Charge Density Distribution Studies Research Articles

Effect of BaSnO3 on structural and electrical properties of lead free Na0.5Bi0.5TiO3 ceramic solid solution

A series of novel lead-free (1-x)(Na0.5Bi0.5)TiO3–xBaSnO3, (x = 0.00, 0.05, 0.10) ceramics were fabricated by solid-state air sintering route and their dielectric and microstructural properties were studied. Various experimental methods to characterize the fabricated ceramics such as PXRD, Raman spectra, SEM-EDS, UV-visible and dielectric studies. All the ceramics were crystallized by rhombohedral symmetry using PXRD and Rietveld profile refinement technique. The experimental atomic charge density distribution studies were performed and the bonding characteristics were analyzed. With increase of BSN content, the average grain size decreased and was characterized by scanning electron microscopy (SEM) technique. Energy dispersive x-ray (EDS) spectra indicate the presence elements and the diffusion of BSN into the rhombohedral phase of NBT matrix. The optical bandgap was determined by UV-Visible spectra and the values are found to be 3.05, 3.10 and 3.12 eV. The temperature dependence of dielectric constant (ε) provides evidence for dielectric anomalous behaviour in the higher doping of BSN concentration.

Structural, Photoluminescence and Electron Density Distribution Analysis of Rutile Phase TiO2

In this work, the mixed anatase and rutile phases of commercial TiO2 sample was purchased and converted to single rutile phase by sintering at 1000°C. Structural and spectroscopic analysis of the single phased rutile TiO2 were analyzed by PXRD, SEM, EDS, PL analysis, respectively. Rietveld profile refinement technique was performed to fit the observed and calculated PXRD profiles. Charge density distribution studies were used to determine the chemical bonding nature of Ti-O bond by maximum entropy method (MEM). From the MEM calculations, Ti-O bond exhibited covalent nature. PL measurements showed that the emission wavelength of rutile TiO2 at around 470 nm which may be due to band to band transitions of Ti and O atoms.

Structural and charge density distribution studies on Tin Oxide nanoparticles for Supercapacitor application

Pure SnO and Mn doped SnO (Mn:SnO) nanoparticles have been successfully prepared by simplest route of the hydrothermal method. Prepared nanoparticles have been characterized by various analyses to understand structural, optical, morphological, elemental composition, Photoluminescence and electrochemical behaviours. The powder X-ray diffraction pattern analysis confirms the formation of crystalline nature of pure and Mn:SnO and its tetragonal structure. Functional group and elemental composition of prepared nanoparticles are confirmed using FTIR and EDX. The electrochemical performances of the prepared materials as working electrodes are analyzed by electrochemical workstation, analyzed parameters such as cyclic voltammetry and galvanostatic charge-discharge. From this study, maximum specific capacitance (Csp) is 246.5 F g − 1 at 5 mA cm−2 is obtained. The optical energy band gap is found to be 3.17 and 2.61 eV for SnO and Mn:SnO nanoparticles, respectively.

Structural and Charge Density Properties of Manganese Sulfide

Single phased Manganese Sulfide was analyzed by powder X-ray diffraction (PXRD) data sets with cubic structure. The simulated XRD data sets were used to analyze the structure of manganese sulfide. The powder profile refinements were done by Rietveld profile refinement technique. The refinement results were subjected to analyze the charge density analysis using structure factors. The chemical bonding nature between Mn and S were analyzed by charge density distribution studies through maximum entropy method. From MEM analsysis, it found that the bonding between Mn and S atoms is ionic in nature.

Structural, electronic, elastic and thermodynamic properties of Al1-xZxNi (Z=Cr, V and x= 0, 0.125, 0.25) alloys: First-principle calculations

The AlNi intermetallic compound is one of the most promising engineering materials for high temperature applications. Unfortunately, this compound has low tensile ductility at high temperature which limit its functional applications. We show that alloying the AlNi compound with the Cr or V will improve its tensile ductility and therefore its industrial applications. In this paper, the structural, electronic, elastic and thermodynamic properties of Al1-xZxNi (Z = Cr, V and x = 0, 0.125, 0.25) alloys have been studied by the first principles calculations in the framework of density functional theory. The calculated formation energy and cohesive energy of the alloys show that, all alloys have stable structures. The valence charge density distribution study reveals that, chemical bonds between the Z and Ni atoms in the alloys have the nature of covalent, which improve the brittleness of the AlNi alloys. The calculated Pugh’s ratio (or the Poisson’s ratio), shear and bulk modules show that, the increasing of hardness by increasing the x. Moreover, the ductility of the alloys decreased when the value of x is nonzero. The calculation results show that the Pugh’s (Poisson’s) ratio is higher than 1.75 (0.26), indicating a ductile nature of these alloys. Furthermore, thermodynamic properties of the alloys including Grüneisen parameter, thermal expansion coefficient, bulk modulus, Debye temperature and constant volume heat capacity have been investigated and discussed under different pressures and temperatures.

