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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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$\mathrm{Perturbo}$: A software package for ab initio electron–phonon interactions, charge transport and ultrafast dynamics

We report Perturbo is a software package for first-principles calculations of charge transport and ultrafast carrier dynamics in materials. The current version focuses on electron–phonon interactions and can compute phonon-limited transport properties such as the conductivity, carrier mobility and Seebeck coefficient. It can also simulate the ultrafast nonequilibrium electron dynamics in the presence of electron–phonon scattering. Perturbo uses results from density functional theory and density functional perturbation theory calculations as input, and employs Wannier interpolation to reduce the computational cost. It supports norm-conserving and ultrasoft pseudopotentials, spin–orbit coupling, and polar electron–phonon interactions for bulk and 2D materials. Hybrid MPI plus OpenMP parallelization is implemented to enable efficient calculations on large systems (up to at least 50 atoms) using high-performance computing. Taken together, Perturbo provides efficient and broadly applicable ab initio tools to investigate electron–phonon interactions and carrier dynamics quantitatively in metals, semiconductors, insulators, and 2D materials.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

Quantum control of Hubbard excitons

Quantum control of the many-body wavefunction is a central challenge in quantum materials research, as it could yield a precise control knob to manipulate emergent phenomena. Floquet engineering, the coherent dressing of quantum states with periodic non-resonant optical fields, has become an important strategy for quantum control. Most applications to solid-state systems have targeted weakly interacting or single-ion states, leaving the manipulation of many-body wavefunctions largely unexplored. Here, in this work, we use Floquet engineering to achieve quantum control of a strongly correlated Hubbard exciton in the one-dimensional Mott insulator Sr 2 CuO 3 . A nonresonant midinfrared optical field coherently dresses the exciton wavefunction, driving its rotation between bright and dark states. We use resonant third-harmonic generation to quantify ultrafast π/2 rotations on the Bloch sphere spanned by these exciton states. Our work advances the quest towards programmable control of correlated states and exciton-based quantum sensing.

36 MATERIALS SCIENCE↗

Combined experimental-theoretical study of electron mobility-limiting mechanisms in SrSnO 3

The discovery and development of ultra-wide bandgap (UWBG) semiconductors is crucial to accelerate the adoption of renewable power sources. This necessitates an UWBG semiconductor that exhibits robust doping with high carrier mobility over a wide range of carrier concentrations. Here we demonstrate that epitaxial thin films of the perovskite oxide Nd x Sr 1 – x SnO 3 (SSO) do exactly this. Nd is used as a donor to successfully modulate the carrier concentration over nearly two orders of magnitude, from 3.7 × 10 18 cm –3 to 2.0 × 10 20 cm –3 . Despite being grown on lattice-mismatched substrates and thus having relatively high structural disorder, SSO films exhibited the highest room-temperature mobility, ~70 cm 2 V –1 s –1 , among all known UWBG semiconductors in the range of carrier concentrations studied. The phonon-limited mobility is calculated from first principles and supplemented with a model to treat ionized impurity and Kondo scattering. This produces excellent agreement with experiment over a wide range of temperatures and carrier concentrations, and predicts the room-temperature phonon-limited mobility to be 76–99 cm 2 V –1 s –1 depending on carrier concentration. This work establishes a perovskite oxide as an emerging UWBG semiconductor candidate with potential for applications in power electronics

36 MATERIALS SCIENCE↗

Modeling the co-assembly of binary nanoparticles

Abstract In this work, we present a binary assembly model that can predict the co-assembly structure and spatial frequency spectra of monodispersed nanoparticles with two different particle sizes. The approach relies on an iterative algorithm based on geometric constraints, which can simulate the assembly patterns of particles with two distinct diameters, size distributions, and at various mixture ratios on a planar surface. The two-dimensional spatial-frequency spectra of the modeled assembles can be analyzed using fast Fourier transform analysis to examine their frequency content. The simulated co-assembly structures and spectra are compared with assembled nanoparticles fabricated using transfer coating method are in qualitative agreement with the experimental results. The co-assembly model can also be used to predict the peak spatial frequency and the full-width at half-maximum bandwidth, which can lead to the design of the structure spectra by selection of different monodispersed particles. This work can find applications in fabrication of non-periodic nanostructures for functional surfaces, light extraction structures, and broadband nanophotonics.

Mohanty, Saurav (ORCID:0009000302592855)↗

First-principles ionized-impurity scattering and charge transport in doped materials

Scattering of carriers with ionized impurities governs charge transport in doped semiconductors. However, electron interactions with ionized impurities cannot be fully described with quantitative first-principles calculations, so their understanding relies primarily on simplified models. Here we show an ab initio approach to compute the interactions between electrons and ionized impurities or other charged defects. It includes the short- and long-range electron-defect (e-d) interactions on equal footing and allows for efficient interpolation of the e-d matrix elements. Here we combine the e-d and electron-phonon interactions in the Boltzmann transport equation to compute the carrier mobilities in doped silicon over a wide range of temperature and doping concentrations, seamlessly spanning the defect- and phonon-limited transport regimes. The individual contributions of the defect- and phonon-scattering mechanisms to the carrier relaxation times and mean-free paths are analyzed. Our method provides a powerful tool to study electronic interactions in doped materials. It broadens the scope of first-principles transport calculations, enabling studies of a wide range of doped semiconductors and oxides with application to electronics, energy, and quantum technologies.

