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DOE OSTI2020

Materials Data on Cs4Ge(PSe3)4 by Materials Project

Cs4Ge(PSe3)4 crystallizes in the orthorhombic Pca2_1 space group. The structure is three-dimensional. there are four inequivalent Cs1+ sites. In the first Cs1+ site, Cs1+ is bonded in a 9-coordinate geometry to ten Se2- atoms. There are a spread of Cs–Se bond distances ranging from 3.78–4.40 Å. In the second Cs1+ site, Cs1+ is bonded in a 8-coordinate geometry to eight Se2- atoms. There are a spread of Cs–Se bond distances ranging from 3.76–4.21 Å. In the third Cs1+ site, Cs1+ is bonded in a 8-coordinate geometry to eight Se2- atoms. There are a spread of Cs–Se bond distances ranging from 3.60–4.26 Å. In the fourth Cs1+ site, Cs1+ is bonded in a 9-coordinate geometry to nine Se2- atoms. There are a spread of Cs–Se bond distances ranging from 3.61–4.27 Å. Ge2+ is bonded in a tetrahedral geometry to four Se2- atoms. There are three shorter (2.40 Å) and one longer (2.41 Å) Ge–Se bond lengths. There are four inequivalent P+4.50+ sites. In the first P+4.50+ site, P+4.50+ is bonded in a trigonal non-coplanar geometry to three Se2- atoms. There are a spread of P–Se bond distances ranging from 2.15–2.36 Å. In the second P+4.50+ site, P+4.50+ is bonded in a trigonal non-coplanar geometry to three Se2- atoms. There are a spread of P–Se bond distances ranging from 2.15–2.33 Å. In the third P+4.50+ site, P+4.50+ is bonded in a trigonal non-coplanar geometry to three Se2- atoms. There are two shorter (2.16 Å) and one longer (2.35 Å) P–Se bond lengths. In the fourth P+4.50+ site, P+4.50+ is bonded in a trigonal non-coplanar geometry to three Se2- atoms. There are a spread of P–Se bond distances ranging from 2.14–2.35 Å. There are twelve inequivalent Se2- sites. In the first Se2- site, Se2- is bonded in a 1-coordinate geometry to three Cs1+ and one P+4.50+ atom. In the second Se2- site, Se2- is bonded in a distorted rectangular see-saw-like geometry to three Cs1+ and one P+4.50+ atom. In the third Se2- site, Se2- is bonded in a distorted water-like geometry to two equivalent Cs1+, one Ge2+, and one P+4.50+ atom. In the fourth Se2- site, Se2- is bonded in a distorted single-bond geometry to four Cs1+ and one P+4.50+ atom. In the fifth Se2- site, Se2- is bonded in a distorted single-bond geometry to three Cs1+ and one P+4.50+ atom. In the sixth Se2- site, Se2- is bonded in a distorted L-shaped geometry to one Cs1+, one Ge2+, and one P+4.50+ atom. In the seventh Se2- site, Se2- is bonded in a 2-coordinate geometry to two Cs1+, one Ge2+, and one P+4.50+ atom. In the eighth Se2- site, Se2- is bonded in a 1-coordinate geometry to four Cs1+ and one P+4.50+ atom. In the ninth Se2- site, Se2- is bonded in a 1-coordinate geometry to three Cs1+ and one P+4.50+ atom. In the tenth Se2- site, Se2- is bonded in a distorted L-shaped geometry to three Cs1+, one Ge2+, and one P+4.50+ atom. In the eleventh Se2- site, Se2- is bonded in a distorted single-bond geometry to four Cs1+ and one P+4.50+ atom. In the twelfth Se2- site, Se2- is bonded in a distorted single-bond geometry to three Cs1+ and one P+4.50+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Co4Cu3(NiSe6)2 by Materials Project

