Structure Optimization Calculations Research Articles

Study on the regulation of ε-CL-20 by an external electric field.

To explore the influence of the external electric field (EEF) on ε-CL-20. The molecular structure, frontier molecular orbitals (FMOs), global reactivity parameters (GRP), surface electrostatic potential, nitro charge, and UV-Vis spectra of ε-CL-20 under EEF were studied using density functional theory (DFT). The calculation results show that the electric field applied along N16-N24 has a significant effect on the structure of ε-CL-20. With an increase in the positive EEF, the bond length of the initiating bond decreases, and the bond order and bond dissociation energy increase, which increases the thermal stability of ε-CL-20 to a certain extent. In addition, with an increase in the positive EEF intensity, the LUMO migrates from both sides of the positive electric field to one side of the nitro group, and the HOMO migrates from the skeleton to the nitro group. It is worth noting that in the negative EEF, when the electric field strength changed from 0 to 0.016 a.u., the negative charge of the total nitro group gradually decreased. When the electric field strength becomes 0.02 a.u., the negative charge of the total nitro group suddenly increases, and ε-CL-20 is significantly polarized. When the electric field strength is sufficiently strong, the occupied and unoccupied orbitals of the ε-CL-20 molecule change, resulting in a change in the energy level difference between the occupied and unoccupied orbitals, which further excites the corresponding excited state, resulting in a new UV-Vis absorption peak. Based on the density functional theory (DFT), the structural optimization and energy calculation were carried out by using B3LYP/6-311 + G(d, p) and B3LYP/def2-TZVPP methods, respectively. After optimization convergence, vibration analysis was performed without imaginary frequencies to obtain stable configurations. Then the molecular structure, frontier molecular orbitals (FMOs), global reactivity parameters (GRP), surface electrostatic potential, nitro charge, and UV-Vis spectra were analyzed.

New insights and reaction mechanisms on ZrO2 (110) surface enhanced catalytic hydrolysis of CFC-12: a density functional theory study.

Freon, a greenhouse gas that contributes to the depletion of the ozone layer, has been the subject of investigation in this study. The catalytic hydrolysis enhancement of CFC-12 by ZrO2 was examined using a density functional theory approach. A detailed reaction mechanism and a new reaction pathway were proposed. The study found that CFC-12 is more likely to be adsorbed on the ZrO2 surface in the CFC-12-TO(F) configuration, while H2O is more likely to be adsorbed on the ZrO2 surface in the H2O-TO(H) configuration. Additionally, H2O replaces CFC-12 on the surface of ZrO2. The hydrolysis of CFC-12 is primarily determined by the first dechlorination process, while the defluorination process is comparatively easier. ZrO2 has a catalytic effect on both dechlorination and defluorination processes, with a more pronounced effect on the former. The production of C-OH bonds is inhibited, which facilitates the dechlorination and defluoridation processes. This work was carried out in the Dmol3 program in the Material Studio 2017, including the geometric structure optimization and energy calculations. The GGA/PBE method was used in this work, along with the DNP basis, spin-polarized set, and DFT-D correction. The possible TSs were guessed based on the linear synchronous transit/quadratic synchronous transit/conjugate gradient (LST/QST/CG) method, and they were further confirmed and reoptimized to ensure that the only one imaginary frequency exists in the TSs.

First principles investigation of Li[formula omitted]Si and Li[formula omitted]Sn alloys: Unraveling atomic-scale influences on material properties

Commercial batteries have currently reached their peak specific capacity, which proves insufficient for the ongoing global energy transition. Consequently, there has been a surge of interest in developing new materials over the last decade, especially those based on silicon (Si) and tin (Sn), known for their high capacity. Despite numerous publications highlighting the advantages of these materials, crucial questions remain regarding volume expansion that must be addressed to propose effective solutions and facilitate their widespread commercial application. In this study, density functional theory was employed to investigate the formation of LixM (M = Si, Sn). Our analysis delves into crystal (c-LixM), amorphous (a-LixM), and amorphous slab (s-LixM) configurations during structural optimization calculations, with the aim of comparing and contrasting relevant findings. The exploration encompasses energetic aspects, volume expansion, and electronic properties. The obtained data enables the simulation of lithiation potential curves for each structural type, directly comparable with experimental results of these materials functioning as anodes in lithium-ion batteries. Notably, the volume expansion of a-LixM exhibits non-linear behavior, correlating with characteristic plateaus in the voltage profile curves.

