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All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

169 Tm ( n , γ ) cross section and statistical decay properties from measurements at the DANCE facility

Background: Radiative neutron capture on thulium, which is a monoisotopic element, plays a role in different applications such as nuclear astrophysics or nuclear burning environments. Considerable discrepancies—reaching 20%—exist between evaluations in the unresolved-resonance region. Furthermore, experimental data on statistical 𝛾 decay in odd-odd rare-earth nuclei is scarce. There are still open questions about the systematics of the so-called scissors mode in the 𝑀⁢1 photon strength function, especially in odd-odd nuclei. Purpose: This work is focused on two main topics—deriving experimental 169 Tm ⁢(𝑛,𝛾) cross section and studying statistical 𝛾 decay of 170 Tm, in particular properties of the scissors mode. Methods: The capture experiments to obtain experimental cross section were performed at the Los Alamos Neutron Science Center using the time-of-flight technique and employing the Detector for Advanced Neutron Capture Experiments. Measured coincident 𝛾-ray spectra were also compared with statistical simulations using the dicebox code to test different models of level density and photon strength functions. Results: The capture cross section was determined from 1.8 eV to 0.97 MeV, the broadest neutron-energy range ever measured for this isotope. Several new resonances have been observed. The statistical 𝛾 decay of 170 Tm cannot be reproduced without a scissors mode resonance centered at ≈ 3.3MeV. Conclusions: The measured cross section in the unresolved-resonance region is generally lower than the latest evaluations. The derived 169 Tm 𝑠-process abundance is expected to increase by a factor of 1.26, while the changes of the abundances of elements heavier than 169 Tm are in the order of 0.2%. The scissors mode properties in 170 Tm are similar to those deduced in previous analyses of neighboring nuclei 168 Er and 166 Ho .

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2023

Ab Initio Simulations of Tritium Diffusion in Al 2 O and Intermetallic Al 12 (TM) 2.34 Aluminide Coating Phases

Density functional theory simulations have been carried out to investigate the diffusion of interstitial tritium in Al 12 (TM) 2.34 and Al 2 O bulk phases. In Al 12 (TM) 2.34 the transition metal (TM) sites are occupied on average by 58.93 at.% Fe, 18.52 at.% Cr, and 22.54 at.% Ni. While the insertion of interstitial tritium in Al 2 O lead to a strong disordering of the structure, we only investigated interstitial tritium in Al 12 (TM) 2.34 and its iron end-member (i.e., Al 12 Fe 2.34 ). Nine diffusion pathways have been investigated along the a-, b-, and c -axis of Al 12 (TM) 2.34 . The direction of fastest diffusion for interstitial tritium is found to be along the b-axis, with a calculated diffusion coefficient of ≈10 -10 m 2 .s -1 at 600 K, which is at least one order of magnitude faster than those previously calculated for interstitial tritium in other Al-rich phases such as Fe2Alx, Fe4Al13, and FeNiAl5 for which D T =10 -11 m 2 .s -1 , ≈10 -12 m 2 .s -1 , and D T ≈10 -13 m 2 .s -1 respectively. The comparison of the energy landscape between Al 12 (TM) 2.34 and Al 12 Fe 2.34 for the fastest diffusion pathways in each axis direction, found that some pathways are not sensitive to transition metal mixing, while other are more affected, leading to higher energy barrier in Al 12 Fe 2.34 in part due to a more energetically favorable formation of Fe—T bond compared to Ni—T. However, we found that both materials have similar diffusion coefficients as the fastest diffusion pathways occurs along pathways that are not very sensitive to transition metal mixing.

36 MATERIALS SCIENCE↗
DOE OSTI2020

GeoMelt{sup R} In-Container Vitrification (ICV){sup TM} for Fukushima Daiichi Water Treatment Secondary Wastes - 20212

