Lattice Dimensions Research Articles

Deciphering Photophysical Carrier Dynamics in Lead-Free Perovskites: Influence of Lattice Dimensionality

Deciphering Photophysical Carrier Dynamics in Lead-Free Perovskites: Influence of Lattice Dimensionality

The Staggered Mesh Method: Accurate Exact Exchange Toward the Thermodynamic Limit for Solids.

In periodic systems, the Hartree-Fock (HF) exchange energy exhibits the slowest convergence of all HF energy components as the system size approaches the thermodynamic limit. We demonstrate that the recently proposed staggered mesh method for Fock exchange energy [Xing, Li, and Lin, Math. Comp., 2024], which is specifically designed to sidestep certain singularities in exchange energy evaluation, can expedite the finite-size convergence rate for the exact exchange energy across a range of insulators and semiconductors when compared to the regular and truncated Coulomb methods. This remains true even for two computationally cheaper versions of this new method, which we call non-SCF and split-SCF staggered mesh. Additionally, a sequence of numerical tests on simple solids showcases the staggered mesh method's ability to improve convergence toward the thermodynamic limit for band gaps, bulk moduli, equilibrium lattice dimensions, energies, and phonon force constants.

Magnetic phase transition and critical behavior in (Pr,Sm)[formula omitted]Fe[formula omitted] compounds: A comprehensive study using macroscopic and local experimental approaches

Achieving a comprehensive understanding of the properties and behaviors of magnetic phase transitions and critical behavior is a key objective of this study. A macroscopic approach utilizing magnetization measurement and a local approach utilizing 57Fe Mössbauer spectrometry were employed. The findings indicate that the critical exponents of Pr2Fe17 and (Pr,Sm)2Fe17 closely approximate those of the 3D-Ising model, as confirmed by the scaling analysis of our critical exponents. Moreover, we observed that isotherms collapse into two distinct and independent universal branches above and below the Curie temperature when utilizing the critical exponents we obtained. Our results indicate that the exponents determined using both conventional methods and Mössbauer spectrometry closely match those of the 3D-Ising model for spins coupled in three dimensions (lattice dimensionality d=3, spin dimensionality n=1) with attractive interactions between spins (J(r)) at the boundary of short-range and long-range decay as J(r)∝r−(3+σ).

Predicting and optimizing the dimensions of rod in lattice structures fabricated by laser powder bed fusion

Laser powder bed fusion (LPBF) is a highly effective method for manufacturing complex parts and is widely used in industry for creating lattice structures. However, during the manufacturing process, the actual dimensions and shapes of the lattice structure rod often deviate significantly from the design model due to limited understanding of the structure-process-property relationship in LPBF. This makes it difficult to carry out targeted structural design and process planning based on the technical characteristics of LPBF. This paper investigates the relationship between melt pool dimensions and lattice structure rod dimensions through theoretical analyses. Based on melt pool dimensions obtained with the help of numerical simulation, a prediction model for the actual dimensions of lattice structure rod is established. We design experiments to validate the accuracy of the predictive model, using LPBF to fabricate rods with varying inclinations, dimensions, and cross-sectional shapes. The actual dimensions are measured under a microscope and compared with the predicted dimensions. The results indicate a difference of no more than 0.1 mm. Furthermore, the experiments reveal a correlation between scan path curvature and actual dimensions. Based on this correlation, the dimensional prediction model is corrected, resulting in an improved generalization performance of the model for parts with varying scan paths. Based on the dimension prediction model, we propose an optimization method to modify the CAD dimensions of the rod to ensure the consistency between the actual and designed dimensions of the rod.

