Total Electron Density Research Articles

First-principle study on the structural, electronic and mechanical properties of High Entropy Alloy TiZrFeRu for hydrogen storage applications

High-entropy alloys are promising for hydrogen storage, especially in terms of their tunable hydrogen storage properties. Although several experimental studies, a fundamental and detailed atomistic comprehension of physical and electronic of the hydrogenation process is still lacking. This work investigated the structural, electronic and mechanical properties of TiZrFeRu high-entropy alloys (HEAs) using first-principle calculation. Indeed, we employed both density functional theory and density functional perturbation theory in the calculations with generalized gradient approximation and plane-waves pseudo-potential formalism. In addition, we used Virtual crystal approximation (VCA) to describe HEA as is well suited for predicting elastic properties. We have calculated relevant physical parameters, including lattice constants, elastic constants, elastic modulus, Poisson's ratio, Pugh's ratio, anisotropy factors and Vickers hardness..etc. Our calculated finding show that that TiZrFeRuH2 is mechanically stable and has a good ductility with a Pugh’s ratio (B/G) greater than 1.75. Lastly, we investigated and discussed electronic bandstructure, the total and partial electronic density of state. The results indicate that this compound exhibit a metallic character concentrated in a zone between -5 and 5 eV. The value of the Poisson ration (0.35) confirm again that this compound is metallic (for metal materials the Poisson ratio is above 0.25).

Investigation on the Influence of Solvents Environment on the Optoelectronic Properties of the Fluorescent Probe 1,3,4-Oxadiazole Analogues: A Combined Theoretical and Experimental Study.

This study investigates the photophysical properties of a nitrobenzene-substituted 1,3,4-oxadiazole derivative (OX-NO) using both theoretical and experimental methods. The impact of the solvent on OX-NO absorption and fluorescence spectra, as well as its fluorescence quantum yield, was initially studied. A noticeable bathochromic shift in the Stokes shift indicated a π→ π* transition within the molecules. Solute-solvent interactions were analysed using Catalan parameters, distinguishing between specific and nonspecific interactions. Excited state dipole moments were derived from Lippert's, Bakshiev's, and Chamma Viallet's equations, showing increased polarity in the excited state compared to the ground state. Ground state dipole moments were determined via solvatochromic shift methods and ab initio techniques. Additionally, detailed analyses of bond length, angles, dihedral angles, Mulliken charge distribution, and HOMO-LUMO energy gap were conducted using the DFT-B3LYP-6-311G basis set in Gaussian-09W. The energy band gap values obtained from theoretical calculations and experimental methods (cyclic voltammetry and UV-Visible spectroscopy) exhibited excellent agreement. Reactive sites such as electrophilic and nucleophilic regions were identified through total electron density, electrostatic maps, molecular electrostatic potential, and 3D plots using DFT computational analysis. Global descriptors were employed to characterize the compounds' chemical reactivity comprehensively. The observed photophysical attributes underscore the potential of these fluorophores in various applications like organic light-emitting diodes, solar cells, and chemosensors. This study contributes crucial insights into the optoelectronic properties of nitrobenzene-substituted 1,3,4-oxadiazole derivatives, paving the way for their future integration in advanced technological domains.

Molecular interaction mechanism and process analysis of separation of cyclohexane/ethyl acetate by extractive distillation