Electronic analysis of n-propyl xanthate complexes with group 12 metals: a theoretical-experimental study.

Xanthates are organic compounds of great interest in coordination chemistry due to their different basic sites, which allow them to form complexes with different coordination modes and geometries. These compounds are relevant in the environment and act as heavy metal collectors in aqueous environments. In this theoretical-experimental work, electronic spectroscopy studies of n-propyl xanthate complexes with group 12 metals were performed. This study verified structural differences in these systems, depending on the environment in which they are inserted. In addition, structural differences were observed when the solid was changed to an n-hexane solution. Thus, it was observed that the complexes assume a mononuclear structure in solution, while they present a polymeric form in the solid phase. The electronic spectra obtained through TD-DFT calculations were compared to those of the previously synthesized complexes. In the final theoretical analysis, the main orbitals involved in these transitions were assigned using population analysis calculations. The synthesis of the complexes was confirmed through infrared (MID and FAR), UV‒Vis, Raman, and NMR-1H spectroscopic analyses. The structures of the mononuclear and polymeric complexes were optimized in vacuum and n-hexane. Under vacuum, DFT levels M06L/6-311 + + G** + LANL2TZ and M06L/def2-TZVP were used for the mononuclear complexes, and M06L/LANL2DZ + LANL2 were used for the polymer complexes. For the calculations of the mononuclear complexes in n-hexane, the same level of theory was used for the solid state. TD-DFT calculations for 300 excited states were performed with the same levels of theory and used the optimized structures of the complexes. Furthermore, population analysis was carried out on all the systems studied. Gaussian 09 software was used for the structure optimization, TD-DFT, and population analysis calculations. GaussSum software was used to evaluate the molecular orbitals and electronic spectra.

Insights into the hydrolysis/alcoholysis/ammonolysis mechanisms of ethylene naphthalate dimer using density functional theory (DFT) method

Hydrolysis, alcoholysis and ammonolysis are viable routes for the efficient degradation and recycling of polyethylene naphthalate (PEN) plastic waste. Various possible hydrolysis/alcoholysis/ammonolysis reaction pathways for the degradation mechanism of the ethylene naphthalate dimer were investigated using the density functional theory (DFT) B3P86/6–31++G(d,p). To determine the thermodynamic and kinetic parameters, geometric structure optimization and frequency calculation were performed on a range of intermediates, transition states, and products associated with the reaction. The calculation results show that the highest energy barrier of the main element reaction step in hydrolysis is about 169.0 kJ/mol, the lowest is about 151.0 kJ/mol for ammonolysis, and the second is about 155.0 kJ/mol for alcoholysis. The main hydrolysis products of the ethylene naphthalate dimer are 2,6-naphthalenedicarboxylic acid and ethylene glycol; the main products of alcoholysis are dimethyl naphthalene-2,6-dicarboxylate and ethylene glycol, and the main products of ammonolysis are naphthalene-2,6-dicarboxamide and ethylene glycol. Furthermore, in the process of ethylene naphthalate dimer hydrolysis/alcoholysis/ammonolysis, the decomposition reaction in the NH3 atmosphere is better than that in methanol, and the reaction in CH3OH is better than that in the H2O molecular environment, and the increase in reaction temperature can increase its spontaneity. Our study presents the molecular mechanism of PEN hydrolysis/alcoholysis/ammonolysis and provides a reference for studying the degradation of other plastic wastes.

A molecular mechanics implementation of the cyclic cluster model

Abstract The implementation of the cyclic cluster model (CCM) for molecular mechanics is presented in the framework of the computational chemistry program deMon2k. Because the CCM is particularly well-suited for the description of periodic systems with defects, it can be used for periodic QM/MM approaches where the non-periodic QM part is treated as a defect in a periodic MM surrounding. To this end, we present here the explicit formulae for the evaluation of the Ewald sum and its first- and second-order derivatives as implemented in deMon2k. The outlined implementation was tested in molecular dynamics (MD) simulations and periodic structure optimization calculations. MD simulations of an argon system were carried out using the Nosé-Hoover chain (NHC) thermostat and the Martyna-Tobias-Klein (MTK) barostat to control the temperature and pressure of the system, respectively. For the validation of CCM structure optimization a set of molecular crystals were optimized using the Ewald method for the evaluation of the electrostatic interactions. Two optimization procedures for the determination of the atomic positions and CCM cell parameters were tested. Our results show that the simultaneous optimization of the atomic positions and cell parameters is most efficient.

