Electrostatic Potential Values Research Articles

Introducing KICK-MEP: exploring potential energy surfaces in systems with significant non-covalent interactions.

Exploring potential energy surfaces (PES) is fundamental in computational chemistry, as it provides insights into the relationship between molecular energy, geometry, and chemical reactivity. We introduce Kick-MEP, a hybrid method for exploring the PES of atomic and molecular clusters, particularly those dominated by non-covalent interactions. Kick-MEP computes the Coulomb integral between the maximum and minimum electrostatic potential values on a 0.001 a.u. electron density isosurface for two interacting fragments. This approach efficiently estimates interaction energies and selects low-energy configurations at reduced computational cost. Kick-MEP was evaluated on silicon-lithium clusters, water clusters, and thymol encapsulated within Cucurbit[7]uril, consistently identifying the lowest energy structures, including global minima and relevant local minima. Kick-MEP generates an initial population of molecular structures using the stochastic Kick algorithm, which combines two molecular fragments (A and B). The molecular electrostatic potential (MEP) values on a 0.001 a.u. electron density isosurface for each fragment are used to compute the Coulomb integral between them. Structures with the lowest Coulomb integral are selected and refined through gradient-based optimization and DFT calculations at the PBE0-D3/Def2-TZVP level. Molecular docking simulations for the thymol-Cucurbit[7]uril complex using AutoDock Vina were performed for benchmarking. Kick-MEP was validated across different molecular systems, demonstrating its effectiveness in identifying the lowest energy structures, including global minima and relevant local minima, while maintaining a low computational cost.

Study on the compounding optimization of surfactants and synergistic effects on the wettability of bituminous coal

To improve the wettability of surfactants on bituminous coal and to explore its wettability and wettability mechanism on bituminous coal, taking the Sandaogou bituminous coal as an example, a single factor experiment was carried out first. Through contact angle and surface tension experiments, three surfactants with good wettability were selected from among the nine surfactants and mixed in equal proportions two by two to determine the optimal compounding method and compounding concentration. The experimental results show that the compounding of nonionic and anionic, nonionic and zwitterionic, anionic and zwitterionic surfactants can have synergistic effects and significantly improve the wettability of bituminous coal. Among them, the 0.5 wt% SDS + 0.5 wt% CAB-50 (R2) compound surfactant had the best wettability on bituminous coal, and the contact angle and surface tension were only 15.24° and 23.62 mN/m, respectively. The surface electrostatic potential values of each material molecule were calculated by Materials Studio software based on the quantum chemistry method, and correlation analysis was carried out with wettability. The results show that the surface electrostatic potentials of CDEA, SDS and CAB-50 were greater than those of water and bituminous coal, and the region of maximum negative electrostatic potential corresponded to oxygen atoms, which are easier to adsorb on bituminous coal and water molecules. Then, through molecular dynamics simulation, the interaction energy and the distribution of contributions along the Z-axis of the water/compound surfactant/bituminous coal system at equilibrium were investigated, and finally, a spray dust reduction test was carried out in the Sandaogou Coal Mine. The results showed that the 0.5 wt% SDS + 0.5 wt% CAB-50 compound solution can be used as a water molecule adsorption carrier, prompting more water molecules to be embedded into coal molecules, increasing the relative concentration of water molecules on the surface of bituminous coal, restricting the diffusion of water molecules, and greatly improving the wettability. After the addition of 0.5 wt% SDS + 0.5 wt% CAB-50 as a spray agent, the concentration of total dust at the driver's position decreased from 65.14 to 9.11 mg/m3, the concentration of exhaled dust decreased from 30.07 to 3.35 mg/m3, and the efficiency of total and exhaled dust reduction compared with that of pure water was 86.01% and 89.35%, respectively.