The selection of efficient and environmentally friendly extractants is crucial for extractive distillation (ED), and the microscopic mechanism of extractants in ED is still unclear. For the benefit of interpreting the microstructure distribution and phase behavior of the mixed system, this paper studied it by quantum chemical (QC) calculation and molecular dynamics (MD) simulation. Firstly, 1,3-dimethylimidazolium hexafluorophosphate [Mmim][PF6], 1-ethyl-3-methylimidazolium hexafluorophosphate [Emim][PF6] and organic solvent DMSO were screened based on COSMO-RS model and relative volatility. The bond length, bond energy, total electron density and deformation charge density of [Mmim][PF6], [Emim][PF6], DMSO extractant and ethyl acetate were analyzed by QC, the intrinsic properties of the chosen extractant and azeotropic system, as well as the interactions among the three extractants and ethyl acetate, were investigated. Then, the effect of extractant on the separation performance of cyclohexane ethyl acetate azeotrope in solvent environment was further studied by MD simulation. The two-dimensional mass density distributions (ANDDs) visualized the mixing behavior and structural distribution of the three extractants with the azeotropic system in the ternary system respectively, and the hydrogen bonding statistics indicated a high number of hydrogen bonds between [Mmim][PF6] and ethyl acetate. The radial distribution function (RDF) indicated that the extraction effect of [Mmim][PF6] was better and [PF6-] played a dominant role in the separation of azeotropic system. The strong interaction between [Mmim][PF6] extractant [PF6-] and ethyl acetate was further verified by the spatial distribution function (SDF). Ultimately, through Aspen Plus software simulation, it was found that the [Mmim][PF6] extractive distillation process was superior to the traditional solvent DMSO process, TAC was reduced by 8 %, and gas emissions were reduced by 5 %. Through the combination of QC, MD, and process simulation offer theoretical guidance for the efficient separation of the cyclohexane-ethyl acetate system and provide a specific reference value for the selection of the optimal extractant.

MISTER-T: An open-source software package for quantum optimal control of multi-electron systems on arbitrary geometries

We present an open-source software package, MISTER-T (Manipulating an Interacting System of Total Electrons in Real-Time), for the quantum optimal control of interacting electrons within a time-dependent Kohn-Sham formalism. In contrast to other implementations restricted to simple models on rectangular domains, our method enables quantum optimal control calculations for multi-electron systems (in the effective mass formulation) on nonuniform meshes with arbitrary two-dimensional cross-sectional geometries. Our approach is enabled by forward and backward propagator integration methods to evolve the Kohn-Sham equations with a pseudoskeleton decomposition algorithm for enhanced computational efficiency. We provide several examples of the versatility and efficiency of the MISTER-T code in handling complex geometries and quantum control mechanisms. The capabilities of the MISTER-T code provide insight into the implications of varying propagation times and local control mechanisms to understand a variety of strategies for manipulating electron dynamics in these complex systems. Program summaryProgram Title: MISTER-TCPC Library link to program files:https://doi.org/10.17632/psymy4ddnw.1Licensing provisions: GNU General Public License 3Programming language: MATLABSupplementary material: animated movies of total electron densities under the influence of optimal control fields for (1) an asymmetric double-well potential for long propagation times, (2) an asymmetric double-well potential for short propagation times, and (3) a triple-well potential with a position-dependent effective mass.Nature of problem: The MISTER-T code solves quantum optimal control problems for interacting electrons within a time-dependent Kohn-Sham formalism. It can handle two-dimensional systems with arbitrary cross-sectional geometries within the effective mass formulation. The user-friendly code uses forward and backward propagator integration methods to evolve the Kohn-Sham equations with a pseudoskeleton decomposition algorithm for enhanced computational efficiency.Solution method: iterative solution of the quantum optimal control equations using finite element methods, effective mass formulation, pseudoskeleton decomposition, sparse matrix linear algebra, and nonuniform fast Fourier transforms.

Using Three-Dimensional Information to Predict and Interpret the Facial Selectivities of Nucleophilic Additions to Cyclic Ketones.

In this study, we devised a new method to predict facial selectivity by quantifying steric and orbital factors for the nucleophile approaching both π-plane faces. Using this method, we quantified the total electron density and frontier orbital distributions of 163 cyclic ketones with various structures and quantitatively explained the surface selectivity of 323 reactions with eight nucleophiles (BH3, LiAlH4, NaBH4, LiAl(OMe)3H, MeLi, MeMgI, PhLi, and PnMgI). Importance analysis showed a large orbital effect for BH3, LiAlH4, and NaBH4 and the dominance of the steric effect for LiAl(OMe)3H, MeLi, MeMgI, PhLi, and PhMgI. Our method analyzes three-dimensional features based on Gaussian cube files, which can be easily obtained using mainstream computational chemistry software packages, and this approach should prove useful for predicting the rates and facial selectivity of other reactions.

