Scholars@Duke
Olivier Delaire

Olivier Delaire

Associate Professor of the Thomas Lord Department of Mechanical Engineering and Materials Science
Thomas Lord Department of Mechanical Engineering and Materials Science
olivier.delaire@duke.edu
387 Gross Hall, Durham, NC 27708
144 Hudson Hall, Box 90300, Durham, NC 27708

Selected Publications

Correlated dynamic disorder, octahedral tilts, and acoustic phonon softening in CsSnBr3 and CsPbBr3

Journal Article Physical Review Materials · June 1, 2025 Metal halide perovskites (MHPs) have emerged as highly promising materials for optoelectronic applications, with all-inorganic MHPs presenting enhanced stability compared to their hybrid counterparts. Here, we investigate the atomic dynamics and structural ... Full text Cite

Enhancing robustness in machine-learning-accelerated molecular dynamics: A multi-model nonparametric probabilistic approach

Journal Article Mechanics of Materials · March 1, 2025 In this work, we present a system-agnostic probabilistic framework to quantify model-form uncertainties in molecular dynamics (MD) simulations based on machine-learned (ML) interatomic potentials. Such uncertainties arise from the design and selection of M ... Full text Cite

Atomic dynamics in MCrX2 (M=Ag,Cu;X= S,Se) across magnetic and superionic transitions

Journal Article Physical Review Materials · March 1, 2025 A systematic study of atomic dynamics and thermal properties of the family of layered chalcogenide compounds MCrX2 (M=Ag,Cu;X=S,Se) was performed, including neutron and x-ray scattering, thermal characterization, and first-principles simulations. In all co ... Full text Cite

Ionic conduction and interfacial stability in Na1+xZr2SixP3−xO12 solid electrolytes: Past, present, and future perspectives

Journal Article Applied Physics Reviews · March 1, 2025 While the development of new solid electrolytes (SEs) is crucial for advancing energy storage technologies, revisiting existing materials with significantly improved knowledge of their physical properties and synthesis control offers significant opportunit ... Full text Cite

Resolving the dynamic correlated disorder in KTa<sub>1-<i>x</i></sub>Nb<sub><i>x</i></sub>O<sub>3</sub>.

Journal Article Proceedings of the National Academy of Sciences of the United States of America · February 2025 Understanding the complex temporal and spatial correlations of ions in disordered perovskite oxides is critical to rationalize their functional properties. Here, we provide insights into the longstanding controversy regarding the off-centering of transitio ... Full text Cite

Liquid-like dynamics in a solid-state lithium electrolyte

Journal Article Nature Physics · January 1, 2025 Superionic materials represent a regime intermediate between the crystalline and liquid states of matter. Despite the considerable interest in potential applications for solid-state batteries or thermoelectric devices, it remains unclear whether the fast i ... Full text Cite

Investigation of Low-Energy Lattice Dynamics and Their Role in Superionic Na Diffusion and Ultralow Thermal Conductivity of Na3PSe4 as a Solid-State Electrolyte

Journal Article Chemistry of Materials · December 10, 2024 The atomic dynamics of Na3PSe4 were investigated using a combination of neutron scattering experiments and ab initio and machine-learned molecular dynamics simulations to probe the interplay of fast ionic diffusion with atomic vibrati ... Full text Cite

Multiple Lattice Instabilities and Complex Ground State in Cs2AgBiBr6

Journal Article Prx Energy · January 1, 2024 Metal-halide perovskites (MHPs) are attracting considerable interest for optoelectronic applications, with Cs2AgBiBr6 one of the main contenders among lead-free systems. Cs2AgBiBr6 crystallizes in a nominally dou ... Full text Cite

Ultrafast lattice disordering can be accelerated by electronic collisional forces

Journal Article Nature Physics · October 1, 2023 Featured Publication In the prevalent picture of ultrafast structural phase transitions, atomic motion occurs in a slowly varying potential energy surface adiabatically determined by fast electrons. However, this ignores non-conservative forces caused by electron–lattice colli ... Full text Cite

Nonthermal Bonding Origin of a Novel Photoexcited Lattice Instability in SnSe.

Journal Article Physical review letters · October 2023 Featured Publication Lattice dynamics measurements are often crucial tools for understanding how materials transform between different structures. We report time-resolved x-ray scattering-based measurements of the nonequilibrium lattice dynamics in SnSe, a monochalcogenide rep ... Full text Cite

Distinct anharmonic characteristics of phonon-driven lattice thermal conductivity and thermal expansion in bulk MoSe2 and WSe2

Journal Article Journal of Materials Chemistry A · September 19, 2023 Using inelastic neutron scattering and X-ray diffraction measurements, together with ab initio and machine-learning molecular dynamics simulations, we bring out the distinct nature of anharmonicity in the phonon spectra of MoSe2 and WSe2 Full text Cite

Extreme phonon anharmonicity underpins superionic diffusion and ultralow thermal conductivity in argyrodite Ag8SnSe6.