Influence of shear strain on the electronic properties of monolayers MoS2, WS2, and MoS2/WS2 vdW heterostructure.

This study investigates the dynamic stability of monolayers MoS2, WS2, and MoS2/WS2 van der Waals heterostructures (vdWHs) and the influence of shear strain on their electronic properties. The computational results of the binding energy and phonon dispersion demonstrate the excellent dynamic stability of MoS2/WS2 vdWHs. The MoS2/WS2 vdWH, with a type-II band alignment and an indirect bandgap, reduces electron-hole recombination, enhancing the efficiency and performance of optoelectronic devices. Under shear strain, the bandgap size and type of monolayers MoS2, WS2, and MoS2/WS2 vdWHs were effectively modulated, along with the interlayer charge redistribution in the MoS2/WS2 vdWHs. This work reveals the tunability of the electronic properties of monolayers MoS2, WS2, and MoS2/WS2 vdWHs under shear strain, offering new possibilities and solutions for developing optoelectronic devices, sensors, and related fields. This work employed the CASTEP module within the Materials Studio software package for first-principles calculations. Ultrasoft pseudopotentials were employed during geometry optimizations to account for ion-electron interactions using the GGA-PBE functional for exchange-correlation potentials. The electronic configurations of the S, Mo, and W atoms were chosen as their typical arrangements: (3s2p4), (4s2p6d55s1), and (5s2p6d46s2), respectively. A vacuum layer of 20Å was added to avoid interactions between the atomic layers. A cutoff energy of 500eV was set for structural optimization and self-consistent calculations, with k-point grids of 6 × 6 × 1 and 9 × 9 × 1. During the structural optimization process, the energy convergence criterion was set to 1 × 10-5eV, and the thresholds for interatomic forces and stresses were set to 0.01eV/Å and 0.01 GPa, respectively. Grimmer's DFT-D2 correction accounted for the interlayer vdW interactions in the MoS2/WS2 vdWH, while the phonon dispersion was calculated using the linear response method.

Influence of Hydroxyl Groups on the Oxidative Reaction Characteristics of Active Groups in Lignite at Room Temperature.

In this paper, through the Fourier infrared spectrum analysis of the Inner Mongolia Hulunbeier Yannan coal mine lignite sample, phenyl and active groups, methoxy (-OCH3) and methylene (-CH2-), were taken as the research objects, and a simple small molecule model of hydroxyl (-OH) at the ortho, meta, and para positions of active groups was constructed. The structural optimization and simulation calculation of simple small molecules were carried out by Gaussview 6.0.16 and Gaussian 16 software at room temperature and pressure. The DFT-B3LYP method and 6-311G(d,p) basis set were used to study the effect of the -OH position on the oxidation reaction characteristics from various aspects of electrostatic potential, frontier orbital, activation energy, enthalpy change, and Gibbs free energy change. The results show that the coexistence of the active groups -OCH3 and -CH2- with -OH makes the small molecule model add an active site, that is, the oxygen atom in -OH, which makes the active groups generate hydrogen radicals (H•). Comparing different positions of -OH, the analysis shows that -OH at the ortho position has a vital impact on the oxidation reaction, and the oxidation reaction releases the largest amount of heat and has the fastest occurrence rate, making it easier to overcome energy barriers and making the reaction easier to proceed. The purpose of this study is to reveal the interaction and complex reaction path of lignite through an in-depth study of its properties, structural composition, and reaction behavior and to accurately grasp its chemical composition, thermal properties, and microstructure, so as to lay a foundation for further efficient conversion and comprehensive utilization.

