Comparative Density Functional Theory Research Articles

Adsorptin of bendomustine anti-cancer drug on Al/B-N/P nanocages: A comparative DFT study

Anti-cancer drug delivery based on nanocages is important step in drug development process due to reducing side effects and drug-releasing near the tumor cell. We have studied the interaction of the bendamustine anti-cancer drug with the Al/B-N/P nanocages with utilization density functional theory (DFT) approach both in gas and water phases at the B3LYP/6-31G (d,p) level of theory. Results show that the nanocages quantum parameters were somewhat varied by the adsorption of the bendamustine drug. The bendamustine drug operates as an electrons donor and can adsorb in the site of the electron?s acceptor of nanocages. The changes in Gibbs energy correspond to a chemisorption in both phases. The results indicated that the bond between studied nanocages and bendamustine is covalent. However, all studied nanocages may be favorable candidates for detecting the bendamustine drug. Yet, pristine B12P12 and B12N12 nanocages appeared to be more suitable for drug delivery than Al12P12 and Al12N12 based on their recovery times.

Adsorption behavior of mercaptopurine and 6-thioguanine drugs on the B12N12, AlB11N12 and GaB11N12 nanoclusters, a comparative DFT study

Lately, drug delivery systems established on nanostructures have become the most proficient to be studied. There are different studies suggested that the BN nanoclusters can be used as drug carriers and transport drugs in the target cell. Therefore, the interactions and adsorption behavior of Mercaptopurine (MC) and 6-thioguanine (TG) as anti-cancer drugs on the B12N12 (BN), AlB11N12 (AlBN) and GaB11N12 (GaBN) nanoclusters were studied by density functional theory (DFT) and quantum mechanics atoms in molecules (QMAIM) methods to find a new drug delivery system. Our results showed strong adsorption obtained in BN-MC/TG and AlBN-MC/TG complexes can be decomposed by the BN and AlBN indicating that these nanostructures are not suitable in drug efficiency of MC and TG drugs. Unlike the BN and AlBN nanoclusters, GaBN significantly makes the MC and TG drugs adsorption energetically favorable. The high solvation energy of GaBN when interacting with MC and TG drugs led it to applicability as nanocarriers for these drugs in the drug delivery systems. Furthermore, GaBN has a short recovery time for MC, and TG drugs desorption compared to BN and AlBN nanoclusters. It is predicted that the MC, and TG drugs over GaBN can be used as a drug delivery system. Communicated by Ramaswamy H. Sarma

C36 and C35E (E=N and B) Fullerenes as Potential Nanovehicles for Neuroprotective Drugs: A Comparative DFT Study

AbstractDoped fullerenes are extraordinary materials with unique electronic and optical properties, which also show potential for diverse biomedical applications. Employing density functional theory (DFT) and time‐dependent density functional theory (TD‐DFT) calculations; we studied the propensity of C36 and C35E (E=N and B) fullerenes as potential nanovehicles for certain neuroprotective drugs that are efficacious for Parkinson's disease. Baclofen, modafinil, rasagiline and rivastigmine were systematically studied to analyze whether they could be carried by small fullerenes. C36 and C35N fullerenes represent promising nanostructure candidates, due to their adsorption energy (physisorption) and favorable electrostatic interaction for the molecular transport of baclofen and rivastigmine drugs. Furthermore, in order to evaluate the effect of temperature on these interactions, ab initio molecular dynamics (AIMD) were also performed. The results from this work are expected to motivate additional investigations concerning these systems, using both theoretical and experimental approaches, in order to demonstrate their versatility as novel carbon‐based nanovehicles.

A comparative DFT study of tetracyanoquinodimethane and its difluoro and tetrafluoro analogs

The optimized molecular structures, harmonic vibrational wavenumbers and corresponding vibrational assignments, frontier molecular orbitals and UV data of 7,7,8,8-tetracyanoquinodimethane, 2,5-difluoro-7,7,8,8-tetracyanoquinodimethane and 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane were computed using quantum mechanical code. Calculations were carried out at Becke-3-Lee-Yang-Parr (B3LYP) functional with density functional theory (DFT) and time-dependent density functional theory (TD-DFT) using the 6–311++G (d,p) basis set. The theoretical results were successfully compared with some of the available experimental data. The influence of fluorine on the structural, vibrational and electronic properties were investigated. The addition of fluorine reduces both the electrical and optical band gaps. The findings of this research can be useful for analogs of the molecules studied which have potential applications in the design of organic semiconductors for electronic devise applications.