Co4Cu3(NiSe6)2 is Spinel-derived structured and crystallizes in the monoclinic C2/m space group. The structure is three-dimensional. there are three inequivalent Co+3.50+ sites. In the first Co+3.50+ site, Co+3.50+ is bonded to six Se2- atoms to form CoSe6 octahedra that share corners with six CuSe4 tetrahedra, edges with two NiSe6 octahedra, and edges with four equivalent CoSe6 octahedra. There are four shorter (2.39 Å) and two longer (2.40 Å) Co–Se bond lengths. In the second Co+3.50+ site, Co+3.50+ is bonded to six Se2- atoms to form CoSe6 octahedra that share corners with six CuSe4 tetrahedra, edges with two equivalent CoSe6 octahedra, and edges with four NiSe6 octahedra. All Co–Se bond lengths are 2.39 Å. In the third Co+3.50+ site, Co+3.50+ is bonded to six Se2- atoms to form CoSe6 octahedra that share corners with six CuSe4 tetrahedra, edges with two NiSe6 octahedra, and edges with four CoSe6 octahedra. There are four shorter (2.39 Å) and two longer (2.40 Å) Co–Se bond lengths. There are three inequivalent Ni2+ sites. In the first Ni2+ site, Ni2+ is bonded to six Se2- atoms to form NiSe6 octahedra that share corners with six CuSe4 tetrahedra, an edgeedge with one NiSe6 octahedra, and edges with five CoSe6 octahedra. There are two shorter (2.41 Å) and four longer (2.42 Å) Ni–Se bond lengths. In the second Ni2+ site, Ni2+ is bonded to six Se2- atoms to form NiSe6 octahedra that share corners with six equivalent CuSe4 tetrahedra and edges with six CoSe6 octahedra. All Ni–Se bond lengths are 2.42 Å. In the third Ni2+ site, Ni2+ is bonded to six Se2- atoms to form NiSe6 octahedra that share corners with six CuSe4 tetrahedra, edges with two equivalent NiSe6 octahedra, and edges with four equivalent CoSe6 octahedra. There are four shorter (2.41 Å) and two longer (2.42 Å) Ni–Se bond lengths. There are three inequivalent Cu2+ sites. In the first Cu2+ site, Cu2+ is bonded to four Se2- atoms to form CuSe4 tetrahedra that share corners with three equivalent NiSe6 octahedra and corners with nine CoSe6 octahedra. The corner-sharing octahedra tilt angles range from 59–60°. All Cu–Se bond lengths are 2.41 Å. In the second Cu2+ site, Cu2+ is bonded to four Se2- atoms to form CuSe4 tetrahedra that share corners with five NiSe6 octahedra and corners with seven CoSe6 octahedra. The corner-sharing octahedra tilt angles range from 58–60°. All Cu–Se bond lengths are 2.41 Å. In the third Cu2+ site, Cu2+ is bonded to four Se2- atoms to form CuSe4 tetrahedra that share corners with four NiSe6 octahedra and corners with eight CoSe6 octahedra. The corner-sharing octahedra tilt angles range from 59–60°. There are three shorter (2.41 Å) and one longer (2.42 Å) Cu–Se bond lengths. There are nine inequivalent Se2- sites. In the first Se2- site, Se2- is bonded to two equivalent Co+3.50+, one Ni2+, and one Cu2+ atom to form a mixture of distorted edge and corner-sharing SeCo2CuNi trigonal pyramids. In the second Se2- site, Se2- is bonded to two equivalent Co+3.50+, one Ni2+, and one Cu2+ atom to form a mixture of distorted edge and corner-sharing SeCo2CuNi trigonal pyramids. In the third Se2- site, Se2- is bonded to two equivalent Co+3.50+, one Ni2+, and one Cu2+ atom to form distorted SeCo2CuNi trigonal pyramids that share corners with twelve SeCo2CuNi trigonal pyramids and edges with three SeCo3Cu trigonal pyramids. In the fourth Se2- site, Se2- is bonded to three Co+3.50+ and one Cu2+ atom to form a mixture of distorted edge and corner-sharing SeCo3Cu trigonal pyramids. In the fifth Se2- site, Se2- is bonded to two equivalent Co+3.50+, one Ni2+, and one Cu2+ atom to form distorted SeCo2CuNi trigonal pyramids that share corners with twelve SeCo2CuNi trigonal pyramids and edges with three SeCoCuNi2 trigonal pyramids. In the sixth Se2- site, Se2- is bonded to three Co+3.50+ and one Cu2+ atom to form a mixture of distorted edge and corner-sharing SeCo3Cu trigonal pyramids. In the seventh Se2- site, Se2- is bonded to two Co+3.50+, one Ni2+, and one Cu2+ atom to form a mixture of distorted edge and corner-sharing SeCo2CuNi trigonal pyramids. In the eighth Se2- site, Se2- is bonded to one Co+3.50+, two Ni2+, and one Cu2+ atom to form a mixture of distorted edge and corner-sharing SeCoCuNi2 trigonal pyramids. In the ninth Se2- site, Se2- is bonded to two Co+3.50+, one Ni2+, and one Cu2+ atom to form distorted SeCo2CuNi trigonal pyramids that share corners with twelve SeCo2CuNi trigonal pyramids and edges with three SeCo3Cu trigonal pyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Cs3Bi11Se18 by Materials Project

Cs3Bi11Se18 is Orthorhombic Perovskite-like structured and crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. there are two inequivalent Cs1+ sites. In the first Cs1+ site, Cs1+ is bonded in a 9-coordinate geometry to nine Se2- atoms. There are a spread of Cs–Se bond distances ranging from 3.72–4.28 Å. In the second Cs1+ site, Cs1+ is bonded in a 9-coordinate geometry to nine Se2- atoms. There are a spread of Cs–Se bond distances ranging from 3.72–4.25 Å. There are seven inequivalent Bi3+ sites. In the first Bi3+ site, Bi3+ is bonded to six Se2- atoms to form a mixture of corner and edge-sharing BiSe6 octahedra. The corner-sharing octahedra tilt angles range from 3–4°. There are a spread of Bi–Se bond distances ranging from 2.80–3.13 Å. In the second Bi3+ site, Bi3+ is bonded to six Se2- atoms to form a mixture of corner and edge-sharing BiSe6 octahedra. The corner-sharing octahedra tilt angles range from 2–10°. There are a spread of Bi–Se bond distances ranging from 2.85–3.07 Å. In the third Bi3+ site, Bi3+ is bonded to six Se2- atoms to form a mixture of distorted corner and edge-sharing BiSe6 octahedra. The corner-sharing octahedra tilt angles range from 6–19°. There are a spread of Bi–Se bond distances ranging from 2.73–3.32 Å. In the fourth Bi3+ site, Bi3+ is bonded to six Se2- atoms to form a mixture of corner and edge-sharing BiSe6 octahedra. The corner-sharing octahedral tilt angles are 4°. There are a spread of Bi–Se bond distances ranging from 2.87–3.15 Å. In the fifth Bi3+ site, Bi3+ is bonded to six Se2- atoms to form a mixture of corner and edge-sharing BiSe6 octahedra. The corner-sharing octahedra tilt angles range from 3–7°. There are a spread of Bi–Se bond distances ranging from 2.82–3.20 Å. In the sixth Bi3+ site, Bi3+ is bonded to six Se2- atoms to form a mixture of corner and edge-sharing BiSe6 octahedra. The corner-sharing octahedra tilt angles range from 2–9°. There are a spread of Bi–Se bond distances ranging from 2.88–3.12 Å. In the seventh Bi3+ site, Bi3+ is bonded to six Se2- atoms to form a mixture of distorted corner and edge-sharing BiSe6 octahedra. The corner-sharing octahedra tilt angles range from 4–19°. There are a spread of Bi–Se bond distances ranging from 2.70–3.45 Å. There are twelve inequivalent Se2- sites. In the first Se2- site, Se2- is bonded in a 4-coordinate geometry to one Cs1+ and three Bi3+ atoms. In the second Se2- site, Se2- is bonded in a 5-coordinate geometry to one Cs1+ and four Bi3+ atoms. In the third Se2- site, Se2- is bonded in a 4-coordinate geometry to two Cs1+ and two Bi3+ atoms. In the fourth Se2- site, Se2- is bonded in a 5-coordinate geometry to two equivalent Cs1+ and three Bi3+ atoms. In the fifth Se2- site, Se2- is bonded to two equivalent Cs1+ and three Bi3+ atoms to form distorted edge-sharing SeCs2Bi3 square pyramids. In the sixth Se2- site, Se2- is bonded to two Cs1+ and four Bi3+ atoms to form distorted SeCs2Bi4 octahedra that share edges with three SeCs2Bi4 octahedra and an edgeedge with one SeCs2Bi3 square pyramid. In the seventh Se2- site, Se2- is bonded to six Bi3+ atoms to form edge-sharing SeBi6 octahedra. In the eighth Se2- site, Se2- is bonded to six Bi3+ atoms to form SeBi6 octahedra that share edges with five SeCs2Bi4 octahedra and an edgeedge with one SeCs2Bi3 square pyramid. In the ninth Se2- site, Se2- is bonded in a 2-coordinate geometry to three Cs1+ and two Bi3+ atoms. In the tenth Se2- site, Se2- is bonded in a 2-coordinate geometry to three Cs1+ and two equivalent Bi3+ atoms. In the eleventh Se2- site, Se2- is bonded in a 5-coordinate geometry to one Cs1+ and four Bi3+ atoms. In the twelfth Se2- site, Se2- is bonded in a 6-coordinate geometry to one Cs1+ and five Bi3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on TlBiSe2 by Materials Project

