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All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on CsMg30SiO32 by Materials Project

CsMg30SiO32 is Caswellsilverite-derived structured and crystallizes in the tetragonal P4/mmm space group. The structure is three-dimensional. Cs is bonded to six O atoms to form CsO6 octahedra that share corners with six MgO6 octahedra and edges with twelve MgO6 octahedra. The corner-sharing octahedral tilt angles are 0°. There are two shorter (2.48 Å) and four longer (2.49 Å) Cs–O bond lengths. There are eight inequivalent Mg sites. In the first Mg site, Mg is bonded to six O atoms to form distorted MgO6 octahedra that share corners with two equivalent CsO6 octahedra, corners with two equivalent MgO6 octahedra, corners with two equivalent SiO6 octahedra, and edges with twelve MgO6 octahedra. The corner-sharing octahedral tilt angles are 0°. There are a spread of Mg–O bond distances ranging from 1.85–2.48 Å. In the second Mg site, Mg is bonded to six O atoms to form MgO6 octahedra that share corners with two equivalent SiO6 octahedra, corners with four equivalent MgO6 octahedra, and edges with twelve MgO6 octahedra. The corner-sharing octahedral tilt angles are 0°. There are four shorter (2.12 Å) and two longer (2.37 Å) Mg–O bond lengths. In the third Mg site, Mg is bonded to six O atoms to form a mixture of edge and corner-sharing MgO6 octahedra. The corner-sharing octahedral tilt angles are 0°. There are a spread of Mg–O bond distances ranging from 2.10–2.22 Å. In the fourth Mg site, Mg is bonded to six O atoms to form MgO6 octahedra that share corners with two equivalent CsO6 octahedra, corners with four equivalent MgO6 octahedra, and edges with twelve MgO6 octahedra. The corner-sharing octahedral tilt angles are 0°. There are two shorter (1.87 Å) and four longer (2.24 Å) Mg–O bond lengths. In the fifth Mg site, Mg is bonded to six O atoms to form MgO6 octahedra that share corners with six MgO6 octahedra, an edgeedge with one CsO6 octahedra, an edgeedge with one SiO6 octahedra, and edges with ten MgO6 octahedra. The corner-sharing octahedra tilt angles range from 0–16°. There are four shorter (2.17 Å) and two longer (2.21 Å) Mg–O bond lengths. In the sixth Mg site, Mg is bonded to six O atoms to form a mixture of edge and corner-sharing MgO6 octahedra. The corner-sharing octahedra tilt angles range from 0–4°. There are a spread of Mg–O bond distances ranging from 2.16–2.18 Å. In the seventh Mg site, Mg is bonded to six O atoms to form MgO6 octahedra that share corners with six MgO6 octahedra, an edgeedge with one SiO6 octahedra, and edges with eleven MgO6 octahedra. The corner-sharing octahedra tilt angles range from 1–16°. There are a spread of Mg–O bond distances ranging from 2.15–2.23 Å. In the eighth Mg site, Mg is bonded to six O atoms to form MgO6 octahedra that share corners with six MgO6 octahedra, an edgeedge with one CsO6 octahedra, and edges with eleven MgO6 octahedra. The corner-sharing octahedra tilt angles range from 0–15°. There are a spread of Mg–O bond distances ranging from 2.12–2.25 Å. Si is bonded to six O atoms to form SiO6 octahedra that share corners with six MgO6 octahedra and edges with twelve MgO6 octahedra. The corner-sharing octahedral tilt angles are 0°. There is four shorter (1.86 Å) and two longer (1.98 Å) Si–O bond length. There are twelve inequivalent O sites. In the first O site, O is bonded to five Mg and one Si atom to form a mixture of edge and corner-sharing OMg5Si octahedra. The corner-sharing octahedra tilt angles range from 0–5°. In the second O site, O is bonded to six Mg atoms to form OMg6 octahedra that share corners with six OMg5Si octahedra and edges with twelve OMg6 octahedra. The corner-sharing octahedra tilt angles range from 0–6°. In the third O site, O is bonded to one Cs and five Mg atoms to form a mixture of distorted edge and corner-sharing OCsMg5 octahedra. The corner-sharing octahedra tilt angles range from 0–6°. In the fourth O site, O is bonded to six Mg atoms to form OMg6 octahedra that share corners with six equivalent OMg6 octahedra and edges with twelve OMg5Si octahedra. The corner-sharing octahedra tilt angles range from 1–4°. In the fifth O site, O is bonded to five Mg and one Si atom to form a mixture of distorted edge and corner-sharing OMg5Si octahedra. The corner-sharing octahedra tilt angles range from 0–15°. In the sixth O site, O is bonded to one Cs and five Mg atoms to form distorted OCsMg5 octahedra that share corners with six OMg5Si octahedra and edges with twelve OMg6 octahedra. The corner-sharing octahedra tilt angles range from 0–15°. The O–Mg bond length is 1.85 Å. In the seventh O site, O is bonded to one Cs and five Mg atoms to form distorted OCsMg5 octahedra that share corners with six OMg5Si octahedra and edges with twelve OMg6 octahedra. The corner-sharing octahedra tilt angles range from 0–15°. There are a spread of O–Mg bond distances ranging from 1.85–2.25 Å. In the eighth O site, O is bonded to six Mg atoms to form a mixture of edge and corner-sharing OMg6 octahedra. The corner-sharing octahedra tilt angles range from 0–10°. In the ninth O site, O is bonded to six Mg atoms to form a mixture of edge and corner-sharing OMg6 octahedra. The corner-sharing octahedra tilt angles range from 0–10°. There are two shorter (2.15 Å) and two longer (2.17 Å) O–Mg bond lengths. In the tenth O site, O is bonded to six Mg atoms to form OMg6 octahedra that share corners with six OCsMg5 octahedra and edges with twelve OMg6 octahedra. The corner-sharing octahedra tilt angles range from 0–9°. In the eleventh O site, O is bonded to one Cs and five Mg atoms to form distorted OCsMg5 octahedra that share corners with six OMg5Si octahedra and edges with twelve OMg6 octahedra. The corner-sharing octahedra tilt angles range from 0–15°. Both O–Mg bond lengths are 2.25 Å. In the twelfth O site, O is bonded to one Cs and five Mg atoms to form distorted OCsMg5 octahedra that share corners with six OMg5Si octahedra and edges with twelve OMg6 octahedra. The corner-sharing octahedra tilt angles range from 0–15°. There are two shorter (2.21 Å) and two longer (2.25 Å) O–Mg bond lengths.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on CsMg6Ga by Materials Project