Rational Preparation of Atomically Precise Non-Alkyl Tin-Oxo Clusters with Theoretical to Experimental Insights into Electrocatalytic CO 2 Reduction Applications

Tin oxides (SnO2) have been widely utilized in electronics, nanolithography, and catalysis. As the atomically precise models of SnO2, tin-oxo clusters (TOCs) not only provide opportunities for mech...

New Insights into H2S Adsorption on Graphene and Graphene-Like Structures: A Comparative DFT Study

The efficient removal of pollutants from different environments has been one of the great challenges for scientists in recent years. However, the understanding of the mechanisms underlying this phenomenon is still the subject of passionate debates, mainly due to the lack of experimental tools capable of detecting events at the atomic scale. Herein, a comparative theoretical study was carried out to capture the adsorption of H2S on metal oxide surfaces such as zinc oxide (ZnO) and beryllium oxide (BeO), as well as graphene and Ni-decorated graphene. A simulation based on density-functional theory (DFT) was carried out by adopting General Gradient Approximation (GGA) under the Perdew–Burke–Ernzerhof (PBE) function. The calculations quantified H2S adsorption on the considered metal oxide sheets as well as on the non-decorated graphene having a physical nature. In contrast, H2S adsorbed on Ni-decorated graphene sheet gave an adsorption energy of −1.64 eV due to the interaction of S and Ni atoms through the formation of a covalent bond, proof of chemisorption. It seems that the graphene sheet decorated with Ni atoms is a more suitable adsorbent for H2S molecules than BeO, ZnO, or non-decorated graphene, providing a theoretical basis for future studies.

Raman spectra of polyethylene glycols: Comparative experimental and DFT study

Experimental Raman spectra of liquid and solid polyethylene glycols (PEGs) with various molecular weights were compared with the results of the density functional theory (DFT) calculations. The structure, energies and Raman spectra of molecules in the trans and 72 helical conformations with various orientations of the terminal groups were calculated for PEG molecule with 9 monomer units. Recorded spectrum of PEG with the average molecular weight of 400 Da (8–9 monomer units) matches very well the calculated spectrum of the most thermodynamically stable g’G(TTG)8g’ conformation. DFT-calculated Raman spectra for the g’G(TTG)ng’ conformation depend on the amount of the monomer units in PEG molecule. The peak position of the PEG Raman line at about 1100 cm−1 can be used to estimate the molecular weight distribution of short molecules.

Highly efficient one pot palladium-catalyzed synthesis of 3,5-bis (arylated) pyridines: Comparative experimental and DFT studies

Many different alkyl and aryl substituted pyridine based organic derivatives have been synthesized due to its uniqueness pyridine core. However, the transition metal catalyzed Suzuki cross coupling reaction has provided an easy route to the synthesis of alkyl and aryl substituted pyridine based organic compounds. Herein, we reported the arylated pyridines derivatives: 3, 5-bis (4-(trifluoromethoxy) phenyl) pyridine (BTFMP), 3,5-bis(4-bromophenyl)pyridine(BBPP), 3,5-bis(4-phenoxyphenyl)pyridine (BPPP) and 3,5-bis(2,5-dimethoxyphenyl)pyridine (BDMPP) by cross coupling Suzuki methodology for the first time. All derivatives have been characterized through 1H NMR, 13CNMR, 19F NMR and FT-IR spectroscopic techniques. Two compounds (BPPP) and (BDMPP) exist in the form of crystals among studied compounds. Therefore, SC-XRD has been performed for BPPP and BDMPP. In addition, computational studies using density functional theory (DFT) have been carried out in order to compare the DFT based data with the experimental findings. The optimization, FT-IR, natural bond orbitals (NBOs), frontier molecular orbitals (FMOs) and nonlinear optical (NLO) calculations of all derivatives have been performed using B3LYP/6-311G(d,p) level. The simulated HOMO-LUMO energy difference is observed to be large which shows the kinetic stability of the molecules. The molecular stability also originating from charge delocalization and hyper conjugative interactions has been elucidated by NBOanalysis. MEP surfaces are also developed of entitled molecules. The NLO data pointed out that the first order hyperpolarizability for BTFMP, BBPP and BPPP is greater among studied molecules than the standard molecule.

