Total Scattering: New Insights in Condensed Matter

Conference: 2021: 71st ACA Annual Meeting
07/31/2021: 12:00 PM - 3:00 PM
1.1.4 
Oral Session 
Virtual  

Description

While crystallography has traditionally dealt with the average, periodic arrangement of atoms in condensed matter, it has long been acknowledged that deviation from ideality is critically important to understanding macroscopic material phenomena. As atomic structure characterization tools have continued to mature, an increasing body of work has accumulated documenting locally perturbed atomic environments, even in materials of nominally high average symmetry. These studies are often complemented by spectroscopy and microscopy methods to confer a nuanced understanding of materials behavior and inform the materials science paradigm.

Beyond the classical examples of diffuse scattering, total scattering and the pair distribution function have been fruitfully applied to numerous contemporary materials science problems, including: ferroic materials, catalysts, strongly correlated electron systems, energy storage materials, as well as bulk/nanoscale variations on each theme.

New experimental techniques have also advanced local structure methodologies, particularly regarding advancements in grazing incidence X-ray PDF measurements of thin films, and advancements in the quantitative treatment of electron PDF data.

This symposium invites discussion of contemporary scientific developments enabled by local structure investigations of condensed matter.

Presentations

Materials on the nanoscale: Total scattering analysis for nanoparticle chemistry

Nanomaterials have come to play a huge role in modern materials chemistry: By nanosizing the functional materials used in a range of different applications, the properties of the materials can be improved, and new applications can arise. This development has challenged the conventional techniques for material characterization. However, total scattering combined with Pair Distribution Function analysis allows us to look further into nanostructure and establish the structure-property relation for advanced functional materials.1 Here, I will present recent work illustrating how we use x-ray total scattering to study atomic structure in advanced nanomaterials, with special focus on transition metal oxide nanoparticles. We observe that new structural motifs, unstable in the bulk form, become dominant in nanoscale materials.2
Apart from studying the synthesized nanoparticles, I will also show how in situ x-ray total scattering allows following the formation of materials. Despite decades of research into nucleation processes, very little is known on how nanoparticle formation during solvothermal synthesis takes places on the atomic scale. We have developed methods which allows using in situ synchrotron X-ray Total Scattering and Pair Distribution Function analysis to follow nanoparticle nucleation and growth in situ.3 In contrast to conventional crystallographic studies, PDF analysis gives structural information from non-crystalline species, allowing obtaining structural information on the atomic scale, all the way from precursor to the final nanoclusters during synthesis. Using x-ray total scattering combined with small angle X-ray scattering, we deduce the atomic structure of prenucleation clusters, present in the processes just before the crystalline nanoparticles have formed. We show that the solvent and synthesis conditions have large influence on the nucleation pathway and the structure of the nano-scale clusters in the synthetic pathway.


1. Christiansen, T. L.; Cooper, S. R.; Jensen, K. M. Ø., There's no place like real-space: elucidating size-dependent atomic structure of nanomaterials using pair distribution function analysis. Nanoscale Adv. 2020, 2 (6), 2234-2254.
2. Christiansen, T. L.; Bøjesen, E. D.; Juelsholt, M.; Etheridge, J.; Jensen, K. M. Ø., Size Induced Structural Changes in Molybdenum Oxide Nanoparticles. ACS Nano 2019, 13 (8), 8725-8735.
3. Juelsholt, M.; Lindahl Christiansen, T.; Jensen, K. M. Ø., Mechanisms for Tungsten Oxide Nanoparticle Formation in Solvothermal Synthesis: From Polyoxometalates to Crystalline Materials. J. Phys. Chem. C 2019, 123 (8), 5110-5119.
4. Aalling-Frederiksen, O.; Juelsholt, M.; Anker, A. S; Jensen, K. M. Ø., Formation and growth mechanism for niobium oxide nanoparticles: Atomistic insight from in situ X-ray total scattering, Nanoscale, 2021, 13 (17), 8087-8097 

View Abstract 667

Author

Kirsten Marie Jensen Frederiksberg

In situ grazing incidence total scattering: new in situ capabilities for pair distribution function analysis of thin films

