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DOE OSTI2020

Materials Data on PrYAl6 by Materials Project

PrYAl6 crystallizes in the hexagonal P-6m2 space group. The structure is three-dimensional. Pr is bonded to twelve Al atoms to form distorted PrAl12 cuboctahedra that share corners with six equivalent PrAl12 cuboctahedra, faces with two equivalent PrAl12 cuboctahedra, and faces with six equivalent YAl12 cuboctahedra. There are six shorter (3.13 Å) and six longer (3.22 Å) Pr–Al bond lengths. Y is bonded to twelve Al atoms to form distorted YAl12 cuboctahedra that share corners with six equivalent YAl12 cuboctahedra, faces with two equivalent YAl12 cuboctahedra, and faces with six equivalent PrAl12 cuboctahedra. There are six shorter (3.11 Å) and six longer (3.23 Å) Y–Al bond lengths. There are two inequivalent Al sites. In the first Al site, Al is bonded in a 10-coordinate geometry to two equivalent Pr, two equivalent Y, and six Al atoms. There are two shorter (2.75 Å) and four longer (2.80 Å) Al–Al bond lengths. In the second Al site, Al is bonded in a 10-coordinate geometry to two equivalent Pr, two equivalent Y, and six Al atoms. Both Al–Al bond lengths are 2.81 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Pr5(SiN3)3 by Materials Project

Pr5(SiN3)3 crystallizes in the orthorhombic Cmce space group. The structure is three-dimensional. there are four inequivalent Pr3+ sites. In the first Pr3+ site, Pr3+ is bonded to seven N3- atoms to form PrN7 pentagonal bipyramids that share corners with two equivalent SiN4 tetrahedra, edges with two equivalent PrN6 octahedra, and edges with four SiN4 tetrahedra. There are a spread of Pr–N bond distances ranging from 2.50–2.67 Å. In the second Pr3+ site, Pr3+ is bonded in a 8-coordinate geometry to eight N3- atoms. There are a spread of Pr–N bond distances ranging from 2.45–3.09 Å. In the third Pr3+ site, Pr3+ is bonded in a 1-coordinate geometry to nine N3- atoms. There are a spread of Pr–N bond distances ranging from 2.38–2.91 Å. In the fourth Pr3+ site, Pr3+ is bonded to six N3- atoms to form distorted PrN6 octahedra that share corners with six SiN4 tetrahedra, an edgeedge with one PrN6 octahedra, and edges with two equivalent PrN7 pentagonal bipyramids. There are a spread of Pr–N bond distances ranging from 2.40–2.79 Å. There are three inequivalent Si4+ sites. In the first Si4+ site, Si4+ is bonded to four N3- atoms to form SiN4 tetrahedra that share corners with four equivalent PrN6 octahedra, corners with two equivalent PrN7 pentagonal bipyramids, and a cornercorner with one SiN4 tetrahedra. The corner-sharing octahedra tilt angles range from 11–74°. There are a spread of Si–N bond distances ranging from 1.75–1.77 Å. In the second Si4+ site, Si4+ is bonded to four N3- atoms to form SiN4 tetrahedra that share corners with three SiN4 tetrahedra and edges with two equivalent PrN7 pentagonal bipyramids. There is three shorter (1.72 Å) and one longer (1.73 Å) Si–N bond length. In the third Si4+ site, Si4+ is bonded to four N3- atoms to form SiN4 tetrahedra that share corners with two equivalent PrN6 octahedra, corners with two equivalent SiN4 tetrahedra, and edges with two equivalent PrN7 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 37°. There is two shorter (1.73 Å) and two longer (1.74 Å) Si–N bond length. There are six inequivalent N3- sites. In the first N3- site, N3- is bonded in a distorted trigonal bipyramidal geometry to four Pr3+ and one Si4+ atom. In the second N3- site, N3- is bonded in a 6-coordinate geometry to five Pr3+ and one Si4+ atom. In the third N3- site, N3- is bonded in a 2-coordinate geometry to three Pr3+ and two Si4+ atoms. In the fourth N3- site, N3- is bonded in a distorted linear geometry to four Pr3+ and two Si4+ atoms. In the fifth N3- site, N3- is bonded in a 1-coordinate geometry to four Pr3+ and one Si4+ atom. In the sixth N3- site, N3- is bonded in a 6-coordinate geometry to five Pr3+ and one Si4+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Pr2SiC(NO2)2 by Materials Project