Computational studies of 4-nitrophenyl- and 2-benzothiazolyl-substituted formazans and tetrazolium salts

Formazans and tetrazolium salts are two structurally related classes of organic compounds that form redox pairs with each other. They have broad application in biomedical research, and as specialty dyes, metal ligands and colorimetric indicators (e.g., for the dosimetry of ionizing radiation). The recent research interest has been focused primarily on formazans, including computational studies of their properties via density functional theory (DFT) and time-dependent DFT (TD-DFT). However, there are, to our knowledge, no computational studies of tetrazolium salts exist. To remedy this situation, we present a comparative DFT and TD-DFT study of eleven pairs of triaryl-substituted formazans and tetrazolium salts, containing phenyl, 4-nitrophenyl, 4-bromophenyl, 2-benzothiazolyl, 6-methoxy-2-benzothiazolyl and 1-naphthyl substituents. Following geometric optimization and selection of the most stable conformer (for formazans), we proceeded to examine the frontier molecular orbitals, global reactivity descriptors, molecular electrostatic potential maps and local reactivity, as well as vertical excitation energies and electronic spectra of the studied materials. Finally, through a comparison of reactivity and electronic spectra, we present a framework for the design of formazan – tetrazolium salt pairs that are suited for specific colorimetric applications.

Adsorption of Phosgene Gas on Pristine and Copper-Decorated B12N12 Nanocages: A Comparative DFT Study.

Nanostructured gas sensors find diverse applications in environmental and agricultural monitoring. Herein, adsorption of phosgene (COCl2) on pure and copper-decorated B12N12 (Cu–BN) is analyzed through density functional theory (DFT) calculations. Adsorption of copper on B12N12 results in two optimized geometries, named Cu@b66 and Cu@b64, with adsorption energies of −193.81 and −198.45 kJ/mol, respectively. The adsorption/interaction energies of COCl2 on pure BN nanocages are −9.30, −6.90, and −3.70 kJ/mol in G1, G2, and G3 geometries, respectively, whereas the interaction energies of COCl2 on copper-decorated BN are −1.66 and −16.95 kJ/mol for B1 and B2, respectively. To examine the changes in the properties of pure and Cu–BN nanocages, geometric parameters, dipole moment, QNBO, frontier molecular orbitals, and partial density of states (PDOS) are analyzed to comprehensively illustrate the interaction mechanism. The results of these parameters reveal that COCl2 binds more strongly onto copper-doped BN nanocages. Moreover, a higher charge separation is observed in COCl2–Cu–BN geometries as compared to copper-decorated BN geometries. Therefore, these nanocages may be considered as potential candidates for application in phosgene sensors.

DFT Comparison the Performance of Pd10Sn5 and Pd10Ag5 Electrocatalyst for Reduction of CO2

CO2 electrocatalysis as a hydrocarbon is a promising means of achieving economical CO2‐mediated hydrogen energy cycling. Hydrocarbons are renewable hydrogen storage materials. The development of reliable metal alloy electrocatalysts is an urgent but challenging task associated with such systems, although there is still a lack of precise reaction mechanism design.In this study, the performance of Pd10Ag5 alloy nanoparticles (NPs) and Pd10Sn5 alloy nanoparticles (NPs) on the electrocatalytic reaction of CO2 was compare. The kinetic and density functional theory (DFT) calculations show that the selectivity of the Pd‐based bimetallic catalyst to the C2 product is greater than that of C1, and the stability of Pd10Ag5 is better and less affected by the reaction environment. However, the catalytic performance of the Pd10Sn5 electrocatalyst in the liquid phase is the best. The insight obtained from the calculations is used to develop criteria for identifying new and improved catalysts for electrochemical CO2 reduction.

