Values Of Bond Lengths Research Articles

Synthesis, covalency parameters, energy calculations and crystal features of acylpyrazolone derived pentavalent Uranyl complex along with DFT and Hirshfeld analysis

A σ-donating acylpyrazolone DMBPMP (4-(3,5-dimethyl benzoyl) 1-phenyl 3-methyl 5-pyrazolone) ligand and its Uranyl acylpyrazolone complex [UO2(DMBPMP)2(EtOH)] were synthesized to analyze the nature of covalency, reactivity, and redox properties. The structure, pentavalent bipyramidal geometry, and complex composition are mainly scrutinized through their single-crystal x-ray crystal data, molar conductivity, gravimetric estimation, FTIR significant vibrations, δ-values of 1H NMR, 13C NMR and TG-DTA plots. The covalency of the Uranyl complex mainly depends on average bond length values on the pentagonal equatorial plane, Uranyl axial bond lengths, stretching frequency values, coordinated solvent on the fifth coordination site, and different aryl group substitution on the first position of the pyrazolone ring; and it can be confirmed through FTIR, single-crystal, and electronic UV–Vis spectral characterization methods. The UV–Vis data was also valuable for identifying n → π*, π → π*, and LMCT transitions and calculating Sinha’s covalency parameters, which shows that the complex can show maximum covalent character in DMSO solvent and covalency decreases in DMSO > DMF > Ethyl acetate > Ethanol > CHCl3 order. DFT calculations were performed to get an excellent correlation and comparison with all experimental values. This correlation and comparision is helpful to identify global index parameters to get an idea of the physical as well as chemical properties of such systems and to confirm the characteristics theoretically by HOMO-LUMO energy gap, theoretical vibrations, natural electronic configuration, and NBO charges. The Hirshfeld surface analysis was also carried out to identify the crystal strength through interaction energies and energy frameworks in the ligand and intermolecular non-covalent surface interactions with fingerprint plot details in both ligand and complex. Electro-chemical analysis in CV-DPV plots provides information on the redox properties of uranyl moiety.

Potential reaction initiation points of polycyclic aromatic hydrocarbons

Reaction initiation points of the 16 priority polycyclic aromatic hydrocarbons (PAHs) have been determined by calculating all the different C-H bond dissociation enthalpy (BDE) values. Six density functional theory methods (B3LYP, B3LYP-D3, B97D3, M06-LD3, M06-2X-D3, and ω B97X-D) in combination with 4 basis sets (6-31G(d), 6-31+G(d,p), 6-311++G(d,p), def2-TZVP) have been applied and the most feasible combination has been selected. The BDE values and the corresponding bond lengths have been used to determine potential attack points on the structures. The studied molecules have been categorized structurally as well, within which the position of the hydrogen atoms is considered. Results show that most of the hydrogens are in zig-zag positions, and the BDE and bond length values for the 16 priority PAHs are in a range between 342.0 and 485.6 kJ/mol and 1.0817–1.952 Å, respectively. Most of the initiation points are represented by armchair and peak hydrogens. The lowest and highest BDE and shortest and longest bond length values belong to fluorene and acenaphthylene where the hydrogens were aliphatic and in peak position, respectively.

Electronic Structure and IR Spectra Analysis of Tetrathiafulvelene (TTF) Using RHF and DFT Quantum Mechanical Methods