Synthesis, spectroscopic analysis (FT-IR, FT-Raman, UV, NMR), non-covalent interactions (RDG, IGM) and dynamic simulation on Bis(8‑hydroxy quinoline) salicylate salicylic acid

Using spectrum techniques and density functional theory (DFT) reckonings, structural, vibrational and electrical characteristics of Bis(8‑hydroxy quinoline) salicylate salicylic acid (8HQSA) were determined. Characterizing the chemical under inquiry involved employing FT-IR, FT-Raman, UV–vis spectral studies and single crystal X-ray diffraction (SCXRD). For the characterization, the B3LYP approach inside the structure of DFT was employed, with a 6–311++G(d,p) basis set. The structural study shows that the stability of 8HQSA crystalline structure arising from N–H⋯O, C–O⋯H and O–H⋯O hydrogen bonding interactions. The 1H and 13C NMR chemical shifts were calculated using Gauge Independent Atomic Orbital (GIAO) technical. Vibrational frequencies and molecular geometry were computed and likened with experimental data. Here, non-covalent interactions were deeply analyzed in terms of topological parameters (AIM), electron localization function (ELF), localized orbital locator (LOL), Hirshfeld surface and reduced density gradient (RDG) method. Weak interactions such as H-bonds, van der Waals and steric effect in 8HQSA were visualized and quantified by the independent gradient density (IGM) based on the trimolecular density. The hyper-conjugative and the delocalization of charge in 8HQSA have been elucidated by natural bonding orbital (NBO) while its chemical reactivity was studied and discussed by using molecular electrostatic potential surface (MEP), frontier molecular orbital (FMOs), density of state (DOS) and partial density of state (PDOS). The positions of the molecule's nucleophilic and electrophilic groups were ascertained using Fukui analysis. To describe the size, structure, and reactive sites of the molecules, the molecular electrostatic potential and total electron density are calculated. With a band gap (2.58 eV), FMO study indicates that the material is both bioactive and stable. The ADMET factor and drug similarity are used to predict 8HQSA's pharmokinetic characteristics. Based on the findings, it can be concluded that the 8HQSA particle is optimally crystallised and recommended as a preventative measure against bacterial and fungal infections. The stability of the title compound has been investigated via molecular dynamics simulations. In-vitro antimicrobial activity results clearly reveal that in all the four strains, activity increases with increase in compound concentration and the inhibition of the strains also increases. From both molecular docking and In-vitro Antimicrobial Activity the title compound can be certified that it inhibits antimicrobial activity.

Investigation of the effect of halide counterions on the potential corrosion inhibitor in imidazolium-based ionic liquids

Imidazolium (IMZ)-based ionic liquids (ILs) with various counter ions were investigated as potential corrosion inhibitors. Furthermore, parameters such as bond lengths, bond angles, and dihedral bonds were investigated to demonstrate the adsorption sites of molecules. Moreover, in order to compare the efficiency of the inhibitors, other parameters such as energy gap, hardness, the LUMO, and the HOMO were investigated. The HOMO and LUMO values increased from −4.370 and −0.106 eV to −4.959 and −0.156 eV, respectively, by changing F− to I−. Moreover, the softness of the IMZ base changed from 0.469 to 0.417 eV by increasing the radius of the halide ion. The trend of the band gap value in going from F− to I− changes from 4.264 to 4.797 eV. The total electron density was computed to show the adsorption sites based on the electron density. According to the molecular reactivity results, the inhibitory efficiency of the inhibitors was in the following order: BMI-F > BMI-Cl > BMI-Br > BMI-I. Investigating the IMZ-based ILs with various counterions to evaluate the inhibition profile of molecules provides useful insights into computational protocols for the study of corrosion inhibitors.

Effects of Plasma Density on the Spatial and Temporal Scale Sizes of Plasmaspheric Hiss

AbstractThe effects of plasma density on the plasmaspheric hiss amplitude and its spatial and temporal scale sizes are investigated using data from Van Allen Probes A and B. The plasmaspheric hiss amplitude and scale sizes are found to be more affected by the small‐scale density variations than the overall density profile of the plasmasphere. In detail, our results suggest that both the hiss wave amplitude and its scale sizes are (a) related to the total electron density when the density is less than ∼1,000 cm−3; (b) independent of the total electron density when the density is greater than ∼1,000 cm−3; and (c) better correlated with the detrended density (removing the background plasmasphere density profile from the total electron density) regardless of the density value.