Defect states in monolayer hexagonal BN: A comparative DFT and DFT-1/2 study

Hexagonal boron nitride (h-BN) acts like a semiconductor vacuum to point defects enabling stable and controllable spin states at room temperature which qualifies them for quantum technological applications. To characterize their properties first-principles techniques constitute indispensable tools. The currently established paradigm for such solid-state electronic structure calculations is the density functional theory (DFT). Recently its variant, so-called DFT-1/2 method was introduced with the promise of accurate band gaps without a computational overhead with respect to ordinary DFT. Here, for the monolayer h-BN we contrast DFT and DFT-1/2 results for carbon substitutional impurities (CB, CN), boron and nitrogen single vacancies (VB, VN), divacancy, and Stone-Wales defects. Comparisons with more sophisticated, yet computationally costly techniques namely, hybrid functional DFT and the GW are also made, where available. From the standpoint of defect states embedded in the band gap region we demonstrate a clear advantage of DFT-1/2 in revealing the localized states otherwise buried within either the valence or conduction band continuum due to well-known gap underestimation syndrome of the standard DFT implementations. Thus, DFT-1/2 can serve for the rapid screening of candidate defect systems before more demanding considerations.

Influence of nitrogen vacancies on selective oxidation of aromatic alcohols on g-C3N4: A comparative DFT study

The development of new metal-free catalysts that effectively oxidise alcohols to aldehydes or ketones is one of the fundamental goals of research on environmental photocatalysis. In this study, the influence of nitrogen vacancies on the catalytic process was investigated. We performed calculations using the density functional theory (DFT) to elucidate the mechanism of selective oxidation of benzyl alcohol to benzaldehyde with molecular O2 on g-C3N4. Through modelling of the pathways of the reaction, we found that vacancy defects strongly promote the formation of aldehyde. Our results clearly depicted that there are different interaction patterns that determine the reaction energy profiles for defective and defect-free systems. Furthermore, we estimated the energy barrier for the postulated rate-limiting step for a few alcohols by using the climbing image nudge elastic band (CI-NEB) method. The obtained values agreed very well with the benzaldehyde yield reported by Ding et al. (2018) [23]. In addition to the energetic effects, the electronic properties of the nitrogen-vacancy-containing g-C3N4 were also discussed. Our results demonstrated the underlying mechanism of selective oxidation of alcohols to aldehydes on both the catalysts in a comprehensive and systematic manner. Thus, by knowing the individual reaction steps, further increase in the substrate conversion may be attained by modification of the catalyst structure.

Influence of alloying transition metals on structural, elastic, electronic and optical behaviors of γ-TiAl based alloys: A comparative DFT study combined with data mining technique

A comparative study of 3d (Cr, Mn, Cu, Zn), 4d (Zr, Nb, Mo) and 5d (Hf, W, Re) transition metals effect with a concentration x = 12.5 at % on γ-TiAl based alloys' structural, elastic, electronic and optical behaviors was carried out using the density functional theory (DFT) within the generalized gradient approximation framework. The site preference, elastic constants, bulk modulus, shear modulus, Young's modulus, hardness, Poisson's ratio, Cauchy pressures, B/G ratio, and melting temperature are systematically presented. From the present work, it can be noted that alloying with Cu, Zn, Mo, W, Re can better improve γ-TiAl ductility and our systems performance, while Zr, Nb, Hf still leave the brittle behavior with x = 12.5 at % doping concentration. However, it was found that Cr and Mn doping elements show a good hardness with appreciable ductility compared with the other systems. The electronic and optical behaviors were also discussed and evaluated to provide a deep insight regarding their trends. Finally, the combination of DFT calculations and data mining tools is very useful to classify the brittle/ductile systems and explore the correlations among alloy properties under study.

