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DOE OSTI2020

Materials Data on Sr(CaSi3)2 by Materials Project

Sr(CaSi3)2 is High Pressure (4-7GPa) Tellurium-derived structured and crystallizes in the monoclinic C2/m space group. The structure is three-dimensional. Sr is bonded to six Si atoms to form distorted SrSi6 octahedra that share edges with two equivalent SrSi6 octahedra and edges with four equivalent CaSi6 octahedra. All Sr–Si bond lengths are 3.13 Å. Ca is bonded to six Si atoms to form distorted CaSi6 octahedra that share edges with two equivalent SrSi6 octahedra and edges with four equivalent CaSi6 octahedra. There are a spread of Ca–Si bond distances ranging from 3.04–3.10 Å. There are three inequivalent Si sites. In the first Si site, Si is bonded in a 6-coordinate geometry to two equivalent Sr, one Ca, and three Si atoms. There are two shorter (2.41 Å) and one longer (2.42 Å) Si–Si bond lengths. In the second Si site, Si is bonded in a 6-coordinate geometry to three equivalent Ca and three Si atoms. The Si–Si bond length is 2.40 Å. In the third Si site, Si is bonded in a 6-coordinate geometry to one Sr, two equivalent Ca, and three Si atoms. Both Si–Si bond lengths are 2.44 Å.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on Te by Materials Project

Te is High Pressure (4-7GPa) Tellurium structured and crystallizes in the orthorhombic P2_12_12 space group. The structure is one-dimensional and consists of two Te ribbons oriented in the (1, 0, 0) direction. Te is bonded in a T-shaped geometry to three equivalent Te atoms. There are one shorter (2.81 Å) and two longer (3.11 Å) Te–Te bond lengths.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on GaAu(I4N)2 by Materials Project

AuI4GaI4N2 is High Pressure (4-7GPa) Tellurium-derived structured and crystallizes in the orthorhombic Pnma space group. The structure is zero-dimensional and consists of eight ammonia molecules, four AuI4 clusters, and four GaI4 clusters. In each AuI4 cluster, Au3+ is bonded in a square co-planar geometry to four I1- atoms. There are two shorter (2.66 Å) and two longer (2.67 Å) Au–I bond lengths. There are two inequivalent I1- sites. In the first I1- site, I1- is bonded in a distorted single-bond geometry to one Au3+ atom. In the second I1- site, I1- is bonded in a distorted single-bond geometry to one Au3+ atom. In each GaI4 cluster, Ga3+ is bonded in a tetrahedral geometry to four I1- atoms. There are two shorter (2.58 Å) and two longer (2.60 Å) Ga–I bond lengths. There are three inequivalent I1- sites. In the first I1- site, I1- is bonded in a single-bond geometry to one Ga3+ atom. In the second I1- site, I1- is bonded in a single-bond geometry to one Ga3+ atom. In the third I1- site, I1- is bonded in a single-bond geometry to one Ga3+ atom.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on Sr2N by Materials Project

Sr2N is High Pressure (4-7GPa) Tellurium-derived structured and crystallizes in the monoclinic C2/m space group. The structure is zero-dimensional and consists of two ammonia molecules and two Sr clusters. In each Sr cluster, Sr is bonded in a single-bond geometry to one Sr atom. The Sr–Sr bond length is 4.45 Å.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on K2ThO3 by Materials Project