Journal Article Nature materials · August 2023 Featured Publication Ultralow thermal conductivity and fast ionic diffusion endow superionic materials with excellent performance both as thermoelectric converters and as solid-state electrolytes. Yet the correlation and interdependence between these two features remain unclea ... Full text Cite

Anisotropic magnon damping by zero-temperature quantum fluctuations in ferromagnetic CrGeTe3.

Journal Article Nature communications · July 2022 Featured Publication Spin and lattice are two fundamental degrees of freedom in a solid, and their fluctuations about the equilibrium values in a magnetic ordered crystalline lattice form quasiparticles termed magnons (spin waves) and phonons (lattice waves), respectively. In ... Full text Cite

Strongly Anharmonic Phonons and Their Role in Superionic Diffusion and Ultralow Thermal Conductivity of Cu7PSe6

Journal Article Advanced Energy Materials · June 1, 2022 Featured Publication The quest for advanced superionic materials requires understanding their complex atomic dynamics, but detailed studies of the interplay between lattice vibrations and ionic diffusion remain scarce. Here inelastic and quasielastic neutron scattering measure ... Full text Cite

Direct Detection of V-V Atom Dimerization and Rotation Dynamic Pathways upon Ultrafast Photoexcitation in VO2

Journal Article Physical Review X · June 1, 2022 Featured Publication Photoinduced ultrafast phase transitions can generate quasiequilibrium states with novel emergent properties modulated by the interplay of electronic and lattice degrees of freedoms. Therefore, accurately probing transient atomic structures and their dynam ... Full text Cite

CHESS: The future direct geometry spectrometer at the second target station.

Journal Article The Review of scientific instruments · June 2022 CHESS, chopper spectrometer examining small samples, is a planned direct geometry neutron chopper spectrometer designed to detect and analyze weak signals intrinsic to small cross sections (e.g., small mass, small magnetic moments, or neutron absorbing mat ... Full text Cite

Solidlike to liquidlike behavior of Cu diffusion in superionic Cu2 X (X= S, Se): An inelastic neutron scattering and ab initio molecular dynamics investigation

Journal Article Physical Review Materials · May 1, 2022 Cu2Se and Cu2S are excellent model systems of superionic conductors with large diffusion coefficients that have been reported to exhibit different solidlike and liquidlike Cu-ion diffusion. In this paper, we clarify the atomic dynamics of these compounds w ... Full text Cite

Observation of a Novel Lattice Instability in Ultrafast Photoexcited SnSe

Journal Article Physical Review X · March 1, 2022 Featured Publication There is growing interest in using ultrafast light pulses to drive functional materials into nonequilibrium states with novel properties. The conventional wisdom is that above-gap photoexcitation behaves similarly to raising the electronic temperature and ... Full text Cite

Observation of photo-induced plasmon-phonon coupling in PbTe via ultrafast x-ray scattering.

Journal Article Structural dynamics (Melville, N.Y.) · March 2022 We report the observation of photo-induced plasmon-phonon coupled modes in the group IV-VI semiconductor PbTe using ultrafast x-ray diffuse scattering at the Linac Coherent Light Source. We measure the near-zone-center excited-state dispersion of the heavi ... Full text Cite

Dynamically Tunable Terahertz Emission Enabled by Anomalous Optical Phonon Responses in Lead Telluride

Journal Article ACS Photonics · December 15, 2021 Lead telluride (PbTe), a narrow bandgap semiconductor commonly used in infrared detectors, exhibits anomalous vibrational and structural properties, making it appealing for thermoelectrics. Despite significant fundamental interest in the microscopic origin ... Full text Cite

A two-dimensional type I superionic conductor.

Journal Article Nature materials · December 2021 Featured Publication Superionic conductors possess liquid-like ionic diffusivity in the solid state, finding wide applicability from electrolytes in energy storage to materials for thermoelectric energy conversion. Type I superionic conductors (for example, AgI, Ag2 ... Full text Cite

Fast Na diffusion and anharmonic phonon dynamics in superionic Na3PS4

Journal Article Energy and Environmental Science · December 1, 2021 Featured Publication The design of new solid electrolytes (SEs) hinges on identifying and tuning relevant descriptors. Phonons describe the atomic dynamics in crystalline materials and provide a basis to encode possible minimum energy pathways for ion migration, but anharmonic ... Full text Cite

Stoichiometric tuning of lattice flexibility and Na diffusion in NaAlSiO4: quasielastic neutron scattering experiment andab initiomolecular dynamics simulations

Journal Article Journal of Materials Chemistry A · August 7, 2021 We have performed quasielastic neutron scattering (QENS) experiments up to 1243 K andab initiomolecular dynamics (AIMD) simulations to investigate the Na diffusion in various phases of NaAlSiO4(NASO), namely, low-carnegieite (L-NASO; trigonal), ... Full text Cite

Two-dimensional overdamped fluctuations of the soft perovskite lattice in CsPbBr3.