Structural disorder in materials that exhibit local deviations from their periodic structure or no long-range ordering at all is effectively described in terms of the atomic pair distribution function (PDF). A PDF represents the probability of finding pairs of atoms at distances r in real space from nearest-neighbors up to correlations on the nanometer scale. The total scattering (TS) approach that enables PDF analysis requires that scattering data is collected over a wide range in reciprocal space and subsequently a Fourier transformation of the entire scattering pattern into direct space. For bulk-type samples, TS has become a standard routine at high-energy beamlines. On the other hand, its application to thin film with thicknesses ranging from below ten to a few hundred nanometers is challenging since the unfavorable thickness ratio of the layer to its substrate (typically tens to hundreds of micrometers or more) limits the detectability of the film signal in transmission geometry, the usual approach for bulk systems and demonstrated for films as described e.g. in Ref. [1]. Therefore, we applied the high-energy surface diffraction technique established for single-crystal surfaces [2] to less ordered films and successfully expanded PDF analysis to thin films of only a few nanometers at acquisition times of seconds. [3,4] Besides polycrystalline and textured metal and oxide layers, we studied amorphous and naocrystalline thin films. All films were deposited on amorphous substrates (glass) which provide for easy scaling of the background signal and straightforward subtraction from the sample data to isolate the film signal. Real thin film devices e.g. for electronic applications, however, typically consist of multiple layers, and the film properties largely depend on the nature of the underlying layer. By scanning the incidence angle on the order of millidegrees, we obtained depth-resolved PDFs from bilayer samples. In this way, we were able to study the structure of the individual layers of different combinations and stackings of amorphous and crystalline materials exhibiting high and low (electron) density and, hence, x-ray scattering power from TiO2 to Pt [5]. As thermal treatment is an essential part of thin film device manufacturing, we are developing a sample stabilization system that keeps the surface in grazing incidence alignment in the micrometer-sized beam and below the critical angle of total external reflection of >0.05°. Based on a specially designed laser interferometer and an active feedback loop, this system enables following structural changes during variable-temperature processes up to several hundred degrees. This presentation will highlight the new in situ capability by the proof-of-concept experiment of crystallizing a 30 nm amorphous HfO2 thin film while continuously acquiring TS data at a time resolution of 0.5 s.

[1] Jensen, K. M. Ø., Blichfeld, A. B., & Goldman, A. I. (1999). Rev. Sci. Instrum. 70, 3554.
[2] Gustafson, J., Shipilin, M., Zhang, C., Stierle, A., Hejral, U., Ruett, U., Gutowski, O., Carlsson, P.-A., Skoglundh, M., Lundgren, E. (2014). Science 343, 758.
[3] Dippel, A.-C., Roelsgaard, M., Böttger, U., Schneller, T., Gutowski, O., Rütt, U. (2019). IUCrJ 6, 290.
[4] Roelsgaard, M., Dippel, A.-C., Borup, K. A., Nielsen, I. G., Broge, N. L. N., Röh, J. T., Gutowski, O., Iversen, B. B. (2019). IUCrJ 6, 299.
[5] Dippel, A.-C., Gutowski, O., Klemeyer, L., Boettger, U., Berg, F., Schneller, T., Hardtdegen, A., Aussen, S., Hoffmann-Eifert, S., Zimmermann, M. v. (2020). Nanoscale 12, 13103. 

View Abstract 661

Author

Ann-Christin Dippel, Deutsches Elektronen-Synchrotron DESY Hamburg

Additional Author(s)

Olof Gutowski, Deutsches Elektronen-Synchrotron Hamburg, GA 
Martin Roelsgaard, Department of Chemistry, Aarhus University Aarhus
Bo B. Iversen, Department of Chemistry, Aarhus University Aarhus
Marina Sturm, Deutsches Elektronen-Synchrotron DESY Hamburg
Martin v. Zimmermann, Deutsches Elektronen-Synchrotron DESY Hamburg

