Electron Density Distribution Research Articles

Experimental electron density distribution of KZnB3O6 constructed by maximum-entropy method

The dynamic charge density of KZnB3O6, which contains edge-sharing BO4 units, has been characterized using laboratory and synchrotron X-ray diffraction techniques. The experimental electron density distribution (EDD) was constructed using the maximum-entropy method (MEM) from single crystal diffraction data obtained at 81 and 298 K. Additionally, MEM-based pattern fitting (MPF) method was employed to refine the synchrotron powder diffraction data obtained at 100 K. Both the room-temperature single crystal diffraction data and the cryogenic synchrotron powder diffraction data reveal an intriguing phenomenon: the edge-shared B2O2 ring exhibits a significant charge density accumulation between the O atoms. Further analysis of high-quality single crystal diffraction data collected at 81 K, with both high resolution and large signal-to-noise ratio, reveals no direct O–O bonding within the B2O2 ring. The experimental EDD of KZnB3O6 obtained aligns with the results obtained from ab-initio calculations. Our work underscores the importance of obtaining high-quality experimental data to accurately determine EDDs.

High-temperature variable range hopping conduction and dielectric relaxation in CoFe2O4 ceramic

CoFe2O4 ceramic was fabricated using a sol-gel auto-combustion process. The cubic spinel structure with F d −3 m space group symmetry was confirmed through the Rietveld refinement of the XRD pattern of CoFe2O4 sintered at 800 °C for 4 h. The cobalt vacancies at the tetrahedral site were verified by electron density distribution calculated through the maximum entropy method. The impedance spectroscopy study revealed that the grain boundary was dominant compared to the grain in the electrical properties of CoFe2O4. The total dc resistivity was fitted by the variable range hopping (VRH) model, demonstrating that the charge carriers for conduction mechanism confirm to the VRH model. The density of localized states (N(EF)) near the Fermi level was found to be 1.07 × 1019 eV−1-cm−3. The hopping energy (EH) and hopping length (R) of the charge carriers were estimated to be 0.29 eV and 2.28 nm, respectively, at 473 K.

Approximating Electrostatic Potential of Molecules with Point Charges Mimicking the Electron Pairs

The electrostatic component used in the traditional force fields significantly impacts their accuracy in modelling the noncovalent interactions peculiar to biomolecular systems, including hydrogen bonding. In this contribution, we present a physical model for approximating the electrostatic potential of a molecule (MEP) based on the first-principle decomposition of its charge density distribution into the localized components. In contrast to conventional schemes, which typically use atom-centered charges to approximate MEP, the proposed approach locates such charges in the positions selected so as to mimic the anisotropy of the electron density distributions related to the electron pairs of atoms or covalent bonds. This peculiarity leads to a more accurate representation of the overall electrostatic potential, as verified by applying the proposed model to approximate the electrostatic component of the intermolecular interaction energy in 145 noncovalently bound molecular complexes from GMTKN55 database. This benchmark showed the root-mean-square difference between the true and approximated values of the electrostatic component of 2.7 kcal/mol, which is 2.2 times lower as compared to the traditional RESP charges method used as a baseline.

About the in-plane distribution of the reaction rate in lithium-ion batteries

Reaction rate distribution and current density distribution of Li-ion batteries largely determine the local aging and heat generation. Homogenous distribution contributes to better durability and safety of Li-ion batteries. This paper focuses on modeling the in-plane distribution of electrochemical reaction current, and the general equation relating space derivatives of the overvoltage to the electrochemical and electronic current densities is derived. Furthermore, this work investigates the impact of various battery parameters on the distribution by considering the cylindrical battery, one of the most used battery types. An explicit closed-form solution for a short time after the current supplied is obtained. It is found that the dimensions of cylindrical batteries, tabbing design, parameters of current collectors, and electrode materials are all indicated to affect the current density distribution. The electronic current density distribution is also demonstrated. This model and related analyses are incredibly beneficial for further optimizing Li-ion batteries’ electronic and electrode properties and as interesting cases for testing battery modeling tools.