A study of charge density distribution and enhanced electrochemical properties of zinc cobaltite/polyaniline nanocomposite for supercapacitor application

Solution combustion method was used to synthesize ZnCo2O4 nanoparticles. Then, physical blending method was used to prepare ZnCo2O4/polyaniline (PANI) composite. The crystallite sizes of the ZnCo2O4 and ZnCo2O4/PANI composites prepared were 17.16 nm and 25.46 nm, respectively, as calculated by XRD studies. The density of nanoparticles, cell parameters, and unit cell volume were calculated by Rietveld refinement technique. The cell volume and lattice constant obtained from the Rietveld method were in good agreement with those of Scherer’s method. Functional groups of the samples were further studied using FTIR. Maximum entropy method (MEM) was employed to study the chemical bonding and electron density distribution of the nanoparticles. The electrochemical properties of the pure and composite materials varied due to the changes in the electron density distribution and chemical bonding. The W–H method and size–strain plot method were used to determine the crystallite size and strain. The results obtained through these methods were in accordance with those of Scherer’s method. The morphological observations made through SEM revealed that the change in morphology of the nanomaterial has enhanced the electrochemical properties of the composite. The shape and size of the pure and nanocomposite observed by SEM and XRD were further confirmed by HR-TEM images. Selected area electron diffraction pattern of HR-TEM images was used to further confirm the crystalline nature of ZnCo2O4 and ZnCo2O4/PANI nanoparticles as examined by XRD. The CV and chronopotentiometry studies were used to study the electrochemical behavior of the samples. The specific capacitance values of pure and composite as obtained from CV study were 711 F/g and 867 F/g, respectively, at the applied current density of 0.5 A/g. Good capacitance retention of 98.9% was achieved for the nanocomposite up to 1000 cycles at a high current density of 4 A/g. The investigation by electrochemical impedance spectrum study also revealed that the nanocomposite exhibited low resistance compared with that of pure. The symmetrical capacitor was assembled by fabricating it with ZnCo2O4/PANI as the electrodes. The high specific capacitance and enhanced efficiency have been achieved due to the presence of PANI in the nanocomposite.

Analysis of structural, optical and charge density distribution studies on Zn1-xMnxS nanostructures

The phasepure nanostructures of Zn1-xMnxS (x = 0.0, 0.04, 0.06 and 0.08) has been synthesized by using chemical precipitation method. The prepared nanostructures are characterized by powder X-ray diffraction (PXRD) method. The structural properties are analyzed through Rietveld refinement analysis. The charge density distribution studies are also done using maximum entropy method (MEM). The bonding features have been analyzed using MEM method. The morphological studies are done using Scanning Electron Microscopy (SEM) and it confirms that the prepared systems are in nano range. The optical characterization has also been done through UV spectrophotometer.

Exploring the Binding of Barbital to a Synthetic Macrocyclic Receptor. A Charge Density Study.

Experimental charge density distribution studies, complemented by quantum mechanical theoretical calculations, of a host-guest system composed of a macrocycle (1) and barbital (2) in a 1:1 ratio (3) have been carried out via high-resolution single-crystal X-ray diffraction. The data were modeled using the conventional multipole model of electron density according to the Hansen-Coppens formalism. The asymmetric unit of macrocycle 1 contained an intraannular ethanol molecule and an extraannular acetonitrile molecule, and the asymmetric unit of 3 also contained an intraannular ethanol molecule. Visual comparison of the conformations of the macrocyclic ring shows the rotation by 180° of an amide bond attributed to competitive hydrogen bonding. It was found that the intraannular and extraannular molecules inside were orientated to maximize the number of hydrogen bonds present, with the presence of barbital in 3 resulting in the greatest stabilization. Hydrogen bonds ranging in strength from 4 to 70 kJ mol-1 were the main stabilizing force. Further analysis of the electrostatic potential among 1, 2, and 3 showed significant charge redistribution when cocrystallization occurred, which was further confirmed by a comparison of atomic charges. The findings presented herein introduce the possibility of high-resolution X-ray crystallography playing a more prominent role in the drug design process.