K2ThO3 is High Pressure (4-7GPa) Tellurium-derived structured and crystallizes in the monoclinic C2/c space group. The structure is three-dimensional. there are three inequivalent K1+ sites. In the first K1+ site, K1+ is bonded to six O2- atoms to form distorted KO6 octahedra that share corners with two equivalent KO6 octahedra, corners with four ThO6 octahedra, edges with four ThO6 octahedra, and edges with eight KO6 octahedra. The corner-sharing octahedra tilt angles range from 16–19°. There are a spread of K–O bond distances ranging from 2.70–3.06 Å. In the second K1+ site, K1+ is bonded to six O2- atoms to form distorted KO6 octahedra that share corners with six KO6 octahedra, edges with six KO6 octahedra, and edges with six ThO6 octahedra. The corner-sharing octahedra tilt angles range from 19–20°. All K–O bond lengths are 2.77 Å. In the third K1+ site, K1+ is bonded to six O2- atoms to form distorted KO6 octahedra that share corners with two equivalent KO6 octahedra, corners with four ThO6 octahedra, edges with four ThO6 octahedra, and edges with eight KO6 octahedra. The corner-sharing octahedra tilt angles range from 15–20°. There are a spread of K–O bond distances ranging from 2.66–3.03 Å. There are two inequivalent Th4+ sites. In the first Th4+ site, Th4+ is bonded to six O2- atoms to form ThO6 octahedra that share corners with six KO6 octahedra, edges with three equivalent ThO6 octahedra, and edges with nine KO6 octahedra. The corner-sharing octahedra tilt angles range from 15–16°. There are four shorter (2.35 Å) and two longer (2.37 Å) Th–O bond lengths. In the second Th4+ site, Th4+ is bonded to six O2- atoms to form ThO6 octahedra that share corners with six KO6 octahedra, edges with three equivalent ThO6 octahedra, and edges with nine KO6 octahedra. The corner-sharing octahedra tilt angles range from 15–16°. There are two shorter (2.35 Å) and four longer (2.36 Å) Th–O bond lengths. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a 6-coordinate geometry to four K1+ and two Th4+ atoms. In the second O2- site, O2- is bonded in a 6-coordinate geometry to four K1+ and two Th4+ atoms. In the third O2- site, O2- is bonded to four K1+ and two Th4+ atoms to form a mixture of distorted corner and edge-sharing OK4Th2 octahedra. The corner-sharing octahedra tilt angles range from 0–14°.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on SbS4N3 by Materials Project

SbN3S4 is High Pressure (4-7GPa) Tellurium-like structured and crystallizes in the triclinic P1 space group. The structure is zero-dimensional and consists of one SbN3S4 cluster. Sb3+ is bonded in a 2-coordinate geometry to two S2- atoms. There are one shorter (2.54 Å) and one longer (2.71 Å) Sb–S bond lengths. There are three inequivalent N+1.67+ sites. In the first N+1.67+ site, N+1.67+ is bonded in a bent 120 degrees geometry to two S2- atoms. There is one shorter (1.61 Å) and one longer (1.70 Å) N–S bond length. In the second N+1.67+ site, N+1.67+ is bonded in a single-bond geometry to one S2- atom. The N–S bond length is 1.58 Å. In the third N+1.67+ site, N+1.67+ is bonded in a single-bond geometry to one S2- atom. The N–S bond length is 1.49 Å. There are four inequivalent S2- sites. In the first S2- site, S2- is bonded in a bent 120 degrees geometry to two N+1.67+ atoms. In the second S2- site, S2- is bonded in a 2-coordinate geometry to one Sb3+ and one S2- atom. The S–S bond length is 2.04 Å. In the third S2- site, S2- is bonded in a distorted water-like geometry to one Sb3+ and one N+1.67+ atom. In the fourth S2- site, S2- is bonded in a distorted single-bond geometry to one N+1.67+ and one S2- atom.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on MnFeSeS by Materials Project

MnFeSeS is High Pressure (4-7GPa) Tellurium-derived structured and crystallizes in the trigonal R3m space group. The structure is three-dimensional. Mn2+ is bonded in a 6-coordinate geometry to three equivalent Se2- and three equivalent S2- atoms. All Mn–Se bond lengths are 2.71 Å. All Mn–S bond lengths are 2.17 Å. Fe2+ is bonded in a 6-coordinate geometry to three equivalent Se2- and three equivalent S2- atoms. All Fe–Se bond lengths are 2.72 Å. All Fe–S bond lengths are 2.19 Å. Se2- is bonded to three equivalent Mn2+ and three equivalent Fe2+ atoms to form distorted edge-sharing SeMn3Fe3 octahedra. S2- is bonded in a 6-coordinate geometry to three equivalent Mn2+ and three equivalent Fe2+ atoms.