Journal Article Nat Mater · July 2021 Featured Publication Lead halide perovskites exhibit structural instabilities and large atomic fluctuations thought to impact their optical and thermal properties, yet detailed structural and temporal correlations of their atomic motions remain poorly understood. Here, these c ... Full text Link to item Cite

Phonons and lithium diffusion in LiAlO2

Journal Article Physical Review B · May 13, 2021 We report on investigations of phonons and lithium diffusion in LiAlO2 based on inelastic neutron scattering measurements of the phonon density of states (DOS) in γ-LiAlO2 from 473 to 1073 K, complemented with ab initio molecular dynamics (AIMD) simulation ... Full text Cite

Soft anharmonic phonons and ultralow thermal conductivity in Mg3(Sb, Bi)2 thermoelectrics.

Journal Article Science advances · May 2021 Featured Publication The candidate thermoelectric compounds Mg3Sb2 and Mg3Bi2 show excellent performance near ambient temperature, enabled by an anomalously low lattice thermal conductivity (κl) comparable to those of much ... Full text Cite

Anisotropic Structural Collapse of Mg3Sb2and Mg3Bi2at High Pressure

Journal Article Chemistry of Materials · January 26, 2021 Alloys between Mg3Sb2 and Mg3Bi2 have recently been shown to be exceptional thermoelectric materials due in part to their anomalously low thermal conductivity. In the present study, in situ high-pressure synchrotron X-ray diffraction was used to investigat ... Full text Cite

Controlling phonon lifetimes via sublattice disordering in AgBiSe2

Journal Article Physical Review Materials · October 12, 2020 Featured Publication Understanding and controlling microscopic heat transfer mechanisms in solids is critical to material design in numerous technological applications. Yet, the current understanding of thermal transport in semiconductors and insulators is limited by the diffi ... Full text Cite

Clathrate BaNi2P4: An Interplay of Heat and Charge Transport Due to Strong Host-Guest Interactions

Journal Article Chemistry of Materials · September 22, 2020 Heat and charge transport properties of the metallic unconventional clathrate BaNi2P4, hosting Ba cations in oversized Ni8P16 cages, are investigated. A novel method of single-crystal growth was developed, yielding 2-3 mm sized crystals of BaNi2P4. We also ... Full text Cite

Extended anharmonic collapse of phonon dispersions in SnS and SnSe

Journal Article Nature Communications · September 4, 2020 Featured Publication AbstractThe lattice dynamics and high-temperature structural transition in SnS and SnSe are investigated via inelastic neutron scattering, high-resolution Raman spectroscopy and anharmonic first-principles simulations. We u ... Full text Cite

Anharmonic lattice dynamics and superionic transition in AgCrSe 2

Journal Article Proceedings of the National Academy of Sciences · February 25, 2020 Featured Publication Significance Unveiling the unusual atomic dynamics in superionic conductors is critical for the design of energy conversion and storage materials, for example to rationalize their thermal transport pr ... Full text Open Access Cite

Lattice dynamics of the hybrid improper ferroelectrics (Ca,Sr)3Ti2 O7

Journal Article Physical Review B · December 6, 2019 Featured Publication The structure and lattice dynamics of the hybrid improper ferroelectric compound Ca3-xSrxTi2O7 (for x=0,0.6, and 0.9) have been studied with a combination of diffraction, inelastic scattering experiments, Raman spectroscopy, and calorimetry measurements, a ... Full text Cite

Orthorhombic to monoclinic phase transition in NbNiTe2

Journal Article Physical Review B · October 11, 2019 The high-temperature structural phase transition of the potential topological material NbNiTe2 has been studied in detail. At high temperatures, the structure is centrosymmetric with orthorhombic space-group P2m2n21a(Pmna), and distorts at 373 K to a monoc ... Full text Cite

High-resolution phonon energy shift measurements with the inelastic neutron spin echo technique

Journal Article Journal of Applied Crystallography · August 1, 2019 The energy resolution of the conventional way of measuring a small change in a phonon dispersion curve using neutron scattering is restricted by the relatively coarse intrinsic resolution ellipsoid of the neutron triple-axis spectrometer (TAS). By implemen ... Full text Cite

Frustrated Magnetism in Mott Insulating (V1-xCrx)2 O3

Journal Article Physical Review X · February 21, 2019 Featured Publication V2O3 famously features all four combinations of paramagnetic versus antiferromagnetic and metallic versus insulating states of matter in response to percent-level doping, pressure in the GPa range, and temperature below 300 K. Using time-of-flight neutron ... Full text Cite

Selective breakdown of phonon quasiparticles across superionic transition in CuCrSe 2

Journal Article Nature Physics · January 1, 2019 Featured Publication Superionic crystals exhibit ionic mobilities comparable to liquids while maintaining a periodic crystalline lattice. The atomic dynamics leading to large ionic mobility have long been debated. A central question is whether phonon quasiparticles—which condu ... Full text Open Access Cite

Momentum-resolved observations of the phonon instability driving geometric improper ferroelectricity in yttrium manganite

Journal Article Nature Communications · December 1, 2018 Featured Publication Magnetoelectrics offer tantalizing opportunities for devices coupling ferroelectricity and magnetism but remain difficult to realize. Breakthrough strategies could circumvent the mutually exclusive origins of magnetism and ferroelectricity by exploiting th ... Full text Open Access Cite

Ultrafast disordering of vanadium dimers in photoexcited VO 2

Journal Article Science · November 2, 2018 Featured Publication Snapshots of a phase transition Time-resolved x-ray scattering can be used to investigate the dynamics of materials during the switch from one structural phase to another. So far, methods provide an e ... Full text Cite

Recent progresses on physics and applications of vanadium dioxide

Journal Article Materials Today · October 1, 2018 Featured Publication As a strongly correlated electron material, vanadium dioxide (VO2) has been a focus of research since its discovery in 1959, owing to its well-known metal–insulator transition coupled with a structural phase transition. Recent years have witness ... Full text Cite

Comparing the Descriptors for Investigating the Influence of Lattice Dynamics on Ionic Transport Using the Superionic Conductor Na3PS4- xSe x.

