Neutron and X-ray Scattering in Materials Science: Energy Materials
Sponsored by: TMS Functional Materials Division, TMS: Chemistry and Physics of Materials Committee
Program Organizers: Michael Manley, Oak Ridge National Laboratory; Chen Li, University of California-Riverside; Jennifer Niedziela, Oak Ridge National Lab; Hillary Smith, Swarthmore College
Tuesday 8:00 AM
March 21, 2023
Room: Aqua 311B
Location: Hilton
Session Chair: Chen Li, University of California, Riverside
8:00 AM Invited
Atomic Dynamics in Energy Materials: Olivier Delaire1; 1Duke University
A detailed view of atomic motions in solids is needed to refine microscopic theories of transport and thermodynamics, and to design improved materials. Our group uses state-of-the-art neutron and x-ray scattering techniques to probe atomic dynamics. By mapping complex spectral functions throughout reciprocal space, phonon anharmonicity and couplings to other degrees of freedom are revealed in detail. Our investigations bring direct insights into phonon scattering mechanisms, including anharmonicity, electron-phonon coupling, spin-phonon coupling, or scattering by defects and nanostructures. Our first-principles simulations enable the quantitative rationalization of these effects, for example with ab-initio molecular dynamics simulations and anharmonic renormalization at finite-temperature, and more recently with the use of machine learning accelerated simulations. This presentation will highlight results from our investigations of atomic dynamics in several classes of materials impacted by strong anharmonicity and lattice instabilities, such as halide perovskite photovoltaics, ferroelectrics / multiferroics, thermoelectrics, or superionic conductors.
8:30 AM Invited
Two-dimensional Local Lattice Distortions in Inorganic Halide Perovskites: Stephan Rosenkranz1; Matthew Krogstad1; Xing He2; Tyson Lanigan-Atkins2; Feng Ye3; Yaohua Liu3; Duck-Young Chung1; Olivier Delaire2; Raymond Osborn1; 1Argonne National Laboratory; 2Duke University; 3Oak Ridge National Laboratory
Inorganic halide perovskites are of interest because of their photoelectronic properties. These systems in general exhibit a cubic structure at high temperature and undergo transitions to tetragonal and orthorhombic symmetry at lower temperatures. While the long-range ordered structures are well understood, lattice fluctuations and local ordering are believed to underlie the optical and thermal properties, but details regarding the short-range ordering, the extent of the correlations, and whether there are commonalties across different families of compounds remain poorly understood. Measuring complete volumes of single-crystal diffuse scattering over large ranges of temperature allows us to investigate local ordering in these systems in detail. We show that the diffuse scattering observed in a number of different compounds can be understood in terms of the halide octahedral tilts that define the lower-temperature long-range ordered structures that persist in short-range ordered, two-dimensional form into the higher-temperature phases. Work supported by DOE BES DMSE
9:00 AM
Characterization of Heterogeneously Disordered Oxides with Total Scattering Experiments: Eric O'Quinn1; Igor Gussev1; Maik Lang1; 1University of Tennessee
Oxides used in many energy technologies must operate under various extremes (e.g., irradiation and high temperature). Improving their performance or developing more robust materials require detailed understanding of induced structural changes under these conditions across all length scales. We present results from X-ray and neutron total scattering experiments, revealing that disorder is in some oxides more complex than previously thought, with atomic arrangements that exhibit a high degree of order. Disordering proceeds heterogeneously with distinct structural changes at the atomic scale and longer length scales. This behavior appears to be more general and can be understood as extension of Pauling’s rules to disordered materials, as demonstrated with data from spinel (AB2O4), weberite-type (A3BO7), and pyrochlore (A2B2O7) oxides. Disorder was induced by various means, including far-from-equilibrium processing, such as exposure to highly ionizing radiation. Our results provide an improved framework by which order-disorder transformations and associated atomic arrangements can be described.