36 MATERIALS SCIENCE↗

DOE OSTI2022

Design of a neutral thermal scattering (NeTS) module for hydrogen in light water

The accurate representation of thermal scattering law (TSL) data is integral to the design and characterization of many modern nuclear systems, particularly those using light water as a moderator/coolant. As a material-dependent distribution over energy-momentum phase space, the TSL may exhibit a variety of unique and relevant conditional (e.g., temperature, pressure) and compositional (e.g., porosity, stoichiometry, radiation damage) dependencies. Currently, there are various approaches to incorporate temperature dependence, which is especially important in coupled neutronic-thermal hydraulic simulations. In each approach, there is an inherent tradeoff between memory consumption and accuracy. Some techniques require tens to hundreds of MBs or more, while others fail to reproduce the underlying data to within 10% error over the considered input domain, despite having a reduced storage burden. This work aims to address both sides of the tradeoff simultaneously by implementing a novel deep learning (DL) approach to TSL representation. The neural thermal scattering (NeTS) concept, which is amenable to an arbitrary number of dependencies, is demonstrated via the inclusion of temperature dependence into a highly compact, highly accurate functional form of the multi- variate TSL (i.e., S(α, β, T)) for hydrogen in light water. Resulting storage requirements are on the order of 100 kB, and median and maximum percent deviations are on the order of 0.1% and 1%, respectively. These measures represent a step improvement over previous techniques. Notably, the developed neural network and feature methodology build on those employed in prior work on beryllium oxide. (authors)

22 GENERAL STUDIES OF NUCLEAR REACTORS↗

DOE OSTI2020

ARES. III. Unveiling the Two Faces of KELT-7 b with HST WFC3

We present the analysis of the hot-Jupiter KELT-7 b using transmission and emission spectroscopy from the Hubble Space Telescope, both taken with the Wide Field Camera 3. Our study uncovers a rich transmission spectrum that is consistent with a cloud-free atmosphere and suggests the presence of H{sub 2}O and H{sup −}. In contrast, the extracted emission spectrum does not contain strong absorption features and, although it is not consistent with a simple blackbody, it can be explained by a varying temperature–pressure profile, collision induced absorption, and H{sup −}. KELT-7 b had also been studied with other space-based instruments and we explore the effects of introducing these additional data sets. Further observations with Hubble, or the next generation of space-based telescopes, are needed to allow for the optical opacity source in transmission to be confirmed and for molecular features to be disentangled in emission.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2022

Improvement of two-phase closure models in CTF using Bayesian inference

Under the Consortium for Advanced Simulation of Light Water Reactors (CASL) program, extensive capabilities have been developed in CTF to analyze light-water reactors (LWRs) for normal operating conditions, departure from nucleate boiling (DNB), and system transients. However, further improvements are required in the modeling and simulation of boiling water reactors (BWRs), which is a focus of the Nuclear Energy Advanced Modeling and Simulation (NEAMS) program. In this work, CTF validation results were used to optimize selected modeling coefficients by calibrating to experimental data using a Bayesian inference approach. Here, calibration studies were conducted to improve (vapor) void fraction prediction without worsening the two-phase pressure drop prediction, as well as to improve the two-phase pressure drop prediction. Calibration was performed for interfacial drag and wall shear models. Surrogates were developed to alleviate the computational expense required for sampling the parameter space using Markov chain Monte Carlo (MCMC). An assessment performed with calibrated models demonstrated an improvement of CTF in its prediction of key parameters such as void fraction and two-phase pressure drop.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗

DOE OSTI2025

Polymorphism and Negative Linear Compressibility in Pyrazine-d4

Pyrazine (1,4-diazine) is a widely used linker in coordination polymers, molecular magnets, and metal–organic frameworks, yet its solid-state polymorphism is controlled by weak C–H···N interactions. Using variable-temperature and high-pressure neutron diffraction, a previously unrecognized low-temperature transition to phase IV is identified, showing that the form stabilized under pressure can also be accessed below ∼90 K at ambient pressure in the perdeuterated compound. The transition from phase III → IV involves a symmetry-breaking lattice distortion driven by the reorganization of C–H···N hydrogen bonds, accompanied by negative linear compressibility, which is primarily accommodated through the reduction in void-space within the structure. Structural analysis reveals that while the overall monoclinic framework of phase IV is preserved under both temperature and pressure routes, the evolution of hydrogen-bonded network is distinct depending on the pathway taken. These results establish pyrazine as a model molecular solid for studying pressure–temperature polymorphism and demonstrate how weak directional interactions can produce anomalous mechanical responses in organic crystals.