Journal Article Journal of the American Chemical Society · October 2018 Recent work on superionic conductors has demonstrated the influence of lattice dynamics and the softness of the lattice on ionic transport. When examining either the changes in the acoustic phonon spectrum or the whole phonon density of states, both a decr ... Full text Cite

Self-compensation induced vacancies for significant phonon scattering in InSb

Journal Article Nano Energy · June 1, 2018 Phonon scattering by point defects via mass differences and strain fluctuations could effectively reduce the lattice thermal conductivity. The atomic mass difference can be maximized by introducing the vacancies thus leading to a significant phonon scatter ... Full text Cite

A practical field guide to thermoelectrics: Fundamentals, synthesis, and characterization

Journal Article Applied Physics Reviews · June 1, 2018 The study of thermoelectric materials spans condensed matter physics, materials science and engineering, and solid-state chemistry. The diversity of the participants and the inherent complexity of the topic mean that it is difficult, if not impossible, for ... Full text Cite

Tuning mobility and stability of lithium ion conductors based on lattice dynamics

Journal Article Energy and Environmental Science · April 1, 2018 Lithium ion conductivity in many structural families can be tuned by many orders of magnitude, with some rivaling that of liquid electrolytes at room temperature. Unfortunately, fast lithium conductors exhibit poor stability against lithium battery electro ... Full text Cite

Mobility and stability descriptors of lithium ion conductors based on lattice dynamics

Conference ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY · March 18, 2018 Featured Publication Link to item Cite

Neutron and x-ray scattering study of phonon dispersion and diffuse scattering in (Na,Bi)Ti O3-xBaTi O3 single crystals near the morphotropic phase boundary

Journal Article Physical Review B · November 10, 2017 Featured Publication Neutron and x-ray scattering measurements were performed on (Na1/2Bi1/2)TiO3-xat%BaTiO3 (NBT-xBT) single crystals (x=4, 5, 6.5, and 7.5) across the morphotropic phase boundary (MPB), as a function of both composition and temperature, and probing both struc ... Full text Cite

The curious case of cuprous chloride: Giant thermal resistance and anharmonic quasiparticle spectra driven by dispersion nesting

Journal Article Physical Review B · September 5, 2017 Strongly anharmonic phonon properties of CuCl are investigated with inelastic neutron-scattering measurements and first-principles simulations. An unusual quasiparticle spectral peak emerges in the phonon density of states with increasing temperature, in b ... Full text Cite

Itinerant Antiferromagnetism in RuO2

Journal Article Physical Review Letters · February 15, 2017 Bulk rutile RuO2 has long been considered a Pauli paramagnet. Here we report that RuO2 exhibits a hitherto undetected lattice distortion below approximately 900 K. The distortion is accompanied by antiferromagnetic order up to at least 300 K with a small r ... Full text Open Access Cite

Lattice dynamics and thermal transport in multiferroic CuCrO2

Journal Article Physical Review B · February 9, 2017 Featured Publication Inelastic neutron and x-ray scattering measurements of phonons and spin waves were performed in the delafossite compound CuCrO2 over a wide range of temperature, and complemented with first-principles lattice dynamics simulations. The phonon dispersions an ... Full text Cite

Anomalously low electronic thermal conductivity in metallic vanadium dioxide.

Journal Article Science (New York, N.Y.) · January 2017 Featured Publication In electrically conductive solids, the Wiedemann-Franz law requires the electronic contribution to thermal conductivity to be proportional to electrical conductivity. Violations of the Wiedemann-Franz law are typically an indication of unconventional quasi ... Full text Cite

Complex optimization for big computational and experimental neutron datasets.

Journal Article Nanotechnology · December 2016 We present a framework to use high performance computing to determine accurate solutions to the inverse optimization problem of big experimental data against computational models. We demonstrate how image processing, mathematical regularization, and hierar ... Full text Cite

Weak coupling of pseudoacoustic phonons and magnon dynamics in the incommensurate spin-ladder compound S r14 C u24 O41

Journal Article Physical Review B · October 21, 2016 Intriguing lattice dynamics have been predicted for aperiodic crystals that contain incommensurate substructures. Here we report inelastic neutron scattering measurements of phonon and magnon dispersions in Sr14Cu24O41, which contains incommensurate one-di ... Full text Open Access Cite

Modeling non-harmonic behavior of materials from experimental inelastic neutron scattering and thermal expansion measurements.