Pr2SiC(NO2)2 crystallizes in the triclinic P-1 space group. The structure is three-dimensional. there are two inequivalent Pr3+ sites. In the first Pr3+ site, Pr3+ is bonded in a 9-coordinate geometry to four N3- and five O2- atoms. There are a spread of Pr–N bond distances ranging from 2.59–3.03 Å. There are a spread of Pr–O bond distances ranging from 2.49–2.62 Å. In the second Pr3+ site, Pr3+ is bonded in a 8-coordinate geometry to two N3- and six O2- atoms. There are one shorter (2.55 Å) and one longer (2.58 Å) Pr–N bond lengths. There are a spread of Pr–O bond distances ranging from 2.33–2.75 Å. Si4+ is bonded in a tetrahedral geometry to four O2- atoms. There are a spread of Si–O bond distances ranging from 1.61–1.67 Å. C4+ is bonded in a linear geometry to two N3- atoms. Both C–N bond lengths are 1.24 Å. There are two inequivalent N3- sites. In the first N3- site, N3- is bonded in a distorted single-bond geometry to three Pr3+ and one C4+ atom. In the second N3- site, N3- is bonded in a distorted single-bond geometry to three Pr3+ and one C4+ atom. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a 1-coordinate geometry to three Pr3+ and one Si4+ atom. In the second O2- site, O2- is bonded in a distorted single-bond geometry to three Pr3+ and one Si4+ atom. In the third O2- site, O2- is bonded in a 1-coordinate geometry to two Pr3+ and one Si4+ atom. In the fourth O2- site, O2- is bonded in a 1-coordinate geometry to three Pr3+ and one Si4+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on PrGa6 by Materials Project

PrGa6 crystallizes in the tetragonal P4/nbm space group. The structure is three-dimensional. Pr is bonded to twelve Ga atoms to form a mixture of distorted edge and face-sharing PrGa12 cuboctahedra. There are four shorter (3.18 Å) and eight longer (3.30 Å) Pr–Ga bond lengths. There are two inequivalent Ga sites. In the first Ga site, Ga is bonded in a 9-coordinate geometry to four equivalent Pr and five Ga atoms. There are one shorter (2.50 Å) and four longer (2.63 Å) Ga–Ga bond lengths. In the second Ga site, Ga is bonded in a 4-coordinate geometry to one Pr and three Ga atoms. The Ga–Ga bond length is 2.50 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Pr2Y2O5 by Materials Project

Pr2Y2O5 crystallizes in the tetragonal P4/mmm space group. The structure is three-dimensional. Pr is bonded in a 5-coordinate geometry to five O atoms. There are four shorter (2.25 Å) and one longer (2.87 Å) Pr–O bond lengths. There are two inequivalent Y sites. In the first Y site, Y is bonded in a body-centered cubic geometry to eight equivalent O atoms. All Y–O bond lengths are 2.40 Å. In the second Y site, Y is bonded in a square co-planar geometry to four equivalent O atoms. All Y–O bond lengths are 2.77 Å. There are two inequivalent O sites. In the first O site, O is bonded to two equivalent Pr and two equivalent Y atoms to form OPr2Y2 tetrahedra that share corners with two equivalent OPr2Y4 octahedra, corners with ten equivalent OPr2Y2 tetrahedra, and edges with five equivalent OPr2Y2 tetrahedra. The corner-sharing octahedral tilt angles are 60°. In the second O site, O is bonded to two equivalent Pr and four equivalent Y atoms to form OPr2Y4 octahedra that share corners with four equivalent OPr2Y4 octahedra, corners with eight equivalent OPr2Y2 tetrahedra, and edges with four equivalent OPr2Y4 octahedra. The corner-sharing octahedral tilt angles are 0°.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on PrMgAg by Materials Project