Ridley, Christopher J. [Oak Ridge National Laborat↗

DOE OSTI2020

Room-temperature skyrmion phase in bulk Cu 2 OSeO 3 under high pressures

Significance Skyrmion materials hold great promise for information technology due to the extremely low current needed to modify the spin configurations and the small size of magnetic domains. To facilitate their application, one great challenge is to break the magnetic field–temperature phase space restriction for the skyrmion state. We found that the temperature region for the skyrmion phase in bulk Cu 2 OSeO 3 can be greatly enhanced under physical pressure, making applications more practical by the use of strained heterostructures, for example. The observation of additional structures suggests that the skyrmion state may be insensitive to the underlying crystal structure. This work will stimulate research on finding skyrmion materials with different crystal structures and retaining the room-temperature skyrmion state at ambient condition.

Deng, Liangzi↗

DOE OSTI2021

Detection of Aerosols at Microbar Pressures in an Exoplanet Atmosphere

The formation of hazes at microbar pressures has been explored by theoretical models of exoplanet atmospheres to explain Rayleigh scattering and/or featureless transmission spectra; however observational evidence of aerosols in the low-pressure formation environments has proved elusive. Here, we show direct evidence of aerosols existing at ~1 microbar pressures in the atmosphere of the warm sub-Saturn WASP-69b using observations taken with the Space Telescope Imaging Spectrograph and Wide Field Camera 3 instruments on the Hubble Space Telescope. The transmission spectrum shows a wavelength-dependent slope induced by aerosol scattering that covers 11 scale heights of spectral modulation. Drawing on the extensive studies of haze in our solar system, we model the transmission spectrum based on a scaled version of Jupiter’s haze-density profile to show that the WASP-69b transmission spectrum can be produced by scattering from an approximately constant density of particles extending throughout the atmospheric column from 40 millibar to microbar pressures. These results are consistent with theoretical expectations based on microphysics of the aerosol particles that have suggested haze can exist at microbar pressures in exoplanet atmospheres.

47 OTHER INSTRUMENTATION↗

DOE OSTI2022

Localized growth and remodelling drives spongy mesophyll morphogenesis

The spongy mesophyll is a complex, porous tissue found in plant leaves that enables carbon capture and provides mechanical stability. Unlike many other biological tissues, which remain confluent throughout development, the spongy mesophyll must develop from an initially confluent tissue into a tortuous network of cells with a large proportion of intercellular airspace. How the airspace in the spongy mesophyll develops while the tissue remains mechanically stable is unknown. Here, we use computer simulations of deformable polygons to develop a purely mechanical model for the development of the spongy mesophyll tissue. By stipulating that cell wall growth and remodelling occurs only near void space, our computational model is able to recapitulate spongy mesophyll development observed in Arabidopsis thaliana leaves. We find that robust generation of pore space in the spongy mesophyll requires a balance of cell growth, adhesion, stiffness and tissue pressure to ensure cell networks become porous yet maintain mechanical stability. The success of this mechanical model of morphogenesis suggests that simple physical principles can coordinate and drive the development of complex plant tissues like the spongy mesophyll.

Science & Technology - Other Topics↗

DOE OSTI2023

Orbital evolution of satellite galaxies in self-interacting dark matter models

Dark matter self-interactions can leave distinctive signatures on the properties of satellite galaxies around Milky Way–like hosts through their impact on tidal stripping, ram pressure, and gravothermal collapse. We delineate the regions of self-interacting dark matter parameter space—specified by interaction cross section and a velocity scale—where each of these effects dominates and show how the relative mass loss depends on the satellite’s initial mass, density profile, and orbit. We obtain novel, conservative constraints in this parameter space using Milky Way satellite galaxies with notably high central densities and small pericenter distances. Furthermore, our results for self-interacting dark matter models, in combination with constraints from clusters of galaxies, favor either velocity-dependent cross sections that lead to gravothermal core collapse in the densest satellites or small cross sections which more closely resemble cold and collisionless dark matter.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2020

Infrared Optical Constants from Pressed Pellets of Powders: I. Improved n and k Values of (NH4)(2)SO(4)from Single-Angle Reflectance