First-principles study of structural, electronic and magnetic properties of diluted magnetic semiconductor and superlattices based‏ on Cr-doped ZnS and ZnSe compounds in wurtzite-type crystal

We performed first-principle calculations to investigate the structural, electronic, and magnetic properties of ZnS and ZnSe binary compounds, Zn0.5Cr0.5S and Zn0.5Cr0.5Se DMS alloys and (ZnS)2/Zn0.5Cr0.5Se and (ZnSe)2/Zn0.5Cr0.5S superlattices in the wurtzite structure using the full potential linear muffin–tin orbital (FP-LMTO) method. Features such as lattice constant, modulus of compressibility and its first derivative, spin-polarized band structures, total and local or partial electronic densities of states and magnetic properties were calculated. The electronic structure shows that Zn0.5Cr0.5S and Zn0.5Cr0.5Se DMS alloys and (ZnS)2/Zn0.5Cr0.5Se and (ZnSe)2/Zn0.5Cr0.5S superlattices are half-metallic ferromagnetic with 100% complete spin polarization. The total magnetic moments calculated show the same integer value of 4 µB, which confirms the ferromagnetic half-metallic behavior of these compounds. We found that the ferromagnetic state is stabilized by the p-d exchange associated with the double-exchange mechanism. Zn0.5Cr0.5S and Zn0.5Cr0.5Se DMS alloys and (ZnS)2/Zn0.5Cr0.5Se and (ZnSe)2/Zn0.5Cr0.5S superlattices are shown to be promising new candidates for applications in the fields of spintronics.

First-principles simulations of magnetic properties of Co- and Ni-doped ZnSe

We purposed to analyze the theoretical ab initio study of ferromagnetism and to estimate Curie temperature of Co2+ and Ni2+ 3d transition metal (TM) ions doped Zn1-x TM x Se compounds for 12.5 % and 6.25 % concentrations of impurity TM(Co, Ni) atoms. The calculations are carried out using the norm-conserving Fritz-Haber-Institute ionic pseudopotentials based on density functional theory within the local spin density approximation and Hubbard U (U(Znd)=4.5 eV; U(Sep)=3.8 eV) corrections. The analysis of the total and partial electron density of states shows the half-metallic ferromagnetic behavior with a half-metallic bandgap. The theoretically obtained total magnetic moments of TM(Co, Ni) doped Zn1-x TM x Se systems are equal to 3 μB and 4 μB, correspondingly.

Investigation of structural, electronic, magnetic, and mechanical stability of a non-trivial topology phase in compound full-Heusler alloys TiHfFeX (X=Al, Ga, In)

In this paper, we present studies relating to the structural, electronic, magnetic and mechanical properties of TiHfFeX ([Formula: see text], Ga, In) full Heusler alloys. We will use the GGA-PBE, TB-mBj, GGA-PBEsol, and GGA-WC approximation implemented in the density functional of the theory as integrated into the Wien2k software. However, the full Heusler alloys studied are considered in the ferromagnetic phase for different structural stabilities of the TiHfFeAl, TiHfFeGa and TiHfFeIn phases. types I, II or III, respectively. Calculation of band structures and total electron density of states shows that these alloys can both exhibit topologically non-trivial semi-metallic characteristics with energy bandgaps of 0.010[Formula: see text]eV, 0.014[Formula: see text]eV and 0.018[Formula: see text]eV. The electronic stability of ’such a Heusler structure will have nothing to do with its mechanical stability. Calculations reveal that the systems exhibit semi-metallic ferromagnetism. The elastic constants and the associated elastic moduli confirm its stability given by different elastic constants namely the Cauchy pressure, Poisson’s ratio, the anisotropy factor, Young’s modulus and the shear modulus.

Highly Sensitive Gas Sensor for Detection of Air Decomposition Pollutant (CO, NOx): Popular Metal Oxide (ZnO, TiO2)-Doped MoS2 Surface.