The Japanese government is supporting development work implemented jointly by Veolia subsidiaries Kurion Japan, K.K., Veolia Nuclear Solutions (VNS), Inc., and Veolia Nuclear Solutions Federal Services, LLC for treating radioactive waste generated from Fukushima Daiichi Nuclear Power Station (NPS) water treatment using the GeoMelt{sup TM} In-Container Vitrification (ICV){sup TM} technology. The initial work consisted of glass formulation and engineering-scale testing which was completed in 2018, in the frame of an IRID (International Research Institute for Nuclear Decommissioning) program as part of a project subsidized by Japan's Ministry of Economy, Trade and Industry (METI). The Fukushima Daiichi NPS Mid- and Long-Term Road-map requires investigation of methods to stabilize solid wastes (and to immobilize radioisotopes in the wastes) generated as a result of emergency response and decommissioning activities. Cooling water treatment has resulted in a significant amount of solid and slurry secondary wastes (mostly adsorbents and ion-exchange materials) which will require processing at some point. GeoMelt{sup R} ICV{sup TM} is a joule-heated melter technology which uses a refractory-lined single-use container combining the melter and disposal container. There is no pouring required nor concerns with refractory corrosion which allows the process to accommodate a wide range of waste chemistries and high waste loadings. The testing described here consisted of three engineering-scale melts, each processing between 212 kg and 240 kg of waste simulants, glass formers, and non-radioactive cesium (Cs) and strontium (Sr) tracers. Continuous isokinetic stack sampling of off-gas emissions was performed for each test in order to calculate Cs and Sr retention in the glass wasteform. Single-pass retention of Cs in the final glass wasteform ranged from 91.46 to 99.30%, and single-pass retention of Sr ranged from 99.76 to 100%. Planned particulate recycle will increase these retention levels. Melt 1 processed a mixture of KUR-EH (a zeolite-based ion-exchange material), simulated Advanced Liquid Processing System (ALPS) Carbonate and Iron Slurries, and glass additives. Melt 2 processed a mixture of KUR-EH, KUR-TSG (a titanate-based adsorbent), and glass additives. Melt 3 processed a mixture of KUR-EH, simulated barium sulfate/iron ferrocyanide sludge (AREVA sludge), and glass additives. Waste loadings for these melts ranged from 70 weight percent (wt%) to 82 wt%. Vitrification produces a waste form much denser than the stored water treatment secondary waste wastes, resulting in significant volume reduction. Volume reductions for the three tests ranged from 74 to 79 vol%. Vitrification produces a chemically durable wasteform. Pacific Northwest National Laboratory (PNNL) tested three glass samples from each engineering-scale melt) by the Materials Characterization Center 1 (MCC-1) test, an international standard leach test of the chemical durability of nuclear waste glasses. PNNL also obtained one U.S. reference glass (EA Glass) and two Japan reference glasses P0798) and tested these under the same MCC-1 conditions (90 deg. C, 10 m-1, DIW, and 7, 14, 28-day) as the GeoMelt{sup R} ICV{sup TM} glasses. The GeoMelt{sup R} ICV{sup TM} glasses exhibited lower total normalized releases and 14- to 28-day normalized release rates than the three reference glasses. These results suggest that the GeoMelt{sup R} ICV{sup TM} glasses have durabilities on par with high-level waste glasses under standard test conditions. Post-melt process sampling and analysis indicated no Cs migration into the melter refractory materials and very little deposition of Cs or Sr onto the melter hood or off-gas piping internals. The results of the testing indicated good Cs retention in the glass, high volume reduction and waste loadings, and excellent chemical durability. These factors are important to minimize treatment costs and to protect workers and the environment. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2020

Materials Data on Tm(NiGe)2 by Materials Project

TmNi2Ge2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Tm is bonded in a 8-coordinate geometry to eight equivalent Ni and eight equivalent Ge atoms. All Tm–Ni bond lengths are 3.17 Å. All Tm–Ge bond lengths are 3.11 Å. Ni is bonded in a 4-coordinate geometry to four equivalent Tm and four equivalent Ge atoms. All Ni–Ge bond lengths are 2.35 Å. Ge is bonded in a 9-coordinate geometry to four equivalent Tm, four equivalent Ni, and one Ge atom. The Ge–Ge bond length is 2.49 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Tm(CuGe)2 by Materials Project

TmCu2Ge2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Tm is bonded in a 8-coordinate geometry to eight equivalent Cu and eight equivalent Ge atoms. All Tm–Cu bond lengths are 3.28 Å. All Tm–Ge bond lengths are 3.09 Å. Cu is bonded to four equivalent Tm and four equivalent Ge atoms to form a mixture of distorted edge, corner, and face-sharing CuTm4Ge4 tetrahedra. All Cu–Ge bond lengths are 2.43 Å. Ge is bonded in a 9-coordinate geometry to four equivalent Tm, four equivalent Cu, and one Ge atom. The Ge–Ge bond length is 2.44 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Tm(CuGe)2 by Materials Project

