Atomic Packing Factor Research Articles

Light emission from multiple self-trapped excitons in one-dimensional Ag-based ternary halides

Abstract Ternary metal halides based on Cu(I) and Ag(I) have attracted intensive attention in optoelectronic applications due to their excellent luminescent properties, low toxicity, and robust stability. While the self-trapped excitons (STEs) emission mechanisms of Cu(I) halides are well understood, the STEs in Ag(I) halides remain less thoroughly explored. This study explores the STE emission efficiency within the A 2AgX 3 (A = Rb, Cs; X = Cl, Br, I) system by identifying three distinct STE states in each material and calculating their configuration coordinate diagrams. We find that the STE emission efficiency in this system is mainly determined by STE stability and influenced by self-trapping and quenching barriers. Moreover, we investigate the impact of structural compactness on emission efficiency and find that the excessive electron–phonon coupling in this system can be reduced by increasing the structural compactness. The atomic packing factor is identified as a low-cost and effective descriptor for predicting STE emission efficiency in both Cs2AgX 3 and Rb2AgX 3 systems. These findings can deepen our understanding of STE behavior in metal halide materials and offer valuable insights for the design of efficient STE luminescent materials. The datasets presented in this paper are openly available in Science Data Bank at https://doi.org/10.57760/sciencedb.12094.

Development of new β Ti and Zr-based alloys in the Ta-(75-x)Ti-xZr system

The main objective of this study was to produce two new biomedical alloys, Ta-(75-x)Ti-xZr (x = 25, 50 wt%), and to carry out a detailed analysis of the crystal structures, phase composition, lattice parameters, hardness, and elastic modulus of the alloys under the influence of heat treatments. After melting (as-cast condition), the two alloys were subjected to two heat treatments carried out at a temperature of 1000 °C: one with slow cooling in the oven (SC) and the other rapidly cooled with ice water (RC). From the structural and microstructural characterizations (XRD, SEM, and Rietveld), it was observed that the Ta-(75-x)Ti-xZr produced are α+β type alloys. However, the Ta–25Ti–50Zr alloy contains a more significant amount of β phase due to the β stabilizing action of Zr combined with Ta as a typical β stabilizing element. Regarding the cooling after heat treatments, rapid cooling (RC) promoted the formation of the metastable α" phase, and heat treatment followed by slow cooling (SC) promoted the formation of the α+β phases. The alloys’ hardness, elastic modulus, and atomic packing factor (APF) were affected by changes in the α and α" phases fraction. The SC treatment increased APF, hardness, and elastic modulus, while the RC treatment decreased elastic modulus, optimizing it for biomedical applications.

Crystal Growth and Structural Characterization of Cs2LiLaBr6:Ce Using Neutron Diffraction

AbstractCe‐doped Cs2LiLaBr6 (CLLB) scintillator crystals, known for their superior neutron/gamma dual‐mode detection capability and exceptional scintillation properties, have garnered significant attention for both fundamental science and practical applications. The role of Ce3+ cations as luminescent centers is pivotal, influencing the scintillation properties as their concentration varies. While the effects of Ce3+ concentration on scintillation performance are well‐documented, the ramifications for crystalline structure remain less explored. In this study, high‐quality CLLB:Ce single crystals are fabricated(atomic packing factor of maximum doped Ce is 0.04%) using the vertical Bridgman (VB) method and subsequently characterized their crystalline structure by neutron diffraction, X‐ray diffraction (XRD), and elemental analysis. The findings reveal a correlation between Ce3+ concentration and the crystal cell parameters, presenting intriguing deviations from Vegard's law. Such observations suggest the potential presence of alternative defects, potentially Li+ interstitials, in CLLB:Ce. This work offers critical insights for advancing the understanding and optimization of CLLB:Ce scintillators.