Journal Article Journal of physics. Condensed matter : an Institute of Physics journal · September 2016 Based on thermodynamic principles, we derive expressions quantifying the non-harmonic vibrational behavior of materials, which are rigorous yet easily evaluated from experimentally available data for the thermal expansion coefficient and the phonon density ... Full text Open Access Cite

Phonon anharmonicity and negative thermal expansion in SnSe

Journal Article Physical Review B · August 9, 2016 The anharmonic phonon properties of SnSe in the Pnma phase were investigated with a combination of experiments and first-principles simulations. Using inelastic neutron scattering (INS) and nuclear resonant inelastic X-ray scattering (NRIXS), we have measu ... Full text Open Access Cite

The origin of incipient ferroelectricity in lead telluride

Journal Article Nature Communications · July 22, 2016 The interactions between electrons and lattice vibrations are fundamental to materials behaviour. In the case of group IV-VI, V and related materials, these interactions are strong, and the materials exist near electronic and structural phase transitions. ... Full text Open Access Cite

Hierarchical optimization for neutron scattering problems

Journal Article Journal of Computational Physics · June 15, 2016 Featured Publication We present a scalable optimization method for neutron scattering problems that determines confidence regions of simulation parameters in lattice dynamics models used to fit neutron scattering data for crystalline solids. The method uses physics-based hiera ... Full text Link to item Cite

Hierarchical domain structure of lead-free piezoelectric (Na1/2 Bi1/2)TiO3-(K1/2 Bi1/2)TiO3 single crystals

Journal Article Journal of Applied Physics · May 4, 2016 Featured Publication Full text Cite

Structural phase transition and phonon instability in Cu12Sb4S13

Journal Article Physical Review B · February 2016 Featured Publication A structural phase transition has been discovered in the synthetic tetrahedrite Cu12Sb4S13 at approximately 88 K. Upon cooling, the material transforms from its known cubic symmetry to a tetragonal unit cell that is characterized by an in-plane ordering th ... Full text Cite

Electronic Instability and Anharmonicity in SnSe

Journal Article Materials Today Physics · 2016 The binary compound SnSe exhibits record high thermoelectric performance, largely because of its very low thermal conductivity. The origin of the strong phonon anharmonicity leading to the low thermal conductivity of SnSe is investigated through first-prin ... Full text Open Access Link to item Cite

Electron-phonon coupling and thermal transport in the thermoelectric compound Mo3Sb(7−x)Te(x)

Journal Article Physical Review B · December 2015 Featured Publication Phonon properties of Mo3Sb(7−x)Te(x) (x=0,1.5,1.7), a potential high-temperature thermoelectric material, have been studied with inelastic neutron and x-ray scattering, and with first-principles simulations. The substitution of Te for Sb leads to pronounce ... Full text Open Access Link to item Cite

Orbitally driven giant phonon anharmonicity in SnSe

Journal Article Nature Physics · December 1, 2015 Featured Publication Understanding elementary excitations and their couplings in condensed matter systems is critical for developing better energy-conversion devices. In thermoelectric materials, the heat-to-electricity conversion efficiency is directly improved by suppressing ... Full text Cite

Nanoscale Structure in AgSbTe2 Determined by Diffuse Elastic Neutron Scattering

Journal Article Journal of Electronic Materials · June 1, 2015 Diffuse elastic neutron scattering measurements have confirmed that AgSbTe2 has a hierarchical structure, with defects on length scales from nanometers to microns. While scattering from this mesoscale structure is consistent with previously prop ... Full text Cite

Twisting phonons in complex crystals with quasi-one-dimensional substructures.

Journal Article Nature communications · April 2015 Featured Publication A variety of crystals contain quasi-one-dimensional substructures, which yield distinctive electronic, spintronic, optical and thermoelectric properties. There is a lack of understanding of the lattice dynamics that influences the properties of such comple ... Full text Cite

Photoinduced suppression of the ferroelectric instability in PbTe

Journal Article · 2015 The interactions between electrons and phonons drive a large array of technologically relevant material properties including ferroelectricity, thermoelectricity, and phase-change behaviour. In the case of many group IV-VI, V, and related materials, these i ... Link to item Cite

Anharmonicity and atomic distribution of SnTe and PbTe thermoelectrics

Journal Article Physical Review B Condensed Matter and Materials Physics · December 29, 2014 The structure and lattice dynamics of rock-salt thermoelectric materials SnTe and PbTe are investigated with single-crystal and powder neutron diffraction, inelastic neutron scattering (INS), and first-principles simulations. Our first-principles calculati ... Full text Cite

Metallization of vanadium dioxide driven by large phonon entropy.

Journal Article Nature · November 2014 Featured Publication Phase competition underlies many remarkable and technologically important phenomena in transition metal oxides. Vanadium dioxide (VO2) exhibits a first-order metal-insulator transition (MIT) near room temperature, where conductivity is suppressed and the l ... Full text Cite

Low-temperature heat capacity and localized vibrational modes in natural and synthetic tetrahedrites

Journal Article Journal of Applied Physics · May 21, 2014 The heat capacity of natural (Cu12-x (Fe, Zn, Ag) x(Sb, As)4S13) and synthetic (Cu 12-xZnxSb4S13 with x = 0, 1, 2) tetrahedrite compounds was measured between 2 K and 3 ... Full text Cite

Phonon self-energy and origin of anomalous neutron scattering spectra in SnTe and PbTe thermoelectrics.