MgPrAg crystallizes in the hexagonal P-62m space group. The structure is three-dimensional. Mg is bonded in a 4-coordinate geometry to four Ag atoms. There are two shorter (2.88 Å) and two longer (3.04 Å) Mg–Ag bond lengths. Pr is bonded in a 5-coordinate geometry to five Ag atoms. There are four shorter (3.21 Å) and one longer (3.25 Å) Pr–Ag bond lengths. There are two inequivalent Ag sites. In the first Ag site, Ag is bonded in a 9-coordinate geometry to six equivalent Mg and three equivalent Pr atoms. In the second Ag site, Ag is bonded in a 9-coordinate geometry to three equivalent Mg and six equivalent Pr atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on PrH18(BrO6)3 by Materials Project

Pr(H2O)9(BrO3)3 crystallizes in the hexagonal P6_3mc space group. The structure is zero-dimensional and consists of six hypobromous acid;dihydrate molecules and two Pr(H2O)9 clusters. In each Pr(H2O)9 cluster, Pr3+ is bonded in a 9-coordinate geometry to nine O2- atoms. There are a spread of Pr–O bond distances ranging from 2.51–2.55 Å. There are three inequivalent H1+ sites. In the first H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.99 Å. In the second H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.99 Å. In the third H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.98 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a water-like geometry to one Pr3+ and two equivalent H1+ atoms. In the second O2- site, O2- is bonded in a water-like geometry to one Pr3+ and two equivalent H1+ atoms. In the third O2- site, O2- is bonded in a water-like geometry to one Pr3+ and two equivalent H1+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on PrBi3 by Materials Project

PrBi3 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Pr is bonded to twelve Bi atoms to form a mixture of corner, edge, and face-sharing PrBi12 cuboctahedra. There are four shorter (3.37 Å) and eight longer (3.65 Å) Pr–Bi bond lengths. There are two inequivalent Bi sites. In the first Bi site, Bi is bonded in a 12-coordinate geometry to four equivalent Pr and four equivalent Bi atoms. All Bi–Bi bond lengths are 3.37 Å. In the second Bi site, Bi is bonded in a square co-planar geometry to four equivalent Pr atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on PrMoBrO4 by Materials Project

PrMoO4Br crystallizes in the triclinic P-1 space group. The structure is three-dimensional. there are two inequivalent Pr3+ sites. In the first Pr3+ site, Pr3+ is bonded in a 8-coordinate geometry to five O2- and three Br1- atoms. There are a spread of Pr–O bond distances ranging from 2.43–2.69 Å. There are two shorter (3.02 Å) and one longer (3.03 Å) Pr–Br bond lengths. In the second Pr3+ site, Pr3+ is bonded in a 8-coordinate geometry to seven O2- and one Br1- atom. There are a spread of Pr–O bond distances ranging from 2.42–2.88 Å. The Pr–Br bond length is 3.08 Å. There are two inequivalent Mo6+ sites. In the first Mo6+ site, Mo6+ is bonded in a tetrahedral geometry to four O2- atoms. There are a spread of Mo–O bond distances ranging from 1.78–1.83 Å. In the second Mo6+ site, Mo6+ is bonded in a tetrahedral geometry to four O2- atoms. There are a spread of Mo–O bond distances ranging from 1.77–1.83 Å. There are eight inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Pr3+, one Mo6+, and three equivalent Br1- atoms. There are a spread of O–Br bond distances ranging from 3.47–3.69 Å. In the second O2- site, O2- is bonded in a distorted linear geometry to one Pr3+, one Mo6+, and one Br1- atom. The O–Br bond length is 3.25 Å. In the third O2- site, O2- is bonded in a 3-coordinate geometry to two Pr3+, one Mo6+, and two equivalent Br1- atoms. There are one shorter (3.45 Å) and one longer (3.54 Å) O–Br bond lengths. In the fourth O2- site, O2- is bonded in a 3-coordinate geometry to two Pr3+, one Mo6+, and two equivalent Br1- atoms. There are one shorter (3.43 Å) and one longer (3.56 Å) O–Br bond lengths. In the fifth O2- site, O2- is bonded in a distorted linear geometry to one Pr3+, one Mo6+, and one Br1- atom. The O–Br bond length is 3.19 Å. In the sixth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to two Pr3+ and one Mo6+ atom. In the seventh O2- site, O2- is bonded in a distorted linear geometry to one Pr3+ and one Mo6+ atom. In the eighth O2- site, O2- is bonded in a 3-coordinate geometry to two Pr3+ and one Mo6+ atom. There are two inequivalent Br1- sites. In the first Br1- site, Br1- is bonded in a distorted water-like geometry to two equivalent Pr3+ atoms. In the second Br1- site, Br1- is bonded in a 2-coordinate geometry to two Pr3+ and nine O2- atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Toward particle-resolved accuracy in Euler–Lagrange simulations of multiphase flow using machine learning and pairwise interaction extended point-particle (PIEP) approximation