Unraveling the abnormal NMR spectra of oxaline and its spiroaminal congeners fungal alkaloids: The spatial effect of quadrupolar nitrogen nuclei

Oxaline is a bioactive alkaloid that acts as an antibiotic and antiproliferative drug affecting tubulin polymerization. Oxaline and meleagrine alkaloids contain an indoline spiroaminal tricyclic system produced from roquefortine as a biosynthetic precursor. These prenylated indoline spiroaminal alkaloids have been identified mainly by NMR spectroscopy and single crystal X-Ray diffraction. The 1H NMR spectrum of the parent alkaloid roquefortine contains three clear signals for vinyllic hydrogens forming an ABX system and two clear and intense singlets for methyl groups at the prenyl unit. On the other hand, the indoline spiroaminal alkaloids produce 1H NMR containing these same signals but they are formed of broad lines, many times as uninterpretable signals. Although it appears that these unusual signals have not become an important obstacle for correct identification of these alkaloids, nonetheless this broadening line phenomenon has not yet been addressed and correctly figured out. In the present study we applied some computational tools contributing to enhance the understanding of this phenomenon. The Density Functional Theory (DFT) studies of interatomic distances, electron density and electrostatic potential distributions led us to consideration of the possible effect of the quadrupolar field of the nitrogen atoms, especially N-14 and N-11, which are the closest to the prenyl hydrogen atoms. The poor resolution in these signals varies with the solvent and the temperature changes. In addition to conformational mobility, our studies also considered the influence of the quadrupolar field of the nitrogen atoms from the triazaspirocycle system on the resonances of neighbor hydrogens. It is known from the literature that the lines of ½ spin nuclei such as 1H attached to nitrogen (I = 1) have their line-shape, multiplicity and relaxation time affected. In the case of these spiroaminal indoline alkaloids, we found that the 1H nuclei from the prenyl group are affected through space, since they are not directly attached to any of the three quadrupolar-N.

Noncovalent Dualism in Perylene-Diimide-Based Keggin Anion Complexes: Theoretical and Experimental studies.

We report the synthesis and comprehensive characterization of organic-inorganic hybrid salts formed by bis-cationic N,N'-bis(2-(trimethylammonium)ethylene)perylene-3,4,9,10-tetracarboxylic acid bisimide (PTCD2+) and Keggin-type [XW12O40]n- (X = Si, n = 4; X = P, n = 3) polyoxometalates. (PTCD)3[PW12O40]2·3DMSO·2H2O (2) and (PTCD)2[SiW12O40]·DMSO·2H2O (3) were structurally characterized by single crystal X-ray diffraction. The cations in both structures exhibited infinite chainlike arrangements through π-π interactions, contrasting with the previously reported cation-anion stacking observed in naphthalene diimide derivatives. A detailed theoretical study employing topological analysis of the electron density distribution within the quantum theory of atoms in molecules approach provided further insights into this structural dualism. Atomic force microscopy analyses revealed the formation of self-assembled supramolecular structures on graphite from molecular monolayers (3 nm of thick) to submicrometer aggregates for 2. Hyperspectral Raman spectroscopy imaging revealed that such heterostructures are likely formed by an enhanced π-π interactions. Both complexes demonstrated interesting electrochemical behavior, photoluminescence and X-ray-induced luminescence. Electron spin resonance analysis confirmed charge separation in both compounds, with enhanced efficiency observed in compound 2. Our findings of these perylene-based organic-inorganic hybrid salts offer the potential for their application in optoelectronic devices and functional materials.

Dual-energy micro-focus computed tomography based on the energy-angle correlation of inverse Compton scattering source.

Inverse Compton scattering (ICS) source can produce quasi-monoenergetic micro-focus X-rays ranging from keV to MeV level, with potential applications in the field of high-resolution computed tomography (CT) imaging. ICS source has an energy-angle correlated feature that lower photon energy is obtained at larger emission angle, thus different photon energies are inherently contained in each ICS pulse, which is especially advantageous for dual- or multi-energy CT imaging. This study proposes a dual-energy micro-focus CT scheme based on the energy-angle correlation of ICS source and tests its function using numerical simulations. In this scheme, high- and low-energy regions are chosen over the angular direction of each ICS pulse, and dual-energy projections of the object are obtained by an angularly-splicing scanning method. The field-of-view (FOV) of ICS source is extended simultaneously through this scanning method, thus the scale of the imaging system can be efficiently reduced. A dedicated dual-energy CT algorithm is developed to reconstruct the monoenergetic attenuation coefficients, electron density, and effective atomic number distributions of the object. A test object composed of different materials (carbon, aluminium, titanium, iron and copper) and line pairs with different widths (15/24/39/60 μm) is imaged by the proposed dual-energy CT scheme using numerical simulations, and high-fidelity monoenergetic attenuation coefficient, electron density, and effective atomic number distributions are obtained. All the line pairs are well identified, and the contrast ratio of the 15 μm lines is 22%, showing good accordance with the theoretical predictions. The proposed dual-energy CT scheme can reconstruct fine inner structures and material compositions of the object simultaneously, opening a new possibility for the application of ICS source in the field of non-destructive testing.