TmCu2Ge2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Tm is bonded in a 8-coordinate geometry to eight equivalent Cu and eight equivalent Ge atoms. All Tm–Cu bond lengths are 3.14 Å. All Tm–Ge bond lengths are 3.26 Å. Cu is bonded in a 9-coordinate geometry to four equivalent Tm, one Cu, and four equivalent Ge atoms. The Cu–Cu bond length is 2.33 Å. All Cu–Ge bond lengths are 2.47 Å. Ge is bonded in a 4-coordinate geometry to four equivalent Tm and four equivalent Cu atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Tm(CoGe)2 by Materials Project

TmCo2Ge2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Tm is bonded in a 8-coordinate geometry to eight equivalent Co and eight equivalent Ge atoms. All Tm–Co bond lengths are 3.20 Å. All Tm–Ge bond lengths are 3.06 Å. Co is bonded to four equivalent Tm and four equivalent Ge atoms to form a mixture of distorted face, edge, and corner-sharing CoTm4Ge4 tetrahedra. All Co–Ge bond lengths are 2.33 Å. Ge is bonded in a 9-coordinate geometry to four equivalent Tm, four equivalent Co, and one Ge atom. The Ge–Ge bond length is 2.55 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Tm(BO2)3 by Materials Project

Tm(BO2)3 crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. there are four inequivalent Tm3+ sites. In the first Tm3+ site, Tm3+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Tm–O bond distances ranging from 2.25–2.50 Å. In the second Tm3+ site, Tm3+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Tm–O bond distances ranging from 2.24–2.84 Å. In the third Tm3+ site, Tm3+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Tm–O bond distances ranging from 2.24–2.58 Å. In the fourth Tm3+ site, Tm3+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Tm–O bond distances ranging from 2.29–2.65 Å. There are six inequivalent B3+ sites. In the first B3+ site, B3+ is bonded to four O2- atoms to form corner-sharing BO4 tetrahedra. There are a spread of B–O bond distances ranging from 1.44–1.53 Å. In the second B3+ site, B3+ is bonded to four O2- atoms to form corner-sharing BO4 tetrahedra. There is two shorter (1.45 Å) and two longer (1.53 Å) B–O bond length. In the third B3+ site, B3+ is bonded to four O2- atoms to form corner-sharing BO4 tetrahedra. There are a spread of B–O bond distances ranging from 1.45–1.54 Å. In the fourth B3+ site, B3+ is bonded to four O2- atoms to form corner-sharing BO4 tetrahedra. There are a spread of B–O bond distances ranging from 1.46–1.53 Å. In the fifth B3+ site, B3+ is bonded to four O2- atoms to form corner-sharing BO4 tetrahedra. There are a spread of B–O bond distances ranging from 1.45–1.52 Å. In the sixth B3+ site, B3+ is bonded to four O2- atoms to form corner-sharing BO4 tetrahedra. There is three shorter (1.47 Å) and one longer (1.48 Å) B–O bond length. There are fifteen inequivalent O2- sites. In the first O2- site, O2- is bonded in a 2-coordinate geometry to two Tm3+ and two B3+ atoms. In the second O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Tm3+ and two B3+ atoms. In the third O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Tm3+ and two B3+ atoms. In the fourth O2- site, O2- is bonded in a 3-coordinate geometry to one Tm3+ and two equivalent B3+ atoms. In the fifth O2- site, O2- is bonded in a distorted trigonal planar geometry to one Tm3+ and two B3+ atoms. In the sixth O2- site, O2- is bonded in a distorted bent 120 degrees geometry to two Tm3+ and two equivalent B3+ atoms. In the seventh O2- site, O2- is bonded in a distorted trigonal planar geometry to one Tm3+ and two equivalent B3+ atoms. In the eighth O2- site, O2- is bonded in a 1-coordinate geometry to three Tm3+ and one B3+ atom. In the ninth O2- site, O2- is bonded in a bent 120 degrees geometry to one Tm3+ and two equivalent B3+ atoms. In the tenth O2- site, O2- is bonded in a distorted bent 120 degrees geometry to two Tm3+ and two B3+ atoms. In the eleventh O2- site, O2- is bonded in a distorted trigonal planar geometry to one Tm3+ and two B3+ atoms. In the twelfth O2- site, O2- is bonded in a 2-coordinate geometry to two Tm3+ and two equivalent B3+ atoms. In the thirteenth O2- site, O2- is bonded in a trigonal planar geometry to three B3+ atoms. In the fourteenth O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Tm3+ and two equivalent B3+ atoms. In the fifteenth O2- site, O2- is bonded in a 3-coordinate geometry to one Tm3+ and two B3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Tm(ClO4)3 by Materials Project