TlBiSe2 is Caswellsilverite-like structured and crystallizes in the tetragonal P4/mmm space group. The structure is three-dimensional. there are four inequivalent Tl1+ sites. In the first Tl1+ site, Tl1+ is bonded to six Se2- atoms to form distorted TlSe6 octahedra that share a cornercorner with one BiSe6 octahedra, corners with five TlSe6 octahedra, edges with four equivalent BiSe6 octahedra, and edges with eight TlSe6 octahedra. The corner-sharing octahedra tilt angles range from 0–16°. There are a spread of Tl–Se bond distances ranging from 2.87–3.48 Å. In the second Tl1+ site, Tl1+ is bonded to six Se2- atoms to form TlSe6 octahedra that share a cornercorner with one BiSe6 octahedra, corners with five TlSe6 octahedra, and edges with twelve TlSe6 octahedra. The corner-sharing octahedra tilt angles range from 0–5°. There are a spread of Tl–Se bond distances ranging from 2.91–3.44 Å. In the third Tl1+ site, Tl1+ is bonded to six Se2- atoms to form a mixture of corner and edge-sharing TlSe6 octahedra. The corner-sharing octahedra tilt angles range from 0–2°. There are a spread of Tl–Se bond distances ranging from 3.07–3.11 Å. In the fourth Tl1+ site, Tl1+ is bonded to six Se2- atoms to form a mixture of corner and edge-sharing TlSe6 octahedra. The corner-sharing octahedral tilt angles are 0°. There are four shorter (3.09 Å) and two longer (3.14 Å) Tl–Se bond lengths. There are five inequivalent Bi3+ sites. In the first Bi3+ site, Bi3+ is bonded to six Se2- atoms to form distorted BiSe6 octahedra that share a cornercorner with one TlSe6 octahedra, corners with five BiSe6 octahedra, edges with four equivalent TlSe6 octahedra, and edges with eight BiSe6 octahedra. The corner-sharing octahedra tilt angles range from 0–16°. There are a spread of Bi–Se bond distances ranging from 2.62–3.48 Å. In the second Bi3+ site, Bi3+ is bonded to six Se2- atoms to form BiSe6 octahedra that share a cornercorner with one TlSe6 octahedra, corners with five BiSe6 octahedra, and edges with twelve BiSe6 octahedra. The corner-sharing octahedra tilt angles range from 0–8°. There are a spread of Bi–Se bond distances ranging from 2.84–3.20 Å. In the third Bi3+ site, Bi3+ is bonded to six Se2- atoms to form a mixture of corner and edge-sharing BiSe6 octahedra. The corner-sharing octahedra tilt angles range from 0–4°. There are a spread of Bi–Se bond distances ranging from 2.89–3.13 Å. In the fourth Bi3+ site, Bi3+ is bonded to six Se2- atoms to form a mixture of corner and edge-sharing BiSe6 octahedra. The corner-sharing octahedral tilt angles are 0°. There are two shorter (3.02 Å) and four longer (3.09 Å) Bi–Se bond lengths. In the fifth Bi3+ site, Bi3+ is bonded to six Se2- atoms to form a mixture of corner and edge-sharing BiSe6 octahedra. The corner-sharing octahedra tilt angles range from 0–4°. There are a spread of Bi–Se bond distances ranging from 2.89–3.13 Å. There are eight inequivalent Se2- sites. In the first Se2- site, Se2- is bonded to six Bi3+ atoms to form SeBi6 octahedra that share corners with six SeBi6 octahedra and edges with twelve SeTlBi5 octahedra. The corner-sharing octahedra tilt angles range from 0–8°. In the second Se2- site, Se2- is bonded to six Bi3+ atoms to form SeBi6 octahedra that share corners with six SeTlBi5 octahedra and edges with twelve SeBi6 octahedra. The corner-sharing octahedra tilt angles range from 0–4°. In the third Se2- site, Se2- is bonded to six Bi3+ atoms to form a mixture of corner and edge-sharing SeBi6 octahedra. The corner-sharing octahedral tilt angles are 0°. In the fourth Se2- site, Se2- is bonded to one Tl1+ and five Bi3+ atoms to form a mixture of corner and edge-sharing SeTlBi5 octahedra. The corner-sharing octahedra tilt angles range from 0–16°. In the fifth Se2- site, Se2- is bonded to five Tl1+ and one Bi3+ atom to form distorted SeTl5Bi octahedra that share corners with six SeTl5Bi octahedra and edges with twelve SeTlBi5 octahedra. The corner-sharing octahedra tilt angles range from 0–16°. In the sixth Se2- site, Se2- is bonded to six Tl1+ atoms to form SeTl6 octahedra that share corners with six SeTlBi5 octahedra and edges with twelve SeTl5Bi octahedra. The corner-sharing octahedra tilt angles range from 0–5°. In the seventh Se2- site, Se2- is bonded to six Tl1+ atoms to form SeTl6 octahedra that share corners with six SeTl5Bi octahedra and edges with twelve SeTl6 octahedra. The corner-sharing octahedra tilt angles range from 0–2°. In the eighth Se2- site, Se2- is bonded to six Tl1+ atoms to form a mixture of corner and edge-sharing SeTl6 octahedra. The corner-sharing octahedral tilt angles are 0°.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on RbBa3Ga5(Se5Cl)2 by Materials Project