This study presents two different machine learning approaches for the modeling of hydrodynamic force on particles in a particle-laden multiphase flow. Results from particle-resolved direct numerical simulations (PR-DNS) of flow over a random array of stationary particles for eight combinations of particle Reynolds number (Re) and volume fraction (φ) are used in the development of the models. The first approach follows a two-step process. In the first flow prediction step, the perturbation flow due to a particle is obtained as an axisymmetric superposable wake using linear regression. In the second force prediction step, the force on a particle is evaluated in terms of the perturbation flow induced by all its neighbors using the generalized Faxén form of the force expression. In the second approach, the force data on all the particles from the PR-DNS simulations are used to develop an artificial neural network (ANN) model for direct prediction of force on a particle. Due to the unavoidable limitation on the number of fully resolved particles in the PR-DNS simulations, direct force prediction with the ANN model tends to over-fit the data and performs poorly in the prediction of test data. In contrast, due to the millions of grid points used in the PR-DNS simulations, accurate flow prediction is possible, which then allows accurate prediction of particle force. This hybridization of multiphase physics and machine learning is particularly important, since it blends the strength of each, and the resulting pairwise interaction extended point-particle model cannot be developed by either physics or machine learning alone.

42 ENGINEERING↗
DOE OSTI2026

Cross-slip and easy-glide CRSS in titanium: Theoretical predictions and in-situ TEM measurements

This study investigates the mechanics of prismatic and first-order pyramidal $\langle$a$\rangle$ slip in titanium (Ti), elucidating the physics of easy-glide and cross-slip through a combination of theory and experiments. Screw-character prismatic (Pr) dislocations in Ti are of particular interest because their complex cores can be stable or unstable, leading to activation by either cross-slip or planar glide. To investigate these mechanisms, site-specific micro tensile samples were prepared using focused ion beam (FIB) milling and mounted on a push-to-pull (PTP) device for in-situ transmission electron microscopy (TEM) tensile testing. The in-situ experiments provide direct observations of the onset of dislocation motion and the precise determination of the critical resolved shear stress (CRSS) for the activated mechanisms, and its evolution with load cycling. A comprehensive theory has been developed to predict the CRSS values for easy glide, cross-slip, and multiplication of dislocations. Predicted critical stresses for pyramidal (π)-to-Pr and reverse cross-slip agree closely with the experimental measurements. The latter cross-slip stress is a factor of two higher than that of unobstructed planar slip. The model accounts for overlapping dislocation cores and employs a Wigner-Seitz based cell to evaluate misfit energies. By combining ab initio density functional theory (DFT) with anisotropic elasticity, the framework identifies minimum energy pathways for dislocation glide, which can be intermittent and zig-zag. A simplified expression utilizing (π) and Pr Schmid factor ratios is proposed for critical stress corresponding to (π)-to-Pr cross-slip transition. The results are strongly dependent on crystal orientation, underscoring non-Schmid behavior. Overall, this study explores key critical stress parameters essential for informing higher-scale simulations of plasticity in Ti.