Optimization radiation shielding properties of aluminum-based spinel minerals through the crystal tetrahedral and octahedral voids and their ions composition

In this research paper, we delve into the influence of crystal structure, void volumes and their ionic composition along with the atomic packing factor on the radiation attenuation properties of Al-based spinel compounds. The study investigates various Al-spinel chemical compositions explores their applications in radiation shielding. Analyzing mass attenuation coefficient (MAC) of six spinel minerals across different energy regions, we observe specific trends in scattering processes with the following sequential order: MACPleonaste > MACGahnite > MACHercynite > MACGalaxite > MACCeylonite > MACSpinel. The results demonstrated that the MAC values were influenced by the spinel chemical composition, crystal structure, and atomic arrangement in the lattice. Furthermore, the correlation between MAC values and the tetrahedral volume (Vtet), octahedral volume (Vocta), and the ratio of void volumes to the unit cell volume (R) was examined. Optimal void volumes and divalent and trivalent ion compositions were determined for different spinel minerals, leading to enhanced radiation shielding efficiency. The findings offer valuable perspectives for refining and optimization of spinel materials for use in radiation applications.

Mining ionic conductivity descriptors of antiperovskite electrolytes for all-solid-state batteries via machine learning

Lithium-rich and sodium-rich antiperovskites (X3BA, X = Li, Na) have been explored as promising inorganic electrolytes for all-solid-state batteries in recent years. To accelerate the design and discovery of high room temperature ionic conductivity antiperovskites, in this work, we apply the machine learning (ML) method to mine material descriptors characterizing ionic conductivity directly. Experimental samples are collected firstly from previous research to construct a small dataset (106 samples) supporting the data-driven strategy. After rough classification learning and exact symbolic regression learning, a simple and comprehensive descriptor t/η is proposed showing negative relationships with logarithmic ionic conductivity, where t and η are the tolerance factor and atomic packing factor, respectively. As a case study, we screen candidates in the family of lithium-based nitro-halide double antiperovskites, in which Li6NClBr2, Li6NBrBr2, and Li6NBrI2 are identified as good conductors by the descriptor and showing over 1 × 10−4 S·cm−1 room temperature bulk ionic conductivity in the ab initio molecular dynamics simulations. The descriptor would be convenient to guide the experimental study of antiperovskite electrolytes. Also, our mining strategy is effective in understanding a latent structure-activity relationship from small and complicated data.

Effect of Cu ratios dopant on ZnSe thin films structural and optical properties

This study focused to prepare poly-crystalline (ZnSe)1-x Cux thin films, where x values vary from 0 to 0.1 %. the effect of Cu ratios dopant on structural, phases and optical properties has been investigated. As prepared thin films were deposited onto a cleaning glass substrate under high vacuum conditions (10-7 mbr) at room temperature using the “ evaporation technique”. The analysis results according to data of the X-ray diffraction technique of all films refer to the growth polycrystalline with hexagonal wurtzite structure of Zn-Se with no presence of any further phases. The changes in numerous parameters such as volume of the unit cell, atomic packing factor, dislocation density, lattice constant and bond length with the Cu ratio were estimated and described. As well, the crystallite sizes,D, the lattice micro-strain,ε and dislocation density,δ have been calculated the results evidence that the micro-structural parameters enhancement with increment Cu atoms. On the other hand, the optical parameters of the as-synthesized films (ZnSe)1-xCux (0 ≤ x ≤ 0.1) were performed utilizing “UV–V is spectro -photometer” with a wavelength range of 300 to 2400 nm. The results show that as the Cu ratio increases, the absorption edge shifts to a higher wavelength and the optical band gap, Eg opt decreases from 2.63 eV to 2.52 eV. Finally, the behaviour of the optical constant parameters as real,εr/ imaginary, εi parts, dissipation factor,tan δ, volume/surface energy loss functions and dispersion parameters were shown to depend on the variation of the Cu ratio and wavelengths.