Aromaticity of six-membered nitro energetic compounds through molecular electrostatic potential, magnetic, electronic delocalization and reactivity-based indices

The electron density depletion associated with π-hole at the ring center typical of energetic compounds was clearly revealed by the molecular electrostatic potential (ESP). In addition, the spatial arrangement of NO2 groups appears to affect the ESP value in the ring center, and therefore sensitivity to detonation. Indeed, for monocyclic nitrobenzene compounds with the same number of NO2 groups, the ESP value in the ring center decreases as the NO2 groups are more closely spaced. As expected, the central rings become less aromatic as NO2 groups are added. The MCI, PDI, PLR, NICSzz(1), FLU indices are all strongly correlated with the ESP values observed in the ring center of the set of nitrobenzenes. Aromaticity indices based on electron delocalization criteria appear to be very sensitive to small variations in aromaticity. Among magnetic-based indices, only NICSzz(1) is capable to predict small changes in aromaticity. The PLR index derived from conceptual DFT is quite relevant for predicting small variations in aromaticity. According to our results, the most suitable aromaticity index is not based on a single criterion, and that selecting it is more subtle. Therefore, it is important to combine information from several criteria to obtain a more complete description of the aromaticity of the studied compounds.

Synthesis and characterization of hydroxamic acid N,3-dihydroxy-2-naphthamide and its copper (II) complex per keto/enol forms and rare earth flotation

Flotation is the most common beneficiation process used for separating minerals, but for rare earth minerals (REMs), performance can suffer due to the dilute nature of the rare earth elements. Furthermore, the REMs tend to possess smaller grain sizes, making the use of traditional flotation cells difficult if total liberation is needed. Consequently, improved efficiencies are needed for extracting REMs from various sources. For these systems, hydroxamic acids are commonly used as flotation collectors. Two such hydroxamic collectors were studied in this work: salicylhydroxamic acid (SHA) and N,3-dihydroxy-2-naphthamide (H2O5). Because there is no documented synthesis route for H2O5, several synthesis approaches were examined. Furthermore, because there is no information on H2O5, important structural and characteristic data was gathered regarding its (1) preferred structural isomer as a Cu2+ complex and (2) electrostatic potential values of the possible dentate groups in different tautomeric forms, thereby allowing H2O5 to be compared to SHA, particularly regarding flotation behavior. Hydrogen nuclear magnetic resonance (H-NMR), Laser Raman Spectroscopy (LRS), and predominantly Fourier-Transform Infrared (FT-IR) spectroscopy showed that both SHA and H2O5 preferred to be keto tautomers when uncomplexed; however, once chelated to Cu2+ ions, the collectors adopted enol forms. Molecular modeling using Spartan software showed an increase in the electrostatic potential of the possible dentate groups in both molecules for the enol form. H2O5 also resulted in an increased recovery by flotation of REMs of about 23% compared to SHA at similar reagent dosages.

Adsorption of drugs on B12N12 and Al12N12 nanocages.

The adsorption behavior of twelve drug molecules (5-fluorouracil, nitrosourea, pyrazinamide, sulfanilamide, ethionamide, 6-thioguanine, ciclopirox, 6-mercaptopurine, isoniazid, metformin, 4-aminopyridine, and cathinone) on B12N12 and Al12N12 nanocages was studied using density functional theory. In general, the drug molecules prefer to bind with the boron atom of the B12N12 nanocage and the aluminium atoms of the Al12N12 nanocage. However, a hydrogen atom is transferred from each of 5-fluorouracil, nitrosourea, 6-thioguanine, ciclopirox, and 6-mercaptopurine to the nitrogen atom of the Al12N12 nanocage. All the drug molecules are found to be chemisorbed on the B12N12 and Al12N12 nanocages. The adsorption energies of the drug/B12N12 system are linearly correlated with the molecular electrostatic potential minimum values of the drug molecules. The transfer of the hydrogen atom from the drug molecules to the nitrogen atom of the Al12N12 nanocage leads to relatively high adsorption energies. We observed significant changes in the reactivity parameters (e.g. electronic chemical potential) of the nanocages due to the chemisorption process. Overall, the QTAIM analysis indicates that the interactions between drug molecules and nanocages have a partial covalent character. Among the studied systems, the adsorption process was more spontaneous for the ciclopirox/Al12N12 system in water.