Structural optimization calculation of methanol spiral tube reformer based on waste heat utilization and experimental verification of reactor performance

Spiral tube is compact, efficient in heat transfer and can make full use of the annular space in the engine, so it can be applied to heat recovery under a variety of operating conditions. This paper developed a three-rate, one-dimensional model combined with simulations, experiments. It can be found that in the hydrogen prediction, the model has an error of 10 % from experiment and 0.91 % from literature; the increase in length from 0.5 m to 1.35 m increases methanol conversion by 7.97 %; the increase in spiral diameter from 4 mm to 7 mm increases methanol conversion by 9.35%; spiral radius from 40 mm to 70 mm, methanol conversion rate decreased by 5%; mass fraction of methanol decreased by 16 % when the pitch was increased from 5 mm to 20 mm. When diameter is 4 mm, length is 1 m, the MSR reaction rate reach 24.1 mol/m3/s, methanol conversion rate is 87.91 %. When spiral pitch is 10 mm, spiral diameter is 40 mm, methanol conversion rate can reach 91.83 %. The spiral tube reactor has a compact structure and can achieve 87.19 % methanol conversion and 0.0955 L/min H2 production at WHSV = 0.9 h−1 and S/C = 1.7.

Strain-induced modification in thermal properties of monolayer 1T-ZrS2 and ZrS2/ZrSe2 heterojunction.

This paper systematically analyzes the phonon dispersion curves of single-layer ZrS2, ZrSe2, and ZrS2/ZrSe2 heterostructures under different strains. The phonon spectra and thermal parameters of the three structures were obtained based on the density functional perturbation theory method. The upper limits of strain that different monolayers and heterojunctions can withstand were studied. The monolayers ZrSe2 and ZrS2 can withstand up to 8% biaxial tensile strain, and the ZrS2/ZrSe2 heterojunction can withstand up to 6% biaxial tensile strain. In addition, the van der Waals force of the heterojunction may cause phonon tearing in the vertical direction. The application of biaxial tensile strain can adjust the thermal properties of the system to a large extent, which is similar to the strain effect in the pristine case. When the temperature rises, the entropy enthalpy of the three structures also gradually increases, the free energy gradually decreases, and the heat capacity of the system gradually increases until it tends to be stable. Taking single-layer ZrS2 as an example, we analyzed the change curve of thermal properties of single-layer ZrS2 under tensile strain. The results show that with the gradual increase of strain, the crystal's entropy, enthalpy, and free energy change differently. In addition, the heat capacity increases slowly under high temperatures. When all systems reach the limit strain, the phonon spectrum appears to have an imaginary frequency, and the thermal properties decrease significantly. This paper uses the first-principle calculation method based on density functional theory, and the PBE exchange-correlation function based on generalized gradient approximation (GGA) is selected for a specific calculation. The density functional perturbation theory (DFPT) calculates the full kinetic matrix. Because the lattice constants of ZrS2 and ZrSe2 are similar and have similar periodicity, the corresponding unit cells are used for structural optimization and property calculation. The Brillouin zone is integrated using the K points generated by the Monkhorst-pack method. For single-layers ZrS2 and ZrSe2, 8 × 8 × 1K-point grid is selected, and for ZrS2/ZrSe2 heterojunction, 8 × 8 × 2K-point grid is selected. A vacuum layer of 30Å was added in the vertical direction to avoid interlayer interaction. The non-conservative pseudopotential method is used to optimize the structure, and the optimization convergence is set as follows: the cutoff energy is set to 700eV, the convergence threshold of the maximum force between atoms is 0.01eV/Å, the convergence threshold of the maximum energy change is set to 1 × 10-9eV, and the convergence threshold of the maximum displacement is 0.001Å.

Bending deformation modulation of the optoelectronic properties of molybdenum ditelluride doped with nonmetallic atoms X (X = B, C, N, O): a first-principles study.