Using Electron Density to Predict Synthon Formation in a 4-Hydroxybenzoic Acid: 4,4′-Bipyridine Cocrystal

Experimental charge density distribution studies complemented by quantum mechanical theoretical calculations of 4-hydroxybenzoic acid (4HBA) (1), 4,4′-bipyridine (44BP) (2), and one polymorphic form of the cocrystal containing 4HBA and 44BP molecules in a 2:1 ratio (3), have been carried out via high resolution single-crystal X-ray diffraction. Synthon formation was found to be the main driving force for crystallization in both (1) and (3) with a carboxylic acid homosynthon present in (1) and a heterosynthon in (3) comprised of a carboxylic acid from 4HBA and a pyridine nitrogen and aromatic hydrogen from 44BP. Topological analysis revealed the bonding in the homosynthon to be stronger than the heterosynthon (305.88 versus. 193.95 kJ mol–1) with a greater number of weak interactions in (3) helping to stabilize the structure. The distance from the hydrogen and hydrogen bond acceptor to the bond critical point (bcp) was also found to be a significant factor in determining bond strength, potentially having a...

Preparation, electronic structure, and chemical bonding of lead-free (1 − x)(K0.5Bi0.5)TiO3-xBaTiO3 solid solution

Polycrystalline lead-free (1 − x)(K0.5Bi0.5)TiO3-xBaTiO3, ((1 − x)KBT-xBT) (x = 0.00, 0.08, 0.12) ceramics were synthesized via solid-state reaction method. The powder X-ray diffraction (PXRD) and structural refinement results confirm that a single-phase tetragonal structure with space group P4mm. Charge density distribution inside the unit cell of (1 − x)KBT-xBT was investigated by the maximum entropy method. Charge density analysis reveals the reduction in ionic nature along K/Bi–O bond and enhancement of covalent nature along Ti–O bond with the addition of BaTiO3. The charge density distribution studies done using maximum entropy method for (1 − x)KBT-xBT have not been done so far. The surface morphology study was done using scanning electron microscopy (SEM). Energy dispersive X-rays spectra (EDS) were used to investigate the elemental compositions present in the system. The dielectric constant and loss tangent were studied as a function of frequency. The dielectric constant and loss were decreased with increase of frequency. Room temperature dielectric constant (ɛ) and loss (tan δ) were measured for x = 0.00 about 511 and 0.51, respectively, at a frequency of 10 kHz.

Investigation on charge density, piezoelectric and ferroelectric properties of (1 − x)Ba(Zr0.2Ti0.8)O3–x(Ba0.7Ca0.3)TiO3 lead-free piezoceramics

The lead-free (1 − x)Ba(Zr0.2Ti0.8)O3–x(Ba0.7Ca0.3)TiO3, (x = 0.4, 0.5 and 0.6) (abbreviated as (1 − x)BZT–xBCT) ceramics were prepared by solid-state reaction method. X-ray diffraction (XRD) study revealed the perovskite phase of the prepared ceramics at room temperature (RT) for all compositions. The XRD powder profile refinement analysis showed no extra phases and the calculated peak intensities matched well with the observed ones. The charge density distribution studies revealed the chemical bonding nature, qualitative and quantitative features of the distributions of the electrons contributed by the dopant atoms in the unit cell. Scanning electron microscopy images revealed the uniform distribution of powder grains. The elemental compositions of the samples were analyzed by energy dispersive X-ray spectrometer. The optical band gap for all the samples has been estimated to be between 3.15 and 3.07 eV. Enhanced piezoelectric constant, d33 = 276 pC/N was obtained for x = 0.5 composition in the morphotropic phase boundary (MPB).

Charge correlation of ferroelectric and piezoelectric properties of (1 − x)(Na0.5Bi0.5)TiO3–xBaTiO3 lead-free ceramic solid solution

Single phased lead-free (1 − x)(Na0.5Bi0.5)TiO3–xBaTiO3 (x = 0.00, 0.04, 0.08 and 0.12) ((1 − x)NBT–xBT) ceramics were synthesized by the solid-state reaction method. The powder X-ray diffraction patterns and profile refinements revealed that, for 0.04 < x < 0.08, the prepared ceramics have been crystallized in morphotropic phase boundary between rhombohedral to tetragonal structures. The charge distribution and bonding behaviour in (1 − x)NBT–xBT unit cell were completely analyzed through charge density distribution studies. UV–visible analysis reveals that, the optical band gap energy of the solid solution increases with addition of BaTiO3 content. The surface morphology and elemental compositions for the sintered powders were analyzed through scanning electron microscopy and energy dispersive X-ray studies. Electrical measurements on the solid solutions showed that the maximum values of the dielectric constant, the remnant polarization and the piezoelectric coefficient are reached at near (x = 0.08) the morphotropic phase boundary (e = 4070 at 100 kHz; Pr = 18.92 µC/cm2; d33 = 122 pC/N). Thus, the (1 − x)NBT–xBT system is expected to be a promising candidate for lead-free piezoelectric material.