Tetrathiafulvalene (C6H4S4) is an organosulfur compound used in the manufacture of organic optoelectronic materials. Restricted Hartree-Fock (RHF) and Density Functional Theory (DFT) were employed for the study of the optimized molecular structure of TTF using different basis sets. All computations were performed using Gaussian 03 package. Parameters such as minimum energy, bond lengths and bond angles, HOMO-LUMO energy gap, chemical reactivity descriptors, Non-linear optical properties (such as isotropic polarizability (α), anisotropy of polarizability (∆∝), and total first hyper-polarizability (βtot)), density of states, vibrational frequencies, and intensities were computed and reported in order to determine the relative stability as well as chemical reactivity of the molecule. The results obtained show that RHF has the lowest average value of bond length of 1.0729Å while that obtained using DFT has the lowest average value of 1.0812Å using the same basis set 6-311++G (d, p). This shows that the value is a bit higher using DFT than RHF which implies that the bonds of TTF molecule will be slightly stronger when optimized using RHF than DFT. The bond angles were found to be slightly higher by using DFT than RHF. The calculated HOMO-LUMO energy gap shows that the molecule will be slightly more stable in chemical reaction using RHF than DFT. The DFT values, 3.59 eV and 3.60 eV obtained for the energy gap are closer to the reported value of 3.63eV compared to those obtained by RHF. From the results obtained for vibrational frequencies using both methods, TTF is stable due to the absence of imaginary frequencies. This confirms the stability of the molecule as stated in the results of HOMO-LUMO energy gap. The calculated vibrational frequencies show that the most intense frequency was obtained to be 752.6293 cm-1 at corresponding intensity of 145.9063KM/mole by RHF/6-31++G (d, p) while at B3LYP/6-31+G(d), the most intense frequency is about 635.0243 cm-1 with corresponding intensity of 138.5738MK/mole. By and large, the studyunveil the potential of Tetrathiafulvalene for optoelectronic applications.

Insight into mercury-laden activated carbon adsorbent product bonding nature by DFT calculations

The coal-fired power plant is the main contributor to anthropogenic mercury emission in China. Adsorbent injection technology has proven to be the most promising and established strategy for controlling mercury release. The ultimate fate of mercury-loaded adsorbent product would be landfilled or reused as architecture materials. Either way, the chemical stability of mercury-containing products is important. The objective of this research is to reveal the binding nature of spent adsorbents. In particular, computational chemistry was utilized. The effects of different oxygen functional groups (carbonyl, carboxyl, lactone, and phenol) on the carbonaceous surface were considered. Furthermore, the influence of chlorine and bromine was also considered. The bond length and Mayer bond order value of chemical bonds of interest were calculated and compared to indicate their bond strength. The electron localization function (ELF) was employed to locate electron high localization regions in the product. Additionally, the Hirshfeld weighting function for decomposing bonding localized molecular orbital (LMO) to the two connected atoms compositions were utilized to characterize different chemical bonds bonding polarity quantitatively. In summary, the results are beneficial for understanding the chemical characteristics and environmental stability of used mercury removal adsorbents.

Intriguing electronic, optical and photocatalytic performance of BSe, M2CO2 monolayers and BSe-M2CO2 (M = Ti, Zr, Hf) van der Waals heterostructures.

Using density functional (DFT) theory calculations, we have investigated the electronic band structure, optical and photocatalytic response of BSe, M2CO2 (M = Ti, Zr, Hf) monolayers and their corresponding BSe–M2CO2 (M = Ti, Zr, Hf) van der Waals (vdW) heterostructures. Optimized lattice constant, bond length, band structure and bandgap values, effective mass of electrons and holes, work function and conduction and valence band edge potentials of BSe and M2CO2 (M = Ti, Zr, Hf) monolayers are in agreement with previously available data. Binding energies, interlayer distance and Ab initio molecular dynamic simulations (AIMD) calculations show that BSe–M2CO2 (M = Ti, Zr, Hf) vdW heterostructures are stable with specific stacking and demonstrate that these heterostructures might be synthesized in the laboratory. The electronic band structure shows that all the studied vdW heterostructures have indirect bandgap nature – with the CBM and VBM at the Γ–K and Γ-point of BZ for BSe–Ti2CO2, respectively; while for BSe–Zr2CO2 and BSe–Hf2CO2 vdW heterostructures the CBM and VBM lie at the K-point and Γ-point of BZ, respectively. Type-II band alignment in BSe–M2CO2 (M = Ti, Zr, Hf) vdW heterostructures prevent the recombination of electron–hole pairs, and hence are crucial for light harvesting and detection. Absorption spectra are investigated to understand the optical behavior of BSe–M2CO2 (M = Ti, Zr, Hf) vdW heterostructures, where the lowest energy transitions are dominated by excitons. Furthermore, BSe–M2CO2 (M = Ti, Zr, Hf) vdW heterostructures are found to be potential photocatalysts for water splitting at pH = 0, and exhibit enhanced optical properties in the visible light zones.