Critical stress↗
DOE OSTI2024

High-entropy Li-rich layered oxide cathode for Li-ion batteries

High-entropy oxides (HEOs) are emerging as promising cathode materials for Li-ion batteries (LIBs) due to their stable solid-state phase and compositional flexibility. Herein, we investigate the structural and electrochemical properties of a novel non-equimolar high-entropy cathode material, termed high-entropy Li-rich layered oxide (HE-LLO, Li 1.15 Na 0.05 Ni 0.19 Mn 0.56 Fe 0.02 Mg 0.02 Al 0.02 O 1.97 F 0.03 ), in comparison to a pristine Li-rich layered oxide (PR-LLO, Li1.2Ni0.2Mn0.6O2). The incorporation of multiple cations (Na + , Al 3+ , Mg 2+ , Fe 3+ ) and anion (F - ) into HE-LLO introduces compositional diversity, enhancing structural stability through the entropy stabilization effect. Theoretical calculations confirm a significantly higher configurational entropy in HE-LLO compared to PRLLO, supporting its high-entropy nature. Electrochemical evaluations demonstrate that HE-LLO exhibits considerable capacity retention, preserving 76.8 % of its discharge capacity at 0.5C after 200 cycles, compared to only 36.2 % for PR-LLO. Even under high-temperature conditions, HE-LLO outperformed PR-LLO, maintaining 76.1 % of its discharge capacity after 100 cycles at 5C, while PR-LLO retained only 12.4 %. These enhancements are attributed to the improved phase reversibility and higher Li + ion diffusion coefficients of HE-LLO, validated by ex-situ characterizations using a synchrotron X-ray technique, along with density functional theory (DFT) calculations. In conclusion, these findings highlight the promise of non-equimolar HEOs as a novel design strategy for highperformance cathode materials.

25 ENERGY STORAGE↗
DOE OSTI2022

Nuclear Structure and Decay Data for A=149 Isobars

Here, experimental nuclear structure and decay data are evaluated for all the 17 known nuclides of mass 149 (Xe, Cs, Ba, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb). Detailed compiled and evaluated spectroscopic information is presented for each reaction and decay dataset, and recommended values are provided for level properties, α, β and γ radiations, and other spectroscopic parameters, based on an evaluation of all the available experimental data for A=149 isobaric nuclides. Although large amounts of nuclear spectroscopic data are available for nuclides of A=149, yet large gaps in knowledge exist, as described below. For the lowest atomic number nuclide 149 Xe, only the isotopic identification has been made, with no data for its ground-state half-life. For 149 Cs, 149 Tm and 149 Yb information is available for only the respective ground states. For 149 Ba, 149 La and 149 Er, limited data exist for excited states. Many of the decay schemes of radioactive nuclei of A=149 are considered as incomplete, either due to large energy differences between the highest observed excited states in daughter nuclides and the respective Q-values, or due to the lack of confirmed γ-ray data, as listed below: 149 Cs → 149 Ba, 149 Ba → 149 La, 149 La → 149 Ce, 149 Ce → 149 Pr, 149 Pr → 149 Nd, 149 Tb(4.17 min) → 149 Gd, 149 Ho(21.0 s and 56 s) → 149 Dy, 149 Er(4 s and 9.6 s) → 149 Ho, and 149 Tm → 149 Er. No data exist for the decay of 149 Yb to 149 Tm. Data for half-lives of the excited states in this mass chain are generally lacking as given below by the number of excited levels of known half-life / approximate number of known levels in a nuclide: 2/17 for 149 Ba, 0/18 for 149 La, 3/53 for 149 Ce, 3/44 for 149 Pr, 17/110 for 149 Nd, 9/90 for 149 Pm, 10/210 for 149 Sm, 2/125 for 149 Eu, 6/270 for 149 Gd, 5/200 for 149 Tb, 3/80 for 149 Dy, 3/90 for 149 Ho, and 3/14 for 149 Er. This work supersedes earlier evaluations of A=149 nuclides published by 2004Si16, 1994Si18, 1985Sz01 and 1976Ho17.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2024