Novel furfural-Complexed approach to synthesizing carbon-Doped ZnO with breakthrough photocatalytic efficacy

IntroductionThe efficiency of zinc oxide (ZnO) nanoparticles for environmental decontamination is limited by their reliance on ultraviolet (UV) light and rapid charge carrier recombination. Carbon doping has been proposed to address these challenges by potentially enhancing visible light absorption and charge separation. ObjectivesThis study aims to introduce a novel, single-step synthesis method for carbon-doped ZnO (C-Z) nanoparticles, leveraging the decomposition of zinc nitrate hexahydrate and furfural under a nitrogen atmosphere to improve photocatalytic activity under visible light. MethodsA series of C-Z variants (C-Z-1 to C-Z-5) and an undoped sample (ZnO-0) were synthesized. The influence of furfural on the synthesis process and doping mechanism was analyzed by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and UV–visible diffuse reflectance spectroscopy (DRS). ResultsXPS confirmed the integration of carbon within the ZnO matrix, and XRD indicated increased lattice dimensions owing to doping. DRS revealed bandgap narrowing, suggesting enhanced charge separation. Among the variants, C-Z-3 significantly outperformed the others, showing a 12-fold increase in the photocatalytic degradation rate of Rhodamine B compared to undoped ZnO. ConclusionThe developed single-step synthesis method for C-Z nanoparticles represents a major advancement in materials engineering for ecological applications. The enhanced photocatalytic activity under visible light, as demonstrated by C-Z-3, underscores the potential of these nanoparticles for environmental decontamination.

Machine learning approaches for predicting mechanical properties in additive manufactured lattice structures

This study examines the mechanical performance of various lattice structures, highlighting the roles of geometric configurations, material properties, and processing conditions. Through advance feature importance analysis and correlation heatmaps, key determinants of mechanical behaviour such as lattice volume, surface roughness, micro-Vickers hardness, and lattice dimensions are identified. The findings reveal that lattice volume and surface roughness are the most significant predictors of displacement, accounting for 24.29 % and 23.71 % of the predictive power, respectively. An inverse relationship between micro-Vickers hardness and displacement emphasizes the need for material hardness optimization in design processes. Scatterplot analyses show complex interactions between surface roughness and micro-Vickers hardness across different conditions. Gyroid and BCC lattices exhibit inverse linear trends, while honeycomb and diamond display distinct linear and horizontal patterns, respectively. These complexities necessitate advanced analytical techniques like machine learning to capture and predict the mechanical behaviours of lattice structures effectively. Machine learning’s ability to handle high-dimensional data and identify non-linear relationships is crucial for accurate predictive models. The study also assesses the impact of post-processing conditions, indicating that stress relief and heat treatment enhances structural integrity and optimizes the material microstructure. This research provides a framework for designing and optimizing lattice structures, guiding informed decisions to meet performance standards.

Realization of higher-order topological lattices on a quantum computer

Programmable quantum simulators may one day outperform classical computers at certain tasks. But at present, the range of viable applications with noisy intermediate-scale quantum (NISQ) devices remains limited by gate errors and the number of high-quality qubits. Here, we develop an approach that places digital NISQ hardware as a versatile platform for simulating multi-dimensional condensed matter systems. Our method encodes a high-dimensional lattice in terms of many-body interactions on a reduced-dimension model, thereby taking full advantage of the exponentially large Hilbert space of the host quantum system. With circuit optimization and error mitigation techniques, we measured on IBM superconducting quantum processors the topological state dynamics and protected mid-gap spectra of higher-order topological lattices, in up to four dimensions, with high accuracy. Our projected resource requirements scale favorably with system size and lattice dimensionality compared to classical computation, suggesting a possible route to useful quantum advantage in the longer term.

Compression-induced crossovers for the ground state of classical dipole lattices on a Möbius strip.

We explore the ground-state properties of a lattice of classical dipoles spanned on the surface of a Möbius strip. The dipole equilibrium configurations depend significantly on the geometrical parameters of the Möbius strip, as well as on the lattice dimensions. As a result of the variable dipole spacing on the curved surface of the Möbius strip, the ground state can consist of multiple domains with different dipole orientations which are separated by domain-wall-like boundaries. We analyze in particular the dependence of the ground-state dipole configuration on the width of the Möbius strip and highlight two crossovers in the ground state that can be correspondingly tuned. A first crossover changes the dipole lattice from a phase which resists compression to a phase that favors it. The second crossover leads to an exchange of the topological properties of the two involved domains. We conclude with a brief summary and an outlook on more complex topologically intricate surfaces.