Journal Article Physical review letters · May 2014 Featured Publication The anharmonic lattice dynamics of rock-salt thermoelectric compounds SnTe and PbTe are investigated with inelastic neutron scattering (INS) and first-principles calculations. The experiments show that, surprisingly, although SnTe is closer to the ferroele ... Full text Cite

Natural nanostructure and superlattice nanodomains in AgSbTe2

Journal Article Journal of Applied Physics · April 14, 2014 AgSbTe2 has long been of interest for thermoelectric applications because of its favorable electronic properties and its low lattice thermal conductivity of ∼0.7 W/mK. In this work, we report new findings from a high-resolution transmission elec ... Full text Cite

Phonon localization drives polar nanoregions in a relaxor ferroelectric.

Journal Article Nature communications · April 2014 Featured Publication Relaxor ferroelectrics exemplify a class of functional materials where interplay between disorder and phase instability results in inhomogeneous nanoregions. Although known for about 30 years, there is no definitive explanation for polar nanoregions (PNRs) ... Full text Cite

Origin of anomalous anharmonic lattice dynamics of lead telluride

Journal Article Applied Physics Express · January 1, 2014 The origin of the anomalous anharmonic lattice dynamics of lead telluride is investigated by molecular dynamics simulations with interatomic force constants (IFCs) obtained up to quartic terms from first principles. The calculations reproduce the asymmetry ... Full text Cite

Integrating advanced materials simulation techniques into an automated data analysis workflow at the spallation neutron source

Conference TMS Annual Meeting · January 1, 2014 This presentation will review developments on the integration of advanced modeling and simulation techniques into the analysis step of experimental data obtained at the Spallation Neutron Source. A workflow framework for the purpose of refining molecular m ... Full text Cite

Origins of large enhancement in electromechanical coupling for nonpolar directions in ferroelectric BaTiO3

Journal Article Physical Review B Condensed Matter and Materials Physics · November 15, 2013 The origins of enhanced piezoelectric coupling along nonpolar crystallographic directions in ferroelectric BaTiO3 are investigated using in situ neutron spectroscopy. It is observed that an electric field applied away from the equilibrium polari ... Full text Cite

Glass-like phonon scattering from a spontaneous nanostructure in AgSbTe2.

Journal Article Nature nanotechnology · June 2013 Featured Publication Materials with very low thermal conductivity are of great interest for both thermoelectric and optical phase-change applications. Synthetic nanostructuring is most promising for suppressing thermal conductivity through phonon scattering, but challenges rem ... Full text Cite

Effects of temperature and pressure on phonons in FeSi1-xAl x

Journal Article Physical Review B Condensed Matter and Materials Physics · May 31, 2013 The effects of temperature and pressure on phonons in B20 compounds FeSi1-xAlx were measured using inelastic neutron scattering and nuclear-resonant inelastic x-ray scattering. The effect of hole doping through Al substitution is comp ... Full text Cite

Phonon Studies

Journal Article · October 12, 2012 AbstractUntil the beginning of the 20th century, the models used to understand the properties of solids were based on the assumption that atomic nuclei are fixed at their equilibrium positions. These models have been very s ... Full text Cite

Microscopic mechanism of low thermal conductivity in lead telluride

Journal Article Physical Review B Condensed Matter and Materials Physics · April 10, 2012 The microscopic physics behind low-lattice thermal conductivity of single-crystal rock salt lead telluride (PbTe) is investigated. Mode-dependent phonon (normal and umklapp) scattering rates and their impact on thermal conductivity were quantified by first ... Full text Cite

Anharmonic phonons and magnons in BiFeO 3

Journal Article Physical Review B Condensed Matter and Materials Physics · February 13, 2012 Featured Publication The phonon density of states (DOS) and magnetic excitation spectrum of polycrystalline BiFeO 3 were measured for temperatures 200≤T≤750K, using inelastic neutron scattering (INS). Our results indicate that the magnetic spectrum of BiFeO 3 Full text Cite

Properties of single crystalline AZn 2Sb 2 (A Ca,Eu,Yb)

Journal Article Journal of Applied Physics · February 1, 2012 Single crystals of CaZn 2Sb 2, EuZn 2Sb 2, and YbZn 2Sb 2 were grown from melts of nominal composition AZn 5Sb 5 (A =Ca,Eu,Yb) with the excess melt being removed at 107 ... Full text Cite

Thermoelectric transport properties of CaMg 2Bi 2, EuMg 2Bi 2, and YbMg 2Bi 2

Journal Article Physical Review B Condensed Matter and Materials Physics · January 11, 2012 The thermoelectric transport properties of CaMg 2Bi 2, EuMg 2Bi 2, and YbMg 2Bi 2 were characterized between 2 and 650 K. As synthesized, the polycrystalline samples are found to have lower ... Full text Open Access Cite

Design and operation of the wide angular-range chopper spectrometer ARCS at the Spallation Neutron Source.

