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All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on Nd(Ga3Co)3 by Materials Project

NdCo3Ga9 crystallizes in the monoclinic C2/m space group. The structure is three-dimensional. Nd is bonded in a 12-coordinate geometry to thirteen Ga atoms. There are a spread of Nd–Ga bond distances ranging from 3.09–3.54 Å. There are three inequivalent Co sites. In the first Co site, Co is bonded in a 8-coordinate geometry to one Co and seven Ga atoms. The Co–Co bond length is 2.75 Å. There are a spread of Co–Ga bond distances ranging from 2.34–2.63 Å. In the second Co site, Co is bonded in a 9-coordinate geometry to two equivalent Co and seven Ga atoms. Both Co–Co bond lengths are 2.70 Å. There are a spread of Co–Ga bond distances ranging from 2.32–2.58 Å. In the third Co site, Co is bonded in a 11-coordinate geometry to three Co and eight Ga atoms. There are a spread of Co–Ga bond distances ranging from 2.55–2.91 Å. There are ten inequivalent Ga sites. In the first Ga site, Ga is bonded in a 10-coordinate geometry to two equivalent Nd and eight Ga atoms. There are a spread of Ga–Ga bond distances ranging from 2.65–2.93 Å. In the second Ga site, Ga is bonded in a 1-coordinate geometry to three Co and seven Ga atoms. There are two shorter (2.61 Å) and two longer (2.82 Å) Ga–Ga bond lengths. In the third Ga site, Ga is bonded in a 10-coordinate geometry to one Nd, two Co, and seven Ga atoms. Both Ga–Ga bond lengths are 2.81 Å. In the fourth Ga site, Ga is bonded in a 4-coordinate geometry to two equivalent Nd, two equivalent Co, and four equivalent Ga atoms. All Ga–Ga bond lengths are 2.80 Å. In the fifth Ga site, Ga is bonded in a 8-coordinate geometry to two equivalent Nd, two equivalent Co, and four equivalent Ga atoms. All Ga–Ga bond lengths are 2.75 Å. In the sixth Ga site, Ga is bonded in a 3-coordinate geometry to five Co and six Ga atoms. There are a spread of Ga–Ga bond distances ranging from 2.94–3.06 Å. In the seventh Ga site, Ga is bonded in a 2-coordinate geometry to two equivalent Nd, three Co, and four Ga atoms. There are one shorter (2.49 Å) and one longer (2.61 Å) Ga–Ga bond lengths. In the eighth Ga site, Ga is bonded in a 6-coordinate geometry to two equivalent Nd, two equivalent Co, and four Ga atoms. The Ga–Ga bond length is 2.57 Å. In the ninth Ga site, Ga is bonded in a 10-coordinate geometry to two equivalent Nd, two equivalent Co, and six Ga atoms. In the tenth Ga site, Ga is bonded in a 11-coordinate geometry to two equivalent Nd, three Co, and six Ga atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Nd(Al5Os)2 by Materials Project

Nd(OsAl5)2 crystallizes in the orthorhombic Cmcm space group. The structure is three-dimensional. Nd is bonded in a 10-coordinate geometry to four equivalent Os and sixteen Al atoms. All Nd–Os bond lengths are 3.49 Å. There are a spread of Nd–Al bond distances ranging from 3.19–3.70 Å. Os is bonded in a 10-coordinate geometry to two equivalent Nd and ten Al atoms. There are a spread of Os–Al bond distances ranging from 2.58–2.77 Å. There are five inequivalent Al sites. In the first Al site, Al is bonded in a 2-coordinate geometry to one Nd and two equivalent Os atoms. In the second Al site, Al is bonded in a distorted linear geometry to two equivalent Nd and two equivalent Os atoms. In the third Al site, Al is bonded in a 2-coordinate geometry to two equivalent Nd and two equivalent Os atoms. In the fourth Al site, Al is bonded in a distorted bent 120 degrees geometry to two equivalent Nd and two equivalent Os atoms. In the fifth Al site, Al is bonded in a 2-coordinate geometry to one Nd and two equivalent Os atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2026

The Stability of Nd Hydroxyl Complexes at Near Neutral to Alkaline pH from 25 to 75 °C: Implications for Monazite Solubility in Hydrothermal Aqueous Fluids