Description of Solvatochromism of Peak Broadening in Absorption Spectra in Solution Using the Reference Interaction Site Model Self-Consistent Fields Spatial Electron Density Distribution.

We quantified and subsequently analyzed bandwidth of ultraviolet and visible photoabsorption spectral lines in solution by applying time-dependent first-order perturbation theory using the Born-Oppenheimer adiabatic potential calculated using the multistate extended-multi-configurational quasi-degenerated second-order perturbation theory (MS-XMCQDPT2) coupled with the reference interaction site model self-consistent field spatial electron density distribution (RISM-SCF-cSED). The proposed method was implemented for 2-thiocytosine in solution, and solvatochromism of the bandwidth of the πSπ* transition was clearly observed. The standard deviation of a characteristic electronic excitation was decomposed into the contributions of the characteristic vibrational mode of 2-thiocytosine. The main vibrational modes contributing to peak broadening were found to be for acetonitrile, methanol, and the aqueous phase. We concluded that the mechanism for peak broadening is qualitatively different for phases of protic and aprotic solvents because of the structural variation in 2-thiocytosine driven by the breakage of the resonance structures.

Laser-induced localized and maskless electrodeposition of micro-copper structure on silicon surface: Simulation and experimental study

The simulation and experimental study of laser-induced localized and maskless electrodeposition of micro-copper (Cu) structures on p-type silicon (Si) surface is investigated. Firstly, calculations of the internal temperature field and free electron density distribution within Si under nanosecond laser irradiation were carried out, to demonstrate the selective enhancing effect of laser irradiation on electrical conductivity via the thermal and photoconductive manner. Secondly, experimental tests of the laser-induced electrodeposition of micro-wires, regional coatings and complicated patterns on Si surface without mask were performed successively, to illustrate the effectiveness of the proposed method. The experimental results indicate that laser pulse width and scanning space significantly affect the quality of the deposited layer. Specifically, dense and flat micro wires can be achieved when the laser pulse width is 100 ns, which is associated with a width of about 71.7 μm and thickness of around 10.9 μm. In addition, the laser scanning space should be well optimized to balance the uniformity of the regional coating and the stray deposition near the edge. Finally, the reduction of Cu2+ and deposition of Cu atom at Si surface were discussed, as well as the development of transitional layer, to supply an in-depth analysis of the electrodeposition mechanism.

Numerical model of a gaseous inductive discharge in oxygen, taking into account the complete scheme of the vibrational kinetics of O2 molecules

In this work, the two-dimensional model of inductively coupled plasma discharge in oxygen was developed. The model includes hydrodynamic equations in drift-diffusion approximation for describing the kinetics of charged (electrons and ions) and neutral plasma particles, Maxwell’s equations for electromagnetic fields, and equations for the temperature and neutral gas flow as well as a detailed scheme of plasma-chemical reactions. The model was tested against theoretical and experimental data in a simple cylindrical chamber. The electron density and temperature distributions were obtained over a wide range of powers deposited in the plasma (100–500 W) and compared with literature data. Also, the complete scheme of the vibrational kinetics of O2 molecules was included in the model. The vibrational distribution function was calculated in low-pressure inductive discharge as well as spatial distributions of plasma parameters (density and temperature of electrons, excited components, neutral gas temperature, etc.) and flows of charged and active neutral particles at the reactor walls.

