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1. Large Polarization and Susceptibilities in Artificial Morphotropic Phase Boundary PbZr _{1− x} Ti _x O ₃ Superlattices

   https://doi.org/10.1002/aelm.201901395  

   Lupi, Eduardo; Ghosh, Anirban; Saremi, Sahar; Hsu, Shang‐Lin; Pandya, Shishir; Velarde, Gabriel; Fernandez, Abel; Ramesh, Ramamoorthy; Martin, Lane_W (January 2020, Advanced Electronic Materials)

   Abstract The ability to produce atomically precise, artificial oxide heterostructures allows for the possibility of producing exotic phases and enhanced susceptibilities not found in parent materials. Typical ferroelectric materials either exhibit large saturation polarization away from a phase boundary or large dielectric susceptibility near a phase boundary. Both large ferroelectric polarization and dielectric permittivity are attained wherein fully epitaxial (PbZr_0.8Ti_0.2O₃)_n/(PbZr_0.4Ti_0.6O₃)_2n(n= 2, 4, 6, 8, 16 unit cells) superlattices are produced such that the overall film chemistry is at the morphotropic phase boundary, but constitutive layers are not. Long‐ (n≥ 6) and short‐period (n= 2) superlattices reveal large ferroelectric saturation polarization (P_s= 64 µC cm⁻²) and small dielectric permittivity (ε_r≈ 400 at 10 kHz). Intermediate‐period (n= 4) superlattices, however, exhibit both large ferroelectric saturation polarization (P_s= 64 µC cm⁻²) and dielectric permittivity (ε_r= 776 at 10 kHz). First‐order reversal curve analysis reveals the presence of switching distributions for each parent layer and a third, interfacial layer wherein superlattice periodicity modulates the volume fraction of each switching distribution and thus the overall material response. This reveals that deterministic creation of artificial superlattices is an effective pathway for designing materials with enhanced responses to applied bias. 

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2. Exploring the Pb _{1− x} Sr _x HfO ₃ System and Potential for High Capacitive Energy Storage Density and Efficiency

   https://doi.org/10.1002/adma.202105967  

   Acharya, Megha; Banyas, Ella; Ramesh, Maya; Jiang, Yizhe; Fernandez, Abel; Dasgupta, Arvind; Ling, Handong; Hanrahan, Brendan; Persson, Kristin; Neaton, Jeffrey_B; et al (October 2021, Advanced Materials)

   Abstract The hafnate perovskites PbHfO₃(antiferroelectric) and SrHfO₃(“potential” ferroelectric) are studied as epitaxial thin films on SrTiO₃(001) substrates with the added opportunity of observing a morphotropic phase boundary (MPB) in the Pb_1−xSr_xHfO₃system. The resulting (240)‐oriented PbHfO₃(Pba2) films exhibited antiferroelectric switching with a saturation polarization ≈53 µC cm⁻²at 1.6 MV cm⁻¹, weak‐field dielectric constant ≈186 at 298 K, and an antiferroelectric‐to‐paraelectric phase transition at ≈518 K. (002)‐oriented SrHfO₃films exhibited neither ferroelectric behavior nor evidence of a polarP4mmphase . Instead, the SrHfO₃films exhibited a weak‐field dielectric constant ≈25 at 298 K and no signs of a structural transition to a polar phase as a function of temperature (77–623 K) and electric field (–3 to 3 MV cm⁻¹). While the lack of ferroelectric order in SrHfO₃removes the potential for MPB, structural and property evolution of the Pb_1−xSr_xHfO₃(0 ≤x < 1) system is explored. Strontium alloying increased the electric‐breakdown strength (E_B) and decreased hysteresis loss, thus enhancing the capacitive energy storage density (U_r) and efficiency (η). The composition, Pb_0.5Sr_0.5HfO₃produced the best combination ofE_B = 5.12 ± 0.5 MV cm⁻¹,U_r = 77 ± 5 J cm⁻³, and η = 97 ± 2%, well out‐performing PbHfO₃and other antiferroelectric oxides. 

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3. Computer‐Assisted 3D Structure Elucidation (CASE‐3D): The Structural Value of ² J _CH in Addition to ³ J _CH Coupling Constants

   https://doi.org/10.1002/ange.201915103  

   Koos, Martin R. M.; Navarro‐Vázquez, Armando; Anklin, Clemens; Gil, Roberto R. (January 2020, Angewandte Chemie)

   Abstract We present a method to use long‐range CH coupling constants to derive the correct diastereoisomer from the molecular constitution of small molecules. A set of 79²J_CHand³J_CHvalues collected from a single HSQMBC experiment on a sample of strychnine were used in the CASE‐3D (computer‐assisted 3D structure elucidation) protocol. In addition to the most commonly used³J_CHcoupling constants, the subset of 32²J_CHvalues alone showed an excellent degree of configuration selection. The study is mainly based on comparison of DFT‐calculated^2,3J_CHvalues with experimental ones, critical for the case of²J_CH. But the configuration selection also works well using³J_CHvalues predicted from a semi‐empirical Karplus‐based equation limited to H−C−C−C fragments. The robustness, shown using strychnine as a proof of concept, makes theJ‐based CASE‐3D analysis a viable option for the application in fields such as peptide and carbohydrate research, organic synthesis, natural‐product identification and analysis, as well as medicinal chemistry. 