Speciation of rare earth elements (REE) in aqueous fluids controls their mobilization during fluid-rock interaction. Thermodynamic modeling provides important insights into the factors controlling REE mobility and fractionation in aqueous fluids, in which aqueous REE hydroxyl complexes are particularly important across a broad pH range. However, the stability of these REE hydroxyl complexes remains poorly determined due to limited experimental data above ambient temperature. In this work, UV–vis spectrophotometry experiments were conducted to determine the cumulative hydrolysis constants for neodymium (Nd) from 25 to 75 °C in near-neutral to alkaline solutions. The color indicator m -cresol purple was used to determine in situ pH. Alkaline NaOH-bearing aqueous solutions were doped with varying initial Nd concentrations (0 to ∼0.155 mmol/kg), which resulted in the release of protons (H + ) and pH decrease during hydrolysis of Nd 3+ according to Nd 3+ + n H 2 O = Nd(OH) n 3– n + H + . The average OH – ligand number coordinated to Nd 3+ was found to increase from 1.0 to 1.6 at 25 °C and from 1.2 to 2.8 at 75 °C over a pH range from 6.3 to 9.0. The measured speciation shows an increased predominance of Nd(OH) 3 0 over the Nd(OH) 2 + and Nd(OH) 2+ species with increased temperature and pH. The increasing cumulative formation constants (log*β° n , n = 1 to 3) retrieved from 25 to 75 °C differ by 0.1 to 1.9 logarithmic units in comparison to existing thermodynamic databases. These updated thermodynamic data have important implications for geochemical modeling of the speciation of Nd hydroxyl complexes and the solubility of monazite as a function of pH.

58 GEOSCIENCES↗
DOE OSTI2021

Absence of moment fragmentation in the mixed B -site pyrochlore Nd 2 GaSbO 7

Nd-based pyrochlore oxides of the form Nd 2 GaSbO 7 have garnered a significant amount of interest owing to the moment fragmentation physics observed in Nd 2 GaSbO 7 and speculated in Nd 2 GaSbO 7 . Notably this phenomenon is not ubiquitous in this family, as it is absent in Nd 2 GaSbO 7 , which features a smaller ionic radius on the B site. Here, we explore the necessary conditions for moment fragmentation in the Nd pyrochlore family through a detailed study of the mixed B-site pyrochlore Nd 2 GaSbO 7 . Furthermore, the B site of this system is characterized by significant disorder and an extremely small average ionic radius. Similarly to Nd 2 GaSbO 7 , we find no evidence for moment fragmentation through our bulk characterization and neutron scattering experiments, indicating that chemical pressure (and not necessarily the B-site disorder) plays a key role in the presence or absence of this phenomenon in this material family. Surprisingly, the presence of significant B-site disorder in Nd 2 GaSbO 7 does not generate a spin-glass ground state and instead the same all-in-all-out magnetic order identified in other Nd pyrochlores is found here.

36 MATERIALS SCIENCE↗
NASA NTRS1993

The Sm-(146,147)-Nd-(142,143) formation interval for the lunar mantle and implications for lunar evolution

Small anomalies in the isotopic abundance of Nd-142 have been measured for two A17 high-Ti basalts, ilmenite basalt 12056, olivine-pigeonite basalt 12039, feldspathic basalt 12038, and two KREEP basalts. These anomalies correlate with Sm-147/Nd-144 for the basalt source regions as calculated from initial Nd-143/Nd-144 ratios in the basalts, and are interpreted to be from decay of Sm-146 (t sub 1/2 = 103 Ma) in distinct lunar mantle reservoirs. A three-stage model for evolution of Nd-143/Nd-144 and Nd-142/Nd-144 yields reservoir Sm-147/Nd-144 ratios which, with the Nd-142/Nd-144 ratios in the basalts, form a 'mantle isochron' giving a lunar mantle formation interval of 94+2230 Ma (2c(rho)). Calculated reservoir Sm/Nd ratios are in the range expected from some earlier models of basalt petrogenesis. The isochron value of Nd-142/Nd-144 at Sm-147/Nd-144 sub CHUR = 0.1967 is within error limits of the average Nd-142/Nd-144 measured for an L6 chondrite, an H5 chondrite, and the Orgueil carbonaceous chondrite. Evolution of Nd-143 and Nd-142 for high-Ti basalt 70135 was modeled precisely, starting from chondritic relative REE and Nd-isotopic abundances and using the initial (Sm-146/Sm-144) sub 0 ratio inferred from a previous study of angrite LEW86010 as the initial solar system value of this parameter. We infer that the initial Sm/Nd ratio in precursor lunar materials was very nearly chondritic (within approximately 8 percent) prior to lunar differentiation.

