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1. Mechanisms of Complete Dissociation of CO ₂ on Iron Clusters

   https://doi.org/10.1002/cphc.202200277  

   Gutsev, Gennady_L; Tibbetts, Katharine_M; Gutsev, Lavrenty_G; Aldoshin, Sergey_M; Ramachandran, Bala_R (August 2022, ChemPhysChem)

   Abstract Dissociation of CO₂on iron clusters was studied by using semilocal density functional theory and basis sets of triple‐zeta quality. Fe₂, Fe₄, and Fe₁₆clusters were selected as the representative host clusters. When searching for isomers of Fe_nCO₂,n=2, 4 and 16 corresponding to carbon dioxide attachment to the host clusters, its reduction to O and CO, and to the complete dissociation, it was found that the total spin magnetic moments of the lowest energy states of the isomers are often quenched with respect to those of initial reagents Fe_n+CO₂. Dissociation pathways of the Fe₂+CO₂, Fe₄+CO₂, and Fe₁₆+CO₂reactions contain several transition states separated by the local minima states; therefore, a natural question is where do the spin flips occur? Since lifetimes of magnetically excited states were shown to be of the order of 100 fs, the search for the CO₂dissociation pathways was performed under the assumption that magnetic deexcitation may occur at the intermediate local minima. Two dissociation pathways were obtained for each Fe_n+CO₂reaction using the gradient‐based methods. It was found that the Fe₂+CO₂reaction is endothermic with respect to both reduction and complete dissociation of CO₂, whereas the Fe₄+CO₂and Fe₁₆+CO₂reactions are exothermic to both reduction and complete dissociation of carbon dioxide. The CO₂reduction was found to be more favorable than its complete dissociation in the Fe₄case. 

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2. Thermal transport in shear-wrinkled hexagonal boron nitride

   https://doi.org/10.1016/j.csite.2025.106199  

   Park, Jungkyu; Dorsey, Fahim; Patel, Aayush; Jeong, Donghwa (April 2025, Case Studies in Thermal Engineering)

   This study examines the effects of shear induced wrinkles on the thermal transport properties of hexagonal boron nitride (hBN) ribbons. Reverse nonequilibrium molecular dynamics simulations were performed using a Tersoff force field to estimate the thermal conductivity of both undeformed and shear-wrinkled hBN nanoribbons of various widths and lengths. The results indicate that the impact of shear induced wrinkling on thermal conductivity is more evident in narrower ribbons, where lattice distortion and bond stretching are more severe. In contrast, wider ribbons exhibit relatively milder distortions and thus less reduction in heat dissipation capability. Notably, the bulk thermal conductivity of the narrowest hBN ribbon simulated in the present study decreased by 47 % at a shear strain of 0.3 compared to its undeformed structure, whereas the widest ribbon simulated in the present research study showed only a 25 % reduction. Phonon density of states analyses revealed substantial alterations in low-frequency acoustic phonons under shear-wrinkling, with flexural acoustic modes identified as the primary contributors to thermal performance degradation. The findings of this study are expected to inform the design of new materials with improved heat dissipation capabilities for flexible electronics. 

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3. Effects of Low-Temperature Heat Treatment on Mechanical and Thermophysical Properties of Cu-10Sn Alloys Fabricated by Laser Powder Bed Fusion

   https://doi.org/10.3390/ma17122943  

   Honu, Edem; Emanet, Selami; Chen, Yehong; Zeng, Congyuan; Mensah, Patrick (June 2024, Materials)

   This study investigated the impact of low-temperature heat treatments on the mechanical and thermophysical properties of Cu-10Sn alloys fabricated by a laser powder bed fusion (LPBF) additive manufacturing (AM) process. The microstructure, phase structure, and mechanical and thermal properties of the LPBF Cu-10Sn samples were comparatively investigated under both the as-fabricated (AF) condition and after low-temperature heat treatments at 140, 180, 220, 260, and 300 °C. The results showed that the low-temperature heat treatments did not significantly affect the phase and grain structures of the Cu-10Sn alloys. Both pre- and post-treatment samples displayed consistent grain sizes, with no obvious X-ray diffraction angle shift for the α phase, indicating that atom diffusion of the Sn element is beyond the detection resolution of X-ray diffractometers (XRD). However, the 180 °C heat-treated sample exhibited the highest hardness, while the AF samples had the lowest hardness, which was most likely due to the generation of precipitates according to thermodynamics modeling. Heat-treated samples also displayed higher thermal diffusivity values than their AF counterpart. The AF sample had the longest lifetime of ~0.19 nanoseconds (ns) in the positron annihilation lifetime spectroscopy (PALS) test, indicating the presence of the most atomic-level defects. 