Tm(O4Cl)3 crystallizes in the hexagonal P6_3/m space group. The structure is three-dimensional. Tm is bonded in a 9-coordinate geometry to nine O atoms. There are six shorter (2.37 Å) and three longer (2.41 Å) Tm–O bond lengths. There are three inequivalent O sites. In the first O site, O is bonded in a single-bond geometry to one Cl atom. The O–Cl bond length is 1.42 Å. In the second O site, O is bonded in a bent 150 degrees geometry to one Tm and one Cl atom. The O–Cl bond length is 1.47 Å. In the third O site, O is bonded in a bent 150 degrees geometry to one Tm and one Cl atom. The O–Cl bond length is 1.47 Å. Cl is bonded in a tetrahedral geometry to four O atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Tm(BRh)4 by Materials Project

TmRh4B4 crystallizes in the tetragonal P4_2/nmc space group. The structure is three-dimensional. Tm is bonded in a 12-coordinate geometry to twelve equivalent Rh and twelve equivalent B atoms. There are four shorter (2.95 Å) and eight longer (3.17 Å) Tm–Rh bond lengths. There are eight shorter (3.02 Å) and four longer (3.16 Å) Tm–B bond lengths. Rh is bonded in a 5-coordinate geometry to three equivalent Tm and five equivalent B atoms. There are two shorter (2.21 Å) and three longer (2.23 Å) Rh–B bond lengths. B is bonded in a 6-coordinate geometry to three equivalent Tm, five equivalent Rh, and one B atom. The B–B bond length is 1.79 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Tm(PO3)3 by Materials Project