Nyquist, L. E.↗
NASA NTRS2011

Sm-Nd and Ar-Ar Studies of DHO 908 and 489: Implications for Lunar Crustal History

It is widely assumed that ferroan anorthosites (FANs) formed as flotation cumulates on a global lunar magma ocean (LMO). A corollary is that all FANs are approximately contemporaneous and formed with the same initial Nd-143/Nd-144 ratio. Indeed, a whole rock isochron for selected FANs (and An93 anorthosite) yields an isochron age of 4.42 +/- 0.13 Ga and initial Nd-143/Nd-144, expressed in epsilon-units, of epsilon(sub Nd,CHUR) = 0.3+/-0.3 relative to the CHondritic Uniform Reservoir , or epsilon(sub Nd,HEDPB)=-0.6+/-0.3 relative to the HED Parent Body. These values are in good agreement with the age (T) = 4.47+/-0.07 Ga, and epsilon(sub Nd,HEDPB) =-0.6 +/- 0.5 for FAN 67075. We also have studied anorthositic clasts in the Dhofar 908 and 489 lunar highland meteorites containing clasts of magnesian anorthosites (MAN) with Mg# approximately 75. Because of their relatively high Mg#, magnesian anorthosites should have preceded most FANs in crystallization from the LMO if both are LMO products. Thus, it is important to determine whether the Nd-isotopic data of MAN and FAN are consistent with a co-magmatic origin. We previously reported Sm-Nd data for white clast Dho 908 WC. Mafic minerals in this clast were too small to be physically separated for an isochron. However, we estimated initial Nd-143/Nd-144 for the clast by combining its bulk ("whole rock") Sm-Nd data with an Ar-39-Ar-40 age of 4.42+/-.04 Ga. Here we report additional Sm-Nd data for bulk samples of Dho 908 and its pair Dho 489.

Nyquist, L. E.↗
DOE OSTI2020

Materials Data on Nd(Al4Co)2 by Materials Project

NdCo2Al8 crystallizes in the orthorhombic Pbam space group. The structure is three-dimensional. Nd is bonded in a 11-coordinate geometry to thirteen Al atoms. There are a spread of Nd–Al bond distances ranging from 3.14–3.36 Å. There are two inequivalent Co sites. In the first Co site, Co is bonded in a 9-coordinate geometry to nine Al atoms. There are a spread of Co–Al bond distances ranging from 2.34–2.57 Å. In the second Co site, Co is bonded in a 9-coordinate geometry to nine Al atoms. There are a spread of Co–Al bond distances ranging from 2.35–2.60 Å. There are nine inequivalent Al sites. In the first Al site, Al is bonded in a 12-coordinate geometry to two equivalent Nd, two equivalent Co, and eight Al atoms. There are a spread of Al–Al bond distances ranging from 2.69–3.02 Å. In the second Al site, Al is bonded in a 2-coordinate geometry to two equivalent Nd, two equivalent Co, and three Al atoms. The Al–Al bond length is 2.69 Å. In the third Al site, Al is bonded in a 2-coordinate geometry to two equivalent Nd, two equivalent Co, and two Al atoms. The Al–Al bond length is 2.71 Å. In the fourth Al site, Al is bonded in a distorted linear geometry to two equivalent Nd, two equivalent Co, and four equivalent Al atoms. In the fifth Al site, Al is bonded in a 3-coordinate geometry to three Co atoms. In the sixth Al site, Al is bonded in a distorted linear geometry to two equivalent Nd, two Co, and six Al atoms. There are two shorter (2.82 Å) and two longer (2.86 Å) Al–Al bond lengths. In the seventh Al site, Al is bonded in a 2-coordinate geometry to two equivalent Nd, two equivalent Co, and six Al atoms. There are one shorter (2.65 Å) and one longer (2.71 Å) Al–Al bond lengths. In the eighth Al site, Al is bonded in a 2-coordinate geometry to two equivalent Nd, two equivalent Co, and five Al atoms. The Al–Al bond length is 2.64 Å. In the ninth Al site, Al is bonded in a 12-coordinate geometry to four equivalent Co and four Al atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Nd(MnFe5)2 by Materials Project