Journal Article The Review of scientific instruments · January 2012 The wide angular-range chopper spectrometer ARCS at the Spallation Neutron Source (SNS) is optimized to provide a high neutron flux at the sample position with a large solid angle of detector coverage. The instrument incorporates modern neutron instrumenta ... Full text Cite

Positive vibrational entropy of chemical ordering in FeV.

Journal Article Physical review letters · September 2011 Inelastic neutron scattering and nuclear resonant inelastic x-ray scattering were used to measure phonon spectra of FeV as a B2 ordered compound and as a bcc solid solution. The two data sets were combined to give an accurate phonon density of states, and ... Full text Cite

Giant anharmonic phonon scattering in PbTe.

Journal Article Nature materials · June 2011 Featured Publication Understanding the microscopic processes affecting the bulk thermal conductivity is crucial to develop more efficient thermoelectric materials. PbTe is currently one of the leading thermoelectric materials, largely thanks to its low thermal conductivity. Ho ... Full text Cite

Nonharmonic phonons in MgB2 at elevated temperatures

Journal Article Physical Review B · May 2011 Full text Cite

Thermoelectric properties of Co-, Ir-, and Os-doped FeSi alloys: Evidence for strong electron-phonon coupling

Journal Article Physical Review B Condensed Matter and Materials Physics · March 28, 2011 The effects of various transition-metal dopants on the electrical and thermal transport properties of Fe1-xMxSi alloys (M = Co, Ir, Os) are reported. The maximum thermoelectric figure of merit ZT max is improved from 0.007 ... Full text Cite

Phonon softening and metallization of a narrow-gap semiconductor by thermal disorder

Journal Article Proceedings of the National Academy of Sciences of the United States of America · March 22, 2011 Featured Publication The vibrations of ions in solids at finite temperature depend on interatomic force-constants that result from electrostatic interactions between ions, and the response of the electron density to atomic displacements. At high temperatures, vibration amplitu ... Full text Cite

Effects of composition, temperature, and magnetism on phonons in bcc Fe-V alloys

Journal Article Physical Review B Condensed Matter and Materials Physics · October 22, 2010 The phonon densities of states of body-centered-cubic Fe-V alloys across the full composition range were studied by inelastic neutron scattering, nuclear resonant inelastic x-ray scattering, and ab initio calculations. The average phonon energy followed th ... Full text Cite

Effects of chemical composition and B2 order on phonons in bcc Fe-Co alloys

Journal Article Journal of Applied Physics · July 15, 2010 The phonon density of states (DOS) gives insight into interatomic forces and provides the vibrational entropy, making it a key thermodynamic function for understanding alloy phase transformations. Nuclear resonant inelastic x-ray scattering and inelastic n ... Full text Cite

Studies of high-temperature electron-phonon interactions with inelastic neutron scattering and first-principles computations

Journal Article Applied Physics A Materials Science and Processing · June 1, 2010 Several recent studies of phonons combining inelastic neutron scattering and first-principles calculations are summarized. Inelastic neutron scattering was used to measure the phonon densities of states of the A15 compounds V 3Si, V3G ... Full text Cite

Temperature and pressure dependence of the Fe-specific phonon density of states in Ba ( Fe1-x Cox)2As2

Journal Article Physical Review B Condensed Matter and Materials Physics · March 4, 2010 Featured Publication The 57Fe -specific phonon density of states (DOS) of Ba (Fe 1-x Cox)2 As2 single crystals (x=0.0,0.08) was measured at cryogenic temperatures and at high pressures with nuclear-resonant inelastic x-ray ... Full text Cite

Effects of vacancies on phonon entropy of B2 FeAl

Journal Article Physical Review B Condensed Matter and Materials Physics · December 21, 2009 The phonon density of states (DOS) and phonon entropy of B2 FeAl were determined as functions of the Fe site vacancy concentration using several scattering techniques and were computed from first principles. Measurements at elevated temperature ... Full text Cite

Phonon density of states and heat capacity of La(3−x)Te4

Journal Article Physical Review B · November 2009 Full text Cite

Phonon density of states of LaFeAsO(1-x)Fx.

Journal Article Physical review letters · October 2008 Featured Publication We have studied the phonon density of states (PDOS) in LaFeAsO(1-x)Fx with inelastic neutron scattering methods. The PDOS of the parent compound (x=0) is very similar to the PDOS of samples optimally doped with fluorine to achieve the maximum Tc (x approxi ... Full text Cite

Adiabatic electron-phonon interaction and high-temperature thermodynamics of A15 compounds.

