B3PW91 Methods Research Articles

Theoretical study about the thermal stability and detonation performance of the nitro-substituted derivatives of 4-(1H-1,2,4-triazol-1-yl) pyrimidine

The nitro groups are introduced into 4-(1H-1,2,4-triazol-1-yl) pyrimidine to substitute the hydrogen atoms successively, through which a total of 31 derivatives are constructed to look for high energy density compounds (HEDCs). To probe the thermal stabilities, the heats of formation (HOFs) are calculated by using the G3MP2 method. To explore the dynamic stability, the natural bond orbital (NBO) analysis is performed to confirm the trigger bond, for which the bond dissociation energy is calculated using the B3PW91 method with the 6-311 + G(d,p) basis set. Furthermore, the detonation velocity (D), the detonation pressure (P), the molecular density (ρ), the explosive heat (Q), and character height (H50) are also predicted. Based on our calculation, it is confirmed that D1, D2, D5, and E are potential high-energy-density compounds with sufficient stability and excellent detonation performance.

Better performance of Hartree–Fock over DFT: a quantum mechanical investigation on pyridinium benzimidazolate types of zwitterions in the light of localization/delocalization issues

ContextWith the advent of fast computing facilities, combined with rapid emerges of many new and intricate quantum mechanical functionals, computations with pure Hartree–Fock (HF) theory are now-a-days regarded as trivial or obsolete, or even considered as not reliable by many researchers. Consequently, current trends in computational chemistry show extensive use of post-HF theories for smaller molecular systems and various DFT methods for organic and inorganic chemistry related problems (larger molecules/systems). In this contribution, I have tried to show that sometimes, HF might be more suitable over DFT methodologies in addressing structure–property correlations. Molecules studied here were previously synthesized by Boyd in 1966 and important experimental data were produced by Alcalde and co-workers in 1987. Comparison of computed and experimental results clearly shows that HF method was more effective in reproducing the experimental data compared to especially the DFT methodologies. Reliability of HF method was further assured from the very similar results shown by the CCSD, CASSCF, CISD and QCISD methods. Current study also indicates that the localization issue associated with HF proved to be advantageous over delocalization issue of DFT based methodologies, in correctly describing the structure–property correlation for zwitterion systems.MethodsAll computations were performed with Gaussian 09. A wide-range of quantum mechanical methodologies, HF, B3LYP, CAM-B3LYP, BMK, B3PW91, TPSSh, LC-ωPBE, M06-2X, M06-HF, ωB97xD, MP2, CASSCF, CCSD, QCISD, CISD and semi-empirical methods like, Huckel, CNDO, AM1, PM3MM and PM6, were used for investigations.Graphical abstract

Theoretical Investigation on Highly Efficient Quinacridone Derivatives for Green Dopant OLEDs: A DFT Simulation

The present computational work deals with the Quinacridone green dopant theoretical organic light emitting diode molecule has been carried out with density functional theory by using Gaussian09 package. All the quantum chemical calculations have been performed with HF, B3LYP and B3PW91 functional methods. The structural parameter, bond topological analysis and the corresponding electrostatic and transport properties of the OLED molecule has been calculated. The laplacian of electron density and bond ellipticity of molecule have been studied for various optimized methods. The atomic charges of the molecule for different optimized methods has been analysed with AIM, MPA and NPA charges. The HLG of the molecule are calculated from different optimized basis sets. The HF method value is 8.49 eV. The B3LYP and B3PW91 methods energy values are 3.13 eV and 3.12 eV respectively. These values are most equal to the energy gap obtained from density of states (DOS) spectrum. Hence, the ESP shows that expend of O-atoms and the charge accumulated through Quinacridone OLED molecule. The grateful Quinacridone green dopant derivative molecule is high quantum efficiency, longer lifetime and very useful to industrial organic pigment of these molecules.

Molecular structure and spectroscopic properties of two radicals of C4H2N: a DFT study.