Anomalous Photocurrent Reversal for the Same Polarization Direction in van der Waals Ferroelectric CuInP2S6

The bulk photovoltaic effect (BPVE) in ferroelectric materials has attracted much attention due to its above-band-gap photovoltage and switchable photoresponse. However, the exact correlation between the photocurrent and spontaneous polarization remains unclear. Here, we report an anomalous reversal of the photocurrent, even for the same polarization direction, in van der Waals (vdW) ferroelectric CuInP2S6 (CIPS). Careful analysis reveals that the relocation of Cu ions into the vdW gap upon thickness reduction causes the current reversal, even though it does not change the polarization direction. By combining theoretical and experimental studies, we show clearly the decoupling of the BPVE photocurrent and electric polarization. This discovery significantly improves our understanding of the BPVE and demonstrates yet another example of the lattice dimensionality effect in vdW ferroelectrics. Published by the American Physical Society 2024

Three-dimensional checkerboard spin structure on a breathing pyrochlore lattice

The standard approach to realize a spin-liquid state is through magnetically frustrated states, relying on ingredients such as the lattice geometry, dimensionality, and magnetic interaction type of the spins. While Heisenberg spins on a pyrochlore lattice with only antiferromagnetic nearest-neighbor interactions are theoretically proven disordered, spins in real systems generally include longer-range interactions. The spatial correlations at longer distances typically stabilize a long-range order rather than enhancing a spin-liquid state. Both states can, however, be destroyed by short-range static correlations introduced by chemical disorder. Here, using disorder-free specimens with a clear long-range antiferromagnetic order, we refine the spin structure of the Heisenberg spinel ZnFe2O4 through neutron magnetic diffraction. The unique wave vector (1,0,12) leads to a spin structure that can be viewed as alternatively stacked ferromagnetic and antiferromagnetic tetrahedra in a three-dimensional checkerboard form. Stable coexistence of these opposing types of clusters is enabled by the bipartite breathing pyrochlore crystal structure, leading to a second-order phase transition at 10 K. The diffraction intensity of ZnFe2O4 is an exact complement to the inelastic scattering intensity of several chromate spinel systems which are regarded as model classical spin liquids. Our results challenge this attribution, and suggest instead of the six-spin ring mode, spin excitations in chromate spinels are closely related to the (1,0,12) type of spin order and the four-spin ferromagnetic cluster locally at one tetrahedron. Published by the American Physical Society 2024

Theoretical study of the complex antiferromagnetic Heusler alloys Pd[formula omitted]MnAl, Pd[formula omitted]MnIn, and Pt[formula omitted]MnAl

The complex antiferromagnetic (AFM) phases displayed by the Heuser alloys Pd2MnAl, Pd2MnIn, and Pt2MnAl, are theoretically studied. The crystalline structure, electronic, and magnetic properties are calculated within the ab initio density functional theory. The super unit cell considered to describe the various magnetic arrangements contains 128 atoms. We analyzed the ferromagnetic (FM) and the three different antiferromagnetic (AFM) phases and found that the Pd2MnAl crystalline structure is orthorhombic with dimensions 6.055, 6.461, 6.026 Å. The AFM state with the lowest energy is the AFM3 with a Mn magnetic moment of 3.813 μB. The Pd2MnIn crystallizes in an orthorhombic structure with lattice parameters 6.249, 6.763, 6.227 Å. The ground state antiferromagnetic arrangement is also of type 3 with a Mn magnetic moment of 3.932 μB. The Pt alloy crystallizes in an orthorhombic structure with lattice dimensions of 6.029, 6.906, and 5.683 Å. In this case, the antiferromagnetic ground state is of type 1 with a Mn magnetic moment of 3.716 μB. The Pd and Pt d states are deep in energy and do not interact much with the Mn d states. This produces, in Pd and Pt, no magnetic polarization.

Ferroics in Hybrid Organic-Inorganic Perovskites: Fundamentals, Design Strategies, and Implementation.