RbBa3Ga5(Se5Cl)2 crystallizes in the triclinic P1 space group. The structure is three-dimensional. Rb1+ is bonded in a 10-coordinate geometry to eight Se2- and two Cl1- atoms. There are a spread of Rb–Se bond distances ranging from 3.49–4.11 Å. There are one shorter (3.25 Å) and one longer (3.37 Å) Rb–Cl bond lengths. There are three inequivalent Ba2+ sites. In the first Ba2+ site, Ba2+ is bonded in a 2-coordinate geometry to eight Se2- and two Cl1- atoms. There are a spread of Ba–Se bond distances ranging from 3.37–3.99 Å. There are one shorter (3.13 Å) and one longer (3.23 Å) Ba–Cl bond lengths. In the second Ba2+ site, Ba2+ is bonded in a 2-coordinate geometry to eight Se2- and two Cl1- atoms. There are a spread of Ba–Se bond distances ranging from 3.37–4.04 Å. There are one shorter (3.12 Å) and one longer (3.19 Å) Ba–Cl bond lengths. In the third Ba2+ site, Ba2+ is bonded in a 10-coordinate geometry to eight Se2- and two Cl1- atoms. There are a spread of Ba–Se bond distances ranging from 3.33–4.01 Å. There are one shorter (3.14 Å) and one longer (3.18 Å) Ba–Cl bond lengths. There are five inequivalent Ga3+ sites. In the first Ga3+ site, Ga3+ is bonded to four Se2- atoms to form corner-sharing GaSe4 tetrahedra. There are a spread of Ga–Se bond distances ranging from 2.42–2.46 Å. In the second Ga3+ site, Ga3+ is bonded to four Se2- atoms to form corner-sharing GaSe4 tetrahedra. There are a spread of Ga–Se bond distances ranging from 2.42–2.46 Å. In the third Ga3+ site, Ga3+ is bonded to four Se2- atoms to form corner-sharing GaSe4 tetrahedra. There are a spread of Ga–Se bond distances ranging from 2.41–2.47 Å. In the fourth Ga3+ site, Ga3+ is bonded to four Se2- atoms to form corner-sharing GaSe4 tetrahedra. There are a spread of Ga–Se bond distances ranging from 2.41–2.44 Å. In the fifth Ga3+ site, Ga3+ is bonded to four Se2- atoms to form corner-sharing GaSe4 tetrahedra. There are a spread of Ga–Se bond distances ranging from 2.42–2.45 Å. There are ten inequivalent Se2- sites. In the first Se2- site, Se2- is bonded in a 2-coordinate geometry to one Rb1+, two Ba2+, and two Ga3+ atoms. In the second Se2- site, Se2- is bonded in a 2-coordinate geometry to three Ba2+ and two Ga3+ atoms. In the third Se2- site, Se2- is bonded in a 2-coordinate geometry to one Rb1+, two Ba2+, and two Ga3+ atoms. In the fourth Se2- site, Se2- is bonded in a 2-coordinate geometry to one Rb1+, two Ba2+, and two Ga3+ atoms. In the fifth Se2- site, Se2- is bonded in a 2-coordinate geometry to one Rb1+, two Ba2+, and two Ga3+ atoms. In the sixth Se2- site, Se2- is bonded in a distorted water-like geometry to one Rb1+, two Ba2+, and two Ga3+ atoms. In the seventh Se2- site, Se2- is bonded in a 2-coordinate geometry to one Rb1+, two Ba2+, and two Ga3+ atoms. In the eighth Se2- site, Se2- is bonded in a distorted water-like geometry to three Ba2+ and two Ga3+ atoms. In the ninth Se2- site, Se2- is bonded in a distorted water-like geometry to one Rb1+, three Ba2+, and two Ga3+ atoms. In the tenth Se2- site, Se2- is bonded in a distorted water-like geometry to one Rb1+, three Ba2+, and two Ga3+ atoms. There are two inequivalent Cl1- sites. In the first Cl1- site, Cl1- is bonded in a tetrahedral geometry to one Rb1+ and three Ba2+ atoms. In the second Cl1- site, Cl1- is bonded in a 4-coordinate geometry to one Rb1+ and three Ba2+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2024

