A considerable challenge is faced by researchers wishing to identify the propagation vector(s) associated with a magnetic structure or a lattice distortion from powder diffraction data, due to the severe destruction of information by powder averaging and search algorithms based on extracted peak positions. In this article a new method is introduced that is based on the points, lines and planes of the Brillouin zone of the crystal structure before the transition. These correspond to different classifications of the translational symmetry of the resultant order and of the Bloch wave that is used to describe the magnetic structure or phonon mode. An automated search algorithm for the study of magnetic structures is described based on reverse-Monte Carlo refinement of moment orientations for a given k vector that markedly reduces the number of false-positives and allows the straight forward analysis of systems that contain contributions from several unrelated k vectors.
This document reports the x-ray powder diffraction main reflections (intensity threshold >= 100) for possible Fe-related phases forming during the metal-organic vapor phase epitaxy (MOVPE) growth of Fe in NH_3/H_2 mixture on wurtzite-GaN/sapphire. The 2θvalues are given for Cu Kα_1 radiation (1.5406 Å) in the range 25-100 deg (ordered by increasing 2θ). The GaN(000l) and Al_2O_3(000l) are also reported for reference.
Presented here is decryst, a software suite for structure determination from powder diffraction, which uses the direct space method, and is able to apply anti-bump constraints automatically and efficiently during the procedure of global optimisation using the crystallographic collision detection algorithm in arXiv:1708.03180. decryst employs incremental computation in its global optimisation cycles, which results in dramatic performance enhancement; it is also designed with parallel and distributed computing in mind, allowing for even better performance by simultaneous use of multiple processo…
Plastic inhomogeneity, particularly localised strain, is one of the main mechanisms responsible for failures in engineering alloys. This work studied the spatial arrangement and distribution of microstructure and their influence in the plastic inhomogeneity of Inconel 718 fabricated by additive manufacturing (AM). In particular, the density and spatial distribution of geometrically necessary dislocations (GNDs) and the crystallographic texture components were examined in relation to the spatial plastic deformation. In-situ tensile testing coupled with microscopy and EBSD was performed to under…
The increasing scientific and technological interest in nanoparticles has raised the need for fast, efficient and precise characterization techniques. Powder diffraction is a very efficient experimental method, as it is straightforward and non-destructive. However, its use for extracting information regarding very small particles brings some common crystallographic approximations to and beyond their limits of validity. Powder pattern diffraction calculation methods are critically discussed, with special focus on spherical particles with log-normal distribution, with the target of determining s…
We report on the crystallographic structure of the layered compound Pb3Mn7O15. Previous analysis based on laboratory X-ray data at room temperature gave contradictory results in terms of the description of the unit cell. Motivated by recent magnetic bulk measurements of this system, we re-investigated the chemical structure with high-resolution synchrotron powder diffraction at temperatures between 15 K and 295 K. Our results show that the crystal structure of stoichiometric Pb3Mn7O15 has a pronounced 2-dimensional character and can be described in the orthorhombic space group Pnma.
A method for crystallographic mapping of an alpha-beta titanium alloy with nanometre resolution using scanning precession electron diffraction and open-source software libraries
Information on the lattice parameter of single crystals with known crystallographic structure allows for estimations of sample quality and composition. In many cases it is suffcient to determine one lattice parameter or the lattice spacing along a certain, high-symmetry direction, e.g. in order to determine the composition in a substitution series by taking advantage of Vegard's rule. Here we present a guide to accurate measurements of single crystals with dimensions ranging from 200 $μ$m up to several millimeter using a standard powder diffractometer in Bragg-Brentano geometry. The correction…