Coffee Break


High Entropy Alloys local structure study by Reversed Monte Carlo method

Many of materials properties of high-entropy alloys (HEAs), including hardness, lowered thermal and electrical conductivity, as well as extremely high volumetric hydrogen density, seems to be bounded with the material crystal structure (observed on average and/or local scale). The HEAs are alloys composed of multiple elements (sometimes up to 5 different atom types) which can significantly differ in atomic radius. Nevertheless, HEAs properties are of a high interest, little is known about the exact structures of those materials.
From the average structure point of view, HEAs crystallizes in simple body centered-cubic structure and transforms into distorted CaF2-type upon deuteration. On the other hand, on a local scale HEAs show local distortions as well as short range order due to elements occupancy ordering.
Therefore, local structure investigations have been performed by using Reversed Monte Carlo method implemented in RMCProfile program. X-Ray and neutron Pair Distribution Function (PDF) data have been modelled. Our aim was to study different atom local environments and local short-range order. Due to the fact that HEAs studied here, were multielement systems (up to 5 elements) it seemed necessary to combine X-Ray and neutron PDF data due to significantly different X-Ray and neutron contrast for used metals and hydrogen/deuterium. This is only because of that, it was possible to model up to 15 partial contributions for relatively simple cubic structure where all partials are overlapped in r space.
Here, we demonstrate how Reversed Monte Carlo method implemented in RMCProfile program can give significant impact on local structure of complicated multielement systems (TiVNb, TiVZrNb, TiVZrNbHf and TiVCrNb) As a next step we performed local structure investigations of hydrated alloys such as TiVNbD5.7, TiVZrNbHfD10, TiVCrNbD2.2 and TiVCrNbD8) in which deuterium atoms occupy both tetrahedral and octahedral interstices with low occupancies. There is a significantly higher portion of occupied sites with nearest-neighbour metals with low valence-electron concentration. This finding, as well as inelastic neutron scattering, and density functional theory suggest higher mobility of hydrogen in between nearby interstitials.

The data has already been published in
[1] Magnus M. Nygård, Wojciech A. Sławiński, Gustav Ek, Magnus H. Sørby, Martin Sahlberg, David A. Keen, Bjørn C. Hauback, Acta Materialia, 199, 2020, 504-513
[2] Magnus M. Nygård, Øystein S. Fjellvåg, Magnus H. Sørby, Kouji Sakaki, Kazutaka Ikeda, Jeff Armstrong, Ponniah Vajeeston, Wojciech A. Sławiński, Hyunjeong Kim, Akihiko Machida, Yumiko Nakamura, Bjørn C. Hauback, Acta Materialia, 205, 2021, 116496 

View Abstract 620

Author

Wojciech Slawinski, University of Warsaw Warsaw

Additional Author(s)

Magnus M. Nygård, Institute for Energy Technology, Department for Neutron Materials Characterization Kjeller
Magnus H. Sørby, Institute for Energy Technology, Department for Neutron Materials Characterization Kjeller

Probing the Local Atomic Structure of High-Entropy Oxides

High entropy oxides (HEOs) have attracted great interest in diverse fields because of their inherent opportunities to tailor and combine materials functionalities. The control of local order/disorder in the class is by extension a grand challenge towards realizing their vast potential. Pair distribution functions (PDF) obtained from total scattering (high energy synchrotron X-ray and Neutron scattering) can reveal both the local and intermediate range structure of crystalline and disordered materials. As we all know that conventional reciprocal space diffraction only probes the average long-range structure of the Bragg planes, and information from EXAFS and XANES is limited to no more than third coordination shell, PDF can reveal both local distortions and measure the structural coherence up to several tens of Ångstrøm. With optimized sample environments PDFs can also be collected under in situ mechanical and electrical fields. A combination of multiple approaches using STEM-EDS, PDFgui (graphical interface built on the PDFfit2 engine), TOPAS v6 (combined reciprocal and real space neutron PDF data) and RMCProfile (Reverse Monte Carlo software) were performed throughout this work. The experimental total scattering PDF activity will be closely supported by density functional theory (DFT) calculations and further Metropolis Monte Carlo simulations (MCS) simulations. This work hints at the exquisite level of detail that may be needed in computational and experimental data analysis to guide structure-property tuning in the emerging HEO materials. 

View Abstract 519

Author

BO JIANG Oak Ridge, TN 

Tuning of disordered local structure in Prussian Blue analogues

Disorder is commonly used in chemistry for designing functional materials. For instance, preparation of solid solutions is nothing else than the introduction of a controlled number of point defects in a crystal. Disordered systems, though, provide more degrees of freedom: not only the number of defects, but also their distribution can be used to optimise the functional properties of materials, however up until now, defect distribution was hard to control and thus was rarely used in practice.

In this talk we will show how to precisely tune distribution of point defects by changing various chemical parameters during crystal growth and characterise it with the single crystal diffuse scattering [1].

We will use Prussian Blue Analogues (PBAs) as our model system. PBAs is a class of cyanide materials with the general formula M[M'(CN)6]1-δ * xH2O where M and M' are transition metals. Depending on the nature of transition metals, PBAs can accommodate a large number of vacancies on the M'(CN)6 site (for instance δ=0.33 for M=Mn and M'=Co) which makes them highly porous and, as a result, attractive for hydrogen storage applications. Distribution of M'(CN)6 vacancies is important for the performance of this material, since more disordered vacancy configurations provide more diffusion pathways through the structure, larger accessible volume, and easier transport.