Indirect effect of elevated temperature on radiation shielding competence through modulations of crystals' intrinsic tetrahedral parameters: A case study of berlinite, SiO2-type AlPO4

This paper investigates the indirect influence of elevated temperature on the radiation protections competence of berlinite (SiO2-type AlPO4) by examining the modulations of its intrinsic tetrahedral parameters. The study focuses on the temperature-dependent changes in the crystal structure of berlinite and their influence on its radiation attenuation properties. The lattice parameter a, and c, c/a ratio, unit cell volume (Vc), atomic packing factor (APF), and other factors such as the atomic arrangement, atomic interactions, and crystal defects are analyzed in relation to the MAC and LAC. The calculations are performed for berlinite AlPO4 samples prepared at temperatures ranging from 25 °C to 631 °C. The results reveal that the LAC values of berlinite AlPO4 are changed from 14.65 to 15.39 cm−1, indicating stable linear attenuation properties across the temperature range. The lattice parameters, Vc, and APF exhibit linear relationships with the LAC values, suggesting their significance in determining the radiation attenuation capabilities.

Interphase corrosion inhibition mechanism of sodium borate on carbon steel rebars in simulated concrete pore solution

Sodium borate (Na2B4O7) corrosion inhibition mechanism was studied on carbon steel rebars in 0.6 mol/L Cl– simulated concrete pore solution (SCPS) at different temperatures and concentrations. Electrochemical testing including cyclic potentiodynamic polarization (CPP), electrochemical impedance spectroscopy (EIS), and Mott–Schottky plots were utilized to understand the influence of inhibitor concentration and temperature on the thermodynamics of the adsorption and activation processes. It was found Na2B4O7 imparts corrosion protection due to the formation of a 3D Fe–B–O stable interphase passive film, achieving an inhibition efficiency up to 86%. This can be attributed to the film having a lower donor current density and less vacancies, according to the Mott–Schottky tests. The formed interphase passive film was more stable and compact with less point defects compared to the blank due to Na2B4O7 adsorption, this phenomenon was substantiated using the atomic packing factor, film thickness, and Mott–Schottky plots. It was revealed, using adsorption isotherms, that Na2B4O7 interacted with the surface via physiochemical adsorption, creating a thinner/compact passive film composed of a rhombohedral calcite-type structure. SEM, XRD, and XPS were used to illustrate that Na2B4O7 aides in the formation of a stable double-layered net structure Fe2O3/FeBO3 passive oxide film. Finally, an interphase corrosion inhibition mechanism of Na2B4O7 was proposed.

Structural, optical and dielectric properties of chemical vapor transport based synthesis of rice-like nanostructured cadmium zinc oxide films

The cadmium zinc oxide (Cd-ZnO) films are synthesized on glass substrate at 200 sccm argon gas flow rate by chemical vapor transport technique. The synthesized Cd-ZnO films are investigated by X-ray diffraction (XRD), scanning electron microscope (SEM), Raman, Fourier transformed infrared spectroscopy (FTIR) and UV spectrometers. The XRD patterns exhibits the development of various diffraction planes related to Zn, ZnO and CdO phases thereby confirms the formation of polycrystalline Cd-ZnO films. The structural parameters like crystallinity, crystallite size, d-spacing, microstrains, dislocation density, degree of distortion, atomic packing fraction, lattice parameter, bond length and atomic packing factor are associated with increasing weights of Cd powder. The formation of chemical bonding, substitution of Cd+ into ZnO are confirmed by Raman, FTIR and SEM analysis. Red shift in absorption edge and increasing transmittance (> 90%) are associated with increasing weights of Cd powder. Refractive index (2.58–2.63) and energy band gap (3.11–2.87 eV) are increased/decreased with increasing weights of Cd powder. The change in optical, electrical and dielectric parameters of synthesized Cd-ZnO films are strongly associated with increasing weights of Cd powder. Results show that the synthesized Cd-ZnO films can be used for optoelectronics devices.

Increase in linear attenuation coefficient by changing crystal structure of materials for radiation shielding and biomedical devices safety

Linear attenuation coefficient of materials plays an important role in shielding and protection from radiation. It has been observed that higher the density of a material, higher is its linear attenuation coefficient. Thus, to make a material more suitable for shielding from hazards of radiation, one should increase its linear attenuation coefficient through increase in density of the material. The present work reports that density and linear attenuation coefficient of a material can be increased if its crystalline structure is changed from simple cubical structure to body centered cube (BCC) and faced centered cube (FCC). Results show that by changing the crystal structure of a material, its atomic packing factor also increases which is responsible for increase in density and linear attenuation coefficient. Results also show that linear attenuation coefficient increased by 30% when a crystal structure is changed from simple cubical to BCC. An increase of 41% is found when simple cubical structure transforms to FCC structure. This enhances the ability of the material to be used for radiation shielding and cancer prevention.