In combination with other parameters, the real, n(?), and imaginary, k(?), components of the complex refractive index, = n + ik, can be used to simulate the optical properties of a material in different forms, e.g. its infrared spectra. But obtaining reliable values of the optical constants n/k for solid materials is challenging due to the lack of optical quality specimens, usually crystals, large enough to measure. An alternative to crystals is to press the powder into a uniform disk. We have produced pellets from ammonium sulfate, (NH4)2SO4, powder and derived the pellets’ n and k values via single-angle reflectance using a specular reflectance device in combination with a Fourier transform infrared spectrometer. The single-angle technique measures amplitude of light reflected from the material as a function of wavelength over a wide spectral domain; the optical constants are determined from the reflectance data using the Kramers-Kronig relationship. We investigate several parameters associated with the pellets and pellet formation and their effects upon delivering the most reliable n/k values. Parameters studied include pellet diameter, mass and density (void space), drying, grinding, sieving and particle size in the pellet formation, as well as pressing pressure and duration. Of these parameters, using size-selected mixtures of dried, small (< 100 µm) particles and pressing at = 10 tons for at least 30 minutes were found key to forming highly reflective samples. Comparison to two sets of previous literature n(?) and k(?) values obtained from crystalline (NH4)2SO4 both as crystal reflectance as well as extinction spectra of aerosols measured in a flow tube show reasonable agreement, but suggests the present values, as confirmed from two independent techniques, represent a substantial improvement for n/k values for (NH4)2SO4, also demonstrating promise to measure the optical constants of other materials.

Optical constants, index of refraction, single-ang↗

DOE OSTI2020

Materials Data on Si2H6O by Materials Project

Si2H6O is High Pressure (4-7GPa) Tellurium structured and crystallizes in the orthorhombic P2_12_12_1 space group. The structure is zero-dimensional and consists of four disiloxane molecules. there are two inequivalent Si sites. In the first Si site, Si is bonded to three H+0.33+ and one O2- atom to form corner-sharing SiH3O tetrahedra. All Si–H bond lengths are 1.49 Å. The Si–O bond length is 1.66 Å. In the second Si site, Si is bonded to three H+0.33+ and one O2- atom to form corner-sharing SiH3O tetrahedra. There is two shorter (1.49 Å) and one longer (1.50 Å) Si–H bond length. The Si–O bond length is 1.65 Å. There are six inequivalent H+0.33+ sites. In the first H+0.33+ site, H+0.33+ is bonded in a single-bond geometry to one Si atom. In the second H+0.33+ site, H+0.33+ is bonded in a single-bond geometry to one Si atom. In the third H+0.33+ site, H+0.33+ is bonded in a single-bond geometry to one Si atom. In the fourth H+0.33+ site, H+0.33+ is bonded in a single-bond geometry to one Si atom. In the fifth H+0.33+ site, H+0.33+ is bonded in a single-bond geometry to one Si atom. In the sixth H+0.33+ site, H+0.33+ is bonded in a single-bond geometry to one Si atom. O2- is bonded in a bent 150 degrees geometry to two Si atoms.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on P4SeO6 by Materials Project

P4SeO6 is High Pressure (4-7GPa) Tellurium-like structured and crystallizes in the monoclinic P2_1/c space group. The structure is zero-dimensional and consists of four P4SeO6 clusters. there are four inequivalent P+3.50+ sites. In the first P+3.50+ site, P+3.50+ is bonded in a distorted trigonal non-coplanar geometry to three O2- atoms. There are a spread of P–O bond distances ranging from 1.65–1.69 Å. In the second P+3.50+ site, P+3.50+ is bonded in a distorted trigonal non-coplanar geometry to three O2- atoms. There are a spread of P–O bond distances ranging from 1.65–1.70 Å. In the third P+3.50+ site, P+3.50+ is bonded in a distorted trigonal non-coplanar geometry to three O2- atoms. There is two shorter (1.67 Å) and one longer (1.70 Å) P–O bond length. In the fourth P+3.50+ site, P+3.50+ is bonded in a distorted tetrahedral geometry to one Se2- and three O2- atoms. The P–Se bond length is 2.06 Å. There is one shorter (1.62 Å) and two longer (1.63 Å) P–O bond length. Se2- is bonded in a single-bond geometry to one P+3.50+ atom. There are six inequivalent O2- sites. In the first O2- site, O2- is bonded in a bent 120 degrees geometry to two P+3.50+ atoms. In the second O2- site, O2- is bonded in a bent 120 degrees geometry to two P+3.50+ atoms. In the third O2- site, O2- is bonded in a bent 120 degrees geometry to two P+3.50+ atoms. In the fourth O2- site, O2- is bonded in a bent 120 degrees geometry to two P+3.50+ atoms. In the fifth O2- site, O2- is bonded in a bent 120 degrees geometry to two P+3.50+ atoms. In the sixth O2- site, O2- is bonded in a bent 120 degrees geometry to two P+3.50+ atoms.

36 MATERIALS SCIENCE↗