We performed neutron powder diffraction measurements on (Bi$_{0.5}$Na$_{0.5+x}$)TiO$_3$ and (Bi$_{0.5+y}$Na$_{0.5}$)TiO$_3$ to study structural evolution induced by the non-stoichiometry. Despite the non-stoichiometry, the local structure ($r$$\leq$ 3.5 Å) from the pair distribution function analysis is barely affected by the sodium deficit of up to -5 mol%. With increasing pair distance, however, the atomic pair correlations weaken due to the disorder caused by the sodium deficiency. Although the sodium and the bismuth share the same crystallographic site, their non-stoichiometry have rather …
MatDiffract: A Material-Informed Automated Analysis Platform for X-ray Powder Diffraction
Institute of High Energy Physics, Chinese Academy of Sciences（中国科学院高能物理研究所）；Spallation Neutron Source Science Center（散裂中子源科学中心）；College of Computer and Information Engineering, Henan Normal University（河南师范大学计算机与信息工程学院）；Dongguan Institute of Materials Science and Technology, Chinese Academy of Sciences（中国科学院东莞材料科学与技术研究所）；Songshan Lake Material Laboratory（松山湖材料实验室）；School of Computer Science, Sun Yat-sen University（中山大学计算机学院）
High-throughput experiments that use combinatorial samples with rapid measurements can be used to provide process-structure-property information at reduced time, cost, and effort. Developing these tools and methods is essential in additive manufacturing where new process-structure-property information is required on a frequent basis as advances are made in feedstock materials, additive machines, and post-processing. Here we demonstrate the design and use of combinatorial samples produced on a commercial laser powder bed fusion system to study 60 distinct process conditions of nickel superalloy…
Two-dimensional (2D) layered magnetic materials are generating a great amount of interest for the next generation of electronic devices thanks to their remarkable properties associated to spin dynamics. The recently discovered layered VI$_3$ ferromagnetic phase belongs to this family, although a full understanding of its properties is limited by an ill-defined crystallographic structure. This is not any longer true. Here, we investigate the VI$_3$ crystal structure upon cooling using both synchrotron X-ray and neutron powder diffraction and provide structural models for the two structural tran…
The solid solution Cs2-xRbxSnCu3F12 (x = 0, 0.5, 1.0, 1.5) has been investigated crystallographically between 100 and 300 K using synchrotron X-ray powder diffraction and, in the case of x = 0, neutron powder diffraction.
Large single crystals of the pyrochlore Pr2Hf2O7 have been successfully grown by the floating zone technique using an optical furnace equipped with high power Xenon arc lamps. Structural investigations have been carried out by both synchrotron X-ray and neutron powder diffraction to establish the crystallographic structure of the materials produced. The magnetic properties of the single crystals have been determined for magnetic fields applied along different crystallographic axes. The results reveal that Pr2Hf2O7 is an interesting material for further investigations as a frustrated magnet. Th…
Ab-initio Crystal Structure Determination from Powder X-Ray Diffraction
University of North Carolina at Charlotte（北卡罗来纳大学夏洛特分校）；North Carolina Battery Complexity, Autonomous Vehicle and Electrification (BATT CAVE) Research Center（北卡罗来纳电池复杂性、自动驾驶与电气化（BATT CAVE）研究中心）
Rust-accelerated powder X-ray diffraction simulation for high-throughput and machine-learning-driven materials science
Faculty of Mechanical Engineering, Czech Technical University in Prague（布拉格捷克理工大学机械工程学院）；Faculty of Nuclear Sciences and Physical Engineering, Czech Technical University in Prague（布拉格捷克理工大学核科学与物理工程学院）；FZU – Institute of Physics of the Czech Academy of Sciences（捷克科学院物理研究所）
A detailed investigation of mesoscopic magnetic and crystallographic phase separation in Ca(1-x)La(x)MnO3, 0.00<=x<=0.20, is reported. Neutron powder diffraction and DC-magnetization techniques have been used to isolate the different roles played by electrons doped into the eg level as a function of their concentration x. The presence of multiple low-temperature magnetic and crystallographic phases within individual polycrystalline samples is argued to be an intrinsic feature of the system that follows from the shifting balance between competing FM and AFM interactions as a function of tempera…
Here we report crystallographic and magnetic studies on high quality samples of the magnetically frustrated S = 1/2 kagome antiferromagnet vesignieite, BaCu3V2O8(OD)2. Powder neutron diffraction data collected from samples obtained by a new hydrothermal synthetic route reveal a previously unobserved trigonal P3121 structure, similar to the isoelectronic mineral SrCu3V2O8(OH)2. The refined structure is consistent with orbital frustration of the eg d-orbitals in a sublattice of the Cu2+ kagome network due to a dynamic Jahn-Teller effect, which persists below the magnetic transition at TN = 9K an…