Combined Experimental and Theoretical Insights: Spectroscopic and Molecular Investigation of Polyphenols from Fagonia indica via DFT, UV-vis, and FT-IR Approaches.

This review deals with computational study of polyphenolic compounds of medicinal importance and interest for drug development. Herein, four polyphenolic compounds comprising catechol (1), caffeic acid (II), gallic acid (III), and pyrogallol (IV) have been isolated from a medicinal specie, Fagonia indica, by applying silica gel column chromatography. These compounds were identified by using gas chromatography-mass spectrometry (GC-MS) analysis and confirmed by geometric computational analysis. According to computational results, caffeic acid has shown the highest biological activation due to higher chemical softness, electronegativity (χ (eV) = -648.644), and electrostatic potential value (-8.424 × 10-2 to +8.424 × 10-2), while smaller values of chemical potential (-0.269), ELUMO (-0.080), and energy gap (ΔE = 0.149). The Mulliken atomic charges were calculated by using DFT/B3LYP with basis set 6-311G for the determination of active sites. The oxygen atom of catechol showed highest nucleophilic characteristic with a more negative charge (08 = -0.695), and pyrogallol indicated a strong electrophilic center at C14 = 0.415 with a higher positive charge. Moreover, UV-visible absorption spectra and a detailed study of vibrational frequencies for all phenolic compounds by employing the DFT approach with 3-21G, 6-31G, and 6-311G basis sets at the ground-state level showed the great agreement with experimental results. ANOVA has been applied to validate the theoretical data. Results suggest that compounds I-IV are suitable in diverse fields.

Potential inhibition of SARS-CoV-2 infection and its mutation with the novel geldanamycin analogue: Ignaciomycin

The impact of novel coronavirus (SARS-CoV-2) is very high; its mutant variants provide a higher transmission rate. Due to many mutations in the omicron-variant, it can evade previously available neutralizing antibodies. The inhibitory effect of the novel compound “Ignaciomycin” was investigated using various computational analyses against the RBD of the SARS-CoV-2 wild-type, Delta, and omicron-variants. Molecular docking revealed the potentially stable interaction of Ignaciomycin with an energy value of −8.65 kcal/mol for the omicron-variant. DFT and Hirshfeld surface calculations showed higher efficiency and reactivity with strong electrostatic potential values. In-silico toxicity studies revealed a significant drug-likeness score (7.5912) with non-toxic properties. MD simulation studies confirmed the stability of Ignaciomycin during ∼ 100 ns simulation. Covariance, PCA, and FEL analyses revealed significant fluctuations in residues and atom mobility in all variants based on the strong interaction of Ignaciomycin. Mutations in the Delta and omicron-variants increased the binding efficiency of the RBD of the SARS-CoV-2 S-glycoprotein with human ACE2. Ignaciomycin had high efficiency in interacting with mutated sites in the RBD, thereby blocking the interaction of the RBD with ACE2. Our findings provide a strong hypothesis for preclinical validation of Ignaciomycin as a potential drug against SARS-CoV-2 and its mutant variants.

Exploring the Co-Crystallization Landscape of One-Dimensional Coordination Polymers Using a Molecular Electrostatic Potential-Driven Approach.

The ability of coordination polymers (CPs) to form multicomponent heteromeric materials, where the key structural features of the parent CP are retained, has been explored via molecular electrostatic potential-driven co-crystallization technologies. Thirteen co-formers presenting hydrogen-bond donors activated through a variety of electron-withdrawing functionalities were employed, and the extent of activation was evaluated using molecular electrostatic potential values. Attempted co-crystallizations of the seven most promising co-formers with a family of nine CPs ([CdX'2(X-pz)2]n; X' = I, Br, and Cl; X = I, Br, and Cl) resulted in six successful outcomes; all four of the structurally characterized compounds displayed the intended hydrogen bond. The rationalization of the main structural features revealed that strict structural and electrostatic requirements were imposed on effective co-formers; only co-formers with highly activated hydrogen-bond donors, and with a 1,4-orientation of electron-withdrawing moieties bearing effective acceptor sites, were successfully implemented into the three-dimensional architectures composed of one-dimensional building units of CPs.