36 MATERIALS SCIENCE↗

Recovering cavity effects in corrugated organic light emitting diodes

Cavity effects play an important role in determining the out-coupling efficiency of an OLED. By fabricating OLEDs on corrugated substrates, the waveguide and SPP modes can be extracted by diffraction. However, corrugation does not always lead to an enhancement in out-coupling efficiency due to the reduction of the electrode reflectance and hence the cavity effects. Based on the results of our rigorous couple-wave analysis (RCWA) simulation, we found that the cavity effects can be partially recovered using a low index Teflon layer inserted between the ITO anode and the substrate due to the enhancement of the reflectance of the corrugated electrodes. To verify the simulation results, we fabricated corrugated OLEDs having a low-index Teflon interlayer with an EQE of 36%, which is 29% higher than an optimized planar OLED. By experimentally measuring the OLED air mode dispersion, we confirm the cavity emission of a corrugated OLED is enhanced by the low index layer.

36 MATERIALS SCIENCE↗

Materials Data on TeI by Materials Project

TeI crystallizes in the triclinic P-1 space group. The structure is one-dimensional and consists of two TeI ribbons oriented in the (1, 0, 0) direction. there are four inequivalent Te sites. In the first Te site, Te is bonded in a distorted single-bond geometry to two Te and one I atom. There are one shorter (2.87 Å) and one longer (2.89 Å) Te–Te bond lengths. The Te–I bond length is 2.78 Å. In the second Te site, Te is bonded in a rectangular see-saw-like geometry to two Te and two I atoms. The Te–Te bond length is 2.87 Å. There are one shorter (3.23 Å) and one longer (3.26 Å) Te–I bond lengths. In the third Te site, Te is bonded in a distorted single-bond geometry to two Te and one I atom. The Te–Te bond length is 2.89 Å. The Te–I bond length is 2.78 Å. In the fourth Te site, Te is bonded in a rectangular see-saw-like geometry to two Te and two I atoms. There are one shorter (3.18 Å) and one longer (3.20 Å) Te–I bond lengths. There are four inequivalent I sites. In the first I site, I is bonded in a single-bond geometry to one Te atom. In the second I site, I is bonded in a single-bond geometry to one Te atom. In the third I site, I is bonded in an L-shaped geometry to two Te atoms. In the fourth I site, I is bonded in an L-shaped geometry to two Te atoms.

36 MATERIALS SCIENCE↗

Materials Data on Te2I by Materials Project

TeITe crystallizes in the orthorhombic Pnma space group. The structure is one-dimensional and consists of four TeITe ribbons oriented in the (1, 0, 0) direction. there are four inequivalent Te sites. In the first Te site, Te is bonded in a rectangular see-saw-like geometry to two equivalent Te and two equivalent I atoms. Both Te–Te bond lengths are 2.92 Å. Both Te–I bond lengths are 3.09 Å. In the second Te site, Te is bonded in a distorted trigonal non-coplanar geometry to three Te atoms. The Te–Te bond length is 2.96 Å. In the third Te site, Te is bonded in a distorted T-shaped geometry to three Te atoms. Both Te–Te bond lengths are 2.90 Å. In the fourth Te site, Te is bonded in a square co-planar geometry to two equivalent Te and two equivalent I atoms. Both Te–I bond lengths are 3.14 Å. There are two inequivalent I sites. In the first I site, I is bonded in an L-shaped geometry to two equivalent Te atoms. In the second I site, I is bonded in an L-shaped geometry to two equivalent Te atoms.

36 MATERIALS SCIENCE↗

Materials Data on TeI4 by Materials Project

TeI4 crystallizes in the tetragonal I4_1/amd space group. The structure is zero-dimensional and consists of four TeI4 clusters. Te4+ is bonded to six I1- atoms to form edge-sharing TeI6 octahedra. There are a spread of Te–I bond distances ranging from 2.80–3.29 Å. There are three inequivalent I1- sites. In the first I1- site, I1- is bonded in a single-bond geometry to one Te4+ atom. In the second I1- site, I1- is bonded in a single-bond geometry to one Te4+ atom. In the third I1- site, I1- is bonded in a 3-coordinate geometry to three equivalent Te4+ atoms.

36 MATERIALS SCIENCE↗

Materials Data on TeI by Materials Project

TeI crystallizes in the triclinic P-1 space group. The structure is one-dimensional and consists of one TeI ribbon oriented in the (1, 0, 0) direction. there are two inequivalent Te sites. In the first Te site, Te is bonded in a 2-coordinate geometry to three equivalent Te and two equivalent I atoms. There are a spread of Te–Te bond distances ranging from 2.96–3.38 Å. There are one shorter (3.12 Å) and one longer (3.13 Å) Te–I bond lengths. In the second Te site, Te is bonded in a distorted single-bond geometry to three equivalent Te and one I atom. The Te–I bond length is 2.80 Å. There are two inequivalent I sites. In the first I site, I is bonded in an L-shaped geometry to two equivalent Te atoms. In the second I site, I is bonded in a single-bond geometry to one Te atom.

36 MATERIALS SCIENCE↗

Materials Data on TeI2 by Materials Project

TeI2 crystallizes in the tetragonal P4_2/mnm space group. The structure is one-dimensional and consists of two TeI2 ribbons oriented in the (0, 0, 1) direction. Te is bonded in a square co-planar geometry to four equivalent I atoms. All Te–I bond lengths are 3.00 Å. I is bonded in an L-shaped geometry to two equivalent Te atoms.

36 MATERIALS SCIENCE↗