When partial discharges occur in air-insulated equipment, the air decomposes to produce a variety of contamination products, resulting in a reduction in the insulation performance of the insulated equipment. By monitoring the concentration of typical decomposition products (CO, NO, and NO2) within the insulated equipment, potential insulation faults can be diagnosed. MoS2 has shown promising applications as a gas-sensitive semiconductor material, and doping metal oxides can improve the gas-sensitive properties of the material. Therefore, in this work, MoS2 has been doped using the popular metal oxides (ZnO, TiO2) of the day, and its gas-sensitive properties to the typical decomposition products of air have been analyzed and compared using density functional theory (DFT) calculations. The stability of the doped system was investigated using molecular dynamics methods. The related adsorption mechanism was analyzed by adsorption configuration, energy band structure, density of states (DOS) analysis, total electron density (TED) analysis, and differential charge density (DCD) analysis. Finally, the practical application of related sensing performance is evaluated. The results show that the doping of metal oxide nanoparticles greatly improves the conductivity, gas sensitivity, and adsorption selectivity of MoS2 monolayer to air decomposition products. The sensing response of ZnO-MoS2 for CO at room temperature (25 °C) reaches 161.86 with a good recovery time (0.046 s). TiO2-MoS2 sensing response to NO2 reaches 3.5 × 106 at 25 °C with a good recovery time (0.108 s). This study theoretically solves the industrial challenge of recycling sensing materials and provides theoretical value for the application of resistive chemical sensors in air-insulated equipment.

Molecular docking, drug-likeness and DFT study of some modified tetrahydrocurcumins as potential anticancer agents

The present study utilized molecular docking and density functional theory (DFT) approaches, and ADMET (absorption, distribution, metabolism, excretion, and toxicity) properties to investigate the binding interactions, reactivity, stability, and drug-likeness of curcumin (1), tetrahydrocurcumin (2), and tetrahydrocurcumin derivatives (3–6) as potential anti-cancer agents. MGL (Molecular Graphic Laboratory) and Discovery Studio Visualizer (DSV) software employed for docking studies. Pharmacokinetic and pharmacodynamic (ADME-Tox) analyses were conducted using SwissADME and pKCSM web servers. Total Electron Density (TED) measurements identified molecular adsorption sites, considering various factors, including quantum chemical characteristics, to assess compound effectiveness using DFT method implanted in the Gaussian software. The binding energy (Eb) from docking simulations was used to evaluate inhibitory potential. ADMET analysis suggested favorable oral bioavailability and pharmacokinetics for all studied substances, excluding compound 4. DFT and docking investigations highlighted compounds 1, 2, and 6 as optimal scaffolds for drug design based on in silico screening tests.

N⋯H[sbnd]N versus O⋯H[sbnd]N intramolecular hydrogen bonding in E- and Z-isomers of para-substituted phenylhydrazones: Differential nature of the H-bonds and the exception of para-CN substituent

The present work demonstrates a computational investigation into the N⋯HN (E-isomer) and O⋯HN (Z-isomer) intramolecular H-bonding (IMHB) in a miscellany of para-substituted phenylhydrazone compounds. The application of resonance-assisted H-bonding theory to N⋯HN H-bonding systems, especially those involving an aromatic nucleus, has remained scarcely addressed. The results of NBO and QTAIM methods indicate that resonance-assistance from aromatic pyridyl nucleus leads to a stronger N⋯HN IMHB in the E-isomer in comparison to the O⋯HN IMHB in Z-isomer with the exception of para-CN substitution (Z-isomer) probably due to an extended conjugation. The results of QTAIM analyses reveal that the N⋯HN IMHB is described by a considerable degree of covalence (total electron density at bond critical point, Hc<0) as contrary to the predominantly electrostatic (Hc>0) interaction describing the O⋯HN H-bond in Z-isomer, with the exception of para-CN substitution showing a shared interaction. The existence of non-hydrogen bonding noncovalent interactions is also established.