CsMg6Ga crystallizes in the orthorhombic Amm2 space group. The structure is three-dimensional. Cs is bonded in a 12-coordinate geometry to eight Mg and two equivalent Ga atoms. There are a spread of Cs–Mg bond distances ranging from 4.06–4.30 Å. Both Cs–Ga bond lengths are 4.07 Å. There are four inequivalent Mg sites. In the first Mg site, Mg is bonded in a distorted single-bond geometry to one Cs, four Mg, and one Ga atom. There are two shorter (3.05 Å) and two longer (3.06 Å) Mg–Mg bond lengths. The Mg–Ga bond length is 2.80 Å. In the second Mg site, Mg is bonded in a 2-coordinate geometry to two equivalent Cs, two Mg, and two equivalent Ga atoms. There are one shorter (3.17 Å) and one longer (3.35 Å) Mg–Mg bond lengths. Both Mg–Ga bond lengths are 2.94 Å. In the third Mg site, Mg is bonded in a 10-coordinate geometry to two equivalent Cs and eight Mg atoms. Both Mg–Mg bond lengths are 3.15 Å. In the fourth Mg site, Mg is bonded in a 8-coordinate geometry to eight Mg atoms. Ga is bonded in a 8-coordinate geometry to two equivalent Cs and six Mg atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on CsNaMg6 by Materials Project

CsNaMg6 crystallizes in the orthorhombic Amm2 space group. The structure is three-dimensional. Cs is bonded to two equivalent Na and ten Mg atoms to form CsNa2Mg10 cuboctahedra that share corners with four equivalent NaCs2Mg10 cuboctahedra, corners with six equivalent CsNa2Mg10 cuboctahedra, edges with two equivalent NaCs2Mg10 cuboctahedra, faces with two equivalent CsNa2Mg10 cuboctahedra, and faces with two equivalent NaCs2Mg10 cuboctahedra. Both Cs–Na bond lengths are 3.40 Å. There are a spread of Cs–Mg bond distances ranging from 3.49–3.60 Å. Na is bonded to two equivalent Cs and ten Mg atoms to form NaCs2Mg10 cuboctahedra that share corners with four equivalent CsNa2Mg10 cuboctahedra, corners with six equivalent NaCs2Mg10 cuboctahedra, edges with two equivalent CsNa2Mg10 cuboctahedra, faces with two equivalent CsNa2Mg10 cuboctahedra, and faces with two equivalent NaCs2Mg10 cuboctahedra. There are a spread of Na–Mg bond distances ranging from 3.47–3.55 Å. There are four inequivalent Mg sites. In the first Mg site, Mg is bonded in a 12-coordinate geometry to two equivalent Cs, two equivalent Na, and eight Mg atoms. There are a spread of Mg–Mg bond distances ranging from 3.36–3.52 Å. In the second Mg site, Mg is bonded in a 11-coordinate geometry to two equivalent Cs, two equivalent Na, and three Mg atoms. The Mg–Mg bond length is 3.29 Å. In the third Mg site, Mg is bonded in a 2-coordinate geometry to two equivalent Na and six Mg atoms. Both Mg–Mg bond lengths are 3.40 Å. In the fourth Mg site, Mg is bonded in a 2-coordinate geometry to two equivalent Cs and eight Mg atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on CsMg6Si by Materials Project