Benzothiazole pyrazole containing emissive azo dyes decorated with ESIPT core: Linear and non linear optical properties, Z scan, optical limiting, laser damage threshold with comparative DFT studies

Abstract Positional isomers of “benzothiazoles-pyrazole based azo dyes containing separate with ESIPT core” are analyzed for their “linear and non-linear optical (NLO)” properties. Dyes are emissive in ACN having Stokes shift in the range of 75 nm. Spectroscopic properties are further utilized to calculate band gap by CV. Band gap obtained by DFT and cyclic voltammetry (CV) are in good agreement with each other. Vertical excitation in six different functionals is compared with experimental absorption maxima. Non-linear absorptive coefficient (β), nonlinear refractive index (ƞ2), third-order non-linear optical susceptibility (χ3) and optical limiting (OL) in acetone, ethanol and DMSO are obtained using Z-scan technique and results are appreciable than previously reported dyes. Satisfactory laser damage threshold (LDT) values are in the range of 7.9–9.7 × 1013 W/m2. TGA study indicates that these compounds are useful in several high-temperature processes in the construction of electronic and optical devices. The geometry of the dyes are optimized at “B3LYP/6-311 + G (d,p) level”. “Molecular Electrostatic Potential” (MEP), “Frontier Molecular Orbitals” (FMO) are presented using “Density Functional Theory (DFT)” to gain structural insights. Relatively new electrophilicity descriptor- “Hyperhardness” for both the molecules are calculated which suggests the stability of molecules. Global hybrid (GH) functional (B3LYP, BHandHLYP) and range separated hybrid (RSH) (CAM-B3LYP, ωB97, ωB97X, and ωB97XD) functional are used to calculate linear and NLO properties. ωB97 is a more suitable functional observed for determining βo and γ. Direct relation in-between “dipole moment” (μ) and “linear polarizability” (α) is also presented. These dyes can emerge as attractive NLOphores in optoelectronic applications.

Theoretical investigations of the structural and electronic properties of boron nitride clusters: DFT comparison of several basis sets

In this present study, Density Functional Theory (DFT) calculations were conducted to study the structural and electronic properties of (1,1), (2,2), (3,3), and (4,4) Boron Nitride (BN) systems. Geometry optimization calculations were carried out to find the stability of BN cluster models. The obtained structural geometries are consistent with that obtained in the previous reported results [1]. The total energies increase when the cluster sizes of BNs increase. For each cluster size of BN, the four total energy values obtained from B3LYP level of theory with employing the basis sets of 6-31++G, 6-31++G**, 6-311++G, and 6-311++G** are close to each. Moreover, our computations revealed that the gap energy values of HOMO-LUMOs in the BN cluster structures have been decreased by following its structure and dimensionality. The calculated HOMO-LUMO gaps are 5.99 eV - 7.68 eV in this study. For the diagrams of molecular electrostatic potential (MEP) surfaces, the regions around the N atoms at the center hold the highest electronegative potential, which can attract more electrons in the BN systems. With a Mulliken population analysis (MPA) scheme, all the boron atoms possess the positive charges, whereas the negative charges were found on the nitrogen atom in the BN systems.

Direct methane conversion to methanol on M and MN4 embedded graphene (M = Ni and Si): A comparative DFT study

The ever increasing global production and dispersion of methane requires novel chemistry to transform it into easily condensable energy carriers that can be integrated into the chemical infrastructure. In this context, single atom catalysts have attracted considerable interest due to their outstanding catalytic activity. We here use density functional theory (DFT) computations to compare the reaction and activation energies of M and MN4 embedded graphene (M = Ni and Si) on the methane-to-methanol conversion near room temperature. Thermodynamically, conversion of methane to methanol is energetically favorable at ambient conditions. Both singlet and triplet spin state of the studied systems are considered in all of the calculations. The DFT results show that the barriers are significantly lower when the complexes are in the triplet state than in the singlet state. In particular, Si-G with the preferred spin multiplicity of triplet seems to be viable catalysts for methane oxidation thanks to the corresponding lower energy barriers and higher stability of the obtained configurations. Our results provide insights into the nature of methane conversion and may serve as guidance for fabricating cost-effective graphene-based single atom catalysts.