A first-principles approach based on density functional theory was used to explore the effect of bending deformation on the electrical structure of molybdenum ditelluride doped with nonmetallic atoms X (X = B, C, N, and O). The study included alternate doping of nonmetallic atoms, as well as a comparison of the effects of intrinsic bending deformation and nonmetallic doping deformation. The results demonstrate that boron atom doping raises the Fermi energy level. Examining the energy band structure indicates that the intrinsic molybdenum ditelluride is a direct band gap semiconductor, which is transformed from a direct band gap to an indirect band gap after doping. We selected boron-doped systems for bending deformation and compared them with the intrinsic systems. With increasing deformation, all systems start to shift from semiconductor to metal. When the deformation reaches 8°, the energy levels fill and the electron energy increases. The intrinsically bent systems transition from direct band gap to indirect band gap and eventually to metal. The indirect band gap semiconductor-to-metal transition process occurs after the bending deformation of the boron-doped atoms. The analytical results show that the absorption and reflection peaks of the molybdenum ditelluride system are blue-shifted after the bending deformation of the boron-doped atoms. Under fundamental principles, this research depends on the density functional theory framework (DFT) using the CASTEP module in the Materials-Studio software. The plane-wave pseudopotential approach with modified gradient approximation and the Perdew-Burke-Ernzerhof (PBE) generalized function is used for structure optimization and total energy calculations of the X-doped (X = B, C, N, O) MoTe2 system at different shape variables. Geometry optimization of the 27-atom superlattice MoTe2 was carried out, followed by alternative doping of tellurium atoms in the molybdenum ditelluride with B, C, N, and O. In this paper, the intrinsic bending deformation and B-doping of molybdenum ditelluride were selected for deformation analysis. Intrinsic bending deformations and boron-doped molybdenum ditelluride with bending angles ranging from 2° to 8° were employed for deformation investigation. In Fig.1, pink is used to represent doped B atoms, orange is used to describe Te atoms, and green is used to represent Mo atoms. For the degree of deformation of molybdenum ditelluride, in this paper, it is expressed by the bending angle, i.e., the angle of the plane of molybdenum ditelluride after bending and deformation of a single layer of molybdenum ditelluride concerning the angle of the plane folded for the deformed plane. How to do it: For ease of presentation, the atomic chains are set to different colors. The purple part on both sides of the figure is bent and deformed, 3-5 atoms are fixed appropriately, and the middle part is deformed. On this basis, the bending deformation of intrinsically doped and boron-doped MoTe2 is comparatively analyzed. The effect of boron-doped atoms on the structure of MoTe2 is systematically investigated to study its structural stability and electronic structure. Fig.1 a1 and a2 The main and side views of intrinsic MoTe2; b1 and (b2) the main and side views of MoTe2 doped with boron atoms bent by 8°.

Synthesis and Comprehensive Analytical Study of β-Li3PS4 Stabilization by Ca- and Ba-Codoped Li3PS4.

Sulfide-based solid electrolytes with high Li+ conductivity, such as Li3PS4, are key materials for the realization of all-solid-state Li+ batteries. One approach to achieving high Li+ conductivity is to combine crystalline-phase stabilization at high temperatures with the introduction of defects at room temperature. In this work, this approach was verified by codoping Li3PS4 with two kinds of divalent cations. The resulting structural changes were comprehensively investigated both experimentally and computationally. The high-temperature β-Li3PS4 phase of Li3PS4 could be stabilized at room temperature by adjusting the amount of Ca or Ba doping. The synthesized samples doped with divalent cations were found to have conductivities about 2 orders of magnitude higher than that of the γ-Li3PS4 phase at room temperature. The resultant Li+ conductivity at room temperature was also higher than that expected from interpolation of results for nondoped β-Li3PS4. It is believed that the structural changes produced by the divalent cation doping contribute to this increase in conductivity. The stability of the β-Li3PS4 phase with divalent cation doping was also demonstrated using density-functional-theory calculations for models with equivalent compositions to the synthesized samples. The Li+ positions obtained by structural optimization calculations showed the presence of diverse and disordered Li sites in the Ca-doped lattice. Such structural changes can contribute to cascade processes involving Li+ collisions, referred to as the "billiard-ball" mechanism, which cannot occur in nondoped β-Li3PS4. This series of experiments involving the synthesis and analyses of β-Li3PS4 with divalent cation doping provides a way to enhance Li+ conductivity through structural modification and optimization.

The regulation of high-energy insensitive compound 2,6-diamino-3,5-dinitropyrazine-1-oxide by external electric field.