Nd(MnFe5)2 crystallizes in the orthorhombic Immm space group. The structure is three-dimensional. Nd is bonded in a 10-coordinate geometry to two equivalent Mn and eighteen Fe atoms. Both Nd–Mn bond lengths are 3.19 Å. There are a spread of Nd–Fe bond distances ranging from 3.03–3.22 Å. Mn is bonded in a 9-coordinate geometry to one Nd, one Mn, and twelve Fe atoms. The Mn–Mn bond length is 2.16 Å. There are a spread of Mn–Fe bond distances ranging from 2.53–2.83 Å. There are four inequivalent Fe sites. In the first Fe site, Fe is bonded to two equivalent Nd, two equivalent Mn, and eight Fe atoms to form a mixture of distorted face, edge, and corner-sharing FeNd2Mn2Fe8 cuboctahedra. There are a spread of Fe–Fe bond distances ranging from 2.33–2.60 Å. In the second Fe site, Fe is bonded in a 12-coordinate geometry to two equivalent Nd, two equivalent Mn, and eight Fe atoms. There are two shorter (2.58 Å) and two longer (2.78 Å) Fe–Fe bond lengths. In the third Fe site, Fe is bonded in a 12-coordinate geometry to two equivalent Nd, two equivalent Mn, and eight Fe atoms. Both Fe–Fe bond lengths are 2.55 Å. In the fourth Fe site, Fe is bonded in a 2-coordinate geometry to one Nd, four equivalent Mn, and nine Fe atoms. The Fe–Fe bond length is 2.36 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Nd(Al5Fe)2 by Materials Project

Al10Fe2Nd crystallizes in the orthorhombic Cmcm space group. The structure is three-dimensional. Nd is bonded in a 10-coordinate geometry to four equivalent Fe and sixteen Al atoms. All Nd–Fe bond lengths are 3.46 Å. There are a spread of Nd–Al bond distances ranging from 3.17–3.67 Å. Fe is bonded in a 10-coordinate geometry to two equivalent Nd and ten Al atoms. There are a spread of Fe–Al bond distances ranging from 2.55–2.75 Å. There are five inequivalent Al sites. In the first Al site, Al is bonded in a 2-coordinate geometry to one Nd, two equivalent Fe, and eight Al atoms. There are a spread of Al–Al bond distances ranging from 2.59–3.03 Å. In the second Al site, Al is bonded in a distorted linear geometry to two equivalent Nd, two equivalent Fe, and eight Al atoms. There are a spread of Al–Al bond distances ranging from 2.72–2.85 Å. In the third Al site, Al is bonded in a 12-coordinate geometry to two equivalent Nd, two equivalent Fe, and eight Al atoms. There are a spread of Al–Al bond distances ranging from 2.75–2.90 Å. In the fourth Al site, Al is bonded in a 2-coordinate geometry to two equivalent Nd, two equivalent Fe, and eight Al atoms. There are one shorter (2.63 Å) and one longer (2.85 Å) Al–Al bond lengths. In the fifth Al site, Al is bonded in a 12-coordinate geometry to one Nd, two equivalent Fe, and nine Al atoms. The Al–Al bond length is 2.70 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Nd(GaFe)6 by Materials Project