Prandtl number effects on extreme mixing events in forced stratified turbulence

Relatively strongly stratified turbulent flows tend to self-organise into a ‘layered anisotropic stratified turbulence’ (LAST) regime, characterised by relatively deep and well-mixed density ‘layers’ separated by relatively thin ‘interfaces’ of enhanced density gradient. Understanding the associated mixing dynamics is a central problem in geophysical fluid dynamics. It is challenging to study LAST mixing, as it is associated with Reynolds numbers $Re := UL/\nu \gg 1$ and Froude numbers $Fr :=(2{\rm \pi} U)/(L N) \ll 1$ ( $U$ and $L$ being characteristic velocity and length scales, $\nu$ the kinematic viscosity and $N$ the buoyancy frequency). Since a sufficiently large dynamic range (largely) unaffected by stratification and viscosity is required, it is also necessary for the buoyancy Reynolds number $Re_{b} := \epsilon /(\nu N^{2}) \gg 1$ , where $\epsilon$ is the (appropriately volume-averaged) turbulent kinetic energy dissipation rate. This requirement is exacerbated for oceanically relevant flows, as the Prandtl number $Pr := \nu /\kappa = {O}(10)$ in thermally stratified water (where $\kappa$ is the thermal diffusivity), thus leading (potentially) to even finer density field structures. We report here on four forced fully resolved direct numerical simulations of stratified turbulence at various Froude ( $Fr=0.5, 2$ ) and Prandtl ( $Pr=1, 7$ ) numbers forced so that $Re_{b}=50$ , with resolutions up to $30\,240 \times 30\,240 \times 3780$ . We find that, as $Pr$ increases, emergent ‘interfaces’ become finer and their contribution to bulk mixing characteristics decreases at the expense of the small-scale density structures populating the well-mixed ‘layers’. However, extreme mixing events (as quantified by significantly elevated local destruction rates of buoyancy variance $\chi _0$ ) are always preferentially found in the (statically stable) interfaces, irrespective of the value of $Pr$ .

Mechanics↗
DOE OSTI2022

Phosphine Ligand Binding and Catalytic Activity of Group 10–14 Heterobimetallic Complexes

We report heterobimetallic complexes have attracted much interest due to their broad range of structures and reactivities as well as unique catalytic abilities. Additionally, these complexes can be utilized as single-source precursors for the synthesis of binary intermetallic compounds. An example is the family of bis(pyridine-2-thiolato)dichloro-germanium and tin complexes of group 10 metals (Pd and Pt). The reactivity of these heterobimetallic complexes is highly tunable through substitution of the group 14 element and the neutral ligand bound to the transition metal. Here, we study the binding energies of three different phosphorous-based ligands, PR 3 (R = Bu, Ph, and OPh) by density functional theory and restricted Hartree–Fock methods. The PR 3 ligand-binding energies follow the trend of PBu 3 > PPh 3 > P(OPh) 3 , in agreement with their sigma-bonding ability. These results are confirmed by ligand exchange experiments monitored with 31 P NMR spectroscopy, in which a weaker binding PR 3 ligand is replaced with a stronger one. Furthermore, we demonstrate that the heterobimetallic complexes are active catalysts in the Negishi coupling reaction, where stronger binding PR 3 ligands inhibit access to an active site at the metal center. Similar strategies could be applied to other complexes to better understand their ligand-binding energetics and predict their reactivity as both precursors and catalysts.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Facile Oxidation of Ce(III) to Ce(IV) Using Cu(I) Salts

The synthesis, luminescence, and electrochemical properties of the Ce(III) compound, [(C 5 Me 5 )2(2,6- i Pr 2 C 6 H 3 O)Ce(THF)], 1, were investigated. Based on the electrochemical data, treatment of 1 with CuX (X = Cl, Br, I) results in the formation of the corresponding Ce(IV) complexes, [(C 5 Me 5 ) 2 (2,6- i Pr 2 C 6 H 3 O)Ce(X)]. Each complex has been characterized using NMR, IR, and UV−vis spectroscopy as well as structurally determined using X-ray crystallography. Additionally, the treatment of [(C 5 Me 5 ) 2 (2,6- i Pr 2 C 6 H 3 O)Ce(Br)] with AgF results in the formation of the putative [(C 5 Me 5 ) 2 (2,6- i Pr 2 C 6 H 3 O)Ce(F)]. Furthermore, the electronic structure of these Ce(IV)−X complexes was investigated by bond analyses and the Ce(IV)−F moiety using quantum chemistry NMR calculations.