Band topology resisted spin-state evolution of perovskite ACoO[formula omitted] (A = Ca, Sr) under pressure

There has been a debate on the theoretical explaining of the spin states in the perovskite ACoO3, especially SrCoO3. The aim of this work was to investigate the magnetic phase stability and to study the evolution of the spin states of the cubic perovskite ACoO3 (A = Ca, Sr) under pressure up to 40 GPa by using the density functional theory and the Hubbard +U parameters (DFT+U). Both CaCoO3 and SrCoO3 exhibit the ferromagnetic and metallic properties under pressure. Our results of the total magnetization and the net-spin density corroborate that a change of the magnetic behaviors on ACoO3 mostly depends on the value of Co-O bond length (dCo−O). We discovered a down-stepwise evolution of the total magnetization as a relationship with the dCo−O decreasing. This stepwise behavior occurs prior to the spin crossover from intermediate spin (IS) state to low spin (LS) state. The total magnetization values non-monotonically decreased from 2.49 to 2.16 μB/f.u. between the dCo−O = 1.88 and 1.80 Å. From our evidence, we indicated that the spin state of Co-3d states resembles the d7L̲2 character with t2g3↑,2↓eg2−x↑,x↓L̲2 state, where x≈0.5 and L̲ denotes the oxygen’s charge transfer from the oxygen ligands. Indeed, we discovered that the stepwise evolution of the total magnetization is associated with the changes in the band topology of the Co-3deg∗ band.

Analytical Model for Bond Behavior Prediction of CFRP-Concrete Joints with End Anchorage.

Use of the end anchorages can significantly control the debonding of CFRP-to-concrete bond interface, and improve the bearing capacity of CFRP strengthened concrete member. An analytical model was presented in this paper to predict the bond behavior and debonding process of CFRP-concrete bonded joint with end anchorage. The calculation formulas of bond failure load and effective bond length for anchored CFRP-concrete joint are derived from the proposed analytical model. According to these models and formulas, the influence of different bond lengths on the mechanical behaviors during the debonding process was analyzed. Results show the load-slip curves of end anchored CFRP-concrete joints could be divided into three branches: elastic stage, stable stage, and enhancement stage. As the bond length increases, the plateau length in stable stage increases. Besides, the bond failure load decreased firstly to a lower limit and then increased with the increase of bond length. The effective bond length of CFRP-concrete joint with end anchorage was longer than that of the external bonded joint, and the value of effective bond length for end anchored joint shall be at least 7.2/AB, where the parameters A and B were related to the interfacial properties of bonded joint. Furthermore, a single shear test was carried out on the end anchored CFRP-concrete bonded joint with different bond lengths, to verify the consistency of the proposed model and formulas. The analytical result of load-slip response at the load end, as well as the strain distribution of CFRP material and the bond failure load, was compared with the experimental result. The comparisons showed that the analytical results had a good agreement with the experimental results.

Flower decorated rod-like Pd @ MnO2 nanocomposite: Focus on photocatalysis, Rietveld refinement analysis and electron density distribution analysis

In this scenario, the Pd doped MnO2nanocatalysts were constructed by hydrothermal route. As-synthesized Pd loaded α-MnO2 nanocomposites were systematically characterized by various characterization techniques, respectively. The FESEM and TEM results reveal the surface morphology, the rose flower-like Pd was evenly decorated on the MnO2 surface. The elemental compositions of the presenting elements Pd, Mn and O are confirmed by XPS spectroscopic analysis. The photocatalytic activity of 2% Pd loaded α-MnO2 for crystal violet (CV) degradation was very high compared to immaculate α-MnO2 under visible light embellishment. Moreover, the radical trapping experiment substantiates that O2•− and •OH plays a vital role in CV abatements. This work will provide new in-depth insights into other photocatalytic nanomaterials with potential applications in the field of environmental compensation. Besides, the electron density distributions analysis was carried out for this catalyst to explain the bond length value between the atoms.