High entropy oxides (HEOs) are a rapidly emerging class of functional materials consisting of multiple principal cations. The original paradigm of HEOs assumes cationic occupations with the highest possible configurational entropy allowed by the composition and crystallographic structure. However, the fundamental question remains on the actual degree of configurational disorder in HEOs, especially, in systems with a low enthalpy barriers for cation anti-site mixing. Considering the experimental limitations due to the presence of multiple principal cations in HEOs, here we utilize a robust and …
A structure analysis of Zn-Mg-Ho icosahedral quasicrystal was carried out by the powder X-ray diffraction method using synchrotron radiation (Lambda=0.73490 A) at SPring-8. The intensity distribution was analyzed by the Rietveld method modified for an icosahedral quasicrystal, in which simplified models were assumed: ellipsoid and spherical windows were assumed at five crystallographic sites in a F-type hypercubic unit cell. The analysis revealed the presence of an almost perfect Penrose tiling with edge length 5.20 A. The vertices are occupied alternatively by Zn and Mg, and almost all of the…
The crystallographic (charge-ordered) and magnetic superstructures of La0.333Ca0.667MnO3 were studied by high-resolution synchrotron x-ray and neutron powder diffraction. In the antiferromagnetic structure, which was refined using a non-collinear model, the a lattice parameter is tripled and the c lattice parameter is doubled with respect to the average crystallographic unit cell (Pnma setting). The crystallographic structure below the charge-ordering temperature (TCO ~ 260 K) is characterized by ordering of the dz2 orbitals of the Jahn-Teller-distorted Mn3+O6 octahedra in the orthorhombic ac …
Generative crystallographic phasing through invariant relationships
The Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences（中国科学院物理研究所凝聚态物理国家实验室）；Shanghai Artificial Intelligence Laboratory（上海人工智能实验室）；Dept. of Comp. Sci. and Tech., Institute for AI, Tsinghua University（清华大学智能产业研究院计算机科学与技术系）；Institute for AIR, Tsinghua University（清华大学智能产业研究院）；Gaoling School of Artificial Intelligence, Renmin University of China（中国人民大学高瓴人工智能学院）；Engineering Research Center of Next-Generation Intelligent Search and Recommendation, MOE（教育部下一代智能搜索与推荐工程研究中心）；Beijing Key Laboratory of Big Data Management and Analysis Methods（北京大数据管理与分析方法重点实验室）；School of Computer Science, Shanghai Jiao Tong University（上海交通大学计算机科学技术学院）；Zhongguancun Academy（中关村学院）
Max-Planck-Institut für Eisenforschung GmbH（马克斯·普朗克钢铁研究所）；The University of Alabama（阿拉巴马大学）；Imperial College London（伦敦帝国理工学院）；The University of Sydney（悉尼大学）
Volumetric crystal structure indexing and orientation mapping are key data processing steps for virtually any quantitative study of spatial correlations between the local chemistry and the microstructure of a material. For electron and X-ray diffraction methods it is possible to develop indexing tools which compare measured and analytically computed patterns to decode the structure and relative orientation within local regions of interest. Consequently, a number of numerically efficient and automated software tools exist to solve the above characterisation tasks. For atom probe tomography (APT…
We have synthesized a new crystallographically ordered quaternary Heusler alloy, MnNiCuSb. The crystal structure of the alloy has been determined by Rietveld refinement of the powder x-ray diffraction data. This alloy crystallizes in the LiMgPdSb type structure with F-43m space group. MnNiCuSb is a ferromagnet with a high TC ~ 690K and magnetic moment of 3.85MuB/f.u. Besides this we have also studied two other off-stoichiometric compositions; one Cu rich and the other Ni rich (MnNi0.9Cu1.1Sb and MnNi1.1Cu0.9Sb) which are also ferromagnets. It must be stressed that MnNiCuSb is one of the very f…
Local magnetic fields in a molecule-based optically chiral magnet [Cr(CN)$_6$][Mn($S$)-pnH(H$_2$O)](H$_2$O) (GN-S) and its enantiomer (GN-R) are studied by means of muon spin rotation and relaxation (muSR). Detailed analysis of muon precession signals under zero field observed below T_c supports the average magnetic structure suggested by neutron powder diffraction. Moreover, comparison of muSR spectra between GN-S and GN-R suggests that they are a pair of complete optical isomers in terms of both crystallographic and magnetic structure. Possibility of magnetic chirality in such a pair is disc…
We report a detailed examination the magnetic structure of anhydrous cupric chloride CuCl2 carried out by powder neutron diffraction, magnetic susceptibility and specific heat measurements on polycrystalline and single crystal samples as well as an evaluation of the spin exchange interactions by first principles density functional theory (DFT) calculations. Anhydrous CuCl2 shows one dimensional antiferromagnetic behavior and long range antiferromagnetic ordering below a Neel temperature of 23.9 K. Neutron powder and single crystal diffraction reveal that, below 23.9K, CuCl2 undergoes a phase t…