HTO and selenate diffusion through compacted Na-, Na–Ca-, and Ca-montmorillonite

Radionuclide transport in smectite clay barrier systems used for nuclear waste disposal is controlled by diffusion, with adsorption significantly retarding transport rates. While a relatively minor component of spent nuclear fuel, 79 Se is a major driver of the safety case for spent fuel disposal due to its long half-life (3.3×10 5 yr) and its low adsorption to clay (K D < 10 L/kg), thus a thorough understanding of Se diffusion through clay is critical for understanding the long-term safety of spent fuel disposal systems. Through-diffusion experiments with tritiated water (HTO, conservative tracer) and Se(VI) were conducted with a well-characterized, purified montmorillonite source clay (SWy-2) under a constant ionic strength (0.1 M) and three different electrolyte compositions: Na + , Ca 2+ , and a Na + -Ca 2+ mixture at pH 6.5 in order to probe the effects of electrolyte composition and interlayer cation composition on clay microstructure, Se(VI) aqueous speciation, and ultimately diffusion. Further, the results were modeled using a reactive transport modeling approach to determine values of porosity (ε), D e (effective diffusion coefficient), and K D (distribution coefficient for adsorption). HTO diffusive flux was higher in Ca-montmorillonite (D e =1.68×10 -10 m 2 s -1 ) compared to Na-montmorillonite (De=7.83×10 -11 m 2 s -1 ). This increase in flux is likely due to a greater degree of clay layer stacking in the presence of Ca 2+ compared to Na + , which leads to larger inter-particle pores. Overall, the Se(VI) flux was much lower than the HTO flux due to anion exclusion, with Se(VI) flux following the order Ca (D e = 1.03×10 -11 m 2 s -1 ) > Na–Ca (D e = 2.12×10 -12 m 2 s -1 ) > Na (D e = 1.28×10 -12 m 2 s -1 ). These differences in Se(VI) flux are due to a combination of factors, including (1) larger accessible porosity in Ca-montmorillonite due to clay layer stacking and smaller electrostatic effects compared to Na-montmorillonite, (2) larger accessible porosity for neutral-charge CaSeO4 species which makes up 32% of aqueous Se(VI) in the pure Ca system, and (3) possibly higher Se(VI) adsorption for Ca-montmorillonite. Through a combination of experimental and modeling work, this study highlights the compounding effects that electrolyte and counterion compositions can have on radionuclide transport through clay. Diffusion models that neglect these effects are not transferable from laboratory experimental conditions to in situ repository conditions.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2022

Selenium-doped copper oxide nanoarrays: Robust electrocatalyst for the oxygen evolution reaction with ultralow overpotential

The oxygen evolution reaction (OER) is the key anodic reaction in electrochemical water splitting. OER is a four-electron process with sluggish reaction kinetics. RuO 2 and IrO 2 are the benchmark catalysts for OER. Thus, finding a low-cost, earth-abundant, and stable electrocatalyst for OER is a big challenge. Here in this work, we report OER over Se-CuO/CF nanoarrays with an ultralow overpotential of 440 mV (at 50 mA/cm 2 current density). Se-CuO/CF nanoarray has a TOF of 0.05 s -1 at 300 mV. The catalyst showed consistent OER performance upto1000 cycles run over a period of 10 h. The OER performance of Se-CuO/CF nanoarrays was compared with RuO 2 /CF catalyst and the overpotential for RuO 2 /CF nanoarray was only 10 mV lower than Se-CuO/CF 50 mA/cm 2 current density. Se-CuO/CF nanoarray showed 50 mV lower overpotential than the state of the art RuO 2 /CF catalyst at a current density of 100 mA/cm 2 . The Tafel slope of Se-CuO/CF is 21 mV/decade lower compared to RuO 2 /CF suggesting faster reaction kinetics of Se-CuO/CF. The electrochemical surface area and the conductivity were increased upon doping Se into CuO/CF nanoarrays which can be attributed to enhanced OER performance of the Se-CuO/CF nanoarrays.

36 MATERIALS SCIENCE↗
DOE OSTI2021

On the quality of tape-cast thin films of sulfide electrolytes for solid-state batteries

All-solid-state lithium batteries (ASSLBs) have the potential to increase energy density, improve safety, and allow for lower manufacturing costs compared to conventional, liquid-based Li-ion batteries. The thickness of solid electrolyte (SE) layer dictates the cell-level energy density and it is desirable to make the SE layer as thin as possible while maintaining uniformity and defect-free. Manufacturing a high- quality, thin sulfide SE layer at large-scale, however, is challenging. Previous studies have addressed the compatibility of materials used for manufacturing thin sulfide SE films, paving the way for further investigation of processing conditions and film quality. Here we report a strong correlation between the solid loading of dispersions and the quality of tape-casted thin sulfide SE films. We also demonstrate a method for quantifying the quality of thin SE films by observing both pin-hole defects and larger heterogeneous agglomerations of particles in the films. Our thin sulfide SE films containing ~5 wt% binder are defect-free and show similar ionic conductivity compared to a cold-pressed, binder-free, thick SE pellet, resulting in an ~11X reduction of area specific resistance. Here, this work on the solid loading of the dispersion used in a scalable tape casting process provides insight for manufacturing high-quality, thin sulfide SE films and to increase the cell-level energy density of ASSLB.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Rogers Quarry Special Studies Report 2024

Rogers Quarry (RQ) has a history of elevated selenium (Se) concentrations in water and fish caused by inputs from the Y-12 National Security Complex Filled Coal Ash Pond (FCAP). Selenium is acutely toxic at high concentrations, and chronic toxicity occurs at low aqueous concentrations because Se bioaccumulates in fish tissues. The US Environmental Protection Agency (EPA) recently developed water quality criteria for Se that include fish tissue as well as aqueous Se concentrations. The water column concentration criterion is 1.5 µg L -1 for lentic ecosystems and 3.1 µg L -1 for lotic ecosystems. The fish tissue criteria include both an egg/ovary concentration (15.1 µg/g dry weight) and a concentration for whole-body (8.5 µg/g dry weight) or fish muscle (11.3 µg/g dry weight). The egg/ovary criterion supersedes the fillet and aqueous concentrations if measured because Se toxicity manifests via reproductive effects in birds and fish. It is maternally transferred through eggs, leading to teratogenicity (i.e., deformities, developmental effects) in young fish. Historical bioaccumulation data suggest that Se is likely the primary contaminant of concern in RQ, but more recent sampling shows that aqueous As concentrations have been elevated in upper McCoy Branch (MB) leading to RQ. More recently, Se concentrations in fish collected from upper MB were found to be above the tissue criterion for Se for whole-body fish. In FY 2019, actions were taken to deepen the constructed wetland just downstream of the FCAP to increase its ability to remove coal ash particulates from the water column before water enters MB. Sampling was conducted throughout MB in FY 2020-2024 to evaluate the effectiveness of the actions taken in the FCAP wetland and to measure Se concentrations in biota throughout the watershed. The methods and results from a water and fish field collection campaign in April 2024 are presented in this report.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2024