Tm(PO3)3 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. there are four inequivalent Tm3+ sites. In the first Tm3+ site, Tm3+ is bonded to six O2- atoms to form TmO6 octahedra that share corners with six PO4 tetrahedra. There are a spread of Tm–O bond distances ranging from 2.20–2.26 Å. In the second Tm3+ site, Tm3+ is bonded to six O2- atoms to form TmO6 octahedra that share corners with six PO4 tetrahedra. There are a spread of Tm–O bond distances ranging from 2.19–2.24 Å. In the third Tm3+ site, Tm3+ is bonded to six O2- atoms to form TmO6 octahedra that share corners with six PO4 tetrahedra. There are a spread of Tm–O bond distances ranging from 2.22–2.24 Å. In the fourth Tm3+ site, Tm3+ is bonded to six O2- atoms to form TmO6 octahedra that share corners with six PO4 tetrahedra. There are two shorter (2.21 Å) and four longer (2.22 Å) Tm–O bond lengths. There are nine inequivalent P5+ sites. In the first P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with two TmO6 octahedra and corners with two PO4 tetrahedra. The corner-sharing octahedra tilt angles range from 9–30°. There are a spread of P–O bond distances ranging from 1.50–1.61 Å. In the second P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with two TmO6 octahedra and corners with two PO4 tetrahedra. The corner-sharing octahedra tilt angles range from 16–28°. There are a spread of P–O bond distances ranging from 1.50–1.61 Å. In the third P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with two TmO6 octahedra and corners with two PO4 tetrahedra. The corner-sharing octahedra tilt angles range from 25–48°. There are a spread of P–O bond distances ranging from 1.50–1.62 Å. In the fourth P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with two TmO6 octahedra and corners with two PO4 tetrahedra. The corner-sharing octahedra tilt angles range from 31–37°. There are a spread of P–O bond distances ranging from 1.49–1.61 Å. In the fifth P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with two TmO6 octahedra and corners with two PO4 tetrahedra. The corner-sharing octahedral tilt angles are 31°. There are a spread of P–O bond distances ranging from 1.50–1.61 Å. In the sixth P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with two TmO6 octahedra and corners with two PO4 tetrahedra. The corner-sharing octahedra tilt angles range from 25–35°. There are a spread of P–O bond distances ranging from 1.50–1.62 Å. In the seventh P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with two equivalent TmO6 octahedra and corners with two PO4 tetrahedra. The corner-sharing octahedra tilt angles range from 11–27°. There is two shorter (1.50 Å) and two longer (1.60 Å) P–O bond length. In the eighth P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with two equivalent TmO6 octahedra and corners with two PO4 tetrahedra. The corner-sharing octahedra tilt angles range from 30–37°. There are a spread of P–O bond distances ranging from 1.50–1.62 Å. In the ninth P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with two TmO6 octahedra and corners with two PO4 tetrahedra. The corner-sharing octahedra tilt angles range from 27–30°. There is two shorter (1.50 Å) and two longer (1.61 Å) P–O bond length. There are twenty-seven inequivalent O2- sites. In the first O2- site, O2- is bonded in a bent 150 degrees geometry to one Tm3+ and one P5+ atom. In the second O2- site, O2- is bonded in a bent 150 degrees geometry to one Tm3+ and one P5+ atom. In the third O2- site, O2- is bonded in a bent 150 degrees geometry to one Tm3+ and one P5+ atom. In the fourth O2- site, O2- is bonded in a bent 150 degrees geometry to one Tm3+ and one P5+ atom. In the fifth O2- site, O2- is bonded in a bent 150 degrees geometry to two P5+ atoms. In the sixth O2- site, O2- is bonded in a bent 120 degrees geometry to two P5+ atoms. In the seventh O2- site, O2- is bonded in a bent 150 degrees geometry to two P5+ atoms. In the eighth O2- site, O2- is bonded in a bent 150 degrees geometry to one Tm3+ and one P5+ atom. In the ninth O2- site, O2- is bonded in a linear geometry to one Tm3+ and one P5+ atom. In the tenth O2- site, O2- is bonded in a distorted linear geometry to one Tm3+ and one P5+ atom. In the eleventh O2- site, O2- is bonded in a bent 150 degrees geometry to one Tm3+ and one P5+ atom. In the twelfth O2- site, O2- is bonded in a bent 150 degrees geometry to one Tm3+ and one P5+ atom. In the thirteenth O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Tm3+ and one P5+ atom. In the fourteenth O2- site, O2- is bonded in a bent 150 degrees geometry to one Tm3+ and one P5+ atom. In the fifteenth O2- site, O2- is bonded in a bent 150 degrees geometry to one Tm3+ and one P5+ atom. In the sixteenth O2- site, O2- is bonded in a bent 150 degrees geometry to one Tm3+ and one P5+ atom. In the seventeenth O2- site, O2- is bonded in a bent 150 degrees geometry to one Tm3+ and one P5+ atom. In the eighteenth O2- site, O2- is bonded in a bent 150 degrees geometry to one Tm3+ and one P5+ atom. In the nineteenth O2- site, O2- is bonded in a bent 150 degrees geometry to one Tm3+ and one P5+ atom. In the twentieth O2- site, O2- is bonded in a distorted bent 120 degrees geometry to two P5+ atoms. In the twenty-first O2- site, O2- is bonded in a bent 150 degrees geometry to two P5+ atoms. In the twenty-second O2- site, O2- is bonded in a distorted bent 120 degrees geometry to two P5+ atoms. In the twenty-third O2- site, O2- is bonded in a bent 150 degrees geometry to two P5+ atoms. In the twenty-fourth O2- site, O2- is bonded in a bent 150 degrees geometry to two P5+ atoms. In the twenty-fifth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to two P5+ atoms. In the twenty-sixth O2- site, O2- is bonded in a linear geometry to one Tm3+ and one P5+ atom. In the twenty-seventh O2- site, O2- is bonded in a bent 150 degrees geometry to one Tm3+ and one P5+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Tm by Materials Project

Tm is Copper structured and crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. Tm is bonded to twelve equivalent Tm atoms to form a mixture of face, edge, and corner-sharing TmTm12 cuboctahedra. All Tm–Tm bond lengths are 3.49 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Tm by Materials Project

Tm is Tungsten structured and crystallizes in the cubic Im-3m space group. The structure is three-dimensional. Tm is bonded in a distorted body-centered cubic geometry to eight equivalent Tm atoms. All Tm–Tm bond lengths are 3.41 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Tm by Materials Project

Tm is Magnesium structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. Tm is bonded to twelve equivalent Tm atoms to form a mixture of face, edge, and corner-sharing TmTm12 cuboctahedra. There are six shorter (3.44 Å) and six longer (3.56 Å) Tm–Tm bond lengths.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Magnetothermal properties of Tm x Dy 1- x Al 2 ( x = 0.25, 0.50 and 0.75)