The Theoretical Investigation by QTAIM Approach to Chemical Bonding of a Di-Rhenium Bis(Triphenylphosphine) Carbonyl Cluster Containing Sulfuric and Hydrido Bridge: [Re2(CO)6(μ-S)(μ-H)(PPh3)2

Scientists used the quantum theory of atoms in molecules (QTAIM) to calculate and interpret various electron density parameters for a di-rhenium bis(triphenylphosphine) carbonyl cluster containing sulfuric and hydrido bridge: [Re2(CO)6(μ-S)(μ-H)(PPh3)2]. They analyzed the bond critical points and compared them with data from previous organometallic system studies. The researchers were able to compare the topological processes of different atom-atom interactions based on these results.
 The calculations showed that there were no bond critical points or identical bond paths between Re-Re in the core of the cluster. The electron density distribution was affected by the position of bridging hydride and sulfur atoms coordinated to Re-Re, which significantly affected the bonds between these transition metal atoms. However, the calculations did confirm the presence of a 6c–8e bonding interaction delocalized over HRe2SP2 in the cluster.
 The scientists found that the Re-H and Re-S bonds in this cluster exhibited typical closed-shell interactions, with small values for ρ(b) and Laplacian ∇2ρ(b) above zero and small positive values for total energy density H(b). Similarly, the bond interactions between phosphine metal atoms and the C atoms of the phenyl ring ligands showed properties similar to open-shell interactions in the QTAIM classification.

Computational studies into the chemical nature, thermal behaviour, solvent role, reactivity and biological evaluation of Rigidin E – A marine alkaloid with potent liver cancer inhibition

The current work includes theoretical studies of Rigidin E (marine alkaloid) molecule with the DFT technique and evaluation of its biological properties in silico. DFT calculations in different media were performed for the title molecule. Gradual changes were noticed in the properties of the title compound when subjected to solvation in polar solvents. Electron density distribution, interaction and excitation were demonstrated using topological studies (ELF, LOL, RDG, and charge transfer) done using Multiwfn software. From FMO analysis, methanol is the solvent in which the title compound has the highest band gap value (3.8972 eV) compared to other solvents, and in the gas phase it has a band gap value of 3.6886 eV. Theoretical UV studies show that n -->π* and n -->σ* electronic transitions are significant in Rigidin E. In water, the title molecule has a first-order hyperpolarizability about 100 times that of the reference substance urea, indicating its powerful NLO potential in aqueous medium. ADMET profile was generated using online tools (ADMET lab 2.0, PreADMET, and SwissADME). For the title molecule, docking was done against select liver cancer targets using AutoDock Tools and the lowest binding affinity was obtained −4.62 kcal/mol against 4H6J protein.

Study on the propagation properties of terahertz waves in spacecraft dusty plasma sheath

Terahertz (THz) wave transmission in non-uniform dielectric layer containing dusty plasmas and aluminum (Al) is investigated by using the Wentzel–Kramer–Brillouin method. The application of magnetic field and increase in electromagnetic waves frequency are up-and-coming solutions for the “blackout” issue. Therefore, this work considers the effect of external magnetic field and electron density distribution. The electron density distributions are assumed to be double Gaussian profile, uniform distribution, Epstein distribution, and both right- and left-hand circularly polarized waves are analyzed. Then the effects of physical parameters and THz frequency on the transmission properties are analyzed. Results show that the presence of Al can shield electromagnetic waves, but we can still control THz waves in lower frequency band to achieve communication. By adjusting THz waves frequency and plasma parameters, waves can pass through the Al plasma sheath effectively under certain circumstances. It is expected to mitigate the blackout issue of hypersonic spacecraft.

Iterative Gradient Correction (IGC) Method for True Height Analysis of Ionograms

AbstractInversion of precise true height electron density profile from the measured virtual heights by the Ionosonde is a quite challenging and ill‐posed problem. In this paper, we present a new method to compute the true height profiles from ionograms that relies on computing the propagation path of radio waves with time. This method does not use predefined polynomial functions to fit the vertical electron density distribution; hence, it is free from fitting errors. Instead, this method implements iterative corrections in the electron density gradient between the successive points and progressively reconstructs the true height profile. This Iterative Gradient Correction (IGC) method assures minimizing the error to below a tolerance limit at all sampled points on the ionogram. The true height profiles derived from this method exhibit better accuracy than those derived from the widely used POLynomial ANalysis, particularly, at cusp and F2‐peak regions. Further, the IGC method gives the best results at higher sampling resolutions of ionograms and is less sensitive to scaling errors.