The influence of external electric fields (EEFs) on chemical substances has always been a hot topic in the field of theoretical chemistry research. 2,6-Diamino-3,5-dinitropyrazine-1-oxide (LLM-105) is an energetic material with excellent comprehensive properties and enormous potential for application. This article explores the molecular structure, electronic structure, energy change, frontier molecular orbitals (FMOs) and density of states (DOS), UV-Vis spectra, and infrared spectra of LLM-105 under various electric field conditions. The results indicate that negative EEF can improve the stability of LLM-105, reflected in the initiation of changes in bond length and HOMO-LOMO gap. EEF has a significant impact on the electronic structure of LLM-105. The polarization of the electronic structure brings about a change in total energy, which is reflected in the analysis of energy changes. In addition, the external electric field will cause the frequency of the infrared spectra and the UV-Vis spectra to have different degrees of blue shift. The results of the analysis are helpful to understand the changes of energetic materials under the applied electric field. Based on the density functional theory (DFT), the structural optimization and energy calculation were carried out by using B3LYP/6-311G(d, p) and B3LYP/def2-TZVPP methods, respectively. After optimization convergence, vibration analysis was performed without imaginary frequencies to obtain stable configurations. Then, the molecular structure, electronic structure, energy changes, molecular orbital and density of states, UV-Vis spectra, and infrared spectra were analyzed.

Study on the Microscopic Mechanism of the Grain Refinement of Al-Ti-B Master Alloy

In the present work, the structure and properties of TinBn (n = 2–12) clusters were studied, and the microstructure of a Al-Ti-B system was simulated by molecular dynamics to determine the grain refinement mechanism of an Al-Ti-B master alloy in Al alloy. Based on the density functional theory method, the structural optimization and property calculations of TinBn (n = 2–12) clusters were carried out. The clusters at the lowest energy levels indicated that the Ti and B atoms were prone to form TiB2 structures, and the TiB2 structures tended to be on the surface of the clusters. The Ti10B10 cluster was determined to be the most stable structure in the range of n from 2 to 12 by average binding energy and second-order difference energy. The analysis of HOMOs and LUMOs suggested that TiB2 was the active center in the cluster; the activity of Ti was high, but the activity of B atoms decreased as the cluster size n increased. Meanwhile, the prediction of reaction sites by Fukui function, condensed Fukui function, and condensed dual descriptor identify that Ti atoms were more active than B atoms. Furthermore, TiB2 structures were found in the Al-Ti-B system simulated by the ab initio molecular dynamics method, and there were Al atoms growing on the Ti atoms in the TiB2. Based on the above analysis, this study suggests that TiB2 may be a heterogeneous nucleation center of α-Al. This work helps to further understand the mechanism of Al-Ti-B induced heterogeneous nucleation in Al alloys, which can provide theoretical guidance for related experiments.

Physical Properties of Piezoelectric Zr3GeO8 Crystal

Based on the density functional theory and first-principal calculations, the physical properties of the Zr3GeO8 crystal for the ground state were calculated. In all calculations, the Density functional theory based ABINIT package program was used. Investigations were made under the local density approximation. The geometric optimization of the Zr3GeO8 crystal, the state density of the valence electrons, the electronic band structure to understand the conductivity character of the crystal, and the linear optical properties to see the response of the material to the electromagnetic wave were calculated. In addition, dynamic-thermodynamic properties were calculated for the Zr3GeO8 crystal. According to the calculated structural optimization and electronic band structure, the band gap of the Zr3GeO8 crystal is 4.4663 eV and it has been obtained that it has an indirect band gap. For the Zr3GeO8 crystal, some constants such as energy loss functions, reflectivity, and absorption coefficient are calculated depending on the ground state linear optical properties and linear optical properties. The phonon distribution, state density and contribution of each atom to the density of state the Zr3GeO8 crystal were calculated. Finally, free energy, internal energy, entropy, and heat capacity were calculated for the Zr3GeO8 crystal.

First-Principles Calculations on Diffusion and Association Behavior of Fluoride Ions in Ba-Doped LaF3 Solid Electrolyte