The cyano propargyl radical (CH2C3N and HC3HCN) is important reaction intermediate in both combustion flames and extraterrestrial environments such as cold molecular clouds and circumstellar envelopes of carbon stars. The acquisition of spectroscopic constants and anharmonic effect facilitates a more in-depth study of this radical. However, the data available in the literature do not allow the precise predictions for it in the interstellar medium. In this work, complete spectroscopic parameters as well as anharmonic constants of two radicals of C4H2N have been evaluated by different DFT methods. The calculated results show that it is reasonable to study the molecular spectroscopic properties of C4H2N by wB97XD/6-311++G theoretical level. On this basis, the sextic centrifugal distortion constants, anharmonic constants, vibration-rotation interaction constants, and so on are predicted for the study of high-precision rovibrational spectrum. In addition, the relationship between the anharmonic effect and vibration mode of CH2C3N and HC3HCN and their infrared spectroscopic characteristics are discussed. The calculation of the anharmonic force fields and spectroscopy properties was performed using B3LYP, B3PW91, CAM-B3LYP, and wB97XD methods combined with the 6-311++G and aug-ccpVTZ basis sets, respectively, by the Gaussian16 program suite. The IR spectra were performed with Multiwfn3.8.

Indazole-derived synthetic cannabinoids: Absolute configuration determination and structure characterization by circular dichroism and DFT calculations

An increasing number of products containing synthetic cannabinoids pose a growing crisis to public health worldwide. Recently, a rising number of cases of serious adverse health effects, intoxications, and death cases associated with synthetic cannabinoids were reported. The current study represents the comprehensive structural analysis of three new synthetic cannabinoids (AB-, ADB- and AMB-FUBINACA) in solution investigated by electronic and vibrational circular dichroism together with the conventional methods of infrared and ultraviolet absorption spectroscopy, all supported by the density functional theory (DFT) calculations. The best level of theory to reproduce the experimental wavenumbers and wavelengths was found to be the B3PW91 method with a 6-311++G(d,p) basis set including the implicit solvent effect simulation. Very good agreement between the experimental and simulated spectra allowed us to determine the absolute configuration and a detailed interpretation of the IR absorption, VCD, ECD and UV spectra of AB-, ADB- and AMB-FUBINACA. In addition, the HOMO and LUMO electronic transitions were calculated.

Density Functional Theory and Ab Initio Hartree-Fock Computational Study of 2-[1-Acetyl-3-Methyl-4,5-Dihydro-1H-1,2,4-Triazol-5-One-4-Yl]-Phenoxyacetic Acide

In the present theoretical study, the 2-[1-acetyl-3-methyl-4,5-dihydro-1H-1,2,4-triazol-5-one-4-yl]-phenoxyacetic acide was optimized by B3PW91 and HF methods 6-311+G (d.p) basis set using the Gaussian G09W program. The molecular structure, HOMO and LUMO energy analysis, electronic transitions, total static dipole moment, the mean polarizability, the anisotropy of the polarizability, the mean first-order hyperpolarizability, electronegativity, chemical hardness, molecular electrostatic potential maps (MEP) and Mulliken charges of 2-[1-acetyl-3-methyl-4,5-dihydro-1H-1,2,4-triazol-5-one-4-yl]-phenoxyacetic acide molecule have been investigated by using B3PW91 and HF methods with the 6-311+G (d, p) basis set. The calculated IR data of titled compound were calculated in gas phase by using of 6311+G (d, p) basis sets of B3PW91 and HF methods and are multiplied with appropriate adjustment factors. Theoretical infrared spectrums are formed from the data obtained according to B3PW91 method. In the identification of calculated IR data was used the veda4f program. 1H-NMR and 13C-NMR spectral data values were calculated according to the method of GIAO using the program package Gaussian G09W Software. Experimental data were obtained from the literature. Experimental and theoretical values were inserted into the graphic according to equitation of δ exp=a+b. δ calc. The standard error values were found via SigmaPlot program with regression coefficient of a and b constants. In addition, in vitro antioxidant properties of this compound was investigated.

Experimentical and Gaussian Calculations of 3-Ethyl-4-(2-Benzenesulfonyloxy)-Benzylideneamino-4,5-Dihydro-1H-1,2,4-Triazol-5-One