CsMg6Si crystallizes in the orthorhombic Amm2 space group. The structure is three-dimensional. Cs is bonded in a 12-coordinate geometry to eight Mg and two equivalent Si atoms. There are a spread of Cs–Mg bond distances ranging from 3.66–3.84 Å. Both Cs–Si bond lengths are 3.72 Å. There are four inequivalent Mg sites. In the first Mg site, Mg is bonded in a distorted single-bond geometry to two equivalent Cs, five Mg, and one Si atom. There are a spread of Mg–Mg bond distances ranging from 2.94–3.23 Å. The Mg–Si bond length is 2.78 Å. In the second Mg site, Mg is bonded to six Mg atoms to form distorted face-sharing MgMg6 pentagonal pyramids. There are four shorter (3.17 Å) and two longer (3.35 Å) Mg–Mg bond lengths. In the third Mg site, Mg is bonded in a distorted water-like geometry to one Cs, four Mg, and two equivalent Si atoms. Both Mg–Si bond lengths are 2.70 Å. In the fourth Mg site, Mg is bonded to two equivalent Cs and six Mg atoms to form a mixture of distorted corner and face-sharing MgCs2Mg6 hexagonal bipyramids. Si is bonded in a 8-coordinate geometry to two equivalent Cs and six Mg atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on CsCeMg14 by Materials Project

CsMg14Ce crystallizes in the orthorhombic Amm2 space group. The structure is three-dimensional. Cs is bonded to ten Mg and two equivalent Ce atoms to form CsCe2Mg10 cuboctahedra that share corners with six equivalent CsCe2Mg10 cuboctahedra, corners with twelve MgMg12 cuboctahedra, edges with two equivalent CeCs2Mg10 cuboctahedra, faces with two equivalent MgMg12 cuboctahedra, and faces with two equivalent CeCs2Mg10 cuboctahedra. There are a spread of Cs–Mg bond distances ranging from 3.36–3.53 Å. Both Cs–Ce bond lengths are 3.15 Å. There are seven inequivalent Mg sites. In the first Mg site, Mg is bonded to twelve Mg atoms to form distorted MgMg12 cuboctahedra that share corners with four equivalent CsCe2Mg10 cuboctahedra, corners with six equivalent MgMg12 cuboctahedra, edges with six MgMg12 cuboctahedra, faces with two equivalent CeCs2Mg10 cuboctahedra, and faces with six MgMg12 cuboctahedra. There are a spread of Mg–Mg bond distances ranging from 3.15–3.47 Å. In the second Mg site, Mg is bonded to twelve Mg atoms to form MgMg12 cuboctahedra that share corners with four equivalent CeCs2Mg10 cuboctahedra, corners with six equivalent MgMg12 cuboctahedra, edges with six MgMg12 cuboctahedra, faces with two equivalent CsCe2Mg10 cuboctahedra, and faces with six MgMg12 cuboctahedra. There are a spread of Mg–Mg bond distances ranging from 3.17–3.42 Å. In the third Mg site, Mg is bonded in a 12-coordinate geometry to two equivalent Cs, eight Mg, and two equivalent Ce atoms. There are a spread of Mg–Mg bond distances ranging from 3.14–3.52 Å. There are one shorter (3.37 Å) and one longer (3.44 Å) Mg–Ce bond lengths. In the fourth Mg site, Mg is bonded to twelve Mg atoms to form distorted MgMg12 cuboctahedra that share corners with four equivalent CsCe2Mg10 cuboctahedra, corners with four equivalent CeCs2Mg10 cuboctahedra, corners with six equivalent MgMg12 cuboctahedra, edges with six MgMg12 cuboctahedra, and faces with six MgMg12 cuboctahedra. There are a spread of Mg–Mg bond distances ranging from 3.12–3.31 Å. In the fifth Mg site, Mg is bonded in a 12-coordinate geometry to one Cs, ten Mg, and one Ce atom. There are a spread of Mg–Mg bond distances ranging from 3.08–3.56 Å. The Mg–Ce bond length is 3.47 Å. In the sixth Mg site, Mg is bonded in a 12-coordinate geometry to eleven Mg and one Ce atom. Both Mg–Mg bond lengths are 3.16 Å. The Mg–Ce bond length is 3.37 Å. In the seventh Mg site, Mg is bonded in a 12-coordinate geometry to one Cs and eleven Mg atoms. Ce is bonded to two equivalent Cs and ten Mg atoms to form CeCs2Mg10 cuboctahedra that share corners with six equivalent CeCs2Mg10 cuboctahedra, corners with twelve MgMg12 cuboctahedra, edges with two equivalent CsCe2Mg10 cuboctahedra, faces with two equivalent CsCe2Mg10 cuboctahedra, and faces with two equivalent MgMg12 cuboctahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Generation of splice switching oligonucleotides targeting the Cockayne syndrome group B gene product in order to change the diseased cell state