We report on the thermodynamic, magnetic properties and the magnetic structure of ludwigite-type Cu2MnBO5. The specific heat, the low-field magnetization and the paramagnetic susceptibility were studied on a single crystal and combined with powder neutron diffraction data. The temperature dependence of the specific heat and the neutron diffraction pattern reveal a single magnetic phase transition at T=92 K, which corresponds to the magnetic ordering into a ferromagnetic phase. The cation distribution and the values and directions of magnetic moments of ions in different crystallographic sites …
Boston College（波士顿学院）；NIST Center for Neutron Research, National Institute of Standards and Technology（美国国家标准与技术研究院中子研究中心）；Carnegie Mellon University（卡内基梅隆大学）；University of California, Berkeley（加州大学伯克利分校）；University of Maryland, College Park（马里兰大学帕克分校）
Millimeter-sized MnBi$_2$Te$_4$ single crystals are grown out of Bi-Te flux and characterized by measuring magnetic and transport properties, scanning tunneling microscope (STM) and spectroscopy (STS). The magnetic structure of MnBi$_2$Te$_4$ below T$_N$ is determined by powder and single crystal neutron diffraction measurements. Below T$_N$=24\,K, Mn$^{2+}$ moments order ferromagnetically in the \textit{ab} plane but antiferromagnetically along the crystallographic \textit{c} axis. The ordered moment is 4.04(13) $μ_{B}$/Mn at 10\,K and aligned along the crystallographic \textit{c}-axis. The e…
First principles density functional theory DFT+U calculations and experimental neutron diffraction structure analyses were used to determine the low-temperature crystallographic and magnetic structure of bixbyite Mn2O3. The energies of various magnetic arrangements, calculated from first principles, were fit to a cluster-expansion model using a Bayesian method that overcomes a problem of underfitting caused by the limited number of input magnetic configurations. The model was used to predict the lowest-energy magnetic states. Experimental determination of magnetic structure benefited from opti…
Frustrated magnetism plays a central role in the phenomenology of exotic quantum states. However, because the magnetic structures of frustrated systems are aperiodic, there has always been the problem that they cannot be determined using traditional crystallographic techniques. Here we show that the magnetic component of powder neutron scattering data is actually sufficiently information-rich to drive magnetic structure solution for frustrated systems, including spin ices, spin liquids, and molecular magnets. Consequently, single-crystal samples are not prerequisite for detailed characterisati…
The crystallographic and magnetic properties of La{0.5+delta}A{0.5-delta}Mn{0.5+epsilon}Ru{0.5-epsilon}O{3} (A= Ca, Sr, Ba) were investigated by means of neutron powder diffraction. All studied samples show the orthorhombic perovskite crystal structure, space group Pnma, with regular (Mn,Ru)O{6} octahedra and no chemical ordering of the Mn3+ and Ru4+ ions. Ferromagnetic spin structures were observed below Tc ~ 200-250 K, with an average ordered moment of ~ 1.8-2.0 Bohr magnetons per (Mn,Ru). The observation of long-range ferromagnetism and the absence of orbital ordering are rationalized in te…
A combination of synchrotron X-ray, neutron powder diffraction, magnetization, heat capacity and electrical resistivity measurements reveals that NdMnAsO is an antiferromagnetic semiconductor with large Neel temperature (TN = 359(2) K). At room temperature the magnetic propagation vector k = 0 and the Mn moments are directed along the crystallographic c-axis (mMn = 2.41(6) BM). Upon cooling a spin reorientation (SR) transition of the Mn moments into the ab-plane occurs (TSR = 23 K). This coincides with the long range ordering of the Nd moments, which are restricted to the basal plane. The magn…
We report the growth of mm-sized Pmnb-Li2FeSiO4 single crystals by means of the optical floating-zone method at high argon pressure and describe the conditions required for a stable growth process. The crystal structure is determined and refined by single-crystal X-ray diffraction. The lattice constants amount to a = 6.27837(3) A, b = 10.62901(6) A and c = 5.03099(3) A at 100 K. In addition, we present high-resolution neutron powder diffraction data that suggest that the slight Li-Fe site exchange seems to be intrinsic to this material. High quality of the crystal is confirmed by very sharp an…