Computational Methods and Molecular Modelling for Some Predicted Tautomers of Pyrimidine Compounds

Introduction: Several molecular modelling techniques and quantum chemical methods have been performed to correlate the chemical structures of the compounds with their physical molecular properties. Methods: Using theoretical parameters help to characterize the molecular structure of the investigated ligands and to study their equlibria mechanism. Molecular modelling data such as the bond length, bond order, bond angles and dihedral angles values were estimated for some pyrimidine compounds, where the data suggested the presence of tautomerism and a dynamic equilibria are deduced between all the detected tautomers in the solid state. Results: Four main tautomers were predicted for barbital and thiobarbituric acid, while three tautomers were for thiouracil. Quantum chemical parameters such as the highest occupied molecular orbital energy (EHOMO), the lowest unoccupied molecular orbital energy (ELUMO), energy gap (ΔE), dipole moment (μ), sum of the total negative charge (STNC), electronegativity (χ), chemical potential (Pi), global hardness (η) and softness (σ) were calculated. Conclusion: These studies display a good correlation between the theoretical and experimental data.

The crystal and coordination chemistry of neptunium in all its oxidation states: An expanded structural hierarchy of neptunium compounds

Structures of 388 neptunium-bearing crystal structures are sorted into an expanded structural hierarchy and examined. The majority of structures contain Np(V) (149), Np(VI) (99), or Np(IV) (91) whereas structures containing Np(II), Np(III), Np(VII), or more than one oxidation state are rare. Coordination geometry of Np(V) and Np(VI) compounds is dominated by the approximately linear neptunyl cation. Actinyl–actinyl interactions (AAIs) are most prevalent in Np(V) compounds and are observed in 48% of these extended structures. Prismatic coordination geometries are commonly observed in Np(IV) compounds. Np(III) organometallic complexes display a variety of coordination modes. Coordination chemistry of Np(VII) compounds is dominated by the tetra-oxido core. Updated average bond length values are provided for Np(IV), Np(V), Np(VI), and Np(VII) compounds and updated bond valence parameters for Np(IV) are reported. A graphical notation system for neptunyl structures coordinated by organic ligands was developed to facilitate discussion and identify similarities between neptunyl compounds coordinated by oxyanions and neptunyl compounds coordinated by organic ligands.

High resolution synchrotron extended x-ray absorption fine structure and infrared spectroscopy analysis of MBE grown CdTe/InSb epifilms

Six CdTe thin epifilms were prepared by using molecular beam epitaxy on ion beam cleaned InSb (001) substrates with Tsub temperatures ranging from 25 to 250 °C. Thickness dependent vibrational and structural characteristics are meticulously examined by far-infrared reflectivity (FIR) and high-resolution synchrotron extended x-ray absorption spectroscopy (HR-XAS), respectively. The FIR measured line shapes and optical modes for samples prepared on ion beam cleaned InSb at Tsub ≤ 100 °C revealed abrupt interfaces while noticing segregated Sb atoms and In2Te3-like precipitates at CdTe-InSb interfaces for films grown on ion beam cleaned InSb at Tsub ≥ 230 °C. Our simulated reflectivity results, using a traditional multilayer (ambient/film/substrate) optics methodology, are compared reasonably well with the experimental data. To substantiate the Berreman effect, we have also investigated the transmission and reflectivity spectra of CdTe/InSb epilayers and (CdTe)m/(ZnTe)n/InSb superlattices at oblique incidence (θI = 45°). A clear distinction of the transverse optical (ωTO) phonons in the s-polarization and ωTO and longitudinal optical (ωLO) modes in the p-polarization has established a valuable method of assessing long wavelength optical phonon frequencies in technologically important materials. Comprehensive analysis of HR-XAS results on the structural characteristics of CdTe/InSb epilayers has provided values of bond lengths and coordination numbers in very good agreement with the existing bulk CdTe data.