Tris(3-nitropentane-2,4-dionato-κ2 O,O′) Complexes as a New Type of Highly Energetic Materials: Theoretical and Experimental Considerations

Decreasing the sensitivity towards detonation of high-energy materials (HEMs) is the ultimate goal of numerous theoretical and experimental studies. It is known that positive electrostatic potential above the central areas of the molecular surface is related to high sensitivity towards the detonation of high-energy molecules. Coordination compounds offer additional structural features that can be used for the adjustment of the electrostatic potential values and sensitivity towards detonation of this class of HEM compounds. By a careful combination of the transition metal atoms and ligands, it is possible to achieve a fine-tuning of the values of the electrostatic potential on the surface of the chelate complexes. Here we combined Density Functional Theory calculations with experimental data to evaluate the high-energy properties of tris(3-nitropentane-2,4-dionato-κ2 O,O′) (nitro-tris(acetylacetonato)) complexes of Cr(III), Mn(III), Fe(III), and Co(III). Analysis of the Bond Dissociation Energies (BDE) of the C-NO2 bonds and Molecular Electrostatic Potentials (MEP) showed that these compounds may act as HEM molecules. Analysis of IR spectra and initiation of the Co(AcAc-NO2)3 complex in the open flame confirmed that these compounds act as high-energy molecules. The measured heat of combustion for the Co(AcAc-NO2)3 complex was 14,133 J/g, which confirms the high-energy properties of this compound. The results also indicated that the addition of chelate rings may be used as a new tool for controlling the sensitivity towards the detonation of high-energy coordination compounds.

Effect of functional groups on VOCs adsorption by activated carbon: DFT study

Volatile organic compounds (VOCs) have attracted increasing attention in the field of environmental control due to their harmful effects on human health and the environment. Activated carbon is promising as an adsorbent for VOCs. The physisorption of six VOCs (methane (CH4), dichloromethane (CH2Cl2), ethylene (C2H4), formaldehyde (HCHO), ethanol (C2H5OH), and toluene (C7H8)) by four activated carbon models (without functional group (NF), with hydroxyl (HD), pyridine (PD), and pyrrole (PR) group, respectively) was studied in combination with their electrostatic potential (ESP). The results show that ESP plays a decisive role in the adsorption of CH4, CH2Cl2, C2H4, HCHO, and C2H5OH, as their adsorption is mainly carried out by H-bonds. The functional group affects the adsorption process by changing the ESP distribution on the activated carbon surface. The orders of the absolute ESP values on the plane and edge of activated carbon are PR>HD>NF>PD and HD>PR>PD>NF, respectively, so that the order of the interaction strength and the physisorption energy are almost the same. Meanwhile, dispersion can enhance adsorption and change the order. For example, the order of CH2Cl2 adsorption at the activated carbon edge is PD>HD>PR>NF. C7H8 is difficult to be adsorbed at the activated carbon edge, but it can be adsorbed on the plane by a π-π stacking interaction whose strength is controlled by the relative molecular mass of activated carbon. This study will guide the design of activated carbon for efficient adsorption of VOCs.

A Wide Bandgap Acceptor with Large Dielectric Constant and High Electrostatic Potential Values for Efficient Organic Photovoltaic Cells.

Low-bandgap materials have achieved rapid development and promoted the enhancement of power conversion efficiencies (PCEs) of organic photovoltaic (OPV) cells. However, the design of wide-bandgap non-fullerene acceptors (WBG-NFAs), required by indoor applications and tandem cells, has been lagging far behind the development of OPV technologies. Here, we designed and synthesized two NFAs named ITCC-Cl and TIDC-Cl by finely optimizing ITCC. In contrast with ITCC and ITCC-Cl, TIDC-Cl can maintain a wider bandgap and a higher electrostatic potential simultaneously. When blending with the donor PB2, the highest dielectric constant is also obtained in TIDC-Cl-based films, enabling efficient charge generation. Therefore, the PB2:TIDC-Cl-based cell possessed a high PCE of 13.8% with an excellent fill factor (FF) of 78.2% under the air mass 1.5G (AM 1.5G) condition. Furthermore, an exciting PCE of 27.1% can be accomplished in the PB2:TIDC-Cl system under the illumination of 500 lux (2700 K light-emitting diode). Combined with the theoretical simulation, the tandem OPV cell based on TIDC-Cl was fabricated and exhibited an excellent PCE of 20.0%.