Hybrid organic-inorganic perovskites (HOIPs) afford highly versatile structure design and lattice dimensionalities; thus, they are actively researched as material platforms for the tailoring of ferroic behaviors. Unlike single-phase organic or inorganic materials, the interlayer coupling between organic and inorganic components in HOIPs allows the modification of strain and symmetry by chirality transfer or lattice distortion, thereby enabling the coexistence of ferroic orders. This review focuses on the principles for engineering one or multiple ferroic orders in HOIPs, and the conditions for achieving multiferroicity and magnetoelectric properties. The prospects of multilevel ferroic modulation,chiral spin textures,and spin orbitronics in HOIPs are also presented.

Treams – a T-matrix-based scattering code for nanophotonics

We report the publication of treams, a new software for electromagnetic scattering computations based on the T-matrix method. Besides conventional T-matrix calculations for individual scatterers and finite clusters of particles, a unique feature of the code is its full support for periodic boundaries in one, two, and all three spatial dimensions. We use highly efficient and quickly converging lattice summation techniques based on the Ewald method to evaluate the arising lattice sums in these cases. In addition to the common use of vector spherical waves as a basis set for the T-matrix, vector cylindrical waves are also implemented. To describe stratified media, vector plane waves are used with an S-matrix description of the electromagnetic scattering. All basis sets and the associated methods can be used together with chiral constitutive relations. Thereby, chiral embedding media are supported, as well as scatterers made from chiral materials.This contribution outlines the basic methods implemented and the program structure. Two interfaces to the implemented functionality are available: a flexible and fast low-level interface and a high-level interface for added convenience and plausibility checks. We conclude with two examples: a demonstration of the field calculation in various lattices and the explorations of quasi-bound states in the continuum. The presented code was already used in calculations for various physical systems: from the mode properties of molecular arrays in cavities to analytical models for metasurfaces and from moiré lattices to the homogenization of artificial photonic materials. With the publication of treams and the associated documentation, we hope to empower more scientists to make an efficient, fast, and precise exploration of nanophotonic systems that can be described in the broader framework of scattering theory. Program summaryProgram title: treamsCPC Library link to program files:https://doi.org/10.17632/2np8snmzfx.1Developer's repository link:https://github.com/tfp-photonics/treamsLicensing provisions: MITProgramming language: Python and CythonNature of problem: Simulating electromagnetic scattering in periodic nanophotonic structures, when different length scales are present or for large parameter sweeps, require specialized tools that can solve Maxwell's equations more efficiently than general-purpose solvers. A possible tool for these computations is the T-matrix method, which needs to be amended by suitable lattice summation schemes in the presence of periodic boundary conditions.Solution method: The properties of the individual scatterers are described by T-matrices, such that the interaction can be solved analytically. The slowly converging lattice sums that appear in the presence of periodic boundary conditions are computed by converting them to two quickly converging series using Ewald's method. Depending on the lattice dimensions and the geometry of the scatterers, vector spherical, cylindrical, or plane waves are used. Using modes of well-defined helicity enables the straightforward inclusion of chiral material parameters for scatterers and embedding media.

ISODISTROTLaMTeO6 (M = Ga3+ and Mn3+): the critical role of electronic configuration and cation ordering in crystal structures.

In this work, PbSb2O6-type oxides LaMTeO6 (M = Ga3+ and Mn3+) were synthesized and structurally characterized by Rietveld refinements against high-resolution X-ray powder diffraction data. The Ga3+/Te6+ partial ordering within the honeycomb-like two-dimensional [GaTeO6]3- anionic layer leads to the loss of the inversion center between Ga3+ and Te6+; however the inversion center on the 3̄-roto-inversion axis is preserved, thereby resulting in a 2-fold PbSb2O6-type superstructure by doubling the c-axis associated with a structural symmetry descending from the original P3̄1m to P3̄1c symmetry. In contrast, LaMnTeO6 (P21/c) adopts a monoclinically distorted 4-fold superstructure with lattice dimensions of a ≈ aH, b ≈ √3aH, c ≈ 2cH, where aH and cH represent the lattice parameters of trigonal PbSb2O6. The formation of this P21/c-superstructure is attributed to the combination of complete Mn3+/Te6+ ordering and the first-order Jahn-Teller distortion of Mn3+ with the electronic configuration of d4. Such a monoclinic distortion can effectively lift the Mn3+ spin moments arranged on the triangular sublattice, resulting in a sharp peak for antiferromagnetic transition, which is in stark contrast to subtle magnetic transitions for PbSb2O6-type tellurates AMn(VI)TeO6 (A = alkaline earth and Pb2+) and LnCrTeO6 (Ln = rare earth) with higher structural symmetry. Our findings highlight that the electronic configuration effects of M-cations play a critical role in controlling the structure symmetry of LaMTeO6, providing a strategy to fine-tune the crystal structures and physical properties.