Nd(FeGa)6 crystallizes in the orthorhombic Immm space group. The structure is three-dimensional. Nd is bonded in a 8-coordinate geometry to twelve Fe and eight Ga atoms. There are four shorter (3.28 Å) and eight longer (3.31 Å) Nd–Fe bond lengths. There are a spread of Nd–Ga bond distances ranging from 2.88–3.03 Å. There are two inequivalent Fe sites. In the first Fe site, Fe is bonded to two equivalent Nd, four Fe, and six Ga atoms to form a mixture of distorted edge, face, and corner-sharing FeNd2Ga6Fe4 cuboctahedra. There are two shorter (2.52 Å) and two longer (2.53 Å) Fe–Fe bond lengths. There are a spread of Fe–Ga bond distances ranging from 2.54–2.63 Å. In the second Fe site, Fe is bonded to two equivalent Nd, four equivalent Fe, and six Ga atoms to form a mixture of edge, face, and corner-sharing FeNd2Ga6Fe4 cuboctahedra. There are a spread of Fe–Ga bond distances ranging from 2.58–2.67 Å. There are three inequivalent Ga sites. In the first Ga site, Ga is bonded in a 1-coordinate geometry to one Nd, six Fe, and three Ga atoms. There are one shorter (2.84 Å) and two longer (3.04 Å) Ga–Ga bond lengths. In the second Ga site, Ga is bonded in a 10-coordinate geometry to one Nd, six Fe, and three Ga atoms. There are one shorter (2.67 Å) and two longer (2.87 Å) Ga–Ga bond lengths. In the third Ga site, Ga is bonded in a 12-coordinate geometry to two equivalent Nd, six Fe, and four Ga atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Nd(SeO4)3 by Materials Project

Nd(SeO4)3 crystallizes in the monoclinic P2_1/m space group. The structure is three-dimensional. Nd is bonded in a 9-coordinate geometry to nine O atoms. There are three shorter (2.48 Å) and six longer (2.51 Å) Nd–O bond lengths. There are two inequivalent Se sites. In the first Se site, Se is bonded in a tetrahedral geometry to four O atoms. There is two shorter (1.67 Å) and two longer (1.68 Å) Se–O bond length. In the second Se site, Se is bonded in a tetrahedral geometry to four O atoms. There is two shorter (1.67 Å) and two longer (1.68 Å) Se–O bond length. There are nine inequivalent O sites. In the first O site, O is bonded in a distorted bent 150 degrees geometry to one Nd and one Se atom. In the second O site, O is bonded in a distorted bent 150 degrees geometry to one Nd and one Se atom. In the third O site, O is bonded in a distorted bent 150 degrees geometry to one Nd and one Se atom. The O–Se bond length is 1.67 Å. In the fourth O site, O is bonded in a bent 150 degrees geometry to one Nd and one Se atom. In the fifth O site, O is bonded in a bent 150 degrees geometry to one Nd and one Se atom. In the sixth O site, O is bonded in a bent 150 degrees geometry to one Nd and one Se atom. The O–Se bond length is 1.68 Å. In the seventh O site, O is bonded in a single-bond geometry to one Se atom. In the eighth O site, O is bonded in a single-bond geometry to one Se atom. In the ninth O site, O is bonded in a single-bond geometry to one Se atom. The O–Se bond length is 1.66 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Experimental and modeling studies of PR and ND oxalate solubility to high ionic strengths: Insight into actinide(III) oxalates