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4. Size and strain effects on mechanical and electronic properties of green phosphorene nanoribbons

   https://doi.org/10.1063/1.5054619  

   Garrison, Evan; Chan, Candace_K; Peng, Xihong (November 2018, AIP Advances)

   Recently, a phosphorus isomer named green phosphorus was theoretically predicted with a similar interlayer interaction compared to that of black phosphorus, thus indicating that individual layers can be mechanically exfoliated to form two-dimensional (2D) layers known as green phosphorene. In this work, we investigated the properties of green phosphorene nanoribbons along both armchair and zigzag directions with ribbon widths up to 57 Å using density functional theory. Effects of ribbon width and strain on the mechanical and electronic properties of the ribbons were studied. The Young’s modulus, effect of quantum confinement on the band gap, and effect of strain on the band structures of the ribbons were investigated. The green phosphorene ribbons were found to exhibit prominent anisotropic properties, with the Young’s modulus in the range of 10-35 GPa for the armchair green phosphorene nanoribbons (AGPNR) and 160-170 GPa for the zigzag green phosphorene nanoribbons (ZGPNR), which are the same order of magnitude as those of the 2D sheets. The work function was found to be between 5 eV ∼ 5.7 eV for the range of widths studied. Both size and strain trigger direct-indirect band gap transitions in the ribbons and their transition mechanisms were discussed. 

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5. The cosmic ultraviolet baryon survey (CUBS) – III. Physical properties and elemental abundances of Lyman-limit systems at z < 1

   https://doi.org/10.1093/mnras/stab1661  

   Zahedy, Fakhri S; Chen, Hsiao-Wen; Cooper, Thomas M; Boettcher, Erin; Johnson, Sean D; Rudie, Gwen C; Chen, Mandy C; Cantalupo, Sebastiano; Cooksey, Kathy L; Faucher-Giguère, Claude-André; et al (July 2021, Monthly Notices of the Royal Astronomical Society)

   null (Ed.)

   ABSTRACT We present a systematic investigation of physical conditions and elemental abundances in four optically thick Lyman-limit systems (LLSs) at z = 0.36–0.6 discovered within the cosmic ultraviolet baryon survey (CUBS). Because intervening LLSs at z < 1 suppress far-UV (ultraviolet) light from background QSOs, an unbiased search of these absorbers requires a near-UV-selected QSO sample, as achieved by CUBS. CUBS LLSs exhibit multicomponent kinematic structure and a complex mix of multiphase gas, with associated metal transitions from multiple ionization states such as C ii, C iii, N iii, Mg ii, Si ii, Si iii, O ii, O iii, O vi, and Fe ii absorption that span several hundred km s−1 in line-of-sight velocity. Specifically, higher column density components (log N(H i)/cm−2≳ 16) in all four absorbers comprise dynamically cool gas with $$\langle T \rangle =(2\pm 1) \times 10^4\,$$K and modest non-thermal broadening of $$\langle b_\mathrm{nt} \rangle =5\pm 3\,$$km s−1. The high quality of the QSO absorption spectra allows us to infer the physical conditions of the gas, using a detailed ionization modelling that takes into account the resolved component structures of H i and metal transitions. The range of inferred gas densities indicates that these absorbers consist of spatially compact clouds with a median line-of-sight thickness of $$160^{+140}_{-50}$$ pc. While obtaining robust metallicity constraints for the low density, highly ionized phase remains challenging due to the uncertain $$N\mathrm{(H\, {\small I})}$$, we demonstrate that the cool-phase gas in LLSs has a median metallicity of $$\mathrm{[\alpha /H]_{1/2}}=-0.7^{+0.1}_{-0.2}$$, with a 16–84 percentile range of [α/H] = (−1.3, −0.1). Furthermore, the wide range of inferred elemental abundance ratios ([C/α], [N/α], and [Fe/α]) indicate a diversity of chemical enrichment histories. Combining the absorption data with deep galaxy survey data characterizing the galaxy environment of these absorbers, we discuss the physical connection between star-forming regions in galaxies and diffuse gas associated with optically thick absorption systems in the z < 1 circumgalactic medium. 

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