3-Ethyl-4-(2-benzenesulfonyloxy)-benzylideneamino-4,5-dihydro-1H-1,2,4-triazol-5-one has been optimized using the DFT/B3LYP and B3PW91 methods with the 6-311G(d,p) basis set in the ground state. The vibrational (IR) frequencies, 1H and 13C NMR chemical shift values (in gas phase and in DMSO solvent), nonlinear optical properties (NLO), HOMO−LUMO analysis and molecular electrostatic potential surfaces of 3-Ethyl-4-(2-benzenesulfonyloxy)-benzylideneamino-4,5-dihydro-1H-1,2,4-triazol-5-one have been calculated using the DFT/B3LYP and DFT/B3PW91 methods with the 6-311G(d,p) basis set. IR absorption frequencies of titled molecule were calculated by same methods. Theoretically calculated IR data are multiplied with appropriate adjustment factors. The data obtained according to DFT/B3LYP and DFT/B3PW91 are formed using theoretical infrared spectrums. The veda4f program was used in defining IR data which were calculated data. 1H-NMR and 13C-NMR isotropic shift values were calculated by the method of GIAO using the program package Gaussian G09W. Experimental and theoretical values were inserted into the grafic according to equatation of δ exp=a+b. δ calc. The spectroscopic and structural data of titled molecule has been calculated by using 6-311G(d,p) basis set with DFT/B3LYP and DFT/B3PW9. The values obtained were compared with experimental values.

Quantum Chemical Investigations on the Hydrogen-Bonded Interactions of Bioactive Molecule N2-(4-Methoxysalicylidene) Arginine Hemihydrate

The geometry optimization, natural bond orbital analysis, and vibrational analysis of a Schiff base compound N2-(4-Methoxysalicylidene) Arginine Hemihydrate (4MSAH) were carried out using the density functional B3PW91 method with the 6–31 G (d,p) basis set. Natural Bond Orbital (NBO) analysis is carried out to examine the various intra and inter molecular interactions of molecular system. Normal coordinate analysis was carried out to elucidate the vibrational modes and the assignments were made on the potential energy distribution. From the vibrational analysis, it is endorsed that the stretching wave number of hydrogen bond donor COO- and hydrogen bond acceptor NH2 + is shifted due to the interaction. MO (Molecular Orbital) analysis was accomplished to propose the biological activity of the molecule and the impact of the transition of electrons from n→π* was studied using the UV transmittance spectrum. The molecular orbital contributions are studied by using DOS spectral analysis. Topological studies of 4MSAH were conducted utilizing the Electron Localization Function (ELF) and the Local orbital locator (LOL). Hirshfeld surface analysis and reduced density gradient analysis were conducted to investigate distinct covalent and non-covalent interactions. Molecular docking was employed on antifungal proteins to explore protein-ligand interactions and verify the compound’s bioactivity.

Spectroscopic details on the molecular structure of pyrimidine‑2‑thiones heterocyclic compounds: computational and antiviral activity against the main protease enzyme of SARS-CoV-2

Computational tools in investigating of spectral heterocyclic compounds ranges based on pyrimidine‑2‑thiones, take some importance in identifying their molecular and electronic behavior. Some charcoal heterocyclic compounds were previously synthesized in our laboratory and their experimental results were compared with the computational evaluation. Computational spectroscopic analytical items (IR, NMR and UV–Vis) were calculated using the more popular DFT methods and the predicted results were compared with the reported experimental ones. Quantum and chemical parameters were calculated and molecular electrostatic surface potential (MEP) was studied which predicted the highly electronic sites around the compounds. Some molecular properties (ionization energy, electron affinity, energy gap, hardness, electronegativity, electrophilicity index, static dipole moment and average linear polarizability) of these Schiff bases which were computed at B3LYP/6-31G(d,p) level in aqueous phase. Benchmark analysis was performed for three ab initio functionals such B3LYP, BPV86 and B3PW91 methods to explain the data resulted from NMR spectra. The docking study of some selected previously synthesized compounds was performed using the viral Mpro enzyme protein in compared to a k36 reference ligand inhibitor. The study indicated the ability of the synthesized compounds to form H-bond and hydrophobic (VDW, π-alkyl and π-sulfur) interactions with Mpro enzyme receptor with high inhibition effect of compound L2.