A COMPUTATIONAL DENSITY FUNCTIONAL THEORY INVESTIGATION OF THE INTERACTION OF BORON NITRIDE NANOSHEETS WITH MULTIPLE MOLECULAR HYDROGENS

In this study, the adsorption of molecular hydrogens (H2) on boron nitride (BN) frameworks was investigated using the density functional theory (DFT) technique. The results of optimized geometric structures revealed that molecular hydrogens were favourably adsorbed on top of nitrogen atoms in the BN monolayers. In addition, the optimized equilibrium geometries were utilized to calculate the electronic structures, including binding energies, energies of the highest and lowest occupied molecular orbitals (HOMO and LUMO), molecular electrostatic potentials (MEPs), and Mulliken atomic charges (MACs). The binding energy values were calculated to be approximately 0.01 eV per molecular hydrogen based on the results. As the number of molecular hydrogens increased in the BN framework, a slight increase was observed in the binding energy value per hydrogen molecule. Furthermore, the HOMO–LUMO gaps were determined with the corresponding energy values of about 6 eV. Regarding the Frontier molecular orbitals (FMOs) diagrams, the electron densities for the HOMOs of the studied systems were primarily focused on the N-edges. Conversely, for the LUMO, the electron density distribution was localized in the B-edges of titled systems. In the context of hydrogen adsorption on BN nanosheets, the MEP maps indicated that hydrogen atoms at the N-edges of the studied systems exhibited the most positive electrostatic potentials in this research. In contrast, surfaces with negative electrostatic potential surfaces were situated in the region close to B-edges. The computed results are consistent with the corresponding Mulliken atomic charge distributions. From the analyses of the Mulliken scheme, all nitrogen atoms displayed negative charge values, and positive charges were found on the boron atoms. The DFT results obtained in this report may serve as the foundation for developing hydrogen storage materials

Cooperativity and topological hydrogen bonding in aromatic diol complexes

AbstractComplexes of three aromatic diols, catechol, naphthalene‐1,8‐diol, and fluorene‐4,5‐diol, with a series of hydrogen bond acceptors (HBAs) that have oxygen, nitrogen, and sulfur acceptor atoms, have been studied by density functional theory (DFT) at the B3LYP/6‐311+G(d,p) level. Binding energies, geometries, infrared spectroscopic (IR) frequencies, nuclear magnetic resonance (NMR) shifts, and measures of the electron density distribution from the Quantum Theory of Atoms in Molecules (QTAIM) are evaluated and compared with data for the corresponding monohydroxy compounds (monols), phenol, naphth‐1‐ol, and fluorene‐4‐ol, in order to assess the importance of cooperativity between intramolecular and intermolecular hydrogen bonding. All measures for all complexes show positive cooperativity whereby both the intermolecular and intramolecular hydrogen bonds are strengthened upon complexation. Cooperativity is weak for catechol and strong for the other two diols and, for all diols, increases with the hydrogen bond basicity of the acceptor. Correlations of IR and NMR metrics against binding energies for a single HBA and all six monols and diols are excellent, but attempts to correlate the same metrics for all HBAs and a single donor are frustrated by differences in intermolecular hydrogen bonding, depending notably on the identity of the acceptor atom in the HBA. Atom–atom interaction energies, calculated by the Interacting Quantum Atoms approach, are used to discuss the covalency of both types of hydrogen bond.

The Adsorption Mechanisms of SF6-Decomposed Species on Tc- and Ru-Embedded Phthalocyanine Surfaces: A Density Functional Theory Study.

Designing high-performance materials for the detection or removal of toxic decomposition gases of sulfur hexafluoride is crucial for both environmental monitoring and human health preservation. Based on first-principles calculations, the adsorption performance and gas-sensing properties of unsubstituted phthalocyanine (H2Pc) and H2Pc doped with 4d transition metal atoms (TM = Tc and Ru) towards five characteristic decomposition components (HF, H2S, SO2, SOF2, and SO2F2) were simulated. The findings indicate that both the TcPc and RuPc monolayers are thermodynamically and dynamically stable. The analysis of the adsorption energy indicates that H2S, SO2, SOF2, and SO2F2 underwent chemisorption on the TcPc monolayer. Conversely, the HF molecules were physisorbed through interactions with H atoms. The chemical adsorption of H2S, SO2, and SOF2 occurred on the RuPc monolayer, while the physical adsorption of HF and SO2F2 molecules was observed. Moreover, the microcosmic mechanism of the gas-adsorbent interaction was elucidated by analyzing the charge density differences, electron density distributions, Hirshfeld charges, and density of states. The TcPc and RuPc monolayers exhibited excellent sensitivity towards H2S, SO2, and SOF2, as evidenced by the substantial alterations in the band gaps and work functions of the TcPc and RuPc nanosheets. Our calculations hold significant value for exploring the potential chemical sensing applications of TcPc and RuPc monolayers in gas sensing, with a specific focus on detecting sulfur hexafluoride.