Fabrication of pebble stone-like PbMoO4 nanostructure: Focus on photocatalysis, photoluminescence and electron density distribution analysis

In this work, the PbMoO4 nanocatalyst is synthesized by the hydrothermal way. The as-prepared PbMoO4 nanomaterial was confirmed by powder X-ray diffraction (P-XRD), UV–visible diffuse reflectance spectroscopy (UV-DRS), photoluminescence (PL), scanning electron microscopy (SEM) and Transmission electron microscopy techniques (TEM). The scanning Electron Microscope result indicates the pebble stone morphology structure of PbMoO4 nanomaterials. The catalytic performance for as-synthesized PbMoO4 nanomaterial was analyzed by the ciprofloxacin (CIP) degradation process. More interestingly, the as-prepared PbMoO4 material is having higher catalytic performance compared to the other previous PbMoO4 nanoparticles reports with an efficiency of above 92%. A photodegradation mechanism and the reaction kinetics of PbMoO4 nanomaterial were also investigated. The aforesaid results are strong enough to suggest the PbMoO4 nanomaterial may be an effective catalyst for environmental application. In addition, the electron density distributions studies were carried out for this PbMoO4 nanomaterial to explain the bond length value between the atoms.

Theoretical research on mercury-laden halogenated activated carbon adsorbent bonding nature

Halogenated activated carbon adsorbents exhibit superior mercury capture performance in the flue gas. Not only the fabrication of effective adsorbents, but the used adsorbents stability is also crucial. It is essentially determined by product bonding nature. Here, Density functional theory was employed to investigate spent halogenated activated carbon adsorbents bonding nature at the atomic level. Seven possible mercury-containing product molecular geometries and effects of halogen species (X = Cl/Br/I) were considered. Specifically, bond length value, and bond order of Hg-C, Hg-X and C-X bonds of interest were calculated to investigate product stability in the gaseous phase. It was found that mercury was attached on the carbonaceous surface with C-Hg Mayer bond order around 0.5 in product structures G and H, suggesting a weak interaction. In other possible product molecular geometries, C-Hg or X-Hg exhibited a single bond character. Moreover, effects of halogen atoms on X-Hg and C-X bond strength were discussed. Electron localization function (ELF) and Localized orbital locator (LOL) were utilized to determine electron high localization regions. Results indicated C-Hg and C-X on the carbonaceous surface are covalent bonds and formed X-Hg bonds are ionic bonds. Furthermore, atom composition in the localized molecular orbital was calculated via the Hirshfeld method. In summary, this study investigated the bonding nature of used halogenated activated carbon adsorbents. The results are beneficial for fabricating more environmental-friendly mercury removal adsorbents in the future.

Synthesis, spectral, molecular modeling, biological and antitumor studies of new nifuroxazide complexes

Series of Zr(IV), Ce(IV) and U(VI) complexes were synthesized with nifuroxazide ligand. Design and formulae of the complexes suggested in the light of analytical, spectral, magnetic and thermal analyses (1HNMR, IR, UV-Vis). The calculated values of molar conductance mean that, all isolated complexes were electrolytes. The data revealed the complexes formation and suggested that nifuroxazide binds as a bidentate at NO sites with metal ions. The kinetic parameters evaluated using Coats Redfern (CR) and Horowitz-Metzeger (HM) methods. The thermodynamic data reflect the thermal stability for all complexes. The calculated bond length and force constant values for UO2 bond are 1.741 Å and 459.409 Nm−1. The research investigations were related to quantum chemical calculations conducted at the theory level of DFT/B3LYP/LANL2DZ. The nifuroxazide, inorganic salts and their metal complexes were assayed against different bacterial species as well as the in vitro growth inhibitory activity against human breast carcinoma (MCF-7) and HCT-116 cell lines. Zr(IV) complex was found to have the highest activity against all the tested organisms and a powerful anti-cancer drug.

Experimental and theoretical studies of chitosan dissolution in ionic liquids: Contribution ratio effect of cations and anions

