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1. New germanate and mixed cobalt germanate salt inclusion materials: [(Rb 6 F)(Rb 4 F)][Ge 14 O 32 ] and [(Rb 6 F)(Rb 3.1 Co 0.9 F 0.96 )][Co 3.8 Ge 10.2 O 30 F 2 ]

   https://doi.org/10.1039/D0CE01099E  

   Carone, Darren ; Usman, Mohammad ; Klepov, Vladislav V. ; Smith, Mark D. ; Kocevski, Vancho ; Besmann, Theodore M. ; zur Loye, Hans-Conrad ( December 2020 , CrystEngComm)

   null (Ed.)

   Single crystals of two new germanates, [(Rb 6 F)(Rb 4 F)][Ge 14 O 32 ] and [(Rb 6 F)(Rb 3.1 Co 0.9 F 0.96 )][Co 3.8 Ge 10.2 O 30 F 2 ], were synthesized via high temperature RbCl/RbF flux growth. Both compounds crystallize in the cubic space group F 4̄3 m and possess the germanium framework of the previously reported salt inclusion material (SIM), [(Cs 6 F)(Cs 3 AgF)][Ge 14 O 32 ], related to the Ge 7 O 16 zeolitic family. These materials demonstrate the ability to accommodate a variety of salt-inclusions, and exhibit chemical flexibility enabling modifications of the framework through incorporation of Co. Alteration of the salt-inclusion led to intrinsic luminescence of [(Rb 6 F)(Rb 4 F)][Ge 14 O 32 ] while modification of the framework resulted in an unanticipated Rb/Co salt/inclusion in [(Rb 6 F)(Rb 3.1 Co 0.9 F 0.96 )][Co 3.8 Ge 10.2 O 30 F 2 ]. Fluorescence measurements were performed on [(Rb 6 F)(Rb 4 F)][Ge 14 O 32 ]. First-principles calculations in the form of density functional theory (DFT) were performed for [(Rb 6 F)(Rb 3.1 Co 0.9 F 0.96 )][Co 3.8 Ge 10.2 O 30 F 2 ] to elucidate its electronic and magnetic properties, and stability at 0 K. 

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2. Chemical Cartography with APOGEE: Mapping Disk Populations with a 2-process Model and Residual Abundances

   https://doi.org/10.3847/1538-4365/ac6028  

   Weinberg, David H. ; Holtzman, Jon A. ; Johnson, Jennifer A. ; Hayes, Christian ; Hasselquist, Sten ; Shetrone, Matthew ; Ting 丁, Yuan-Sen 源森 ; Beaton, Rachael L. ; Beers, Timothy C. ; Bird, Jonathan C. ; et al ( June 2022 , The Astrophysical Journal Supplement Series)

   We apply a novel statistical analysis to measurements of 16 elemental abundances in 34,410 Milky Way disk stars from the final data release (DR17) of APOGEE-2. Building on recent work, we fit median abundance ratio trends [X/Mg] versus [Mg/H] with a 2-process model, which decomposes abundance patterns into a “prompt” component tracing core-collapse supernovae and a “delayed” component tracing Type Ia supernovae. For each sample star, we fit the amplitudes of these two components, then compute the residuals Δ[X/H] from this two-parameter fit. The rms residuals range from ∼0.01–0.03 dex for the most precisely measured APOGEE abundances to ∼0.1 dex for Na, V, and Ce. Thecorrelationsof residuals reveal a complex underlying structure, including a correlated element group comprised of Ca, Na, Al, K, Cr, and Ce and a separate group comprised of Ni, V, Mn, and Co. Selecting stars poorly fit by the 2-process model reveals a rich variety of physical outliers and sometimes subtle measurement errors. Residual abundances allow for the comparison of populations controlled for differences in metallicity and [α/Fe]. Relative to the main disk (R= 3–13 kpc), we find nearly identical abundance patterns in the outer disk (R= 15–17 kpc), 0.05–0.2 dex depressions of multiple elements in LMC and Gaia Sausage/Enceladus stars, and wild deviations (0.4–1 dex) of multiple elements inωCen. The residual abundance analysis opens new opportunities for discovering chemically distinctive stars and stellar populations, for empirically constraining nucleosynthetic yields, and for testing chemical evolution models that include stochasticity in the production and redistribution of elements.

    

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3. From antiferromagnetic and hidden order to Pauli paramagnetism in U M 2 Si 2 compounds with 5 f electron duality

   https://doi.org/10.1073/pnas.2005701117  

   Amorese, Andrea ; Sundermann, Martin ; Leedahl, Brett ; Marino, Andrea ; Takegami, Daisuke ; Gretarsson, Hlynur ; Gloskovskii, Andrei ; Schlueter, Christoph ; Haverkort, Maurits W. ; Huang, Yingkai ; et al ( December 2020 , Proceedings of the National Academy of Sciences)

   null (Ed.)