Patterning of Protein-Sequestered Liquid-Crystal Droplets Using Acoustic Wave Trapping.

Development of spatially organized structures and understanding their role in controlling kinetics of multistep chemical reactions are essential for the successful design of efficient systems and devices. While studies that showcase different types of methodologies for the spatial organization of various colloidal systems are known, design and development of well-defined hierarchical assemblies of liquid-crystal (LC) droplets and subsequent demonstration of biological reactions using such assemblies still remain elusive. Here, we show reversible and reconfigurable one-dimensional (1D) assemblies of protein-bioconjugate-sequestered monodisperse LC droplets by combining microfluidics with noninvasive acoustic wave trapping technology. Tunable spatial geometries and lattice dimensions can be achieved in an aqueous medium comprising ≈19 or 62 μm LC droplets. Different assemblies of a mixed population of larger and smaller droplets sequestered with glucose oxidase (GOx) and horseradish peroxidase (HRP), respectively, exhibit spatially localized enzyme kinetics with higher initial rates of reaction compared with GOx/HRP cascades implemented in the absence of an acoustic field. This can be attributed to the direct substrate transfer/channeling between the two complementary enzymes in close proximity. Therefore, our study provides an initial step toward the fabrication of LC-based devices for biosensing applications.

Uniformity of Electrodeposited Coatings Onto Additively Manufactured Graphite Lattice Electrodes

The ability to uniformly electrodeposit metallic coatings onto geometrically complex substrates plays a significant role in developing specialized applications from coating detailed RF components to depositing catalytic coatings onto ordered foams electrodes for electrochemical flow reactors. However, there presently lacks guidelines for electrodeposition in porous media due to the problem’s multi-scale complexity. We present a framework for deconvoluting this process through continuum-level modeling and experimental validation of electrodeposited copper onto additively manufactured conductive lattice structures. Through numerical simulations we can predict thickness profiles and validate the model prediction and coating quality through micro-computed tomography. We further devise scaling laws with the aim of facilitating control over deposition uniformities on different lattice architectures and dimensions under fluid flow. In extension, the manufacturing platform for functionalized electrodes is extended to battery applications as use in novel electrode geometries within rechargeable secondary batteries as well as plating thickness evolution in custom redox flow battery cathodes for grid scale energy storage.This work is performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344 within the LDRD program 20-ERD-056. LLNL-ABS-847849.

The Efficiency of Embedding-Based Attacks on the GGH Lattice-Based Cryptosystem

The Goldreich-Goldwasser-Halevi (GGH) cryptosystem is declared broken due to the modified versions of the embedding attacks, known as Nguyen's σ, Nguyen's 2σ and Lee-Hahn's attacks. Despite using the same approach as the original embedding attack, these attacks deployed different strategies and resulted in different performances for breaking the GGH cryptosystem. In this paper, we described those strategies in detail. Moreover, we investigated the mathematical factors behind these attacks' ability and performance discrepancies. Mathematical proof examines and discusses the factors that triggered those variances. As a result, the expected lattice gap and implemented lattice dimensions are mathematically proven as the factors that significantly influenced these attacks' performance. By demonstrating how the attacks manipulated these factors, any lattice-based cryptosystem that relies on the hardness of the CVP could avoid repeating the same slipup as the GGH. Hence, precautionary action could be proactively taken to prevent it from being threatened by embedding-based attacks.