Crystal and magnetic structures of a series of novel quantum spin trimer system Ca3Cu3xNix(PO4)4 (x=0,1,2) were studied by neutron powder diffraction at the temperatures 1.5-290 K. The composition with one Ni per trimer (x=1) has a monoclinic structure (space group P 21 /a, no. 14) with the unit cell parameters a = 17.71 A, b = 4.89 A, c = 8.85 A and = 123.84 deg at T=290 K. The (x=2) composition crystallizes in the C 2/c space group (no. 15) with the doubled unit cell along c-axis. Each trimer is formed by two crystallographic positions: one in the middle and the second one at the ends of the…
We have studied the phase diagram of La$_{1-x}$Ca$_{x}$MnO$_{3}$ for $0.5\leq x\leq 0.9$ using neutron powder diffraction and magnetization measurements. At 300 K all samples are paramagnetic and single phase with crystallographic symmetry $Pnma$. As the temperature is reduced a structural transition is observed which is to a charge-ordered state only for certain x. On further cooling the material passes to an antiferromagnetic ground state with Neel temperature $T_N$ that depends on x. For $0.8\leq x\leq 0.9$ the structural transformation occurs at the same temperature as the magnetic transit…
Effect of Niobium Doping on the Crystal Structure and Hydrogen Sorption Properties of TiFe: Combined Synchrotron X-ray Diffraction and Extended X-ray Absorption Fine Structure Study
University of Stavanger（斯塔万格大学）；Institute for Energy Technology（能源技术研究所）
Na$_{4-δ}$NiTeO$_{6}$ is a rare example in the transition-metal tellurate family of realizing an $S$ = 1 spin-chain structure. By performing neutron powder diffraction measurements, the ground-state magnetic structure of Na$_{4-δ}$NiTeO$_{6}$ is determined. These measurements reveal that below $T\rm_{N}$ ${\sim}$ 6.8(2) K, the Ni$^{2+}$ moments form a screwed ferromagnetic (FM) spin-chain structure running along the crystallographic $a$ axis but these FM spin chains are coupled antiferromagnetically along the $b$ and $c$ directions, giving rise to a magnetic propagation vector of $k$ = (0, 1/2…
The physical properties of polycrystalline materials depend on their microstructure, which is the nano-to-centimeter-scale arrangement of phases and defects in their interior. Such microstructure depends on the shape, crystallographic phase and orientation, and interfacing of the grains constituting the material. This article presents a new non-destructive 3D technique to study bulk samples with sizes in the cm range with a resolution of hundred micrometers: time-of-flight three-dimensional neutron diffraction (ToF 3DND). Compared to existing analogous X-ray diffraction techniques, ToF 3DND en…
Polycrystalline samples of Sr2Mn2CuAs2O2, Sr2Mn3As2O2, and Sr2Zn2MnAs2O2 were synthesized. Their temperature- and applied magnetic field-dependent structural, transport, thermal, and magnetic properties were characterized by means of x-ray and neutron diffraction, electrical resistivity rho, heat capacity, magnetization and magnetic susceptibility measurements. These compounds have a body-centered-tetragonal crystal structure (space group I4/mmm) that consists of MO2 (M = Zn and/or Mn) oxide layers similar to the CuO2 layers in high superconducting transition temperature Tc cuprate superconduc…
While certain magnetic sublattices have long been known theoretically to give rise to emergent physics via competing magnetic interactions and quantum effects, finding such configurations in real materials is often deeply challenging. Here we report the synthesis and characterization of a new such material, NaCo2(SeO3)2(OH) which crystallizes with a highly frustrated sublattice of sawtooth Co2+ chains. Single crystals of NaCo2(SeO3)2(OH) were synthesized using a low-temperature hydrothermal method. X-ray single crystal structure analysis reveals that the material crystallizes in orthorhombic s…
We have successfully induced multiferroic behavior in the A-type antiferromagnet SmMnO3 by the substitution of Y at the Sm site. A magnetic transition develops at 24 K for Sm1-xYxMnO3 (x=0.4,0.5) which is not present in the parent compound. This transition coincides with the onset of electric order, with an electric polarization measured along the c axis. It is proposed that the effect of Y doping is to bring about a subtle distortion of the MnO6 octahedra, causing a magnetic ordering of the Mn3+ moments similar to that reported for the well studied multiferroic TbMnO3. Following on from our p…
Magnetization measurements and time-of-flight neutron powder-diffraction studies on the high-temperature (300--980 K) magnetism and crystal structure (321--1200 K) of a pulverized YCrO$_3$ single crystal have been performed. Temperature-dependent inverse magnetic susceptibility coincides with a piecewise linear function with five regimes, with which we fit a Curie-Weiss law and calculate the frustration factor $f$. The fit results indicate a formation of magnetic polarons between 300 and 540 K and a very strong magnetic frustration. By including one factor $η$ that represents the degree of spi…