The molecular structure, spectroscopic properties and partition functions of C3H2S isomers: An ab initio study

The anharmonic force fields, spectroscopic constants and partition functions of three isomers of C3H2S have been studied employing B3LYP, B3PW91, M06-2X, MP2 or CCSD(T) methods with 6-311++G (2d,2p) or 6-311++G (3df,2pd) basis sets. The equilibrium geometries, energies, rotational constants, harmonic and fundamental frequencies, centrifugal distortion constants and partition functions of three isomers of C3H2S are calculated and compared with the existing data. The MP2/6-311++G (3df,2pd) results well reproduce the previous theoretical or experimental results, so we predict other spectroscopic properties of C3H2S based on the MP2/6-311++G (3df,2pd) theoretical level. The relationship between structure and spectroscopic properties for three isomers of C3H2S is also analyzed in detail. We hope that the obtained spectroscopic constants and partition functions of C3H2S isomers can provide strong support for further research of spectroscopic properties.

Theoretical Investigation of 1H and 13C NMR Spectra of Diethanol Amine Dithiocarbamate RAFT Agent

In this study, quantum chemical studies of diethanolamine dithiocarbamate (DADC) RAFT compound were carried out. For this purpose, the composite was optimized by using the DFT / B3LYP method 6-311G and the B3PW91 method SDD basis set. By using the optimized structure obtained according to the GIAO method, 1H and 13C NMR chemical shift values in the gas phase were calculated. According to the results obtained, it was seen that the theoretical data were coherent with the experimental data. In addition, in the theoretical part of the study, the FT-IR frequency values of the compound synthesized by using the same methods and basic set were compared experimentally and theoretically. In addition, the structure details and analysis of molecules, electronic properties such as HOMO and LUMO energies, molecular electrostatic potential (MEP) and thermodynamic properties have been performed. The electric dipole moment (μ) and the initial hyperpolarizability (β) values of the studied molecule were calculated by using ab initio quantum mechanical calculations. In addition, the calculated results show that the (DADC) molecule can have nonlinear optical (NLO) behavior with nonzero values. Neutral Band Orbital (NBO) analysis has been calculated with DFT / B3PW91/SDD basis set.

Adsorption of doxepin drug on the surface of B12N12 and Al12N12 nanoclusters: DFT and TD-DFT perspectives

The adsorption of Doxepin (DOX) drug on the surfaces of B12N12 and Al12N12 nanoclusters was studied by using DFT and TD-DFT calculations at the B3PW91 method and 6–31 + G* basis set in the solvent (water). The adsorption effect of the DOX drug on the bond lengths, electronic properties, and dipole moment of the B12N12 and Al12N12 nanoclusters was studied. The change in λmax was assessed by an investigation of calculated UV spectra. NBO analysis displayed a charge transfer between DOX and two nanoclusters. The LOL and ELF values of the B–N bond are the greater than B–O, Al–O, and Al–N bonds, confirming stronger interaction between the boron atom of B12N12 nanocluster and the nitrogen atom of the DOX drug. It is found that the B12N12 nanocluster can be suitable as a drug carrier system for the delivery of DOX drug. The results of our study can be used to design a suitable carrier for the DOX drug.

Effects of auxiliary electron-withdrawing moieties on the photovoltaic properties of D-π-A’-π-A phosphonic acid-based DSSCs

Dye-Sensitized Solar Cells (DSSCs) that are based on a donor-bridge-acceptor-bridge-donor (D-π-A’-π-A) oligothiophene dye-containing benzothiadiazole mono-functionalized by a phosphonic acid were theoretically studied during the changing of the auxiliary acceptor (A’) by six other auxiliary acceptors. To further understand the molecular structure of these series of dyes, a density functional theory (DFT) calculation was performed to study the molecular geometries, frontier molecular orbitals (FMO) by employing the method B3PW91 with the basis set 6-311G(d) for the soft atoms (H, C, N, O, P, Si, S) and LANL2DZ for the heavy atoms (Se, Te). The optical properties of the free and the adsorbed dyes were modelled using TD-DFT simulations employing the functional BHandH. The calculated absorption spectra of the designed dyes indicate that the change of electron-withdrawing groups increases the absorption wavelength significantly. Our results showed that the BTD, BXD, BTED, BSED, BIA, and BSD dyes exhibit a narrower HOMO–LUMO energy gap than BTZ dye. This led to a broader optical absorption and lower oscillator strength in dyes containing Benzimidazole, Benzosiladiazole, Benzoselenodiazole, and Benzotellurodiazole moieties that were verified to be better auxiliary acceptor units. The simulated absorption spectra of the adsorbed dyes on (TiO2)9 are red-shifted compared to the free dye. The adsorption energies of all dyes are similar which reveals that the adsorption energy is not depending on the auxiliary moiety but rather on the anchor group. Therefore, it is expected that the results obtained from this investigation will have a substantial impact on the development of DSSC of phosphonic acid-based dyes.