Enhancement on selenium volatilization for phytoremediation: role of plant and soil microbe interaction

This study aimed at quantifying the potential effects of plant and soil microbial interaction on selenium (Se) volatilization, with the specific objectives of identifying soil bacteria associated with rabbitfoot grass (Polypogon monspeliensis) and demonstrating the enhancement of Se volatilization in the soil-Indian mustard (Brassica juncea) system through inoculation of the soil with the identified best Se-volatilizing bacterial strain. Soil bacteria were isolated from topsoil and rhizosphere soils of rabbitfoot grass, and the bacterial colonies were characterized via PCR-DGGE and DGGE band analysis prior to their identification using 16S rDNA sequencing technique.Bacillus cereusproduced over 500-fold more volatile Se in a culture medium treated with 15 µg Se/mL (equal mixture of SeO 4 2- , SeO 3 2- and selenomethionine) than any of the other eight identified bacterial strains. Inoculation of Indian mustard vegetated soil with the best Se volatilizing bacterial strainB. cereusresulted in a significant (p<0.05) increase in Se volatilization during a 7-day time period, compared to the soil-plant system without inoculation ofB. cereus. Thus, inoculation of the soil withB. cereussubstantially enhanced Se removal via biogenic volatilization in the soil-Indian mustard system. This study evaluated the role ofB. cereusin enhancing Se volatilization in soil-plant systems, and demonstrated the importance of plant and soil microbial interaction for Se phytoremediation.

Plant Sciences↗
DOE OSTI2022

Selenite and Selenate Sequestration during Coprecipitation with Barite: Insights from Mineralization Processes of Adsorption, Nucleation, and Growth

Coprecipitation of selenium oxyanions with barite is a facile way to sequester Se in the environments. However, the chemical composition of Se-barite coprecipitates usually deviates from that predicted from thermodynamic calculations. This discrepancy was resolved by considering variations in nucleation and growth rates controlled by ion–mineral interactions, solubility, and interfacial energy. For homogeneous precipitation, ~10% of sulfate, higher than thermodynamic predictions (<0.3%), was substituted by Se(IV) or Se(VI) oxyanion, which was attributed to adsorption-induced entrapment during crystal growth. For heterogeneous precipitation, thiol- and carboxylic-based organic films, utilized as model interfaces to mimic the natural organic-abundant environments, further enhanced the sequestration of Se(VI) oxyanions (up to 41–92%) with barite. Such enhancement was kinetically driven by increased nucleation rates of selenate-rich barite having a lower interfacial energy than pure barite. In contrast, only small amounts of Se(IV) oxyanions (~1%) were detected in heterogeneous coprecipitates mainly due to a lower saturation index of BaSeO 3 and deprotonation degree of Se(IV) oxyanion at pH 5.6. Finally, these roles of nanoscale mineralization mechanisms observed during composition selection of Se-barite could mark important steps toward the remediation of contaminants through coprecipitation.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2020

Materials Data on KAsSe2 by Materials Project

KAsSe2 crystallizes in the triclinic P1 space group. The structure is three-dimensional. there are four inequivalent K1+ sites. In the first K1+ site, K1+ is bonded in a 7-coordinate geometry to seven Se2- atoms. There are a spread of K–Se bond distances ranging from 3.28–3.76 Å. In the second K1+ site, K1+ is bonded to six Se2- atoms to form distorted corner-sharing KSe6 pentagonal pyramids. There are a spread of K–Se bond distances ranging from 3.49–3.66 Å. In the third K1+ site, K1+ is bonded in a 7-coordinate geometry to seven Se2- atoms. There are a spread of K–Se bond distances ranging from 3.28–3.76 Å. In the fourth K1+ site, K1+ is bonded to six Se2- atoms to form distorted corner-sharing KSe6 pentagonal pyramids. There are a spread of K–Se bond distances ranging from 3.49–3.66 Å. There are four inequivalent As3+ sites. In the first As3+ site, As3+ is bonded in a trigonal non-coplanar geometry to three Se2- atoms. There are one shorter (2.35 Å) and two longer (2.49 Å) As–Se bond lengths. In the second As3+ site, As3+ is bonded in a trigonal non-coplanar geometry to three Se2- atoms. There are a spread of As–Se bond distances ranging from 2.34–2.50 Å. In the third As3+ site, As3+ is bonded in a trigonal non-coplanar geometry to three Se2- atoms. There are one shorter (2.35 Å) and two longer (2.49 Å) As–Se bond lengths. In the fourth As3+ site, As3+ is bonded in a trigonal non-coplanar geometry to three Se2- atoms. There are a spread of As–Se bond distances ranging from 2.34–2.50 Å. There are eight inequivalent Se2- sites. In the first Se2- site, Se2- is bonded in a 5-coordinate geometry to four K1+ and one As3+ atom. In the second Se2- site, Se2- is bonded in a 4-coordinate geometry to two K1+ and two As3+ atoms. In the third Se2- site, Se2- is bonded to four K1+ and one As3+ atom to form distorted SeK4As square pyramids that share corners with five SeK4As square pyramids and edges with three SeK3As2 square pyramids. In the fourth Se2- site, Se2- is bonded to three K1+ and two As3+ atoms to form a mixture of distorted corner and edge-sharing SeK3As2 square pyramids. In the fifth Se2- site, Se2- is bonded in a 5-coordinate geometry to four K1+ and one As3+ atom. In the sixth Se2- site, Se2- is bonded in a 4-coordinate geometry to two K1+ and two As3+ atoms. In the seventh Se2- site, Se2- is bonded to four K1+ and one As3+ atom to form distorted SeK4As square pyramids that share corners with five SeK4As square pyramids and edges with three SeK3As2 square pyramids. In the eighth Se2- site, Se2- is bonded to three K1+ and two As3+ atoms to form a mixture of distorted corner and edge-sharing SeK3As2 square pyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on RbPSe6 by Materials Project