Effect of CO2 and methyl groups reaction kinetics on the ignition and combustion of diesel surrogate fuel: Part Ⅰ. Reaction mechanisms

The study aims to examine the impact of CO2 concentration gradient on the ignition and combustion of a diesel surrogate fuel composed of 70% C7H16 and 30% C7H8. The investigation focuses on the weak oxidation of CO2 through its reaction with methyl groups (CH, CH2, and CH3 radicals). Firstly, the molecular bond-breaking recombination process between CO2 and methyl groups is calculated using Born-Oppenheimer molecular dynamics with the UB3LYP/6–311++g (d, p) level of theory. Subsequently, the electronic distribution and competition of the molecule surface are analyzed through various wave function analyses to identify the reactive sites. Secondly, the precise potential energy surface and reaction rate are calculated based on the acquired reaction process information. This calculation employs the B2PLYP/def2-TZVP level of theory and transition state theory. Finally, extensive molecular dynamics simulations of CO2 and methyl groups are conducted using reaction force fields. These simulations provide insights into the temperature-energy variation within the system and the resulting chemical reaction network. The optimized combustion mechanism for the binary fuel is derived, focusing exclusively on the influences of CO2 and O2 while excluding those of N2 and other extraneous gases. The results demonstrate exothermic reactions of CO2 with CH and CH2 radicals at 850 K, yielding ΔG values of −238.91 kJ/mol and −209.96 kJ/mol, respectively. Conversely, CO2 reacts with CH3 radicals in heat-absorbing reactions at 850 K, resulting in a ΔG of 491.73 kJ/mol. Additionally, the chemical impact of CO2 exhibits both promotional and inhibitory effects on combustion. The CO2 molecule exhibits weak oxidation properties due to the presence of active sites on its surface characterized by minimal values of electrostatic potential (-50.17 kJ/mol) and average local ionization energy (61.92 kJ/mol) at the O-atomic end. The molecular dynamics process involving the methyl groups and CO2 system exhibits a heat absorption phenomenon. This behavior can be attributed to the participation of CO2 not only in the reactions with methyl groups but also with formaldehyde and ethylene, among others.

Theoretical exploration and experimental regulation of the degradation of Δ9-tetrahydrocannabinol in hemp seed oil by density functional theory

Δ9-tetrahydrocannabinol (Δ9-THC) in hemp seed oil is a psychoactive cannabinoid, and the content of Δ9-THC can be reduced. Density functional theory (DFT) was used to simulate the degradation path of Δ9-THC, and the ultrasonic treatment was used to degrade the Δ9-THC in hemp seed oil. Results found that the reaction of Δ9-THC degradation to cannabinol (CBN) was a spontaneous exothermic reaction, which required a certain amount of external energy to initiate reaction process. Through the surface electrostatic potential analysis, the minimum value of electrostatic potential of Δ9-THC was −37.68 kcal/mol, and the maximum value was 40.98 kcal/mol. The frontier molecular orbitals analysis found that the energy level difference of Δ9-THC was lower than that of CBN, indicating that the reactivity of Δ9-THC was stronger. The degradation process of Δ9-THC could be divided into two stages, which needed to cross the reaction energy barriers of 3197.40 and 3087.24 kJ/mol, respectively. Ultrasonic treatment was used to degrade Δ9-THC standard solution, it was found that Δ9-THC can be effectively degraded into CBN through intermediate. Subsequently, ultrasonic technology was applied to hemp seed oil, under the conditions of ultrasonic power 150 W and ultrasonic time 21 min, the Δ9-THC was degraded to 10.00 mg/kg.

