE06 functionals, to systematically investigate the impact of A-site cation and X-site halogen substitutions on the structural and electronic properties of these materials. We varied the A-site cation, considering ammonium, methylammonium, dimethylammonium, trimethylammonium, and phosphonium, and the X-site halogen, trying Cl, Br, and I. Our calculations reveal that both these substitutions significantly affect the band gap and the lattice parameters. Increasing A-site cation size generally enlarges the unit cell, while halogen electronegativity directly correlates with the band gap, yielding the lowest values for iodine-containing systems. We predict a broad range of band gaps (from ~4.79 eV for (PH4)2ZrCl6 down to ~2.11 eV for MA2ZrI6 using HSE06). The (PH4)2ZrX6 compounds maintain cubic crystal symmetry, unlike the triclinic of the ammonium-derived systems. Finally, our calculations show that the MA cation yields the smallest band gap among the ones studied, a result that is attributed to its size and the charges of the hydrogen atoms attached to nitrogen. Thus, our findings offer crucial theoretical insights into A2ZrX6 structure–property relationships, demonstrating how A-site cation and halogen tuning enables control over electronic and structural characteristics, thus guiding future experimental efforts for tailored lead-free perovskite design.

Computational studies are very important to gain an insight into reaction mechanisms and in interpreting and understanding complicated experimental observations. This report contains a discussion on computational studies performed on bimetallic catalysis and on X-ray absorption spectroscopy of insulators. The viability of a bimetallic rhodium and cobalt catalysts for industrially important hydroformylation and aldehyde-water shift catalysis (AWS) is discussed. Density functional theory (DFT) studies were used for bimetallic catalysis and time-dependent DFT studies were used for excited state dynamics. These studies were performed using Gaussian 09 package and NWChem. Hydroformylation is experimentally performed in acetone and 30% water/acetone systems and results in dicationic dirhodium complexes and monocationic dirhodium complexes respectively. DFT studies were used to determine the active catalyst and possible intermediates. Computational studies support the mechanism proposed by Prof. Stanley for hydrofomylation in acetone, but DFT studies demonstrate a different mechanism for hydroformylation in water/acetone which contains mono-bridging complexes. A detailed discussion on this is given in chapter 2. DFT studies were used to study the AWS catalysis with the bimetallic [rac-Rh2(μ-CO)2(CO)2(et,ph-P4)]2+ complex. These studies were performed in both vacuum and using explicit water molecules, and lower energies were obtained when explicit water molecules were used. The computations support an alternate mechanism with protonated acid intermediates different from the originally proposed mechanism. This mechanism is discussed in great detail in chapter 3. DFT studies are also performed to study the suitability of dicobalt analogs for hydroformylation and AWS catalysis. The most suitable active catalyst and possible mechanism for hydroformylation using Co2(μ-H)(μ-CO)(CO)3(H)(et,ph-P4)]2+ (Co_2), [rac- and [rac-Co2(μ-H)2(CO)4(et,ph-P4)]2+ (Co_2*) and [rac-Co2(μ-CO)2(CO)2(H)2(et,ph-P4)]2+ (Co_2**) are discussed in chapter 4. The capability of [rac-Co2(CO)4(et,ph-P4)]2+ (Co_4*) catalyst for AWS catalysis is also discussed in chapter 4. Chapter 5 discusses a method to generate X-ray absorption spectra of insulators using time-dependent DFT. α-Quartz was used as a model for insulators. Bulk-mimicking embedded finite cluster models, atom-centered basis sets, tuned range-separated functionals and molecular orbital-based absorbing boundary conditions were utilized to model near and above ionization spectral features without experimental parameterization. The calculated spectra match well with the experimental results over the range of approximately 105 – 130 eV.