Comparison between Schiff-base and its iron complex as steel corrosion inhibitors used by the petroleum industry in marine environments

ABSTRACT The Schiff-base N,N-bis(2-furaldehyde)−1,3-diaminopropane (FDP) and its complex with iron (FDPIC) were prepared and used as corrosion inhibitors for mild-steel (MS) in a 3.5% NaCl medium as an artificial marine environment to evaluate the functional groups’ efficiency within the structure of the compounds for corrosion inhibition. To predict the effect of the researched inhibitors’ ability to suppress corrosion, weight loss measurements and a variety of complex analytical techniques, including potentiodynamic-polarisation and electrochemical-impedance tests, were applied. Experimental results revealed that (FDPIC) has a higher corrosion inhibition efficacy than (FDP). According to electrochemical measurements, inhibitors showed significant resistance to charge transfer through the electrolyte–metal interface and mixed-type inhibitor behaviour. Furthermore, the film formed on the surface of the mild steel was examined using a scanning electron microscope (SEM). Quantum chemical calculations using semi-empirical molecular orbital PM3 and Molecular Dynamics (MD) were used to investigate inhibitor adsorption and inhibition on the mild-steel surface. The geometry of the Schiff-base and its complex structures, as well as electron density distribution in LUMO, HOMO, and QSAR properties of each atom for their conceivable interaction mode with the mild-steel surface, were used in chemical quantum calculations. According to molecular dynamic simulations, all of the inhibitor molecules adhered to the surface in a parallel direction.

An investigation of the effects of porosity and N-defects of 2D CxNy membranes on the wettability behavior and separation capability of water and oil mixtures

In this study, three different structures of two dimentional (2D) CxNy were investigated experimentally and theoretically to determine their wettability behavior and separation capability based on their porosity, surface defect structure, and surface energy. The C3N, C1N1, and graphitic-C3N4 (g-C3N4) were synthesized and coated on stainless steel mesh. Wettability characteristics of the C3N, C1N1, and g-C3N4-coated mesh showed hydrophobic/oleophilic, hydrophilic/ underwater super-oleophobic, and super-hydrophilic/underwater super-oleophobic, respectively. The experimental results showed that the best performance of C3N with the highest surface area was obsereved in oil removal and the best performance of g-C3N4 with the highest pyridinic-N/pyrrolic-N XPS peak-area ratio was observed in water removal. Since electrostatic interaction plays an important role in water-removing state, increasing the number of pyridinic-N increases the electrostatic potential of water with the surface during water removal. Based on surface energy calculations, the highest dispersed surface energy is found in C3N, whereas the strongest polar component is found in g-C3N4, confirming their hydrophobic and hydrophilic wettability, respectively. Density functional theory investigations confirmed the higher hydrophilicity of g-C3N4 due to its non-uniform electron density distribution. The adsorption energies of water and decalin molecules are proportional to the amounts of charge transfer between porous substrates and adsorbents.

Quantifying weak interactions in ferroelectric and paraelectric phases of phenazine and chloroanilic acid co-crystal using experimental and theoretical electron densities.

The co-crystal of phenazine and chloroanilic acid is known to display paraelectric properties at room temperature. It shows a paraelectric to ferroelectric phase transition at 253 K and has an incommensurately modulated ferroelectric phase below 137 K. High-resolution synchrotron X-ray data were collected at 160 K to model the experimental electron-density distributions, and derived topological properties from the electron density were used to quantify the weak interactions responsible for the origin of the ferroelectric phase. The structure and non-covalent interactions are analysed using Hirshfeld surfaces and energy frameworks. The topological properties, energies, atomic charges and molecular electrostatic potential surfaces are determined from the experimental data, further supported by theoretical calculations. The results from the ferroelectric phase are compared with the paraelectric phase. Although the structural descriptions indicate neutral phenazine and chloroanilic acid molecules in the ferroelectric phase, the topological properties of the electron density indicate a considerable amount of proton transfer in the O-H...O hydrogen bond. Indeed, the displaced H atom in the O-H...O hydrogen bond suggests a mixed covalent/polar nature of chemical bonding. Subtle changes in the chemical bonding and proton-transfer pathways could be detected from the high-resolution electron-density studies.