Comparison of Ionospheric Bite‐Outs Between Observations From Beidou GEO TEC and Ionosonde Over East Asia

AbstractIn this study, the daytime bite‐outs were systematically compared between the total electron content (TEC) and peak electron density of F2 layer (NmF2) data using observations from Beidou GEO receivers and ionosondes over East Asia. Moreover, the Thermosphere‐Ionosphere Electrodynamics Global Circulation Model simulations were also employed to analyze the underlying physical mechanisms. There was an obvious difference in the occurrence rate of bite‐outs between TEC and NmF2, although bite‐outs from both data sets showed similar seasonal and latitudinal dependences. Interestingly, the differences in the bite‐out occurrence rates also varied with season and latitude. Their difference, which showed the opposite trend to the occurrence rates themselves, became prominent in equinoxes and less evident in June solstice, peaking at the equatorial ionization anomaly crest. In addition, the occurrence times of bite‐outs were different as observed in TEC and NmF2 sometimes. Bite‐out in TEC tended to start earlier than that in NmF2 at middle latitudes, whereas an opposite pattern was seen at low latitudes. On the contrary, TEC bite‐out often died away earlier than NmF2 bite‐out regardless of the latitudes. The simulations suggested that the vertical E × B drifts associated with zonal equatorial electric fields and the meridional neutral winds could play crucial roles in the characteristics of both bite‐outs.

Cyclopropene System: A Theoretical Investigation into Secular Determinants, π-Energy, Delocalization Energy, Wave Functions, Electron Density and Charge Density

In this study, we exploit the distinctive attributes of the Hückel method to gain valuable insights into the Cyclopropene system. Alongside quantifying the delocalization energy within the conjugated Cyclopropene ring framework, we employ a theoretical framework to derive secular equations, total energy values, wave functions, electron density, and charge density for the C3H3+ (cation), C3H3- (anion), and C3H3* (Radical) species. By applying the Hückel methods secular determinant, we ascertain orbital energies, electron and charge densities, thus comprehensively characterizing this stable configuration. Our approach offers an accessible means for graduate and post-graduate students to understanding the stable systems configuration analysis and associated parameters. It rests upon assumptions of local comparability such as coulomb integrals, exchange integrals, and overlap integrals. The Cyclopropene system can be thoroughly investigated through our simplified hypothetical approach, facilitating an in-depth understanding of its intrinsic electrical properties.

Theoretical aspects of the adsorption of normal and modified base pairs of DNA on graphene models toward DNA sequencing

A theoretical understanding of the adsorption of DNA base pairs (GC, AT, CAF-T and CAF-C) on the graphene models (Gr, SiGr and SiGr-COOH) is investigated. Among the complexes, SiGr-COOH_AT is found to have the highest adsorption energies of −202.83 kcal/mol. The strong adsorption between DNA base pairs and the SiGr-COOH model leads to concomitant charge transfer responsible for the stability of the corresponding models and is verified with NBO analysis. AIM analysis discloses the high orbital overlap that signifies the strong interaction. Closed-shell interactions are observed through the positive values of total electron density, and it is also observed that Si-O(N) interaction has both covalent and electrostatic characteristics. This is the first theoretical attempt to investigate the adsorption of DNA base pairs on SiGr-COOH, which is more favourable than other models and may call for further experimental studies, which is crucial in developing new bio-sensors. Communicated by Ramaswamy H. Sarma

Synthesis, crystal structure, DFT studies, and Hirshfeld surface analysis of a new Strontium Polyphosphate Form [formula omitted

The α-Sr(PO3)2 was synthesized at 273.15 K and P = 1.01325 bar and characterized by single crystal X-ray diffraction analysis, IR & Raman spectroscopy, and Computational simulation (ELF, HSA & DFT) studies. This compound crystallizes in the centrosymmetric triclinic space group P-1 (Z = 4) with a = 5.7938(3) (Å), b = 7.2039(4) (Å), c = 8.0673(4) (Å), α = 97.800(2)°, β = 104.590 (2)°, γ = 106.647(2)° & V = 304.25(3)Å3. The 3D structure contains Sr(PO3)2 chains, which form wavy layers between which exist layers of (PO3)- ions. In addition, theoretical calculations were performed using the DFT/B3LYP/LanL2DZ basis set for crystal molecular structure, Infrared and Raman spectra, and HOMO-LUMO properties of the title compound. 3D-MEPs and the α-Sr(PO3)2-(HOMO/LUMO) were used to assess the total electron density(Global reactivity) and the reactive centres(Local reactivity). Molecular orbital contributions are evaluated by DOS. A comparative study by the SD is in the range DFT/XRD; 0.06 in % for bond lengths and 0.016 in % for angles. The Intermolecular α-Sr(PO3)2 interactions were quantified by HAS. The ELF identifies (non-binding and binding) regions of space that can be associated with electron pairs for elaborated material. The IR spectrum confirms the existence of the functional groups in the elaborated material. The complete vibrational assignments and analysis of the observed fundamental bands of the molecule were carried out.