Highlights: • We designed and synthesized 24 SSO sequences to skip exon 3 in CSB mRNA. • SSO generated an additional nonsense mutation at the upstream region of PGBD3. • Such SSO up-regulated several gene expression levels in CS cells. • SSO treatment might allow CS cells to mimic UV{sup S}S cell. Cockayne syndrome (CS) is a severe disorder with no effective treatment. The Cockayne syndrome group B (CSB) gene is one gene responsible for CS and also causes UV sensitive syndrome (UV{sup S}S), a disorder that causes mild symptoms. How the CSB gene determines a patient's fate is unknown, but one intriguing point is that in UV{sup S}S patient cell, there are nonsense mutations in both alleles at the same position in each upstream region of the PiggyBac transposable element derived 3 (PGBD3) inserted region. In contrast, in CS patient cells, there is at least one allele with several mutations downstream of the PGBD3 inserted region, or there are homozygous mutations in exon 1. Here, we designed and synthesized 24 splice switching oligonucleotides (SSOs) to skip exon 3 in CSB mRNA. Use of these SSOs induced a frame shift in order to generate an alternative stop codon at the upstream region of the PGBD3 invasion site. As a result, a reduction of mitochondrial membrane potential following H{sub 2}O{sub 2} treatment in CS cell was recovered. It was demonstrated that up-regulation of several gene expression brought about by SSOs are related to mitochondrial dysfunction in CS cells.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2018

Excess Lead-210 and Plutonium-239+240: Two suitable radiogenic soil erosion tracers for mountain grassland sites

Highlights: • First application of excess Lead-210 as soil tracer in alpine grasslands. • {sup 239+240}Pu/{sup 137}Cs ratios indicated 75% Chernobyl contribution to {sup 137}Cs inventory. • {sup 239+240}Pu is compared to more mature radioisotopic tracers (i.e. {sup 210}Pb{sub ex} and {sup 137}Cs). • {sup 210}Pb{sub ex}, {sup 137}Cs and {sup 239+240}Pu yielded comparable estimates of soil redistribution. The expected growing population and challenges associated with globalisation will increase local food and feed demands and enhance the pressure on local and regional upland soil resources. In light of these potential future developments it is necessary to define sustainable land use and tolerable soil loss rates with methods applicable and adapted to mountainous areas. Fallout-radionuclides (FRNs) are proven techniques to increase our knowledge about the status and resilience of agro-ecosystems. However, the use of the Caesium-137 ({sup 137}Cs) method is complicated in the European Alps due to its heterogeneous input and the timing of the Chernobyl fallout, which occurred during a few single rain events on partly snow covered ground. Other radioisotopic techniques have been proposed to overcome these limitations. The objective of this study is to evaluate the suitability of excess Lead-210 ({sup 210}Pb{sub ex}) and Plutonium-239+240 ({sup 239+240}Pu) as soil erosion tracers for three different grassland management types at the steep slopes (slope angles between 35 and 38°) located in the Central Swiss Alps. All three FRNs identified pastures as having the highest mean (± standard deviation) net soil loss of −6.7 ± 1.1, −9.8 ± 6.8 and −7.0 ± 5.2 Mg ha{sup -1} yr{sup -1} for {sup 137}Cs, {sup 210}Pb{sub ex} and {sup 239+240}Pu, respectively. A mean soil loss of −5.7 ± 1.5, −5.2 ± 1.5 and-5.6 ± 2.1 was assessed for hayfields and the lowest rates were established for pastures with dwarf-shrubs (−5.2 ± 2.5, −4.5 ± 2.5 and −3.3 ± 2.4 Mg ha{sup -1} yr{sup -1} for {sup 137}Cs, {sup 210}Pb{sub ex} and {sup 239+240}Pu, respectively). These rates, evaluated at sites with an elevated soil erosion risk exceed the respective soil production rates. Among the three FRN methods used, {sup 239+240}Pu appears as the most promising tracer in terms of measurement uncertainty and reduced small scale variability (CV of 13%). Despite a higher level of uncertainty, {sup 210}Pb{sub ex} produced comparable results, with a wide range of erosion rates sensitive to changes in grassland management. {sup 210}Pb{sub ex} can then be as well considered as a suitable soil tracer to investigate alpine agroecosystems.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2025

Establishing a silica gel zone in well annulus and evaluating its performance in blocking vertical water flow