Here, we describe magnetic, thermal, and magnetocaloric properties of rare earth intermetallic compounds Tm x Dy 1-x Al 2 with 0.25, 0.5 and 0.75. Using model Hamiltonian we consider contributions of the crystalline electric field anisotropy in both Tm and Dy magnetic sublattices, disorder in exchange interactions among Tm-Tm, Dy-Dy and Tm-Dy magnetic ions, and the Zeeman effect. Employing earlier reported and new experimental measurements, we first determine a single free variable – the intersublattice magnetic exchange parameter – to properly model the temperature and magnetic field dependencies of heat capacity and magnetization, and then use the modeling results to explain the emergence of an anomalous spin reorientation transition and its influence on the magnetocaloric effect in the title compounds. Theoretical results agree with experimental data reasonably well.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Thermodynamics of Tritium Trapping by Point Defects in Intermetallic Al 12 (TM) 2.35 Aluminide Coating Phase

Density functional theory simulations have been carried out to investigate the potential for tritium trapping by metal vacancies in intermetallic Al 12 (TM) 2.35 phase (TM = Fe, Cr, and Ni) as function of temperature and tritium partial pressure. It was found that tritium could be favorably trapped by Fe and Ni vacancies and not favorably trapped by Al and Cr vacancies. However, due to the presence of partially occupied Al sites in bulk Al 12 (TM) 2.35 , leading to the approximate number of ~255 Al atoms in the unit cell, 86 sites were found energetically favorable to the creation of an Al vacancy. While adding a tritium atom in an Al vacancy is not energetically favorable, the tritiated defect still has a negative Gibbs free energy because the energy gain for creating an Al vacancy overcome the energy cost of adding the tritium species. Based on the calculated Gibbs free energy, the first tritiation of a metal vacancy, at conditions relevant to in-reactor operations, should be more favorable for Al, followed Fe, Ni, and Cr vacancies. By comparing the behavior of tritium in Al 12 (TM) 2.35 with previously studied Fe-Al coating phases (i.e., FeNiAl 5 , Fe 4 Al 13 , and Fe 2 Al 5.6 ), we found that there is a correlation between interstitial tritium solubility and the potential for vacancy trapping. The current trend suggests that if the insertion of an interstitial tritium cost more than 0.3 eV, then trapping by metal vacancies should be preferred. By combining the simulations results obtained to date, we noticed different trapping mechanisms of tritium in the Al coating. Tritium is mostly trapped by Fe and Ni vacancies in the outer Fe-Al coating phase Al 12 (TM) 2.35 while tritium should be preferentially trapped by Al and Fe vacancies for the inner Fe-Al coating phases (FeNiAl 5 , Fe 4 Al 13 , Fe 2 Al 5.6 ). Altogether, these studies show that tritium interacts differently with the various Fe-Al aluminide phases, they also suggest that tritium trapping and retention could be more efficient if metal defects are present and if the solubility of interstitial tritium in the different phases is low.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Tm(MnGe)2 by Materials Project

Tm(MnGe)2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Tm is bonded in a 8-coordinate geometry to eight equivalent Ge atoms. All Tm–Ge bond lengths are 3.04 Å. Mn is bonded to four equivalent Ge atoms to form a mixture of corner and edge-sharing MnGe4 tetrahedra. All Mn–Ge bond lengths are 2.42 Å. Ge is bonded in a 9-coordinate geometry to four equivalent Tm, four equivalent Mn, and one Ge atom. The Ge–Ge bond length is 2.55 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Tm(MnSn)6 by Materials Project

TmMn6Sn6 crystallizes in the hexagonal P6/mmm space group. The structure is three-dimensional. Tm is bonded to eight Sn atoms to form distorted edge-sharing TmSn8 hexagonal bipyramids. There are two shorter (2.99 Å) and six longer (3.14 Å) Tm–Sn bond lengths. Mn is bonded in a 12-coordinate geometry to six Sn atoms. There are a spread of Mn–Sn bond distances ranging from 2.73–2.82 Å. There are three inequivalent Sn sites. In the first Sn site, Sn is bonded in a 6-coordinate geometry to six equivalent Mn atoms. In the second Sn site, Sn is bonded in a 8-coordinate geometry to one Tm, six equivalent Mn, and one Sn atom. The Sn–Sn bond length is 3.01 Å. In the third Sn site, Sn is bonded in a 12-coordinate geometry to three equivalent Tm and six equivalent Mn atoms.

36 MATERIALS SCIENCE↗