Actinide oxalates are chemical compounds important to nuclear industry, ranging from actinide separation in waste reprocessing, to production of specialty actinides, and to disposal of high level nuclear waste (HLW) and spent nuclear fuel (SNF). In this study, the solubility constants for Pr 2 (C 2 O 4 ) 3 •10H 2 O and Nd 2 (C 2 O 4 ) 3 •10H 2 O by performing solubility experiments in HNO 3 and mixtures of HNO 3 and H 2 C 2 O 4 at 23.0 ± 0.2 °C have been determined. The targeted starting materials, Pr 2 (C 2 O 4 ) 3 •10H 2 O and Nd 2 (C 2 O 4 ) 3 •10H 2 O, were successfully synthesized at room temperature using PrCl 3 , NdCl 3 and oxalic acid as the source metrials. Then, we utilized the targeted solubility-controlling phases to conduct solubility measurements. There was no phase change over the entire periods of experiments, demonstrating that Pr 2 (C 2 O 4 ) 3 •10H 2 O and Nd 2 (C 2 O 4 ) 3 •10H 2 O were the solubility-controlling phases in our respective experiments. Based on our experimental data, we have developed a thermodynamic model for Pr 2 (C 2 O 4 ) 3 •10H 2 O and Nd 2 (C 2 O 4 ) 3 •10H 2 O in the mixtures of HNO 3 and H 2 C 2 O 4 to high ionic strengths. The model for Pr 2 (C 2 O 4 ) 3 •10H 2 O reproduces well the reported experimental data for Pu 2 (C 2 O 4 ) 3 •10H 2 O, which are not utilized for the model development, demonstrating that Pr(III) is an excellent analog for Pu(III). Similarly, the model for Nd 2 (C 2 O 4 ) 3 •10H 2 O reproduces the solubility of Am 2 (C 2 O 4 ) 3 •10H 2 O and Cm 2 (C 2 O 4 ) 3 •10H 2 O. The Pitzer model was used for the calculation of activity coefficients. Based on the published, well established model for dissociation constants for oxalic acid and stability constants for actinide-oxalate complexes [i.e., AmC 2 O 4 + , and Am(C 2 O 4 ) 2 - ] to high ionic strengths, we have obtained the solubility constants (log 10 K 0 ) for the following reactions at 25 °C, Pr 2 (C 2 O 4 ) 3 •10H 2 O ⇌ 2Pr 3+ + 3C 2 O 4 2- + 10H 2 O(l). Nd 2 (C 2 O 4 ) 3 •10H 2 O ⇌ 2Nd 3+ + 3C 2 O 4 2- + 10H 2 O(l). to be -30.82 ± 0.30 (2σ), and - 31.14 ± 0.35 (2σ), respectively. These values for can be directly applied to Pu 2 (C 2 O 4 ) 3 •10H 2 O, Am 2 (C 2 O 4 ) 3 •10H 2 O and Cm 2 (C 2 O 4 ) 3 •10H 2 O. The model established for actinide oxalates by this study provides the needed knowledge with regard to solubilities of actinide/REE oxalates at various ionic strengths, and is expected to find applications in many fields, including the geological disposal of nuclear waste and the mobility of REE under the surface conditions, as Pr 2 (C 2 O 4 ) 3 •10H 2 O and Nd 2 (C 2 O 4 ) 3 •10H 2 O can be regarded as the pure Pr and Nd end-members of deveroite, a recently discovered natural REE oxalate with the following stoichiometry, (Ce 1.01 Nd 0.33 La 0.32 Pr 0.11 Y 0.11 Sm 0.01 Pb 0.04 U 0.03 Th 0.01 Ca 0.04 ) 2.01 (C 2 O 4 ) 2.99 •9.99H 2 O. Regarding its importance in the geological disposal of nuclear waste, Am 2 (C 2 O 4 ) 3 •10H 2 O/Pu 2 (C 2 O 4 ) 3 •10H 2 O/Cm 2 (C 2 O 4 ) 3 •10H 2 O can be the source-term phase for actinides, as demonstrated by the instance in the disposal in clay/shale formations. This is exemplified by the stability of Am 2 (C 2 O 4 ) 3 •10H 2 O in comparison with Am(OH) 3 (am), Am(OH) 3 (s) and AmCO 3 (OH)(s) under the relevant geological repository conditions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Guiding Principles for Geochemical/Thermodynamic Model Development and Validation in Nuclear Waste Disposal: A Close Examination of Recent Thermodynamic Models for H + —Nd 3+ —NO 3 - (—Oxalate) Systems