Effects of trapped electrons on the sheath at the boundary of a dusty plasma

In the present paper, the characteristic behaviors of the sheath in an unmagnetized dusty plasma that contained trapped electrons, cold ions, and variable-charged dusts are investigated, based on the Sagdeev potential approach. The result shows that both the formation and structure of the sheath are modified by the trapped electrons. At the sheath edge, the critical ion Mach number decreases as the trapping parameter β increases. It is noted that the effect of electron trapping on the ion-entering-sheath-velocity is indirect, and closely related to the dust charge variation. In the sheath, the increased β leads to the enlargement of the sheath thickness and the absolute value of electrostatic potential, which results in the redistribution of particle densities. Moreover, the results of the Maxwellian case are essentially recovered when β = 1. As expected, the present results can give more insight into the interaction processes that happened on the plasma-wall interface.

Novel copper (II) and zinc (II) complexes with enrofloxacin and oxolinic acid: synthesis, characterization, Hirshfeld surface and DFT/CAM-B3LYPD3BJ studies: NBO, QTAIM and RDG analysis

This study aimed to investigate the crystal structure of the synthesized complexes of Cu (II) and Zn (II) with enrofloxacin and oxolinic acid. The characterization of the complexes was carried out using single–crystal x-ray diffraction, Hirshfeld surface and 1H NMR spectroscopy. In addition, a DFT/6-31g(d) investigation was conducted to assess the performance of two exchange-correlation functionals CAM-B3LYP and CAM-B3LYPD3BJ to predict both covalent and non-covalent bonds lengths, and the vibrational frequencies of the metallic complexes.The main findings of this study indicate that the interaction between each metallic ion and the corresponding ligand leads to significant modifications in bond lengths, Mulliken charge distribution and electrostatic potential values in the complex molecules as compared to the ligands alone. To gain further insights into these complexes, several calculations were performed, such as Natural Atomic orbitals (NAO), Natural Bond orbitals (NBO), and Quantum Theory of Atoms in Molecules (QTAIM) analysis. The non-covalent interactions were explored and visualized in two and three-dimensional spaces with the help of the Reduced electron Density Gradient (RDG) approach.

An Adaptive Local Iterative Method for Fast Calculation of Electrostatic Interactions between Charged Polymers in Dielectric Inhomogeneous System

AbstractThe motion of charged polymers in the 3D dielectric inhomogeneity system is investigated using a hybrid simulation approach that combines a finite difference method with a Brownian dynamics model (FD‐BD) for the polymer chain. The interface difference scheme of the two‐dielectric model is first derived to achieve a smooth extension of the electrostatic potential values and it is verified that it has a second‐order convergence order. In addition, it is displayed that the local iteration method greatly accelerates the efficiency of calculating the electrostatic interaction forces. However, it is found that the computational efficiency improvement of the traditional local iteration is less significant (about three times) for polymer simulations such as 3D diagonal type. Therefore, a new strategy, the banded local iteration method, is proposed and the simulation results demonstrate that it can better adapt the effects of the deformation of the polymer during its motion, where the computational efficiency is increased by 29 times at most, while the relative error is controlled to less than 5.15e−4. The work can be helpful for accelerating the solution of electrostatic forces under dielectric inhomogeneity, and confer new insights into the optimization of iteration for polymer chains with different geometries in large electrostatic systems.