   Using inelastic X-ray scattering beyond the dipole limit and hard X-ray photoelectron spectroscopy we establish the dual nature of the U 5 f electrons in U M 2 S i 2 (M = Pd, Ni, Ru, Fe), regardless of their degree of delocalization. We have observed that the compounds have in common a local atomic-like state that is well described by the U 5 f 2 configuration with the Γ 1 ( 1 ) and Γ 2 quasi-doublet symmetry. The amount of the U 5 f 3 configuration, however, varies considerably across the U M 2 S i 2 series, indicating an increase of U 5f itineracy in going from M = Pd to Ni to Ru and to the Fe compound. The identified electronic states explain the formation of the very large ordered magnetic moments in U P d 2 S i 2 and U N i 2 S i 2 , the availability of orbital degrees of freedom needed for the hidden order in U R u 2 S i 2 to occur, as well as the appearance of Pauli paramagnetism in U F e 2 S i 2 . A unified and systematic picture of the U M 2 S i 2 compounds may now be drawn, thereby providing suggestions for additional experiments to induce hidden order and/or superconductivity in U compounds with the tetragonal body-centered T h C r 2 S i 2 structure. 

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4. Chemical abundances of open clusters from high-resolution infrared spectra – II. NGC 752

   https://doi.org/10.1093/mnras/stz3008  

   Böcek Topcu, G. ; Afşar, M. ; Sneden, C. ; Pilachowski, C. A. ; Denissenkov, P. A. ; VandenBerg, D. A. ; Wright, D. ; Mace, G. N. ; Jaffe, D. T. ; Strickland, E. ; et al ( October 2019 , Monthly Notices of the Royal Astronomical Society)

   We present a detailed near-infrared chemical abundance analysis of 10 red giant members of the Galactic open cluster NGC 752. High-resolution (R ≃ 45000) near-infrared spectral data were gathered with the Immersion Grating Infrared Spectrograph, providing simultaneous coverage of the complete H and K bands. We derived the abundances of H-burning (C, N, O), α (Mg, Si, S, Ca), light odd-Z (Na, Al, P, K), Fe-group (Sc, Ti, Cr, Fe, Co, Ni), and neutron-capture (Ce, Nd, Yb) elements. We report the abundances of S, P, K, Ce, and Yb in NGC 752 for the first time. Our analysis yields solar-metallicity and solar abundance ratios for almost all of the elements heavier than the CNO group in NGC 752. O and N abundances were measured from a number of OH and CN features in the H band, and C abundances were determined mainly from CO molecular lines in the K band. High-excitation $\rm{C\,\small {I}}$ lines present in both near-infrared and optical spectra were also included in the C abundance determinations. Carbon isotopic ratios were derived from the R-branch band heads of first overtone (2−0) and (3−1) 12CO and (2−0) 13CO lines near 23 440 Å and (3−1) 13CO lines at about 23 730 Å. The CNO abundances and 12C/13C ratios are all consistent with our giants having completed ‘first dredge-up’ envelope mixing of CN-cyle products. We independently assessed NGC 752 stellar membership from Gaia astrometry, leading to a new colour–magnitude diagram for this cluster. Applications of Victoria isochrones and MESA models to these data yield an updated NGC 752 cluster age (1.52 Gyr) and evolutionary stage indications for the programme stars. The photometric evidence and spectroscopic light element abundances all suggest that the most, perhaps all of the programme stars are members of the helium-burning red clump in this cluster.

    

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5. The open cluster NGC 2345: a study of chemical abundances with near-infrared IGRINS high-resolution spectra

   https://doi.org/10.1093/mnras/stad3280  

   Holanda, N. ; Roriz, M. P. ; Drake, N. A. ; Junqueira, S. ; Daflon, S. ; da Silva, J. R. P. ; Pereira, C. B. ( October 2023 , Monthly Notices of the Royal Astronomical Society)

   Open clusters are relatively young and numerous. These systems are distributed throughout the Galactic disc and provide insights on the chemistry of the Milky Way. In this study, we provide a near-infrared spectroscopic analysis of four stars of the young open cluster NGC 2345. Our infrared data present a resolving power of R ≈ 45 000, covering the H- and K-bands (1.5–2.5 μm), and high-signal-to-noise ratio, which are gathered with the Immersion Grating Infrared Spectrograph (IGRINS) at the Gemini Observatory. From atmospheric parameters previously derived via optical spectroscopy, we obtain abundances for C (12C16O), N (12C14N), O (16OH), F (H19F), Na, Mg, Al, Si, P, S, K, Ca, Sc, Ti, Cr, Fe, Ni, Ce, Nd, and Yb. Additionally, the 12C/13C (13C16O), 16O/17O (12C17O), and 16O/18O (12C18O) isotopic ratios are obtained. We compare the infrared results with a previous work based on optical spectral analysis, but chemical species such as F, S, P, K, and Yb are determined for the first time in stars of NGC 2345. We also confirm a low metallicity ([Fe/H]  =  −0.32 ± 0.04) and slight enrichment in s-process elements, as already noticed in works available in the literature, but we do not find any enrichment in F. Our results demonstrate excellent agreement between our measured isotopic ratios 12C/13C and 16C/17O and models of stellar nucleosynthesis, while we find that the abundance of 18O is overestimated in comparison to our measurements. Finally, we assess our findings in comparison to the chemical patterns observed in open clusters, classified by both their age and Galactocentric distances, and highlight the need for a more comprehensive sample of young clusters within the 9–11 kpc range for a proper comparison.

    

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