RbPSe6 crystallizes in the orthorhombic Pca2_1 space group. The structure is three-dimensional. Rb1+ is bonded in a 12-coordinate geometry to twelve Se1- atoms. There are a spread of Rb–Se bond distances ranging from 3.57–4.22 Å. P5+ is bonded in a tetrahedral geometry to four Se1- atoms. There are a spread of P–Se bond distances ranging from 2.18–2.34 Å. There are six inequivalent Se1- sites. In the first Se1- site, Se1- is bonded in a distorted single-bond geometry to two equivalent Rb1+ and one P5+ atom. In the second Se1- site, Se1- is bonded in a distorted single-bond geometry to two equivalent Rb1+, one P5+, and one Se1- atom. The Se–Se bond length is 2.37 Å. In the third Se1- site, Se1- is bonded in a distorted trigonal non-coplanar geometry to two equivalent Rb1+ and two Se1- atoms. The Se–Se bond length is 2.45 Å. In the fourth Se1- site, Se1- is bonded in a 4-coordinate geometry to two equivalent Rb1+ and two Se1- atoms. The Se–Se bond length is 2.42 Å. In the fifth Se1- site, Se1- is bonded in a distorted single-bond geometry to one Rb1+, one P5+, and one Se1- atom. In the sixth Se1- site, Se1- is bonded in a distorted single-bond geometry to three equivalent Rb1+ and one P5+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on KCeSe4 by Materials Project

KCeSe4 crystallizes in the tetragonal P4/nbm space group. The structure is three-dimensional. K1+ is bonded in a 8-coordinate geometry to eight equivalent Se+1.25- atoms. All K–Se bond lengths are 3.48 Å. Ce4+ is bonded in a 8-coordinate geometry to eight equivalent Se+1.25- atoms. All Ce–Se bond lengths are 3.05 Å. Se+1.25- is bonded in a 5-coordinate geometry to two equivalent K1+, two equivalent Ce4+, and one Se+1.25- atom. The Se–Se bond length is 2.46 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on C(Se2Br)2 by Materials Project

C(Se2Br)2 crystallizes in the orthorhombic Pna2_1 space group. The structure is zero-dimensional and consists of four C(Se2Br)2 clusters. C4+ is bonded in a trigonal planar geometry to three Se2- atoms. There are a spread of C–Se bond distances ranging from 1.85–1.87 Å. There are four inequivalent Se2- sites. In the first Se2- site, Se2- is bonded in a 3-coordinate geometry to one C4+, one Se2-, and one Br2+ atom. The Se–Se bond length is 2.41 Å. The Se–Br bond length is 2.97 Å. In the second Se2- site, Se2- is bonded in a distorted L-shaped geometry to two Se2- atoms. The Se–Se bond length is 2.42 Å. In the third Se2- site, Se2- is bonded in a 3-coordinate geometry to one C4+, one Se2-, and one Br2+ atom. The Se–Br bond length is 3.01 Å. In the fourth Se2- site, Se2- is bonded in a T-shaped geometry to one C4+ and two Br2+ atoms. There are one shorter (2.55 Å) and one longer (2.62 Å) Se–Br bond lengths. There are two inequivalent Br2+ sites. In the first Br2+ site, Br2+ is bonded in a 1-coordinate geometry to two Se2- atoms. In the second Br2+ site, Br2+ is bonded in a 2-coordinate geometry to two Se2- atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ba2As2Se5 by Materials Project

Ba2As2Se5 crystallizes in the monoclinic P2_1 space group. The structure is three-dimensional. there are four inequivalent Ba2+ sites. In the first Ba2+ site, Ba2+ is bonded in a 9-coordinate geometry to nine Se2- atoms. There are a spread of Ba–Se bond distances ranging from 3.34–3.81 Å. In the second Ba2+ site, Ba2+ is bonded in a 8-coordinate geometry to eight Se2- atoms. There are a spread of Ba–Se bond distances ranging from 3.33–3.57 Å. In the third Ba2+ site, Ba2+ is bonded in a 9-coordinate geometry to nine Se2- atoms. There are a spread of Ba–Se bond distances ranging from 3.34–3.61 Å. In the fourth Ba2+ site, Ba2+ is bonded in a 8-coordinate geometry to eight Se2- atoms. There are a spread of Ba–Se bond distances ranging from 3.32–3.71 Å. There are four inequivalent As3+ sites. In the first As3+ site, As3+ is bonded in a trigonal non-coplanar geometry to three Se2- atoms. There are a spread of As–Se bond distances ranging from 2.43–2.55 Å. In the second As3+ site, As3+ is bonded in a distorted trigonal non-coplanar geometry to three Se2- atoms. There are a spread of As–Se bond distances ranging from 2.41–2.44 Å. In the third As3+ site, As3+ is bonded in a 3-coordinate geometry to three Se2- atoms. There are a spread of As–Se bond distances ranging from 2.41–2.55 Å. In the fourth As3+ site, As3+ is bonded in a distorted trigonal non-coplanar geometry to three Se2- atoms. There are a spread of As–Se bond distances ranging from 2.39–2.46 Å. There are ten inequivalent Se2- sites. In the first Se2- site, Se2- is bonded in a 1-coordinate geometry to three Ba2+ and one As3+ atom. In the second Se2- site, Se2- is bonded in a 4-coordinate geometry to three Ba2+ and one As3+ atom. In the third Se2- site, Se2- is bonded in a 4-coordinate geometry to two Ba2+ and two As3+ atoms. In the fourth Se2- site, Se2- is bonded in a 4-coordinate geometry to two equivalent Ba2+ and two As3+ atoms. In the fifth Se2- site, Se2- is bonded to four Ba2+ and one As3+ atom to form a mixture of distorted corner and edge-sharing SeBa4As square pyramids. In the sixth Se2- site, Se2- is bonded to four Ba2+ and one As3+ atom to form a mixture of distorted corner, edge, and face-sharing SeBa4As square pyramids. In the seventh Se2- site, Se2- is bonded to four Ba2+ and one As3+ atom to form a mixture of distorted corner and face-sharing SeBa4As square pyramids. In the eighth Se2- site, Se2- is bonded in a 5-coordinate geometry to four Ba2+ and one As3+ atom. In the ninth Se2- site, Se2- is bonded in a 5-coordinate geometry to four Ba2+ and one As3+ atom. In the tenth Se2- site, Se2- is bonded in a 5-coordinate geometry to four Ba2+ and one As3+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ta3(Se4Br3)2 by Materials Project