Electronic structure, thermodynamic properties and metallic behaviours of hydrogen

One-dimensional metallic hydrogen chain composed of 50 hydrogen atoms in eight different lengths are theoretically investigated in different aspects and some properties are generalised to three cubic systems. Also, electrochemical and thermodynamic properties including density, pressure, specific volume, atomic packing factor and Gibbs free energies of their redox reactions are calculated and compared with experimental results, if any. It was found that chains with length close to 45 Å (corresponding to interatomic distance of ∼1 Å) and less are metallic, with regard to Wigner-Huntington transition pressure. Finally, density of states of the one-dimensional systems were calculated to get insight into their metallic behaviour. Highlights Density and pressure of metallic hydrogens are estimated in different states. One-dimensional metallic hydrogen chains are theoretically evaluated. Calculated properties are generalised to three cubic systems and close results to experimental reports were found.

Influence of Fe cations on the structural and optical properties of alkali-alkaline borate glasses

To explore the impact of iron oxide (Fe2O3) on the structure and optical features of some borate glasses. A glass system with the formulation [(10.5 CaO+ 16.5 Na2O+ (73-x) B2O3+ x Fe2O3), where x = 0, 1, 2.5, 5 and 10.5 mol. %] was prepared using the melt-quench technique. The structure of obtained glasses were characterized and the physical parameters such as density, molar volume, atomic packing factor and bond length were calculated. The optical absorption spectra of the glasses were recorded in the wavelength range 190–1100 nm. Absorption bands observed around 450-550 nm in absorption spectra is due to the d-d transition of 6A1g(S) → 4T2g(G) which indicates the presence of iron ion in trivalent state (Fe3+) with distorted octahedral symmetry. The amorphous nature was confirmed by comparing the experimental and empirical density values. Moreover, these values of the experimental and empirical density were employed to expect the crystallization that occur at x= 37.2 mol % of Fe2O3. The obtained results show a decrement in the chemical bond energy, and bond force constant with Fe2O3 increasing. The expermental density and molar volume show an increasing behaviour with Fe2O3 increment.

High lithium anodic performance of reduced Sn particles on Co metal-organic frameworks for lithium-ion batteries with a long-cycle life

In recent years, lithium-ion batteries (LIBs) have become the battery technology of choice for portable devices, electric vehicles and grid storage due to their superior electrochemical performance and portability. Despite the successful commercialization of lithium-ion batteries in portable electronic devices, intensive research on high-energy density anode materials for lithium ion batteries is still ongoing to meet the ever-increasing high energy demand for upcoming advanced self-powering smart portable electronics and large-scale applications ranging from electric vehicles to power grids. In this regard, Surfactant-assisted cobalt metal-organic framework is synthesized through a solvo-thermal method and after Sn deposition uses as an anode in lithium-ion batteries. Using PEG400 resulted in a MOF with different trigonal (rhombohedral) lattice while a monoclinic structure is obtained when no surfactant is used. The presence of PEG400 polymeric surfactant with its role of orientation leads to the creation of special structural order and creates an array of structural units with a trigonal network (rhombone), which is completely different from the composition, creates in the same synthesis conditions with monoclinic structure. Different electrochemical behavior toward lithium insertion/extraction is attributed to different atomic packing factor. The trigonal structure synthesized at the presence of PEG400 shows better electrochemical performance compared to MOF1 at the absence of surfactant. Discharging capacity of the trigonal structure in the first cycle is about 615 mA h.gr−1, which is increased by 3% in the second cycle and reaches 634 mAhgr−1. Also, the amount of discharging capacity in 207 cycles is reduced to about 400 mAhgr−1, which results in approximately twice the electrochemical performance of the pure tin and tin-cobalt alloy synthesized anodes by the electrochemical method and also indicates superior electrochemical performance in comparison with common graphite anodes.