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4. Photovoltaic Diode Effect Induced by Positive Bias Poling of Organic Layer‐Mediated Interface in Perovskite Heterostructure α‐HC(NH ₂ ) ₂ PbI ₃ /TiO ₂

   https://doi.org/10.1002/admi.201600267  

   Feng, Hong‐Jian; Huang, Jinsong; Zeng, Xiao_Cheng (July 2016, Advanced Materials Interfaces)

   It is shown that in the formamidinium (FA) lead iodide/titania heterostructure α‐HC(NH₂)₂PbI₃/TiO₂the organic layer‐mediated interface, i.e., FAI/TiO₂, can induce photovoltaic diode effect via positive bias poling. The band gap of the heterostructure is reduced to zero upon the positive poling due to combined effects of ion diffusion, rotation of organic moieties, and ferroelectric redistribution. The perovskite part in the organic layer‐mediated interface FAI/TiO₂gives rise to a strong polarization of 18.69 μC cm⁻², compared to that (0.89 μC cm⁻²) in the inorganic layer‐mediated interface PbI₂/TiO₂. The strong polarization of the organic layer‐mediated interface is closely related to the diode effect associated with the reordering of the ferroelectric polarization and charge distribution, as a consequence of the mobility and rotation of organic moieties in FAI/TiO₂upon the positive bias poling. The latter effect also provides an explanation on why the FAPbI₃‐based devices can largely reduce the scanning hysteresis in theJ–Vcurves (Yang et al.,Science2015,348, 1234) and why the organic layer‐mediated halide perovskite heterostructure is one of the most promising candidates for the fabrication of highly efficient solar cells or optoelectronic devices. 

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5. Even redder than we knew: Color and A _V evolution up to z = 2.5 from JWST/NIRCam photometry

   https://doi.org/10.1051/0004-6361/202555488  

   van_der_Wel, A; Martorano, M; Marchesini, D; Wuyts, S; Bell, E F; Meidt, S E; Gebek, A; Brammer, G B; Whitaker, K E; Bezanson, R; et al (September 2025, Astronomy & Astrophysics)

   Aims.JWST/NIRCam provides rest-frame near-IR photometry of galaxies up toz = 2.5 with exquisite depth and accuracy. This affords us an unprecedented view of the evolution of the UV/optical/near-IR color distribution and its interpretation in terms of the evolving dust attenuation,A_V. Methods.We used the value-added data products (photometric redshift, stellar mass, rest-frameU − VandV − Jcolors, andA_V) provided by the public DAWN JWST Archive. These data products derive from fitting the spectral energy distributions obtained from multiple NIRCam imaging surveys, augmented with preexisting HST imaging data. Our sample consists of a stellar-mass-complete sample of ≈28 000M_⋆ >  10⁹ M_⊙galaxies in the redshift range 0.5 <  z <  2.5. Results.TheV − Jcolor distribution of star-forming galaxies evolves strongly, in particular for high-mass galaxies (M_⋆ >  3 × 10¹⁰ M_⊙), which have a pronounced tail of very red galaxies reachingV − J >  2.5 atz >  1.5 that does not exist atz <  1. Such redV − Jcan only be explained by dust attenuation, with typical values forM_⋆ ≈ 10¹¹ M_⊙galaxies in the rangeA_V ≈ 1.5 − 3.5 atz ≈ 2. This redshift evolution went largely unnoticed before. Today, however, photometric redshift estimates for the reddest (V − J >  2.5), most attenuated galaxies have markedly improved thanks to the new, precise photometry, which is in much better agreement with the 25 available spectroscopic redshifts for such galaxies. The reddest population readily stands out as the independently identified population of galaxies detected at submillimeter wavelengths. Despite the increased attenuation,U − Vcolors across the entire mass range are slightly bluer at higherz. A well-defined and tight color sequence exists at redshifts 0.5 <  z <  2.5 forM_⋆ >  3 × 10¹⁰ M_⊙quiescent galaxies, in bothU − VandV − J, but inV − Jit is bluer rather than redder compared to star-forming galaxies. In conclusion, whereas the rest-frame UV-optical color distribution evolves remarkably little fromz = 0.5 toz = 2.5, the rest-frame optical/near-IR color distribution evolves strongly, primarily due to a very substantial increase with redshift in dust attenuation for massive galaxies. 

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