Orbital character and vibrational spectra study on carbon monoxide and nitrosyl compound Mn(NO)3CO

The geometry, electronic structure, energy and vibrational spectra of Mn(NO) 3 CO have been studied using B3P86, B3LYP and B3PW91 methods at 6-31G basis set level. Three states have been found and all states have been fully investigated employing the molecular orbital theory and vibrational analysis. From the calculation, we have found that the singlet state is the most stable one.

Theoretical research on cage-like furazan-based energetic compounds and its derivatives.

In this manuscript, we reported the design and prediction of two furazan-based cage-like molecules and their derivatives using density function theory (DFT). The heat formation and detonation properties were calculated using Hess's law and Kamlet-Jacobs equations with the B3PW91 method. The molecular stability and geometry were analyzed using the M06-2X method, and molecular crystal structures were predicted based on Monte Carlo simulation, while chemical reactive sites were judged using the PBE0 method based on Fukui function. The theoretical calculation result proved that the designed molecules exhibit ideal symmetric cage-like geometry and show superior physicochemical and detonation properties. Compared with traditional energetic materials, the designed molecules display more positive solid heat formation and lower sensitivity. The designed molecules could be considered promising high energy density material candidates with potential synthesis and application value. Two designed molecules display superior detonation performance and ideal completely symmetric cage-like geometry, which were proved theoretically as a promising HEDM candidate. A series of derivatives also exhibited excellent crystal density and physicochemical properties, while with more stable structure.

Quantum chemical study of 5,5-dimethyl-1,3-dioxane isomerization to 2,2-dimethyl-3-methoxypropanal, - the general reaction scheme

The results of quantum chemical simulation by B3PW91 method in the 6-31G(d,p) basis for formation of 2,2-dimethyl-3-methoxypropanal from 5,5- dimethyl- 1,3- dioxane in the presence of proton are given. The proposed reaction scheme involves protonation of the parent molecule - formation of the oxonium ion, breaking of C-0 bond with receipt of alkoxycarbenium ion, rearrangement of the alkoxycarbenium ion by two successive 1,3-displacement or 1,5 displacement of positive charge, deprotonation of the oxycarbenium ion with formation of the reaction product. Data on the structure and energy characteristics of molecular products, ions, and transition states are obtained not only for the states characterized minimum Gibbs energy (G298, δG298, δG# 298), but also for possible conformers and transitions between them. Based on the calculations, an energy diagram is drawn up in accordance with the general reaction scheme.Comparison of the estimated activation barriers (δG# 298) for implementation of the reaction in two stages (1,3-migrations) and one-stage 1,5-migration showed that they are comparable in size, the difference is about 2 kcal/mol. Since conversion of 5,5- dimethyl- 1,3- dioxane to 2,2-dimethyl-3-methoxypropanal is an endothermal reaction with heat absorption of 3.4 kcal/mol, it can be assumed that in real conditions transformation of ions as per the reaction coordinate will include both two-stage and one-stage conversion of alkoxycarbenium ion to the oxycarbenium ion.

Hydroxyl Radical Reactivity with Cytosine and Thymine: A Computational Study

Addition of hydroxyl radical (OH) at the different sites of cytosine and thymine were studied at the different levels of theory of the density functional theory (DFT). All the molecular geometries were optimized at B3LYP, B3PW91, WB97XD, and MPW1PW91 methods with 6-31G (d,p) basis set. The binding energies at the different sites of these two DNA bases were calculated at all the mentioned levels of theory in gas phase and also in different solvents of dielectric constant varying from lower to higher values. The dependence of binding energies in water, methanol, ethanol, acetone, toluene and benzene reveals that binding energies are not much affected by salvation.