Wells are often constructed for monitoring purposes with relatively long screen lengths (e.g., >10 m). Vertical water flows can occur within the artificial or natural filterpack annulus that surrounds the screened interval, bypassing packer assemblies installed inside the wellbore. Attempts to isolate discrete vertical zones during groundwater sampling are unsuccessful when annular flow occurs and lead to remedy decisions based on biased or incorrect interpretations. Blocking vertical annular water flow and contaminant transport will help obtain more accurate concentrations of contaminants from sampling in targeted depth intervals. The application of silica gels formed from the injected colloidal silica CS suspensions is a novel approach to minimize or prevent movement of vertical movement of groundwater in the surrounding filterpack annulus. In this work, we tested the feasibility of injecting CS suspensions to target locations and developed a modified CS formulation that is injectable and prevents gravity sinking. We studied the distribution and penetration of silica gel at laboratory scale in mock well annulus with surrounding formations. We evaluated the performance of the silica gel in blocking vertical water flow in the annulus and in minimizing chemical transport through the gel zone. CS suspension formulations have been defined that are ready for injection, stay in target locations, and form gel within desired time frames. Injection of CS suspensions achieved uniform distribution in a well annulus filter pack, fully occupied the annulus pore space, and penetrated the formation surrounding the filter packer with a sufficient distance to create a hydraulic annular seal when the injection was applied at a sufficient rate. The depth of penetration into the formation was dependent on the permeability contrast between the filter pack and the surrounding formation. Silica gel that formed in the annulus blocked vertical water flow and stopped the chemical transport through the gel zone. In conclusion, this research reveals that using CS suspension injection and sequential gelation (CS-GEL) is a promising technology for blocking vertical water flow and chemical transport through the filter pack in targeted zones within the annulus of long-screened well systems.

Colloidal silica suspension↗
DOE OSTI2019

Rare earth silicates and germanates crystallizing in the wadeite and related structure types

Single crystals of six new alkali lanthanide silicates and germanates were synthesized via the flux growth method. A2CeSi3O9 (A = Rb, Cs) and Cs2CeGe3O9 crystallize in the Wadeite structure with space group P63/m and lattice parameters a = 7.1950(2) Å and c = 10.5109(3) Å for the Rb analogue. K2CeSi3O9 crystallizes in a previously unobserved monoclinic distortion of the Wadeite structure with space group P21/n and lattice parameters a = 7.0801(2) Å, b = 10.458(2) Å, c = 12.238(2) Å and β = 90.07(3)°. Finally, Cs8Dy2Ge16O39 and Cs8Dy2Ge16O38F2 crystallize in two new structure types that are related to each other and to the Wadeite structure. Cs8Dy2Ge16O39 crystallizes in the monoclinic space group P2/c with lattice parameters a = 12.4054(3) Å, b = 7.4310(2) Å, c = 24.5761(6) Å, and β = 90.8849(16)° and Cs8Dy2Ge16O38F2 crystallizes in the orthorhombic space group Pnn2 with lattice parameters a = 12.3489(4) Å, b = 12.4805(5) Å, and c = 7.3802(3) Å. The synthesis and structure of the six compounds are reported and the crystallochemical reasons for the formation of each structure are discussed.

nuclear, materials and chemistry by design, synthe↗
DOE OSTI2025

Mechanical properties and strengthening mechanisms of cold sprayed Al-Mg alloys

This paper investigates the mechanical properties and strengthening mechanisms of cold sprayed Al-Mg alloys as a function of Mg content. Cold spray (CS) is a solid-state deposition process that can be used as a repair technique for structural components. However, the limited ductility of cold sprayed materials is an unsettled issue in CS community. Herein, reproducible, and significantly increased elongation to failure (∼15%) in as-deposited conditions is reported in CS Al-Mg binary alloys with low Mg content (≤ 2.5 wt%). Furthermore, reducing Mg content down to 2.5 wt% in CS Al-Mg binary alloys demonstrated comparable mechanical strength to its wrought counterparts. Strengthening mechanisms were analyzed in wrought and CS Al-Mg alloys based upon microstructural characteristics, such as grain size, Mg solute concentration, and dislocation density. A quantitative evaluation of yield strength revealed that grain boundary strengthening is predominant in CS Al-Mg alloys as compared with their wrought counterparts. When comparing among CS Al-Mg binary alloys of different compositions, Mg solute concentration, and dislocation density governed mechanical strength. In conclusion, the underlying mechanism for the variation of mechanical properties and strengthening mechanisms is discussed in terms of these microstructural characteristics.