Aromatic compounds↗
DOE OSTI2020

Pushing the limits of the electrochemical window with pulse radiolysis in chloroform

Pulse radiolysis (PR) enables the full redox window of a solvent to be accessed, as it does not require electrodes or electrolyte which limit the potentials accessible in voltammetry measurements. PR in chloroform has the additional possibility to enable reaching highly positive potentials because of its large ionization potential (IP). We report PR experiments demonstrated the formation of the (deuterated) chloroform radical cation CDCl 3 + ˙, identifying it as the source of the broad absorption in the visible part of the spectrum. Results indicated that solutes with a redox potential up to +3.7 V vs. Fc/Fc + can be oxidized by CDCl 3 + ˙, which is far beyond what is possible with electrochemical techniques. Oxidation is not efficient because of rapid geminate recombination with chloride counterions, but also due to rapid decomposition of CDCl 3 + ˙ which limits the yield of otherwise longer-lived free ions. The rapid, 6 ± 3 ns, decomposition, confirmed by two independent experiments, means that a solute must be present at a concentration >100 mM to capture >90% of the free holes formed. Addition of ethene removes the broad, overlapping absorptions from ubiquitous (chlorine atom, solute) complexes created by PR in halogenated solvents enabling clear observation of solute cations. The results also unravel the complex radiation chemistry of chloroform including the large reported value G (–CHCl 3 ) = 12 molecules/100 eV for the decomposition of chloroform molecules.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

The effect of rare earth (RE 3+ ) ionic radii on transparent lanthanide-tellurite glass-ceramics: correlation between ‘hole-formalism’ and crystallization

Rare earth (RE) doped transparent tellurite glass-ceramics (GCs) are widely explored for their application as advanced photonic materials. Specifically, the growth of RE based “anti-glass” crystalline phases in transparent GCs enhances their effective functionality. Enormous studies on the properties of GCs revealed that optimization of glass composition and heat-treatment schedule are the foremost factors that affect the transparency of the GCs. Nevertheless, the direct effect of RE 3+ ions on the crystallization mechanism of glass has hardly been reported. Therefore, a base glass of the composition La 2 O 3 –Gd 2 O 3 –TiO 2 –TeO 2 (LGTT) is doped with RE 3+ ions (Ce 3+ , Pr 3+ , Nd 3+ , Sm 3+ , Eu 3+ , Tb 3+ , and Dy 3+ ) with varied ionic radii. Rietveld refinement from XRD of GCs confirms that (La/Gd) 2 Te 6 O 15 phases are precipitated, where dopants Ce, Pr and Nd occupy La sites, while Sm, Eu, Tb, and Dy occupy Gd sites. The configurational heat-capacity (ΔC p ) from DSC is found to be lower for larger ionic radii REs (Ce, Pr, Nd) than smaller ionic radii REs (Sm, Eu, Tb, Dy) thereby exhibiting higher chemical ordering followed by faster crystal growth rate in the former. However, the transparency retention profile of different RE-doped GCs follows the trend Eu:Tb > Sm:Dy > Nd > Pr > Ce, confirming the ionic radii effect. In addition to the ionic radii effect, in this work, we propose a ‘Hole-Formalism’ concept to explain the observed trend. It is further corroborated with an identical neutron diffraction pattern and ΔC p values for these ion pairs Sm 3+ : Dy 3+ (4f 5 : 4f 9 ) and Eu 3+ : Tb 3+ (4f 6 : 4f 8 ) results in a similar crystallization mechanism, transmission profile and fine-scale microstructures of these RE-based tellurite GCs.

36 MATERIALS SCIENCE↗