High electrical conductivity in the epitaxial polar metals LaAuGe and LaPtSb

Polar metals are an intriguing class of materials that simultaneously host free carriers and polar structural distortions. Despite the name “polar metal,” however, most well-studied polar metals are poor electrical conductors. Here, we demonstrate the molecular beam epitaxial growth of LaPtSb and LaAuGe, two polar metal compounds whose electrical resistivity is an order of magnitude lower than the well studied oxide polar metals. These materials belong to a broad family of ABC intermetallics adopting the stuffed wurtzite structure, also known as hexagonal Heusler compounds. Scanning transmission electron microscopy reveals a polar structure with unidirectionally buckled BC (PtSb and AuGe) planes. Magnetotransport measurements demonstrate good metallic behavior with low residual resistivity (ρLaAuGe = 59.05 μΩ cm and ρLaAPtSb = 27.81 μΩ cm at 2 K) and high carrier density (nh ∼ 1021 cm−3). Photoemission spectroscopy measurements confirm the band metallicity and are in quantitative agreement with density functional theory (DFT) calculations. Through DFT-chemical pressure and crystal orbital Hamilton population analyses, the atomic packing factor is found to support the polar buckling of the structure although the degree of direct interlayer B–C bonding is limited by repulsion at the A–C contacts. When combined with predicted ferroelectric hexagonal Heuslers, these materials provide a new platform for fully epitaxial, multiferroic heterostructures.

Structural and optical characterization of Sm-doped ZnO nanoparticles

Micro-structural changes in zinc oxide (ZnO) nanoparticles induced by the substitution of $$\hbox {Zn}^{2+}$$ in ZnO by a rare earth (RE) metal ion, $$\hbox {Sm}^{3+}$$ , are investigated. Both pristine and Sm-doped ZnO with a nominal doping concentration of 1, 2 and 4% of Sm using a simple wet-chemical synthetic route followed by calcination at a high temperature of $$900{^{\circ }}\hbox {C}$$ , are synthesized. Structural investigations are primarily conducted using X-ray powder diffraction (XRPD) and scanning electron microscopy techniques. Evolution of structural parameters (unit cell parameters, average crystallite size, crystallinity percentage, lattice strain, stress, energy density and atomic packing factor) upon Sm doping is investigated together with Rietveld refinement and Le Bail analysis techniques. XRPD data confirmed that the synthesized nanostructures crystallize in a wurtzite hexagonal structure, the dopant Sm is incorporated into the Zn lattice and the annealing treatment plays a crucial role in determining the structural and optical properties of RE-metal-doped nanoparticles. Values of the optical band gap energy estimated from optical absorbance measurements reveal a widening of the band gap.

Theoretical Study of Size Effect on Melting Entropy and Enthalpy of Sn, Ag, Cu, and In Nanoparticles

The size effect of small particles has been extensively studied from a theoretical as well as experimental point of view. However, the size-dependence of melting entropy and enthalpy of nanostructures has not been fully explored. In the current study, considering the effect induced by atomic packing factor of different crystal structures, a modified formula is put forward to predict the size-dependent depression of melting entropy and enthalpy associated with the metallic nanoparticles based on Kumar and Sharma model. We have studied the melting entropy and enthalpy of Sn, Ag, Cu, and In nanoparticles according to the modified formula. The experimental data has matched the model predictions, thus supporting the theory developed herein.

First-principles investigation of the effect of crystal structure on sulfur isotope fractionation in sulfide polymorphs