Structural and electrical study of novel Ba3SrNb2O9 triple perovskite based solid electrolyte for LT-SOFCs

Solid Electrolytes (SOE) with high ionic conductivity highly desirable in order to improve the efficiency of SOFCs at lower functioning temperature range) (350–500 °C). Triple perovskite Ba3SrNb2O9 based proton ion conductor have up-and-coming to enhance ionic conductivity at Low temperature range (LT) (350–500 °C). With this motivation we have successfully synthesized Ba3SrNb2O9 (BSNO) by solgel combustion method. Powder X-ray diffraction (XRD) confirms the formation of Triclinic crystal structure having space group P1, having lattice dimensions (a = 5.89340 Å, b = 5.88760 Å, c = 7.27360 Å). Rietveld Refinement of XRD data was carried out to get detail structural information by Full-Prof suite software. Electrical performance of the BSNO system were systematically studied by Electrochemical Impedance spectroscopy at functioning temperature 350–500 °C with interval of 50 °C. BSNO system exhibit conductivity of the order of 5.8 × 10−3 Scm−1 at 500 °C with the activation energy of the range of 0.48 eV. Charge Relaxations phenomenon very systematically explored by impedance loss spectra and it is very correlate with Modulus (M’’) as a function of frequency at several temperatures which used to clarify the charge relaxation dynamics in proton ion conducting BSNO material.

Electron Spin Decoherence Dynamics in Magnetic Manganese Hybrid Organic-Inorganic Crystals: The Effect of Lattice Dimensionality.

Organic-inorganic metal hybrids with their tailorable lattice dimensionality and intrinsic spin-splitting properties are interesting material platforms for spintronic applications. While the spin decoherence process is extensively studied in lead- and tin-based hybrids, these systems generally show short spin decoherence lifetimes, and their correlation with the lattice framework is still not well-understood. Herein, we synthesized magnetic manganese hybrid single crystals of (4-fluorobenzylamine)2MnCl4, ((R)-3-fluoropyrrolidinium)MnCl3, and (pyrrolidinium)2MnCl4, which represent a change in lattice dimensionality from 2D and 1D to 0D, and studied their spin decoherence processes using continuous-wave electron spin resonance spectroscopy. All manganese hybrids exhibit nanosecond-scale spin decoherence time τ2 dominated by the symmetry-directed spin exchange interaction strengths of Mn2+-Mn2+ pairs, which is much longer than lead- and tin-based metal hybrids. In contrast to the similar temperature variation laws of τ2 in 2D and 0D structures, which first increase and gradually drop afterward, the 1D structure presents a monotonous rise of τ2 with the temperatures, indicating the strong correlation of spin decoherence with the lattice rigidity of the inorganic framework. This is also rationalized on the basis that the spin decoherence is governed by the competitive contributions from motional narrowing (prolonging the τ2) and electron-phonon coupling interaction (shortening the τ2), both of which are thermally activated, with the difference that the former is more pronounced in rigid crystalline lattices.

Tailoring gas hydrate lattice dimensions for enhanced methane selectivity in biogas upgrading

Gas hydrates, specifically clathrate hydrates, have emerged as a potential separation medium for biogas containing methane (CH4) and carbon dioxide (CO2). However, the efficient separation of CH4 and CO2 remains challenging due to their similar cage occupation behavior within the hydrate structure. This study aimed to enhance CH4 selectivity by modifying the hydrate lattice to exclude CO2 from large cages and reduce the size of small cages through lattice engineering. To achieve this, tert-butyl alcohol (TBA) and trimethylene oxide (TMO) were employed as thermodynamic promoters, inducing strong and weak cage expansion, respectively. The results revealed that TMO hydrates, with their weak cage expansion, exhibited improved CH4 selectivity compared to TBA hydrates, which displayed strong cage expansion due to the larger size of TBA. Multi-stage separation experiments demonstrated that TMO hydrates required four unit stages, while TBA hydrates necessitated more than five unit stages to obtain purified CH4 (> 85%) from an initial gas mixture of CH4 (50%) and CO2 (50%). Additionally, TMO hydrates consistently exhibited higher separation factors than TBA hydrates in all unit stages. The findings emphasize the influence of the thermodynamic promoter's size on the separation performance of gas hydrates in separating CH4 from CH4 + CO2 mixtures. The study provides valuable insights into enhancing CH4 selectivity through lattice engineering and offers guidance in selecting suitable thermodynamic promoters for gas hydrate-based biogas upgrading applications.