Typical hydrogen bonding information (hydrogen bonds, hydrogen bond lengths, and average bond lengths) and weak interaction energy (ΔH) of four ionic liquids (ILs), anion/chitobiose, cation/chitobiose, and IL/chitobiose complexes were determined using density functional theory (DFT) calculations to elucidate the contribution ratio effect of ions (cations or anions of ILs) upon chitosan dissolution.For [Emim]Ac and [Bmim]Ac with same acetate anion, contribution ratio (Rc) values of cations in [Bmim]Ac and [Emim]Ac increased from 37.88% to 38.14%. For [Bmim]Cl and [Etmim]Cl with same chloride anion, contribution ratio (Rc) values of cations increased slightly from 39.39% to 41.65%. As for [Bmim]Cl and [Bmim]Ac with same cation, contribution ratio (Rc) values of Cl- anion in [Bmim]Cl (60.61%) was lower than that of acetate anion in [Bmim]Ac (62.12%).These changes revealed that cations of ILs played more important role in chitosan dissolution.Hydrogen-bond basicity values (β values) of ILs were closely related to the DFT simulation results (weak interaction energy and average hydrogen bond length values) of ILs. Chitosan dissolved faster in acetate based imidazolium ILs ([Emim]Ac and [Bmim]Ac) than the chloride based ILs ([Bmim]Cl and [Etmim]Cl). The chitosan dissolution performance in ILs was consistent with DFT simulation results (weak interaction energy values and average hydrogen bond length values) of IL/chitobiose and hydrogen-bond basicity values of ILs.

Syntheses, crystal structures, antioxidant, in silico DNA and SARS-CoV-2 interaction studies of triorganotin(IV) carboxylates

Triorganotin(IV) carboxylate complexes R3SnL, where R = C4H9 (1), CH3 (2) and L = 2-chlorophenyl ethanoate, were synthesized and characterized by elemental analysis, FT-IR, NMR (1H, 13C, 119Sn) and X-ray single crystal analysis. The solid state analyses confirmed a bridging bidentate coordination mode for the carboxylate ligand rendering the tin ion a penta-coordinated center in the synthesized complexes. NMR spectra revealed a change in the coordination number (5→4) for tin when in the solution. The structural geometry and the electronic properties of complexes were calculated by using the density functional theory (DFT) method at B3LYP level 6–31G(d, p) and Lanl2DZ basis sets. A fairly good agreement was found between the observed and theoretical bond length and bond angle values for the complex (1) and (2). The in vitro antioxidant potential of the complexes was investigated by DPPH, ferrous ion chelation, ferric ion reducing, total antioxidant and hydroxyl free radical scavenging assays. The nature of the tin bonded R groups has apparently a significant impact on the antioxidant activity of the complexes. Molecular docking studies suggest intercalation as possible mode of complex-DNA interactions. Docking studies also confirm that interactions of the two complexes with some active site residues of SARS-CoV-2 nucleocapsid protein and angiotensin-converting enzyme 2 (ACE2) are probable.

Synthesis, characterization, computational studies and DPPH scavenging activity of some triazatetracyclic derivatives

Some dihydrobenzo[4,5]imidazo[1,2-c]quinazolines have been synthesized from aldehydes and ketones, using the ketones as both reagents and solvents and tetrahydrofuran (THF) as the solvent for the aldehydes, to yield the triazatetracyclics. The compounds have been characterized with spectroscopy and microanalysis. The crystal structures of 9,9-dimethyl-8,10,17-triazatetracyclo[8.7.02,7.011,16]heptadeca-1(17),2,4,6,11(16),12,14-heptaene (I), 9-butyl-9-methyl-8,10,17-triazatetracyclo[8.7.0.02,7.011,16]heptadeca-(17),2,4,6,11(16),12,14-heptaene (III) and 9-phenyl-8,10,17-triazatetracyclo[8.7.0 02 7.011,16]heptadeca-1(17),2,4,6,11(16),12,14-heptaene (VIII) have been discussed. The computed NMR, IR, molecular electrostatic potential and frontier molecular orbitals of compounds I, III and VIII have been discussed. The M06 functional gave most of its values closest to the experimental values for the bond lengths and bond angles of compounds I and III. For compound VIII, none of the functionals gave values for bond lengths and bond angles that were consistent with the experimental values, but M06 gave values closest to experimental values. The 1,1-diphenyl-2-picrylhydrazyl (DPPH) scavenging activity of the triazatetracyclics showed that compound I exhibits significant DPPH scavenging activity with an IC50 of 56.18 µM compared to 2.37 µM for ascorbic acid.