Selective and Efficient Gold Extraction from E-Waste by Pyrrolidinium-Based Ionic Liquids with Various N-Substituents

With environmental problems and a shortage of resources, it is urgent to recover gold from electronic waste (e-waste). Meanwhile, it is necessary to explore the relationships between the structures and extraction performances of ionic liquids (ILs) to further improve the extraction capacities of ILs for gold. Herein, three pyrrolidinium-based ILs with various N-substituents were synthesized for solvent-free extraction of Au(III). The three pyrrolidinium-based ILs exhibited ultrahigh extraction capacities for Au(III) with the order of [Pyr-EA][NTf2] (524.6 mg·g–1) > [Pyr-Bu][NTf2] (457.3 mg·g–1) > [Pyr-C2OC2][NTf2] (403.5 mg·g–1). The effects of N-substituents on extraction performances were quantitatively investigated by electrostatic potential (ESP) and quantitative NMR. Among them, the ester group (−COOR) is the most beneficial to the extraction process, which is associated with an increased ESP value and boosted hydrophobicity. Notably, [Pyr-EA][NTf2] displayed outstanding selectivity in multimetal solutions; especially, it could selectively and efficiently extract Au(III) from the actual CPU. Furthermore, [Pyr-EA][NTf2] possesses significant reuseability and can maintain superior extraction efficiency of 84.3% after five cycles. These excellent performances together with low cost ($0.44·g–1 [Pyr-EA][NTf2]) and considerable profit ($29.72·g–1 [Pyr-EA][NTf2]) confirmed that [Pyr-EA][NTf2] is a promising prospect for sustainable recovery of gold from e-waste.

Prediction of CO2 adsorption properties of azo, azoxy and azodioxy-linked porous organic polymers guided by electrostatic potential

CO2 adsorption properties of azo, azoxy and azodioxy-linked porous organic polymers can be predicted from the calculated electrostatic potential values.

Density Functional Simulation Study of Surface Wettability of Coal Molecules with Different Degrees of Defects.

To explore the adsorption mechanism of H2O molecules on the surfaces of defective coal molecules and perfect bituminous coal molecules, the energy band structure, electronic density of states, electrostatic potential, and front orbitals on the surfaces of three coal molecule models were investigated using quantum chemical density functional theory (DFT) simulations. The adsorption energy and Mulliken charge layout of H2O molecules with the surfaces of defective coal molecules and perfect bituminous coal molecules were similarly investigated. The results of the DFT calculations showed that the widths of the forbidden bands of the defective coal molecular surfaces were narrower, and the electrostatic potential values were smaller. In addition, they each had an increased conduction band near the Fermi energy level, a larger electronic density of states near the Fermi energy level, and a higher electron activity and electron density than those of the perfect bituminous coal molecular surface. While stable adsorption of H2O molecules occurred on the surfaces of the single-vacancy-defective coal molecules, double-vacancy-defective coal molecules, and perfect bituminous coal molecules, the adsorption energy values were -39.401, -30.002, and -29.844 kJ/mol for the more stable configurations, corresponding to -0.022, -0.013, and -0.011 electrons gained by H2O molecules, respectively. Wettability improved with the appearance of defects, and the order of improvement was single-vacancy-defective coal molecule > double-vacancy-defective coal molecule > no-defect coal molecule.

A DFT approach towards understanding the thermal stability of TKX-50 and their key precursors through band gaps and MESP.

TKX-50 (dihydroxylammonium 5,5'-bistetrazolate-1,1'-dioxide) is a recent time invention by Klapotke et. al. in the field of high energy materials, and it outperforms all the existing materials by means of performance parameters. It is rising as potential energetic material due to favorable thermal insensitivity, low toxicity and safe handling. The decomposition temperature (Tmax) values of precursors such as glyoxime (I), 1,2-dichloroglyoxime (II), 1,2-diazidoglyoxime (III), and bistetrazoledihydroxide (IV) and ending products TKX-50 (V) and ABTOX (VI) have been attempted to correlate with the results obtained from molecular electrostatic potentials and band gaps calculated from the difference of ionization potential and electron affinity. The molecular electrostatic potential values of azido attached -NO group of III are much less than that of hydro/chloro attached -NO group of I/II and that of tetrazole groups IV, V, and VI. The band gaps calculated from stability trend in the increasing order of III < II < I < IV < V < VI are well corroborated with stability trend drawn from experimentally determined decomposition temperatures. Further, employing conceptual density functional theory (DFT) molecular descriptors, band gap values were calculated via the difference of ionization potential and electron affinity to understand the thermal stability of TKX-50, ABTOX, and its precursors.