[1] Simonov, Arkadiy, et al. "Hidden diversity of vacancy networks in Prussian blue analogues." Nature 578.7794 (2020): 256-260. 

View Abstract 686

Author

Arkadiy Simonov

Additional Author

Yevheniia Kholina, ETH Zurich Zurich

Elucidating Ionic Mobility in Multivalent Spinel Oxides

With lithium-ion batteries seemingly reaching their developmental limits, researchers are exploring new chemistries to obtain the higher energy densities needed for electric vehicles to become more competitive for universal market adoption. Batteries based on Mg chemistries could achieve these goals. Oxides with a spinel structure are predicted to provide a favorable combination of properties to function as attractive magnesium cathodes; however, traditionally, Mg2+ intercalation suffers from sluggish mobility. Theory has predicted the energy barriers for the Mg2+ hops between tetrahedral sites via the vacant octahedral sites are low enough to enable sufficient room temperature transport. Experimental studies have shown potential Mg2+ migration at comparable timescales. While the activation barriers could be extracted, the path followed by the Mg2+ cation during a hop remains to be elucidated.
To better understand the trajectories for multivalent ion mobility in spinel oxides, variable temperature neutron diffraction and pair distribution function (PDF) are used to examine the average and local structure. Reverse Monte Carlo (RMC) profiling is then used to map the ionic pathways via large-box modeling of the crystal structure. Further contrast is provided by studying similarly structured samples where hopping is predicted to face higher activation barriers than Mg and, thus, show slower migration. Insight into how ion mobility is achieved in spinel structured oxides will better inform the design of new battery cathode host structures and electrolytes to help push Mg batteries into commercialization. 

View Abstract 625

Author

Megan Murphy Chicago, IL 

Additional Author(s)

Grant C.B. Alexander, University of Illinois at Chicago Chicago, IL 
Mark Hirmiz, University of Illinois at Chicago Chicago, IL 
Ryan D. Bayliss, Corning Inc
Matt Tucker, Oak Ridge National Laboratory Oak Ridge, TN 
Jordi Cabana, University of Illinois at Chicago Chicago, IL 

Neutron PDF study of catalysts and battery materials: current status and future opportunities

Pair distribution function (PDF) analysis has emerged as a powerful tool to study the complex structure of functioning disordered crystalline materials and nanomaterials. The real-space-based PDF analysis utilizes both Bragg scattering and diffuse scattering information, and thus is very sensitive to short-range ordering (SRO) in disordered crystalline materials or intermediate-range/surface structure in nanoscale materials. Particularly, the application of neutron PDF method to investigate catalysts and battery materials have attracted broad interests in recent years. There are several advantages in using neutron diffraction to study these materials: neutron scattering is very sensitive to light elements (Li, C, N and O), which are key ingredients of Li/Na-ion battery materials and varies catalysts. It is also capable of distinguishing adjacent 3d transition metal cations, which are broadly used in battery cathode or low-cost heterogeneous catalysts. The nuclear scattering lengths do not decrease with momentum transfer (Q), making it more accurate in determining the atomic environments of light elements. Moreover, it is highly penetrating and non-destructive, making it an ideal tool to probe structure changes in large devices like Li/Na-ion batteries or gas flowing cell without disturbing the electrochemical/catalytic reactions. Despite these great advantages, neutron PDF characterization of charged and discharged electrode materials or reacted catalysts, has remained somewhat limited. This is in large part due to the difficulty in optimizing the ex-situ sample preparation (for neutron scattering experiments) and the complex sample environment required for in situ neutron diffraction/PDF studies. In this talk, I will discuss the recent progress on the development of in situ/ex situ neutron diffraction/PDF capabilities at NOMAD. Two examples will be presented: one on the in situ neutron total scattering investigation of the structural origin of thermal runaway of high energy density battery cathode materials; the other on quantitative structure study of nano-catalysts using neutron PDF. Perspective on future opportunities will also be discussed. 

View Abstract 554

Author

JUE LIU, Oak Ridge National Laboratory Oak Ridge, TN 

Additional Author(s)

KATHARINE PAGE, University of Tennessee Oak Ridge, TN 
Zili Wu, Oak Ridge National Lab