Synthesis, Characterization, Crystal Structure and Quantum Chemical Calculations of 2-oxo-2H-chromen-3-yl Acetate

This paper is focused on a combined experimental and theoretical study of 3-substituted coumarin derivative, the 2-oxo-2H-chromen-3-yl acetate (I). The compound was synthesized by reacting chroman-2,3-dione and acetic anhydride in dried diethyl ether in the presence of dried pyridine and crystallized in the orthorhombic crystal system with Pbca space group. The lattice parameters of the structure are a=14.6770 (1), b=7.1079 (1), c=17.6767 (2) Å, α=β=γ=90° with 8 molecules per unit cell (Z=8). The compound has been characterized structurally by Spectroscopy utilizing ¹H NMR, ¹³C NMR and IR techniques and by crystallography using the X-Ray diffraction (XRD) analysis. In the crystallographic study, the positions of the atoms were determined by direct methods and refined to a final R value of 0.038 for 1768 independent reflections. The stabilization of the structure is provided by intermolecular C-H•••O hydrogen bonds extending along [010] direction. Likewise, the presence and nature of intermolecular contacts are determined by the 3-D molecular Hirshfeld surface and 2-D fingerprint plot analysis which indicate the main contributions to the Hirshfeld surface, 38.7% for O ••• H and 28.7% for H •• H. Moreover, the molecular geometry of (I) was as well minimized utilizing density functional theory (DFT/RB3LYP), the frequency calculations with RB3LYP method, the basic <i>ab initio</i> model i.e the restricted Hartree-Fock (RHF) and the exchange component of Perdew and Wang’s 1991 functional B3PW91 methods with the 6-311⁺⁺G(d, p) basis set in ground state. The derived structural parameters highlight very good correlation with the crystallographic results. Frontier molecular orbitals (HOMO-LUMO), their energy gap, the non-linear optical effects (NLO) and related reactive parameters were also computed to better apprehend the properties of the molecule.

A computational study of the SNAr reaction of 2-ethoxy-3,5-dinitropyridine and 2-methoxy-3,5-dinitropyridine with piperidine

Abstract A computational study of the chemical kinetics and thermodynamics study of the SNAr between 3,5-dinitroethoxypyridine 1a and 3,5-dinitromethoxypyridine 1b with piperidine 2 in the gas phase is reported using hybrid density functional theory method B3PW91 and 6–31G(d,p) basis set. The reaction was modeled via both the catalyzed and base-catalyzed pathways which proceeded with the initial attack of the nucleophile 2 on the substrates 1 to yield the Meisenheimer complex intermediate that is stabilized with hydrogen bonding. Calculations show that the reaction goes via the formation and decomposition of a Meisenheimer complex, which was observed to be stabilized by hydrogen bonding. Along the uncatalyzed pathway, the decomposition of the Meisenheimer complex was the slow step and requires about 28 kcal/mol. This barrier was reduced to about 14.8 kcal/mol with the intervention of the base catalyst, thus making the formation of the Meisenheimer complex rate determining. All reactions were calculated to be exothermic, about −6.5 kcal/mol and −0.6 kcal/mol, respectively, for the reaction of 1a and 1b with 2.

Synthesis and characterization of Manganese(III) tetraphenylporphyrinato chloride immobilized on multi-wall carbon nanotubes, and its application as an efficient and reusable catalyst in the biomimetic oxidation of sulfides: A comprehensive experimental and computational study

In the present study, manganese(III) tetraphenylporphyrinato choloride, was immobilized on multiwall carbon nanotubes by covalent bonding. The structures of [Mn(TPP)Cl]@AP-MWC catalyst was confirmed by FT-IR, UV–vis spectroscopic techniques and scanning electron microscopy (SEM). Then, the ability of this novel heterogeneous catalyst was investigated in the oxidation of linear and cyclic sulfides under magnetic stirring conditions. Also, the DFT computational method (B3PW91 method with LanL2DZ basis set) was used for further analysis of this catalyst. Based on this method, the molecular geometries and frequencies of vibrations, chemical shifts, absorbed wavelengths, hyper-conjugative interactions, electron transitions between electron surfaces, positive and negative charges, HOMO and LUMO gap, wavelength (λ), chemical potential (µ), ionization energy (IE), global hardness (η), global softness (S), electrophilicity index (ω) and electronegativity (α) of the most intensity electronic transition for carbon nanotubes and [Mn(TPP)Cl]@AP-MWCNT catalyst were calculated. The activity and efficiency of this catalyst were then investigated in the biomimetic oxidation of sulfides. The [Mn(TPP)Cl]@AP-MWC heterogeneous catalyst showed the advantages such as high efficiency, good to excellent yield, short reaction times, easy separation and high reusability of the catalyst.