Additive manufacturing↗
DOE OSTI2017

Acquisition of STEM Images by Adaptive Compressive Sensing

Compressive Sensing (CS) allows a signal to be sparsely measured first and accurately recovered later in software [1]. In scanning transmission electron microscopy (STEM), it is possible to compress an image spatially by reducing the number of measured pixels, which decreases electron dose and increases sensing speed [2,3,4]. The two requirements for CS to work are: (1) sparsity of basis coefficients and (2) incoherence of the sensing system and the representation system. However, when pixels are missing from the image, it is difficult to have an incoherent sensing matrix. Nevertheless, dictionary learning techniques such as Beta-Process Factor Analysis (BPFA) [5] are able to simultaneously discover a basis and the sparse coefficients in the case of missing pixels. On top of CS, we would like to apply active learning [6,7] to further reduce the proportion of pixels being measured, while maintaining image reconstruction quality. Suppose we initially sample 10% of random pixels. We wish to select the next 1% of pixels that are most useful in recovering the image. Now, we have 11% of pixels, and we want to decide the next 1% of “most informative” pixels. Active learning methods are online and sequential in nature. Our goal is to adaptively discover the best sensing mask during acquisition using feedback about the structures in the image. In the end, we hope to recover a high quality reconstruction with a dose reduction relative to the non-adaptive (random) sensing scheme. In doing this, we try three metrics applied to the partial reconstructions for selecting the new set of pixels: (1) variance, (2) Kullback-Leibler (KL) divergence using a Radial Basis Function (RBF) kernel, and (3) entropy. Figs. 1 and 2 display the comparison of Peak Signal-to-Noise (PSNR) using these three different active learning methods at different percentages of sampled pixels. At 20% level, all the three active learning methods underperform the original CS without active learning. However, they all beat the original CS as more of the “most informative” pixels are sampled. One can also argue that CS equipped with active learning requires less sampled pixels to achieve the same value of PSNR than CS with pixels randomly sampled, since all the three PSNR curves with active learning grow at a faster pace than that without active learning. For this particular STEM image, by observing the reconstructed images and the sensing masks, we find that while the method based on RBF kernel acquires samples more uniformly, the one on entropy samples more areas of significant change, thus less uniformly. The KL-divergence method performs the best in terms of reconstruction error (PSNR) for this example [8].

Xie, Weiyi↗
DOE OSTI2021

Reducing Surface Recombination Velocity of Methylammonium-Free Mixed-Cation Mixed-Halide Perovskites via Surface Passivation

We control surface recombination in the mixed-cation, mixed-halide perovskite, FA0.83Cs0.17Pb(I0.85Br0.15)3, by passivating nonradiative defects with the polymerizable Lewis base (3-aminopropyl)trimethoxysilane (APTMS). We demonstrate average minority carrier lifetimes >4 µs, nearly single exponential monomolecular photoluminescence decays, and high external photoluminescence quantum efficiencies (>20%, corresponding to ~97% of the maximum theoretical quasi-Fermi-level splitting) at low excitation fluence. We confirm both the composition and valence band edge position of the FA0.83Cs0.17Pb(I0.85Br0.15)3 perovskite using multi-institutional, cross-validated, X-ray photoelectron spectroscopy and UV photoelectron spectroscopy measurements. We extend the APTMS surface passivation to higher bandgap double-cation (FA and Cs) compositions (1.7, 1.75, and 1.8 eV) as well as the widely used triple-cation (FA, MA, and Cs) composition. Finally, we demonstrate that the average surface recombination velocity decreases from ~1000 to ~10 cm/s post APTMS passivation for FA0.83Cs0.17Pb(I0.85Br0.15)3. Our results demonstrate that surface-mediated recombination is the primary nonradiative loss pathway in many methylammonium (MA)-free mixed-cation mixed-halide films with a range of different bandgaps, which is a problem observed for a wide range of perovskite active layers and reactive electrical contacts. Our study also provides insights to develop passivating molecules that help reduce surface recombination in MA-free mixed-cation mixed-halide films and indicates that surface passivation and contact engineering will enable near-theoretical device efficiencies with these materials.

14 SOLAR ENERGY↗
DOE OSTI2025

Data-Driven Mapping of the Cesium Cadmium Bromide Phase Space Utilizing a Soft-Chemistry Approach

Soft-chemistry techniques provide a versatile approach to synthesizing inorganic materials under mild conditions, enabling access to compositions and structures that are challenging to achieve through traditional thermodynamically driven solid-state methods. However, these solution-based routes often result in phase competition, requiring precise control over reaction conditions to achieve selective product formation. While one-variable-at-a-time (OVAT) approaches have traditionally been used for phase selection, data-driven strategies are emerging as more efficient methods for navigating complex synthetic spaces. Ternary metal halides, such as cesium cadmium bromides (Cs–Cd–Br), are of growing interest due to their potential in wide and ultrawide band gap applications. Unlike the well-studied cesium lead halide phases, the compositional diversity and solution-based synthesis of ternary Cs–Cd–Br phases remain largely unexplored. This study systematically investigates the synthetic phase space of the Cs–Cd–Br system by constructing a data-driven phase map. Using a common set of precursors and a standardized experimental procedure, we successfully synthesize all four known Cs–Cd–Br phases—CsCdBr 3 , Cs 2 CdBr 4 , Cs 3 CdBr 5 , and Cs 7 Cd 3 Br 13 —each exhibiting distinct structures, morphologies, and optical properties. Our findings highlight the potential of soft-chemistry methods for expanding the library of ternary metal halides and provide key insights into the thermodynamic and kinetic factors governing phase formation.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