The photocatalytic degradation performance of Dion-Jacobson-type layered perovskites AMCa2Ta3O10 (AM=Rb, Cs): A DFT study

Effect of Ti modification on Structural, Electronic and Electrochemical properties of Li2FeSiO4—A DFT study using FPLAPW approach

2-amino-3-cyanopyridines are good starting reagents that have been used in synthesis of many heterocyclic compounds such as pyridopyrimidines, [1,2,4]triazolo and [1,2,3,4] tetrazolo derivatives which have biological activities as anti-microbial and cytotoxic activities. Meanwhile [1,2,4]triazolo and [1,2,3,4]tetrazolo derivatives are well known to possess many physiological activities, such as anticancer , antifungal, muscle relaxant, hypnotic, anti-inflammatory, diuretic and antihypertensive activities. A broad class of heterocyclic compounds has been studied to demonstrate their biological activity on the structures of DNA and RNA. Several of important functions make Tankyrases acts as targets in potential drug. The article focuses on synthesis of [1,2,4]triazolo and [1,2,3,4]tetrazolo derivatives and their theoretical calculations that suggest they are anti-cancer substances. DFT and computational studies were performed on the structural properties of experimental molecules experimentally, and significant theoretical calculations were performed based on density functional theory (DFT) with Becke's three-parameter exchange function21-22 of correlation functional Lee Yang Parr (B3LYP) with the basis set 6-31G (d,p) using Gaussian 03 software23. Geometrical parameters of the optimized structures were calculated and also the charge on each atom (Mulliken charge). Chemcraft program24 was used to visualize the optimized structure and ChemBio3D ultra 12.0 was used to visualize the highest occupied and lowest unoccupied molecular orbitals. Preliminary screening in five studied ligands acts as inhibitors for different active sites along the target. The molecular docking study also revealed that the compound 6c was the most effective compounds in inhibiting Tankyrase I enzyme (2rf5), this result can help strongly in inhibition of carcinogenic cells and cancer treatment. We have described a new practical cyclocondensation synthesis for a series of [1,2,4]triazolo[4,3- c]pyrido[3,2-e] pyrimidine and pyrido[2',3':4,5] pyrimido[6,1-c][1,2,4] triazine from 2-amino-3-cyano-4.6- diarylpyridines. Also polyheterocyclic compounds containing [1,2,4]triazolo and [1,2,3,4]tetrazolo moieties were also synthesized through the reactions of 3-hydrazino-8,10-diaryl [1,2,4]triazolo[4,3-c]pyrido[3,2- e]pyrimidine with both formic acid and the formation of diazonuim salt respectively. Newly synthesized heterocycles structures were confirmed using elemental analysis, IR, 1H-NMR, 13C-NMR and mass spectral data. DFT and computational studies were carried out on five of the synthesized poly heterocyclic compounds to show their structural and geometrical parameters involved in the study. Molecular docking using Tankyrase I enzyme as a target showed how the studied heterocyclic compounds act as a ligand interacting most of active sites on Tankyrase I with a type of interactions specified for H-bonding and VDW. We investigated that the five studied ligands act as inhibitors for different active sites along the target. The molecular docking study also revealed that the compound 6c was the most effective compounds in inhibiting Tankyrase I enzyme (2rf5), this result can help strongly in inhibition of carcinogenic cells and cancer treatment.

In this work, a Density Functional Theory (DFT) study has been carried out to investigate the structural and electronic properties of H3PO4/ZSM-5 (extra-framework and framework modification). Cluster models at different T sites (T6, T9, and T12) are suggested. The local structure of the extra-framework modified cluster for H3PO4/ZSM-5 shows that there is a hydrogen bond interaction between the hydrogen atoms in H3PO4 and the oxygen atoms in the zeolite framework, involving O4 and Ha. Additionally, the Ozeo always tends to keep in a straight line distribution. Mulliken charge analysis of the cluster models concerned shows that the charge indeed transfers from the oxygen atoms toward P, Al and H atoms. The charge transfer from ZSM-5 to H3PO4 could enhance the interaction between the H3PO4 and the ZSM-5. Based on the DFT study above, the mutual relationship between the acidic sites on ZSM-5 and phosphoric acid might be more clearly confirmed.