Ab initio Monte Carlo simulations of structure and electronic properties of copper-tin clusters

This study investigated the structural and electronic properties of (CuSn)n clusters with n = 1–6 using ab initio Monte Carlo Simulations and density functional theory calculations. Monte Carlo simulations were performed using a large number of initial structures of neutral, cationic, and anionic copper-tin clusters. Their stable structures were determined using B3LYP/def2-TZVP model chemistry and the most stable structures of neutral, cationic, and anionic copper-tin clusters were established. The values of bond angles and bond lengths, atomization energies, second differences of the energies, HOMO-LUMO gaps, Mulliken population analysis, adiabatic ionization potentials, and adiabatic electronic affinities were determined as a function of n.

Defect-mediated ab initio thermodynamics of metastable γ-MoN(001).

Refractory transition metal nitrides exhibit a plethora of polymorphic expressions and chemical stoichiometries. To afford a better understanding of how defects may play a role in the structural and thermodynamics of these nitrides, using density-functional theory calculations, we investigate the influence of point and pair defects in bulk metastable γ-MoN and its (001) surface. We report favorable formation of Schottky defect pairs of neighboring Mo and N vacancies in bulk γ-MoN and apply this as a defect-mediated energy correction term to the surface energy of γ-MoN(001) within the ab initio atomistic thermodynamics approach. We also inspect the structural distortions in both bulk and surfaces of γ-MoN by using the partial radial distribution function, g(r), of Mo-N bond lengths. Large atomic displacements are found in both cases, leading to a broad spread of Mo-N bond length values when compared to their idealized bulk values. We propose that these structural and thermodynamic analyses may provide some insight into a better understanding of metastable materials and their surfaces.

Thermal, microstructural and magnetic properties of manganese substitution cobalt ferrite prepared via co-precipitation method

Manganese-substituted cobalt nano-ferrites, Co(1−x)Mn(x)Fe2O4 (x = 0.0, 0.2, 0.4, 0.6, 0.8 and 1.0) were synthesized using chemical co-precipitation method. Physical properties of Co(1−x)Mn(x)Fe2O4 nano-ferrites were then characterized using thermal gravimetric—differential thermal analysis (TGA/DTA), X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectrometer, transmission electron microscopy (TEM) and vibrating sample magnetometer (VSM). TGA/DTA study indicates that the thermal stability of the prepared manganese doped cobalt ferrite nanoparticles. X-ray diffraction patterns of all the prepared ferrite samples show good in quality, pure nanosized, single-phased cubical spinel structures, with ferromagnetic behavior. We demonstrated that the expansion of lattice constant (a) and crystallite size (D) induced by manganese substituted of cobalt ferrites exerted remarkable effects on its structural and magnetic properties. The lattice constant (a) and crystallite size (D) increase with increasing manganese substituted cobalt ferrites. Williamson–Hall (W–H) method was used to evaluate the crystallite size and lattice strain of the Co(1−x) Mn(x)Fe2O4 nanoparticles samples by peak broadening. The calculated crystal size of Co(1−x) Mn(x)Fe2O4 nanoparticles on the W–H plots were highly intercorrelated with the HR-TEM and results of Scherrer Deby equation. The other physical parameters, such as X-ray density, hopping length, ionic radius, bond length, tetrahedral edge, octahedral edge, and unshared octahedral edge values were estimated from the highest intensity peak (311) of X-ray diffraction. The Fourier transform infrared (FT-IR) spectrometer of the Co–Mn ferrite nanoparticles systems were recorded in the frequency range of 200–1000 cm−1. FT-IR spectra show the two fundamental absorption bands of interstitial sub-lattice sites (M–O). The high absorption band (ν1) and the low absorption band (ν2) corresponds to the tetrahedral [A] and octahedral (B) sites, respectively, confirming the formation of single cubic spinel ferrite lattice system. The TEM results show that the ferrite nanoparticles have a nearly spherical shape with some agglomerations. From the analysis of VSM, the values of saturation magnetization (Ms) increases from 31.46 to 37.16 emu/g, then decreases with increasing Mn2+ ions substitution in the Co-ferrite system. The coercivity of the Mn2+ ions substituted cobalt ferrites increases up to x = 0.6 followed by a decrease. The optimized magnetic parameters suggest that the material with composition Co0.6Mn0.4Fe2O4 may be suitable for longitudinal magnetic recording media and other various technological applications.