9:20 AM
Mutual Spin-phonon Driving Effects and Phonon Eigenvector Renormalization in Nickel (II) Oxide: Qiyang Sun1; Bin Wei2; Yaokun Su1; Hillary Smith3; Jiao Lin4; Douglas Abernathy4; Chen Li1; 1University of California, Riverside; 2Henan Polytechnic University; 3Swarthmore College; 4Oak Ridge National Laboratory
The physics of mutual interaction of phonon quasiparticles with electronic spin degrees of freedom, leading to unusual transport phenomena of spin and heat, has been a subject of continuing interests for decades. The effect of spin-phonon coupling on the phonon system, especially acoustic phonon properties, has so far been elusive.By means of inelastic neutron scattering and first-principles calculations, anomalous scattering spectral intensity from acoustic phonons was identified in the exemplary collinear antiferromagnetic nickel (II) oxide. A clear magnetic scattering signature of the measured neutron scattering intensity from acoustic phonons is demonstrated by its momentum transfer and temperature dependences, suggesting the presence of spin precession driven by phonon. The renormalization of phonon eigenvector is indicated by the observed “geometry-forbidden” neutron scattering intensity from transverse acoustic phonon. Our results provide a new approach to identify and quantify strong spin-phonon interactions, shedding lights on engineering functional spin-caloritronic materials through these interactions.
9:40 AM Break
9:55 AM
Probing the Gas Sorption Mechanism in Spin-crossover MOFs by Neutron Scattering: Jose Alberto Rodriguez-Velamazan1; Angel Fernandez-Blanco1; Roberta Poloni2; 1Institut Laue-Langevin; 2CNRS, Grenoble-INP, SIMaP, University of Grenoble Alpes
The research of materials with promising properties for the efficient capture and release of harmful and toxic gases is an extremely topical and burgeoning field. In this context, spin-crossover Hofmann-type porous compounds with formula {Fe(pz)[MII(CN)4]} (pz = pyrazine, MII = Ni, Pd, Pt) represent a remarkable class of materials. In these systems, the bistability of the host network can be exploited to modify the adsorption properties through control of the host spin state. We have employed different neutron scattering techniques (diffraction and inelastic neutron scattering) combined with density functional theory calculations to study the adsorption mechanisms of gas molecules like SO2 into the {Fe(pz)[MII(CN)4]} porous compounds. Our findings include the position of the guest molecule in the pores, the main modes involved in the binding and the relative orientation of the aromatic rings of the host, shedding light on the gas sorption mechanism in these promising materials.
10:15 AM
Quasi-elastic Neutron Scattering Measurements of Hydrogen Diffusion in Zirconium: Brent Heuser1; Timothy Prisk2; Jun-Li Lin1; Tanya Dax2; Yongfeng Zhang3; 1University of Illinois; 2NIST; 3INL
The diffusivity of hydrogen in zirconium is an important property for nuclear reactor fuel cladding. The often used value dates to the 1970s and employed a variation of a diffusion couple technique. We have used QENS and the HFBS to directly measure the self-diffusion (in the absence of concentration gradients). We find significant departure from from this earlier work above 400C, with a reduction in activation energy from 0.46eV to 0.36eV. Density functional theory simulations implicate solute-impurity trapping as a possible explanation for the lower activation energy above 400C. Fixed window scans also allow us to directly measure the phase boundary upon heating and cooling. Discussion will focus on a comparison of our results and those of others in an attempt to reconcile conflicting diffusivity measurements in this system that data to the 1950s.
10:35 AM
Entropy Contributions to Explain Thermal Expansion: Thermodynamics of the Invar Effect: Stefan Lohaus1; Pedro Guzman1; Camille Bernal-Choban1; Claire Saunders1; Brent Fultz1; 1California Institute of Technology
The anomalously low thermal expansion observed in some metals, known as the Invar effect, has long been associated with magnetism. Its microscopic underpinnings, however, are still an open scientific question, long after C.E. Guillaume received the 1920 physics Nobel Prize for its discovery. We explore a new method for obtaining the thermal expansion from the pressure dependence of the entropy. By combining two nuclear X-ray scattering techniques, we probe contributions from phonons and spins to the entropy of Fe-Ni. We show that the Invar behavior stems from a competition between phonons and spins, resulting in a cancellation of their entropy contributions. Ab initio phonon calculations reveal a spin-lattice coupling at the root of the Invar anomaly. Such couplings of excitations from phonons and spins go beyond the case of Invar, and could be the cause of the thermal expansion behavior in other magnetic materials. Supported by NSF Grant No. 1904714.