Fluoride ion batteries, which generate electrical energy through the fluorination/de-fluorination reaction of electrode active materials, are expected to be the next-generation storage batteries with high energy density. LaF3 with a tysonite-type structure is known as one of the representative solid-state fluoride ion conductors. Substitutional solid solution of divalent cations such as Ba or Sr ions at La sites forms fluoride ion vacancies as charge compensation, resulting in fluoride ion conductivity. The main objective of this study is to analyze the formation behavior of point defects in LaF3 through quantitative evaluation of their formation energies using first-principles calculations, and to elucidate the conduction mechanism of fluoride ions in LaF3.The plane-wave basis PAW method implemented in VASP code was used for the electronic structure calculations. The electron correlation treatment uses the PBEsol-type potential based on the generalized gradient approximation. Calculations for given point defects were performed. The cutoff energy of the plane wave basis sets was set to 420 eV, and the structure optimization calculations were performed until the Hellmann-Feynman force acting on each atom was less than 0.02 eV/Å.There are three fluoride ion sites (12g, 4d, and 2a) in the unit cell of LaF3. Using the supercell model, we calculated the defect formation energies of fluoride ion vacancies at each site. The formation energies at the 12g, 4d, and 2a sites are 0.17 eV, 0.52 eV, and 0.52 eV, respectively. According to the defect formation energies, fluoride ion vacancies are most likely to form at the 12g sites.To elucidate the elementary processes of fluoride ion transfer between 12g sites by the vacancy mechanism, we performed first-principles calculations and transition state search using the Nudged Elastic Band method. From symmetry, four different pathways exist in the lattice of undoped LaF3. The pathway with the highest energy barrier is shown to have very low transfer energies, 0.17 eV, and the energy barriers of the other pathways are less than 0.1 eV. These results suggest that LaF3 has a potential for very fast fluoride ionic conductivity by the vacancy mechanism. In the presentation, the mechanism of fluoride ion conduction in Ba-doped LaF3 will also be reported. This work was supported by the RISING2 (JPNP16001) and the RISING3 (JPNP21006) projects from the New Energy and Industrial Technology Development Organization (NEDO), Japan.

First-Principles study of the structural, electronic, elastic, lattice dynamics and thermoelectric properties of the newly predicted half-heusler alloys NaYZ (Z = Si, Ge, Sn)

In this study, we applied Density Functional Theory (DFT) and Boltzmann Transport Theory to investigate the structural, electronic, lattice dynamic, elastic and thermometric properties of new half-Heusler compounds NaYZ (Z = Si, Ge, Sn). The structural optimization calculations revealed that the ZXY (1/4,1/2,0) phase have the most stable state with the least energy among others. Our calculated lattice constants in (Å) are found to be 6.861, 6.899, and 7.284 for NaYZ (Z = Si, Ge, Sn). Also, the calculated elastic constants satisfied the Born-Huang criteria and were found to be mechanically and elastically stable. The Density Functional Perturbation Theory (DFPT) was used to examined the lattice dynamics of the compounds and the results shown non-existence of negative frequencies all through dispersion band structures, thus all the compounds are dynamically stable. The Seebeck coefficient of the compounds at room temperature for the p-type (n-type) are 143.79 (−48.91) μ V/K, 132.49 (−48.86) μ V/K, 154.75 (−60.24) μ V/k for NaYZ (Z = Si, Ge, Sn). The modified Slack's approach was used to compute lattice thermal conductivity (kp) within the experimental range and the kp values obtained for NaYZ (Z = Si, Ge, Sn) at room temperature are 17.265 Wm −1 K −1, 14.671 W m−1K−1, 10.693 W m−1K−1, respectively. The computations of charge carriers relaxation time (τ = F(T)) as a function of temperature through deformation potential theory and the effective mass of charge carriers were used to evaluate the figure of merit (zT) for p-type and n-type of the materials. The maximum zT at 1200 K of τ = F(T) (τ = 10−13 s) are 1.76 (1.67), 1.73 (1.65), and 1.91 (1.88). These results show that τ = F(T) has improvement in determining the figure of merit as compared to the constant relaxation time (τ).

Effect of doping and defects on the optoelectronic properties of ZrSe2 based on the first principle.

Based on the first principles under the framework of density functional theory, it calculates the effect of vacancy defects in single Zr and single Se atoms and the replacement of Se atoms in ZrSe2 with O, Se, and Te atoms on the optoelectronic properties of monolayer ZrSe2, including geometry, energy band structure, electronic density of states, and optical properties. The doping of the three non-metallic atoms was n-type doping for the O and S atoms and p-type doping for the Te atom. Defects in the Zr atoms and O-atom doping significantly affect the peak reflectance and absorption coefficient of the ZrSe2 system. All Density Functional Theory calculations were carried out using the CASTEP module in the Materials-Studio (MS) software. The generalized gradient approximation plane-wave pseudopotential method and the Perdew-Burke-Ernzerfhof (PBE) generalized function were used for structural optimization and total energy calculation of the defect and doping systems. After convergence tests, the plane wave truncation energy was set to 500eV, and the Brillouin zone K-point grid was set to 4 × 4 × 1. The atomic energy convergence criterion is 1.0 × 10-6eV/atom, the interatomic interaction force convergence criterion is 0.02eV/Å, the maximum atomic displacement convergence criterion is 0.001Å, and the internal crystal stress convergence criterion is 0.05 GPa. In order to avoid the influence of the interaction forces between the layers, a vacuum layer of 15Å is placed in the Z-axis direction.