Journal Article Physical review letters · September 2008 Featured Publication Inelastic neutron scattering was used to measure the phonon densities of states of the A15 compounds V3Si, V3Ge, and V3Co at temperatures from 10 to 1,273 K. It was found that phonons in V3Si and V3Ge, which are superconducting at low temperatures, exhibit ... Full text Cite

Electron-phonon interactions and high-temperature thermodynamics of vanadium and its alloys

Journal Article Physical Review B Condensed Matter and Materials Physics · June 25, 2008 Inelastic neutron scattering was used to measure the phonon densities of states (DOSs) for pure V and solid solutions of V with 6 to 7at% of Co, Nb, and Pt, at temperatures from 10 K to 1323 K. Ancillary measurements of heat capacity and thermal expansion ... Full text Cite

Phonons in aluminum at high temperatures studied by inelastic neutron scattering

Journal Article Physical Review B Condensed Matter and Materials Physics · January 3, 2008 Inelastic neutron scattering measurements on aluminum metal were performed at temperatures of 10, 150, 300, 525, and 775 K using direct-geometry Fermi chopper spectrometers. The temperature dependent phonon density of states (DOS) was determined from the s ... Full text Cite

Neutron scattering measurements of phonons in nickel at elevated temperatures

Journal Article Physical Review B Condensed Matter and Materials Physics · March 9, 2007 Measurements of elastic and inelastic neutron scatterings from elemental nickel were made at 10, 300, 575, 875, and 1275 K. The phonon densities of states (DOSs) were calculated from the inelastic scattering and were fit with Born-von Kármán models of the ... Full text Cite

Charge redistribution and phonon entropy of vanadium alloys.

Journal Article Physical review letters · December 2006 Featured Publication The effects of alloying on the lattice dynamics of vanadium were investigated using inelastic neutron scattering. Phonon densities of states were obtained for bcc solid solutions of V with 3d, 4d, and 5d transition metal solutes, from which vibrational ent ... Full text Cite

Vibrational thermodynamics of vanadium and dilute vanadium alloys

Conference Proceedings of an International Conference on Solid Solid Phase Transformations in Inorganic Materials 2005 · December 1, 2005 Using inelastic neutron scattering, we measured the phonon densities of states for pure vanadium and solid solutions of vanadium with 6 to 7at% of Co, Ni, Pd, Pt, at temperatures up to 1273 K for the alloys and 1673 K for pure vanadium. At room temperature ... Cite

Entropy of the γ- α martensitic transformation in Fe 71Ni29

Conference Proceedings of an International Conference on Solid Solid Phase Transformations in Inorganic Materials 2005 · December 1, 2005 The low-temperature martensitic phase transformation in FeriNija was studied by x-ray diffractometry, differential scanning calorimetry and inelastic neutron scattering. From inelastic neutron scattering spectra, the phonon density of states of the high-te ... Cite

Vibrational entropy of the γ- Martensitic transformation in Fe 71Ni29

Journal Article Philosophical Magazine · October 21, 2005 The low-temperature martensitic phase transformation in Fe71Ni29 was studied by X-ray diffractometry, differential scanning calorimetry (DSC) and inelastic neutron scattering. From inelastic neutron scattering spectra, the phonon density of states of the h ... Full text Cite

Vibrational entropy of spinodal decomposition in FeCr

Journal Article Physical Review B Condensed Matter and Materials Physics · July 1, 2005 Inelastic neutron-scattering spectra were measured on stoichiometric Fe0.50 Cr0.50 prepared as a body-centered-cubic (bcc) solid solution, and after increasing amounts of chemical unmixing on the bcc lattice induced by annealing the solid solution at 773 K ... Full text Cite

Entropy of the gamma-alpha martensitic transformation in Fe71Ni29

Conference Solid-Solid Phase Transformations in Inorganic Material 2005, Vol 2 · January 1, 2005 Link to item Cite

Vibrations of micro-eV energies in nanocrystalline microstructures.

Journal Article Physical review letters · November 2004 Featured Publication The phonon density of states of nanocrystalline bcc Fe and nanocrystalline fcc Ni3Fe were measured by inelastic neutron scattering in two different ranges of energy. As has been reported previously, the nanocrystalline materials showed enhancements in thei ... Full text Cite

Negative entropy of mixing for vanadium-platinum solutions.

Journal Article Physical review letters · October 2004 Featured Publication The phonon densities of states for pure vanadium and the solid solutions V-6.25% Ni, Pd, Pt were determined from inelastic neutron scattering measurements. The solute atoms caused a large stiffening of the phonons, resulting in large, negative vibrational ... Full text Cite

Determination of the alloying content in the matrix of Zr alloys using synchrotron radiation microprobe X-ray fluorescence

Journal Article Journal of Nuclear Materials · September 15, 2003 The alloying element content in the α-Zr matrix of Zr alloys was studied using synchrotron radiation microprobe X-ray fluorescence, coupled with Monte Carlo simulation of the fluorescence process for quantification of the concentrations. The agreement betw ... Full text Cite

Synchrotron radiation study of secondphase particles and alloying elements in zirconium alloys

Conference ASTM Special Technical Publication · January 1, 2002 We have conducted a study of second phase particles and matrix alloying element concentrations in zirconium alloys using synchrotron radiation from the Advanced Photon Source (APS) at Argonne National Laboratory. The high flux of synchrotron radiation deli ... Full text Cite

Observation of second-phase particles in bulk zirconium alloys using synchrotron radiation

Journal Article Journal of Nuclear Materials · April 1, 2001 To further advance the mechanistic understanding of microstructural evolution in zirconium alloys for high burnup applications, it is important to obtain a quantitative measurement of the volume fractions of second-phase precipitates present in the bulk al ... Full text Cite