A comparative DFT study about surface reactivity and catalytic activity of Pd- and Ni-doped BN nanosheets: NO reduction by CO molecule

Today, the emission of poisonous gases in the atmosphere has caused many serious health and environmental problems. So, the finding of efficient methods for reducing or removing these toxic gases from the atmosphere is of great interest. The main goal of this study is to compare catalytic activity of Pd- and Ni-doped boron nitrite nanosheets (Pd-/Ni-BNNS) for the reduction of nitric oxide (NO) by CO molecule. To this aim, density functional theory (DFT) calculations are performed to calculate adsorption energies, geometric parameters, charge-transfer values, and reaction barriers. The results of DFT calculations show that the reduction of NO proceeds through a dimer mechanism. At first, two NO molecules are attached together to form (NO)2 dimer. Next, (NO)2 is decomposed into N2O and Oads species. The Oads is then removed by CO molecule: CO + Oads → CO2. All other possible reactions over these surfaces are studied in details. Our findings demonstrate that the catalytic activity of Pd-BNNS for the reduction of NO is higher than that of Ni-BNNS.

Adsorption of volatile organic and iodine compounds over silver-exchanged mordenites: A comparative periodic DFT study for several silver loadings

The ability of Ag-exchanged mordenite (Ag-MOR) to capture iodine species such as I2 and CH3I as released for instance during a nuclear accident could be severely limited by the presence of volatile organic compounds (VOCs) that can disrupt their adsorption in the zeolite. Here, using density functional theory (DFT), we investigate in detail the adsorption process of several hydrocarbons (methane, cyclohexane, benzene, and 1,3-dimethylbenzene) and oxygenated compounds (methanol, ethanol, propan-2-ol and propanone) and compare it with the adsorption of I2 and CH3I for different values of the Si/Al ratio of the Ag-exchanged mordenite. It is found that the adsorption process of the iodine species becomes favorable as the Si/Al ratio is decreased. Indeed at high Si/Al ratio, some VOCs such as benzene, 1, 3-dimethylbenzene and propan-2-ol exhibit strong inhibiting effects, while at low Si/Al ratio, only the adsorption of CH3I is limited by the presence of aromatic hydrocarbons. Also, in addition to the elongation of the II bond upon the adsorption of the iodine molecule in Ag-MOR with a high silver content, we found that there is a significant electron transfer between the Ag and I atoms. Thus, our results indicate that the II bond becomes weaker during the adsorption and therefore the formation of AgI precipitates is favored.

Synergetic effect in RuxMo(1-x)S2/SBA-15 hydrodesulfurization catalysts: Comparative experimental and DFT studies

The effect of introducing Ru impurities into the MoS2 crystalline structure of the sulfided RuxMo(1-x)S2/SBA-15 catalysts have been investigated using density functional theory (DFT) calculations and the catalyst characterization by different techniques (chemical analysis (ICP-AES), temperature-programmed reduction (TPR), X-ray diffraction (XRD), N2 physisorption, DRIFTS of adsorbed pyridine (DRIFTS-Py) and X-ray photoelectron spectroscopy (XPS)). The catalyst activity was tested in the hydrodesulfurization (HDS) of dibenzothiophene (DBT) reaction carried out in a batch reactor, T = 320 °C and total H2 pressure of 5.5 MPa. From electronic structure DFT calculations is was concluded that the 4d orbitals of both Mo and Ru played an important role in the catalyst optimization being the processes of transport and charge transference the most important ones. It was found that the enrichment with Ru, promotes a greater electronic participation (DOS at the Fermi level) of the different atoms in the RuxMo(1-x)S2 phase leading to metallization of the Mo ions. The catalyst activity in HDS of DBT reaction demonstrated a similar behavior to that of theoretical density of states (DOS) calculated via DFT. All bimetallic systems presented the synergetic effect between Ru and Mo in the HDS of DBT reaction over RuxMo(1-x)S2/SBA-15 catalysts. The highest activity observed for Ru content of x = 0.4 was consistent with theoretical results predicting that the optimum DOS contributions should be around x = 0.44. The most active Ru0.4Mo0.6S2/SBA-15 exhibit the best hydrogenation properties linked with the Ru-induced metallization of Mo ions in the Ru0.4Mo0.6S2 phase. This catalyst showed two-fold higher hydrogenation properties than CoMoS/γ-Al2O3 reference catalyst. The linear dependencies of initial activity on Brønsted-to-Lewis acidities ratio (from DRIFT-Py) and total metal surface exposure (from XPS) were observed.