Ta3(Se4Br3)2 crystallizes in the triclinic P-1 space group. The structure is two-dimensional and consists of one Ta3(Se4Br3)2 sheet oriented in the (0, 1, 0) direction. there are three inequivalent Ta+4.67+ sites. In the first Ta+4.67+ site, Ta+4.67+ is bonded in an octahedral geometry to six Br1- atoms. There are a spread of Ta–Br bond distances ranging from 2.50–2.56 Å. In the second Ta+4.67+ site, Ta+4.67+ is bonded to eight Se1- atoms to form distorted face-sharing TaSe8 hexagonal bipyramids. There are a spread of Ta–Se bond distances ranging from 2.61–2.75 Å. In the third Ta+4.67+ site, Ta+4.67+ is bonded to eight Se1- atoms to form distorted face-sharing TaSe8 hexagonal bipyramids. There are a spread of Ta–Se bond distances ranging from 2.61–2.76 Å. There are eight inequivalent Se1- sites. In the first Se1- site, Se1- is bonded in a 2-coordinate geometry to two Ta+4.67+ and one Se1- atom. The Se–Se bond length is 2.39 Å. In the second Se1- site, Se1- is bonded in a 2-coordinate geometry to two Ta+4.67+ and one Se1- atom. The Se–Se bond length is 2.41 Å. In the third Se1- site, Se1- is bonded in a 2-coordinate geometry to two Ta+4.67+, one Se1-, and one Br1- atom. The Se–Br bond length is 3.38 Å. In the fourth Se1- site, Se1- is bonded in a 2-coordinate geometry to two equivalent Ta+4.67+ atoms. In the fifth Se1- site, Se1- is bonded in a 2-coordinate geometry to two equivalent Ta+4.67+ atoms. In the sixth Se1- site, Se1- is bonded in a 2-coordinate geometry to two equivalent Ta+4.67+ atoms. In the seventh Se1- site, Se1- is bonded in a 2-coordinate geometry to two equivalent Ta+4.67+ atoms. In the eighth Se1- site, Se1- is bonded in a 4-coordinate geometry to two Ta+4.67+, one Se1-, and one Br1- atom. The Se–Br bond length is 3.26 Å. There are six inequivalent Br1- sites. In the first Br1- site, Br1- is bonded in a distorted single-bond geometry to one Ta+4.67+ and one Se1- atom. In the second Br1- site, Br1- is bonded in a distorted single-bond geometry to one Ta+4.67+ and one Se1- atom. In the third Br1- site, Br1- is bonded in a single-bond geometry to one Ta+4.67+ atom. In the fourth Br1- site, Br1- is bonded in a single-bond geometry to one Ta+4.67+ atom. In the fifth Br1- site, Br1- is bonded in a distorted single-bond geometry to one Ta+4.67+ atom. In the sixth Br1- site, Br1- is bonded in a distorted single-bond geometry to one Ta+4.67+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Cu7PSe6 by Materials Project

Cu7PSe6 crystallizes in the orthorhombic Pna2_1 space group. The structure is three-dimensional. there are seven inequivalent Cu1+ sites. In the first Cu1+ site, Cu1+ is bonded in a distorted T-shaped geometry to three Se2- atoms. There are a spread of Cu–Se bond distances ranging from 2.40–2.45 Å. In the second Cu1+ site, Cu1+ is bonded in a 4-coordinate geometry to four Se2- atoms. There are a spread of Cu–Se bond distances ranging from 2.46–2.64 Å. In the third Cu1+ site, Cu1+ is bonded in a 4-coordinate geometry to four Se2- atoms. There are a spread of Cu–Se bond distances ranging from 2.42–2.84 Å. In the fourth Cu1+ site, Cu1+ is bonded to four Se2- atoms to form CuSe4 tetrahedra that share corners with two equivalent PSe4 tetrahedra. There are a spread of Cu–Se bond distances ranging from 2.41–2.59 Å. In the fifth Cu1+ site, Cu1+ is bonded in a 4-coordinate geometry to four Se2- atoms. There are a spread of Cu–Se bond distances ranging from 2.46–2.61 Å. In the sixth Cu1+ site, Cu1+ is bonded in a bent 150 degrees geometry to two Se2- atoms. There are one shorter (2.34 Å) and one longer (2.41 Å) Cu–Se bond lengths. In the seventh Cu1+ site, Cu1+ is bonded in a 4-coordinate geometry to four Se2- atoms. There are a spread of Cu–Se bond distances ranging from 2.41–2.91 Å. P5+ is bonded to four Se2- atoms to form PSe4 tetrahedra that share corners with two equivalent CuSe4 tetrahedra. There are a spread of P–Se bond distances ranging from 2.23–2.25 Å. There are six inequivalent Se2- sites. In the first Se2- site, Se2- is bonded to three Cu1+ and one P5+ atom to form corner-sharing SeCu3P tetrahedra. In the second Se2- site, Se2- is bonded to three Cu1+ and one P5+ atom to form distorted corner-sharing SeCu3P tetrahedra. In the third Se2- site, Se2- is bonded to three Cu1+ and one P5+ atom to form corner-sharing SeCu3P trigonal pyramids. In the fourth Se2- site, Se2- is bonded to three Cu1+ and one P5+ atom to form distorted corner-sharing SeCu3P tetrahedra. In the fifth Se2- site, Se2- is bonded in a 6-coordinate geometry to six Cu1+ atoms. In the sixth Se2- site, Se2- is bonded in a 7-coordinate geometry to seven Cu1+ atoms.

36 MATERIALS SCIENCE↗