Adsorption and dissociation of SO3 on N-doped TiO2 supported Au overlayers investigated by van der Waals corrected DFT

Bacteria derived bioactive compounds: A valuable tool for the electrochemical detection of arsenic (III) ions in contaminated water

Synthesis, spectroscopic characterization, DFT studies and antibacterial assays of a novel silver(I) complex with the anti-inflammatory nimesulide

Melamine derivatives as effective corrosion inhibitors for mild steel in acidic solution: Chemical, electrochemical, surface and DFT studies

Lab-scale experiments and Density Functional Theory (DFT) studies were carried out to investigate the efficiency of Napier grass-derived adsorbent (CNP_600) and alkaline modification (CNP_0.2NaOH_600) as low-cost adsorption materials for fluoride removal. CNP that had been treated with an alkaline solution cloud contained more fluoride than the CNP that had been used initially. The NaOH modification of prepared materials promoted a change in surface characteristics that could enhance fluoride removal efficiency. Those adsorbents fitted well with the pseudo-2nd-order kinetic model and declared that the adsorption process was chemisorption. The isotherm study exhibited the best fit with the Langmuir model, resulting in mono-layer adsorption. The experimental adsorption behavior of fluoride ions (F–) onto CNPs was investigated. The proposed adsorption process involved electrostatic attraction and hydrogen bonding, which were found to be consistent with the results of a Density Functional Theory (DFT) study. The results indicated that the -OH and -COOH groups on the CNPs displayed electron acceptors from the F– ions. Additionally, the fluoride removal of actual groundwater from the prepared adsorbents was 17 %. The small percentage of adsorption efficiency in groundwater was because of pH and co-exiting ions. Finally, the use of biomass waste as a biochar adsorbent to control the fluoride excess in groundwater in the problematic area could promote the sustainability of water safety for the community, especially in the northern part of Thailand. HIGHLIGHTS The adsorption process removes fluoride using Napier grass biochar (CNP_600) and NaOH functionalization (CNP_0.2NaOH_600). Based on the function groups of the materials, we can use the DFT study results to confirm the behavior of F–ions in the biomass samples. The experimental study's adsorption mechanism followed a similar pattern to the DFT studies. This confirms that CNPs help F–ions form strong H-bonds. The O-H bond lengthened from 0.97 Å to 1.40 Å, confirming the strong interaction between CNP and fluoride ions. GRAPHICAL ABSTRACT

Synthesis, structural properties, DFT studies, antimicrobial activities and DNA binding interactions of two newly synthesized organotin(IV) carboxylates

Experimental results have shown that palladium complexes with chelating aryl- and alkyl-substituted bis-NHC ligands, including [(H3C-Im)2CH2]PdBr2, [(C6H5-Im)2CH2]PdBr2, and [(H3CO-C6H4-Im)2CH2]PdBr2 are excellent catalysts for the Mizoroki-Heck reaction. To better understand and improve the catalysts, a density functional theory (DFT) study of the Heck reaction has been performed at the B3LYP/6-31G* level of theory, complemented by M06/def2-TZVP single-point calculations. Different mechanistic pathways have been investigated and compared to available experimental results. The most likely mechanism is a cationic catalytic cycle involving the palladium oxidation states 0 and +II. We also looked at other oxidation states, but on the basis of the calculated Gibbs free energy a +II/+IV mechanism can be excluded. Aryl substitution with electron-donating groups at the para position (e.g., the methoxy group in [(H3CO-C6H4-Im)2CH2]PdBr2) was found to reduce the reaction barrier of the rate-determining step. This is in agreement with the experimental findings for the catalysts. The experimentally observed cis selectivity could also be explained by the DFT study.

The complexation of levofloxacin hemihydrate with divalent metal ions in aqueous medium at variable temperatures: Combined UV–Visible spectroscopic and DFT studies

Structures and energetics of lithium adatom and its dimer on graphene–a DFT study