A Family of Layered Phosphates Crystallizing in a Rare Geometrical Isomer of the Phosphuranylite Topology: Synthesis, Characterization, and Computational Modeling of A 4 [(UO 2 ) 3 O 2 (PO 4 ) 2 ] (A = Alkali Metal) Exhibiting Intralayer Ion Exchange

Single crystals of eight new layered uranyl phosphates were grown from alkali chloride fluxes: Cs 1.4 K 2.6 [(UO 2 ) 3 O 2 (PO 4 ) 2 ], Cs 0.7 K 3.3 [(UO 2 ) 3 O 2 (PO 4 ) 2 ], Rb 1.4 K 2.6 [(UO 2 ) 3 O 2 (PO 4 ) 2 ], K 4 [(UO 2 ) 3 O 2 (PO 4 ) 2 ], K 2.9 Na 0.9 Rb 0.2 [(UO 2 ) 3 O 2 (PO 4 ) 2 ], K 2.1 Na 0.7 Rb 1.2 [(UO 2 ) 3 O 2 (PO 4 ) 2 ], Cs 1.7 K 4.3 [(UO 2 ) 5 O 5 (PO 4 ) 2 ], and Rb 1.6 K 4.4 [(UO 2 ) 5 O 5 (PO 4 ) 2 ]. All structures crystallize in the monoclinic space group, P 2 1 / c and contain uranyl phosphate layers with alkali metals located between the layers for charge balance. Ion exchange experiments on Cs 0.7 K 3.3 [(UO 2 ) 3 O 2 (PO 4 ) 2 ], Rb 1.4 K 2.6 [(UO 2 ) 3 O 2 (PO 4 ) 2 ], and K 4 [(UO 2 ) 3 O 2 (PO 4 ) 2 ] demonstrated that Cs and Rb cations cannot be exchanged for K cations; however, K cations can be readily exchanged for Na, Rb, and Cs. Enthalpies of formation were calculated from density functional theory (DFT) and volume-based thermodynamics (VBT) for all six structures. A value for the enthalpy of formation of the phosphuranylite sheet, [(UO 2 ) 3 O 2 (PO 4 ) 2 ] 4– , was derived using single-ion additive methods coupled with VBT. Finally, DFT and VBT calculations were used to justify results of the ion exchange experiments. Cs 0.7 K 3.3 [(UO 2 ) 3 O 2 (PO 4 ) 2 ], Rb 1.4 K 2.6 [(UO 2 ) 3 O 2 (PO 4 ) 2 ], and K 4 [(UO 2 ) 3 O 2 (PO 4 ) 2 ] exhibit typical luminescence of the uranyl group.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2025

Driving Force Dependent Photoinduced Charge Transfer Dynamics in Polymer-Wrapped Semiconducting Single-Walled Carbon Nanotubes

Here, we investigate the thermodynamic driving-force dependences of photoinduced charge separation (CS) and subsequent charge transfer dynamics in single-walled carbon nanotube (SWNT)–perylenediimide (PDI) donor–acceptor (D–A) superstructures. Pump–probe spectroscopy reveals that [SWNT (•+)n ]-(PDI –• ) n CS states form on an ∼100 fs time scale following photoexcitation; these dynamics are invariant across an ∼400 mV driving force range, indicating that SWNT hole polaron formation time scales are determined by nanotube lattice and solvent relaxation. These CS states feature SWNT hole polarons adjacent to (geminate) and nearby (nongeminate) PDI radical anions. Analysis of the free energy dependence for charge recombination (CR) of [SWNT •+ ] geminate -(PDI –• ) CS states highlights an ∼2 meV value for D–A electronic coupling (HAB) and ∼0.93 eV for the total reorganization energy (λ T ). A corresponding driving force dependence of the CR dynamics for [SWNT •+ ] nongeminate -(PDI –• ) CS states indicates a diminished H AB value (∼0.6 meV) and a larger λ T (∼1.1 eV), consistent with larger transfer distances. SWNT excitons that persist following photoinduced CS drive photooxidation of PDI –• components of [SWNT (•+)n ]-(PDI –• ) n CS states ( 1 SWNT* + PDI •– → PDI + SWNT •– ); this reaction manifests a significantly reduced λ T value (∼0.67 eV) as the initially prepared SWNT reduced state bears the character of a conduction band injected electron ([SWNT •– ] CB ). This reaction thus gives rise to relaxed, nongeminate SWNT electron and hole polarons on the same nanotube; these polarons react on a 10 2 ps time scale independent of the electronic structure of these SWNT-PDI superstructures.