Electron-Lattice Coupling in Armchair Graphene Nanoribbons.

We report the effects of electron-lattice coupling on the charge density distribution study of armchair graphene nanoribbons (GNRs). Here, we perform a theoretical investigation explaining the unexpected electronic density states observed experimentally. By means of a tight-binding approach with electron-lattice coupling, we obtained the same characteristic pattern of charge density along the C-C bonds suggested by both scanning tunneling and transmission electron microscopic measurements. Our results suggest electronic localized states whose sizes are dependent on the GNR width. We also show that our model rescues the quasi-particle charge-transport mechanism in GNRs. The remarkable agreement with experimental evidence allows us to conclude that our model could be, in many aspects, a fundamental tool when it comes to the phenomenological understanding of the charge behavior in this kind of system.

Peculiarities of the M–π interaction in phosphacymantrene derivatives upon the Mn(CO)3 fragment orientation: Experimental and theoretical electron density study

Abstract The results of the single crystal X-ray diffraction analysis of 2,5-diphenylphosphacymantrene (η5-C4H2Ph2P)Mn(CO)3 (1) and experimental charge density distribution study of [(η4-C4H2Ph2P(O)H)Mn(СO)3]−[NH2Et2]+ (2) are discussed. The resultant density was analyzed using the quantum theory of atoms in molecules (QTAIM). Here, we focused on the analysis of the interaction between the metal atom and the π-ligand depending on the mutual orientation of the Mn(CO)3 moiety and the heterocyclic fragment (cis and trans conformers). The electronic structures of cis and trans conformers of both the complexes 1 and 2 have also been studied by ab initio density functional theory calculations, showing rather a good agreement with the experiment. Redistribution of the electron density in the vicinity of the metal atom upon the reorientation of the carbonyl groups causes the changes in the geometric and electronic characteristics of the heterocycle. The most significant changes occur in the molecular topology, in particular, in the connectivity of the metal atom with the π-ligand.

Charge Density Analysis of a Pentaborate Ion in an Ammonium Borate: Toward the Understanding of Topological Features in Borate Minerals

Structural and charge density distribution studies have been carried out on a single crystal data of an ammonium borate, [C(10)H(26)N(4)][B(5)O(6)(OH)(4)](2), synthesized by solvothermal method. Further, the experimentally observed geometry is used for the theoretical charge density calculations using the B3LYP/6-31G** level of theory, and the results are compared with the experimental values. Topological analysis of charge density based on the Atoms in Molecules approach for B-O bonds exhibit mixed covalent/ionic character. Detailed analysis of the hydrogen bonds in the crystal structure in the ammonium borate provides insights into the understanding of the reaction pathways that could result in the formation of borate minerals. The net atomic charges and electrostatic potential isosurfaces also give additional input to evaluate chemical and physical properties in such systems.

Local distortion in Co-doped LSMO from entropy-maximized charge density distribution

Perovskite structure manganites La 0.67Sr 0.22Mn 1.11− x Co x O 3 were prepared by the solid state reaction method. An X-ray analysis of the structure was undertaken using the Rietveld technique on the experimental powder X-ray diffraction data and, then, a charge density distribution study was undertaken, using the maximum entropy method (MEM). The charge density in the unit cell was reconstructed and the effect of Co 3+ doping in the Mn–O matrix was studied. Local distortions due to Co doping were analyzed and the results are now discussed.

Experimental and theoretical charge density distribution studies in ZnSiAs 2

Experimental and theoretical charge density distributions have been studied in the chalcopyrite ZnSiAs 2. The X-ray diffraction technique has been adopted in determining the experimental valence charge density maps. The comparison with the self-consistently obtained pseudocharges shows similar features particularly in the bonding region.

Thermal dissociation of 1,2‐dioxethane. I. Charge density distribution along the reaction path and in different HF solutions

AbstractA charge density distribution study, based on ab initio SCF–6‐31G wave functions, on the optimized geometry of 1,2‐dioxethane indicates its high instability which results from (i) the high ring strain, (ii) the large amount of charge contained on the nonbonded sides of the oxygen nuclei, and (iii) the weak binding character of the charge density in the OO bond region. The redistribution of the charge density when 1,2‐dioxethane undergoes change in its nuclear configuration has been discussed. This redistribution of charge along the reaction path (the dissociation of 1,2‐dioxethane to formaldehyde products) shows clearly the preceding nature of the electron cloud. The characteristic features of the charge density distribution of the two Hartree–Fock solutions to which the SCF procedure converges have been analyzed and discussed.