Development of a defensible source-term model (STM), usually a thermodynamical model for radionuclide solubility calculations, is critical to a performance assessment (PA) of a geologic repository for nuclear waste disposal. Such a model is generally subjected to rigorous regulatory scrutiny. In this article, we highlight key guiding principles for STM model development and validation in nuclear waste management. We illustrate these principles by closely examining three recently developed thermodynamic models with the Pitzer formulism for aqueous H + —Nd 3+ —NO 3 - (—oxalate) systems in a reverse alphabetical order of the authors: the XW model developed by Xiong and Wang, the OWC model developed by Oakes et al., and the GLC model developed by Guignot et al., among which the XW model deals with trace activity coefficients for Nd(III), while the OWC and GLC models are for concentrated Nd(NO 3 ) 3 electrolyte solutions. The principles highlighted include the following: (1) Principle 1. Validation against independent experimental data: A model should be validated against experimental data or field observations that have not been used in the original model parameterization. We tested the XW model against multiple independent experimental data sets including electromotive force (EMF), solubility, water vapor, and water activity measurements. The results show that the XW model is accurate and valid for its intended use for predicting trace activity coefficients and therefore Nd solubility in repository environments. (2) Principle 2. Testing for relevant and sensitive variables: Solution pH is such a variable for an STM and easily acquirable. All three models are checked for their ability to predict pH conditions in Nd(NO 3 ) 3 electrolyte solutions. The OWC model fails to provide a reasonable estimate for solution pH conditions, thus casting serious doubt on its validity for a source-term calculation. In contrast, both the XW and GLC models predict close-to-neutral pH values, in agreement with experimental measurements. (3) Principle 3. Honoring physical constraints: Upon close examination, it is found that the Nd(III)-NO 3 association schema in the OWC model suffers from two shortcomings. Firstly, its second stepwise stability constant for Nd(NO 3 ) 2+ (log K 2 ) is much higher than the first stepwise stability constant for NdNO 3 2+ (log K 1 ), thus violating the general rule of (log K 2 –log K 1 ) < 0, or $\frac{K1}{K2}$>1. Secondly, the OWC model predicts abnormally high activity coefficients for Nd(NO 3 ) 2 + (up to ~900) as the concentration increases. (4) Principle 4. Minimizing degrees of freedom for model fitting: The OWC model with nine fitted parameters is compared with the GLC model with five fitted parameters, as both models apply to the concentrated region for Nd(NO 3 ) 3 electrolyte solutions. The latter appears superior to the former because the latter can fit osmotic coefficient data equally well with fewer model parameters. The work presented here thus illustrates the salient points of geochemical model development, selection, and validation in nuclear waste management.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
NASA NTRS1979

Repetitively Q-switched Nd:BeL lasers

The thermal and mechanical characteristics which will ultimately limit the performance of Nd:BeL at high average power levels were investigated. The output beam characteristics (pulse width, peak power, beam dimensions and collimation) were determined at high repetition rates for both Nd:BeL and Nd:YAG. The output of Nd:BeL was shown to exceed that of Nd:YAG by a factor of 2.7 at low Q-switched repetition rates (1 Hz). This result follows from the smaller stimulated emission cross section of x-axis Nb:BeL compared to that of NdYAG by the same factor. At high repetition rates (10 Hz) the output of Nd:Bel falls to a level of three-fifths of its low repetition rate value while under similar tests the output of Nd:YAG remains essentially constant. A comparison of the measured values of the elasto-optic coefficients, the dn/dT values and the linear expansion coefficients for BeL and YAG failed to provide an explanation for the performance of BeL; however, thermal lensing was observed in Nd:BeL. Results imply that the output of a high repetition rate Q-switched Nd:BeL laser (high thermal loading) could be dramatically increased by utilization of a resonator design to compensate for the thermal lensing effects.

Degnan, J.↗
NASA NTRS2009

Sm-Nd and Rb-Sr Ages for Northwest Africa 2977, A Young Lunar Gabbro from the PKT

Northwest Africa (NWA) 2977 is an olivine gabbro cumulate equivalent to one of the lithologies in lunar mare breccia NWA 773 [1,2,3]. The Ar-39-Ar-40 age is 2.77+/-0.04 Ga based on the last approx.57% of the gas release [4], similar to results for NWA 773 [5]. A Sm-Nd age (T) of 2.865+/-0.031 Ga and Epsilon(sub Nd) = -7.84+/-0.22 for the NWA 773 gabbro reported by [6] has been revised to T = 2.993+/-=0.032 Ga, Epsilon(sub Nd) -4.5+/-0.3 [7]. Sm-147-Nd-143 isochron for NWA 2977: Whole rock, pyroxene, olivine, plagioclase, whole rock leachate (approx.phosphate) and the combined leachates from the mineral separates yield a well defined Sm-Nd isochron for an age T = 3.10+/-0.05 Ga and Epsilon(sub Nd-CHUR) = -3.74+/-0.26 [8], or Epsilon(sub Nd-HEDR) = -4.61+/-0.26 [9]. Rb-87-Sr-87 isochron: NWA 2977 contains only a modest amount of Rb and/or Sr contamination. The Sr-isotopic composition of the contaminant closely resembles that of seawater. The whole rock residue after leaching combined with leach residues for plagioclase and pyroxene define an isochron age of 3.29+/-0.11 Ga for initial Sr-87/Sr-86 = 0.70287+/-18. The olivine residue, with lower Sr abundance of approx 1.5 ppm, is only slightly displaced from the isochron. The relatively small uncertainties of the Rb-Sr isochron parameters and near-concordancy with the Sm-Nd age indicate that both the Rb-Sr and the Sm-Nd ages are reliable.