In order to study the effect of crystal structure on S isotope fractionation properties of sulfide polymorphs, the reduced partition function ratios of S-34/S-32 (10(3)ln beta(34-32)) for FeS2, CoAsS, ZnS, CdS and MnS polymorphs are calculated in the present study. Our calculations show that 10(3)ln beta(34-32) decreases in the order of pyrite > marcasite > cobaltite > alloclasite > sphalerite approximate to wurtzite > gamma-MnS > hawleyite approximate to greenockite > alabandite. The S coordination number exerts a strong influence on the equilibrium partitioning of S isotopes in these sulfides, and there exist significant S isotope fractionations between the sulfides with different S coordination numbers (CNS), such as alabandite (CNS = 6) and other sulfides (e.g., FeS2, CoAsS, ZnS and CdS polymorphs) (CNS = 4). There is a broad negative correlation between the average bond lengths of all the bonds formed by S and 10(3)ln beta(34-32) values. The compactness of atom packing plays an important role in determining S isotope fractionation properties of sulfides, and S-34 generally tends to concentrate in the phases with higher atomic packing factor (APF). The linear correlation between APF and 10(3)ln beta(34-32) can predict the change of 10(3)ln beta(34-32) with increasing pressure, but pressure has a negligible effect on S isotope fractionation factors between sulfides.

Theoretical calculation of atomic and physical properties of some low-dimensional nanomaterials

Low-dimensional nanomaterials have drawn much attention among the researchers due to exhibition of superior material properties. No literature values are available for some of the most important physical and atomic properties of these low-dimensional materials. So the present work investigates and reports some of the most important atomic and physical properties like atomic packing factor, theoretical density and coordination number of low-dimensional nanomaterials e.g. fullerene (zero-dimensional), carbon nanotube (one-dimensional), graphene, silicene and germanene (two-dimensional), which are otherwise not calculated before. The atomic packing factor varies with dimension and structure of material, while the theoretical density varies with dimension of material. Graphene and fullerene shows the highest and lowest packing efficiency respectively, while CNT and silicene shows the highest and lowest theoretical density. All the low-dimensional materials have same coordination number because of their hexagonal structure

Models Manufacturing of Crystal Systems: An Introduction to Ceramic Materials

It is presented a teaching methodology that uses models to better understanding and visualization of crystal systems, considering the large number of students with limited vision spatial perception. The understanding of the relationship between the structure of materials with their properties is essential for engineering students in which it’s possible to relate mechanical properties through knowledge of the crystalline structure of the material, such as machining, heat treatment, mechanical forming processes, etc. The parameter identification of: number of atoms, coordination number, atomic packing factor and density is emphasized in the crystalline systems. Students first study the structure of the crystalline solid and the main crystal systems, key issues for further understanding of the remaining content. Knowing the structure of crystalline solids and understanding its applicability in engineering, makes all the difference to motivate students during the course. With the inclusion of this methodology there has been a better understanding of the concepts related to crystalline systems, as the students build their own structures with the most suitable material chosen by them.

Crystallization and solid solution attainment of samarium doped ZnO nanorods via a combined ultrasonic-microwave irradiation approach

An advanced sol-gel method is developed via combined ultrasound-microwave irradiation and utilized for the crystallization of pristine and samarium doped zinc oxide nanorods. Organic structure directing agents directed one dimensional growth and air-annealing was applied as post-thermal treatment. Microstructural, optical, and solid state survey was pursued by PXRD, FESEM, TEM, EDS, FTIR, DRS, PL, micro-Raman, H2-TPR, and ESR techniques. Phase analysis by diffraction patterns confirmed the efficacy of irradiation strategy as it improves the crystallinity degree, expedites the hexagonal close pack morphology, and conducts lattice imperfection. Accordingly, aspect ratio and electronic evolution parallel to dopant content is favored. Electron microscopy demonstrated the flake-like rearrangement of nanorods as well as a structure-related growth where a direct proportion exists between atomic packing factor in lattice and aspect ratio. Textural investigation by EDS and FTIR rejected the presence of any impurity verifying an integrated composition. Reflectance and luminescence spectra exhibited characteristic optical behavior with shifts corresponding to dopant concentration. Also, band gap energies increased with samarium addition depicting an opposite trend with respect to unit cell variation. Finally, Raman, TPR, and ESR spectra provided detailed dopant-dependent trends on the internal solid state and defect chemistry of the nanorods. In this regard, maximum shifts in E2high and E1LO phonon modes duly correlated with the vibrations of zinc and oxygen atoms, surface oxygen and bulk ZnO reduction bands, emergence and alteration of samarium centers, along with the dominance of zinc and oxygen vacancies were all resulted due to the utmost lattice imperfection in SZO1.