anions↗
DOE OSTI2018

Bond Valences and Anharmonicity in Vacancy-Ordered Double Perovskite Halides

We report that anharmonic lattice dynamics are intimately linked with optical and electronic properties in perovskite halides semiconductors. Vacancy-ordered double perovskites are a subset of the perovskite halide family containing isolated octahedral units. The absence of polyhedral connectivity engenders the vacancy-ordered double perovskites with additional degrees of dynamic freedom, which presents an ideal structural framework to study dynamic-property relationships in perovskite halide semiconductors. In the present study, we examine the structure and bonding origins of anharmonicity in the vacancy-ordered double perovskites Cs 2 Sn 1-x Te x I 6 . While X-ray diffraction indicates that all members adopt the cubic vacancy-ordered double perovskite structure, the local coordination environment probed by X-ray pair distribution function (XPDF) analysis reveals asymmetry of the Cs–I/I–I pair correlation that smoothly decreases with increasing tellurium content. Temperature-dependent neutron total scattering suggests that this asymmetry in the PDF occurs due to anharmonic lattice dynamics arising from octahedral tilting and Cs + displacements, as supported by Reverse Monte Carlo simulations of the Cs 2 SnI 6 and Cs 2 TeI 6 end members. We further correlate the trends in asymmetry and anharmonicity with the bond valence sum of the Cs + ion, and find that the anharmonicity vanishes when the bonding preferences of the Cs + are satisfied by the size of the cuboctahedral void. Lastly, this study presents a simple and effective approach for understanding the origin of anharmonicity in vacancy-ordered double perovskite materials.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Discrepancy in the Critical State Void Ratio of Poorly Graded Sand due to Shear Strain Localization

The critical state (CS) concept is a theoretical framework that models the constitutive behavior of soils, including sand and other granular materials. It supports the notion of a unique postfailure state, where the soil ultimately experiences continuous shearing with no change in the plastic volumetric strain. However, the published literature has frequently noted the nonconvergence of sand specimens with different initial densities to a unique CS in the compression plane due to many factors such as specimen fabric, particle morphology, breakage, and grain size distribution. This paper examines the CS for poorly graded (uniform) glass beads and 3 different types of silica sands using 50 conventional triaxial compression (CTC) experiments, 12 oedometer tests, and in situ synchrotron microcomputed tomography (SMT) scans for 10 CTC experiments. The results of the 50 CTC experiments revealed a diffused CS zone in the compression plane, which was further examined using the in situ SMT scans. A thorough three-dimensional image analysis of the SMT scans accurately quantified the evolution of the local void ratio (elocal) versus axial compression within zones of intensive shearing toward the center of the specimen. The evolution of the void ratio was also measured using the entire volume of the specimen (eglobal). At the CS, the elocal/eglobal ratio was assessed to be ~1.25 when a single shear band developed within the scanned specimens and ~1.1-1.15 for specimens that failed via external bulging that was internally manifested by the development of multiple shear bands. This finding suggests that the CS zone in the compression plane can be attributed to the common wrong consideration of eglobal evolution in lieu of elocal within the developing shear bands. Furthermore, the lack of shear band development in uniaxial compression has made the results of the oedometer test reliable in quantifying the CS parameters in the compression plane.

58 GEOSCIENCES↗
DOE OSTI2015

Kinetic model of force-free current sheets with non-uniform temperature

The kinetic model of a one-dimensional force-free current sheet (CS) developed recently by Harrison and Neukirch [Phys. Rev. Lett. 102(13), 135003 (2009)] predicts uniform distributions of the plasma temperature and density across the CS. However, in realistic physical systems, inhomogeneities of these plasma parameters may arise quite naturally due to the boundary conditions or local plasma heating. Moreover, as the CS spatial scale becomes larger than the characteristic kinetic scales (the regime often referred to as the MHD limit), it should be possible to set arbitrary density and temperature profiles. Thus, an advanced model has to allow for inhomogeneities of the macroscopic plasma parameters across the CS, to be consistent with the MHD limit. In this paper, we generalise the kinetic model of a force-free current sheet, taking into account the inhomogeneity of the density and temperature across the CS. In the developed model, the density may either be enhanced or depleted in the CS central region. The temperature profile is prescribed by the density profile, keeping the plasma pressure uniform across the CS. All macroscopic parameters, as well as the distribution functions for the protons and electrons, are determined analytically. Applications of the developed model to current sheets observed in space plasmas are discussed.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