Clove bud extract mediated green synthesis of bimetallic Ag–Fe nanoparticles: Antimicrobial, antioxidant and dye adsorption behavior and mechanistic insights of metal ion reduction

Metal nanoparticle synthesis by metal ion reduction from plant extract has paid immense attention to researchers owing to its low cost, easy synthesis and eco-friendly nature compared to other biological methods. Compared to monometallic nanoparticles, syntheses of bimetallic nanoparticles have great importance due to the possibility of better performance of bimetallic nanoparticles compared to their monometallic counterpart. To explore this possibility, we synthesized bimetallic Ag–Fe nanoparticles of different compositions using aqueous phase co-reduction of Ag+ and Fe3+ metal ions in different ratios by clove (Syzygium aromaticum) flower bud extract. Prepared nanoparticles were characterized by Ultraviolet–visible spectroscopy, powder X-ray diffraction and Scanning Electron Microscopic studies, etc. All bimetallic nanoparticles exhibited multifaceted applications as antimicrobial agents, antioxidants and dye adsorbents. Among the different nanoparticles, bimetallic nanoparticles having Ag–Fe ratio 80:20 exhibit better performance for antimicrobial and dye adsorption activity than mono as well as other bimetallic nanoparticles. As depicted by the powder X-ray diffraction study, the synergy between metals is attributed to the prevention of oxidation of silver to silver oxide in the presence of iron. However, antioxidant activity is directly related to silver content as both silver and silver oxide exhibit almost similar antioxidant properties. The synergy between the metals in bimetallic nanoparticles provided the opportunity to enhance the activity of nanomaterials for various applications along with lowering the cost. Besides the synthesis and activity study of bimetallic nanoparticles, we tried to provide theoretical evidence for the mechanism of metal ion reduction by Eugenol (a major phytochemical present in the clove extract). Structural optimization and thermodynamic parameter calculation using DFT methods suggest that eugenol is preferred to oxidize itself and theoretically calculated reduction potential is ∼ -3.40V at 300K in the gaseous phase.

Composites based on alginate containing formylphosphazene-crosslinked chitosan and its Cu(II) complex as an antibiotic-free antibacterial hydrogel dressing with enhanced cytocompatibility

Hydrogels based on chitosan or alginate biopolymers are believed to be desirable for covering skin lesions. In this research, we explored the potential of a new composite hydrogels series of sodium alginate (Alg) filled with cross-linked chitosan to use as hydrogel wound dressings. Cross-linked chitosan (CSPN) was synthesized by Schiff-base reaction with aldehydated cyclophosphazene, and its Cu(II) complex was manufactured and identified. Then, their powder suspension and Alg were transformed into hydrogel via ion-crosslinking with Ca2+. The hydrogel constituents were investigated by using FTIR, XRD, rheological techniques, and thermal analysis including TGA (DTG) and DSC. Moreover, structure optimization calculations were performed with the Material Studio 2017 program based on DFT-D per Dmol3 module. Examination of Alg's interactions with CSPN and CSPN-Cu using this module demonstrated that Alg molecules can be well adsorbed to the particle's surface. By changing the dosage of CSPN and CSPN-Cu, the number and size of pores, swelling rate, degradation behavior, protein absorption rate, cytotoxicity and blood compatibility were changed significantly. Subsequently, we employed erythromycin as a model drug to assess the entrapment efficiency, loading capacity, and drug release rate. FITC staining was selected to verify the hydrogels' intracellular uptake. Assuring the cytocompatibility of Alg-based hydrogels was approved by assessing the survival rate of fibroblast cells using MTT assay. However, the presence of Cu(II) in the developed hydrogels caused a significant antibacterial effect, which was comparable to the antibiotic-containing hydrogels. Our findings predict these porous, biodegradable, and mechanically stable hydrogels potentially have a promising future in the wound healing as antibiotic-free antibacterial dressings.