Nyquist, L. E.↗
NASA NTRS2012

885-nm Pumped Ceramic Nd:YAG Master Oscillator Power Amplifier Laser System

The performance of a traditional diode pumped solid-state laser that is typically pumped with 808-nm laser diode array (LDA) and crystalline Nd:YAG was improved by using 885-nm LDAs and ceramic Nd:YAG. The advantage is lower quantum defect, which will improve the thermal loading on laser gain medium, resulting in a higher-performance laser. The use of ceramic Nd:YAG allows a higher Nd dopant level that will make up the lower absorption at the 885-nm wavelength on Nd:YAG. When compared to traditional 808-nm pump, 885-nm diodes will have 30% less thermal load (or wasted heat) and will thus see a similar percentage improvement in the overall laser efficiency. In order to provide a more efficient laser system for future flight missions that require the use of low-repetition- rate ( 1% Nd. To make certain that the absorption at 885 nm is on the same par as the 808-nm diode, the Nd:YAG material needs to be doped with higher concentration of Nd. Ceramic Nd:YAG is the only material that can be tailored to specific needs.

Yu, Anthony↗
DOE OSTI2020

Materials Data on Nd(NiSn)2 by Materials Project

Nd(NiSn)2 crystallizes in the tetragonal P4/nmm space group. The structure is three-dimensional. Nd is bonded in a 12-coordinate geometry to eight Ni and eight Sn atoms. There are four shorter (3.31 Å) and four longer (3.43 Å) Nd–Ni bond lengths. There are four shorter (3.37 Å) and four longer (3.44 Å) Nd–Sn bond lengths. There are two inequivalent Ni sites. In the first Ni site, Ni is bonded in a 9-coordinate geometry to four equivalent Nd and five Sn atoms. There are one shorter (2.51 Å) and four longer (2.58 Å) Ni–Sn bond lengths. In the second Ni site, Ni is bonded in a 8-coordinate geometry to four equivalent Nd and four equivalent Sn atoms. All Ni–Sn bond lengths are 2.57 Å. There are two inequivalent Sn sites. In the first Sn site, Sn is bonded in a 9-coordinate geometry to four equivalent Nd and five Ni atoms. In the second Sn site, Sn is bonded in a 12-coordinate geometry to four equivalent Nd and four equivalent Ni atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Nd(NiBi)2 by Materials Project

Nd(NiBi)2 crystallizes in the tetragonal P4/nmm space group. The structure is three-dimensional. Nd is bonded in a 12-coordinate geometry to eight Ni and nine Bi atoms. There are four shorter (3.34 Å) and four longer (3.62 Å) Nd–Ni bond lengths. There are a spread of Nd–Bi bond distances ranging from 3.49–3.65 Å. There are two inequivalent Ni sites. In the first Ni site, Ni is bonded in a 9-coordinate geometry to four equivalent Nd and five Bi atoms. There are one shorter (2.57 Å) and four longer (2.66 Å) Ni–Bi bond lengths. In the second Ni site, Ni is bonded in a 8-coordinate geometry to four equivalent Nd and four equivalent Bi atoms. All Ni–Bi bond lengths are 2.66 Å. There are two inequivalent Bi sites. In the first Bi site, Bi is bonded in a 5-coordinate geometry to five equivalent Nd and five Ni atoms. In the second Bi site, Bi is bonded in a 4-coordinate geometry to four equivalent Nd and four equivalent Ni atoms.

36 MATERIALS SCIENCE↗