Decoding Chemical Bonds: Assessment of the Basis Set Effect on Overlap Electron Density Descriptors and Topological Properties in Comparison to QTAIM.

Quantum chemical bonding descriptors based on the total and overlap density can provide valuable information about chemical interactions in different systems. However, these descriptors can be sensitive to the basis set used. To address this, different numerical treatments of electron density have been proposed to reduce the basis set dependency. In this work, we introduce overlap properties (OPs) obtained through numerical treatment of the electron density and present the topology of overlap density (TOP) for the first time. We compare the basis set dependency of numerical OP and TOP descriptors with their quantum theory of atoms in molecules (QTAIM) counterparts, considering the total electron density. Three single (C-C, C-O, and C-F) bonds in ethane, methanol, and fluoromethane and two double (C═C and C═O) bonds in ethene and formaldehyde were analyzed. Diatomic molecules Li-X with X = F, Cl, and Br were also analyzed. Eight parameters, including QTAIM descriptors and OP/TOP descriptors, are used to assess the basis dependency at the ωB97X-D level of theory using 28 basis sets from three classes: Pople, Ahlrichs, and Dunning. The study revealed that the topological overlap electron density properties exhibit comparatively lesser dependence on the basis set compared to their total electron density counterparts. Remarkably, these properties retain their chemical significance even with reduced basis set dependency. Similarly, numerical OP descriptors show less basis set dependency than their QTAIM counterparts. The excess of polarization functions increases charge concentration in the interatomic region and influences both QTAIM and OP descriptors. The basis sets Def2TZVP, 6-31++G(d,p), 6-311++G(d,p), cc-pVDZ, cc-pVTZ, and cc-pVQZ demonstrate reduced variability for the tested bond classes in this study, with particular emphasis on the triple-ζ quality Ahlrichs' basis set. We recommend against using basis sets with numerous polarization functions, such as augmented Dunning's and Ahlrichs' quadruple-ζ.

Evaluating the performance of empirical models of total electron density and whistler-mode wave amplitude in the Earth’s inner magnetosphere

Empirical models have been previously developed using the large dataset of satellite observations to obtain the global distributions of total electron density and whistler-mode wave power, which are important in modeling radiation belt dynamics. In this paper, we apply the empirical models to construct the total electron density and the wave amplitudes of chorus and hiss, and compare them with the observations along Van Allen Probes orbits to evaluate the model performance. The empirical models are constructed using the Hp30 and SME (or SML) indices. The total electron density model provides an overall high correlation coefficient with observations, while large deviations are found in the dynamic regions near the plasmapause or in the plumes. The chorus wave model generally agrees with observations when the plasma trough region is correctly modeled and for modest wave amplitudes of 10–100 pT. The model overestimates the wave amplitude when the chorus is not observed or weak, and underestimates the wave amplitude when a large-amplitude chorus is observed. Similarly, the hiss wave model has good performance inside the plasmasphere when modest wave amplitudes are observed. However, when the modeled plasmapause location does not agree with the observation, the model misidentifies the chorus and hiss waves compared to observations, and large modeling errors occur. In addition, strong (&amp;gt;200 pT) hiss waves are observed in the plumes, which are difficult to capture using the empirical model due to their transient nature and relatively poor sampling statistics. We also evaluate four metrics for different empirical models parameterized by different indices. Among the tested models, the empirical model considering a plasmapause and controlled by Hp* (the maximum Hp30 during the previous 24 h) and SME* (the maximum SME during the previous 3 h) or Hp* and SML has the best performance with low errors and high correlation coefficients. Our study indicates that the empirical models are applicable for predicting density and whistler-mode waves with modest power, but large errors could occur, especially near the highly-dynamic plasmapause or in the plumes.