Optical emission line diagnostics, which are a common tool for constraining the properties of the interstellar medium (ISM) of galaxies, become progressively inaccessible at higher redshifts for ...ground-based facilities. Far-infrared (FIR) emission lines, which are redshifted into atmospheric windows that are accessible for ground-based submillimetre facilities, could provide ISM diagnostics alternative to optical emission lines. We investigated FIR line ratios involving CII λ 158 μm, OIII λ 88 μm, OIII λ 52 μm, NII λ 122 μm, and NIII λ 57 μm using synthetic emission lines applied to a high-resolution ( m gas = 883.4 M ⊙ ) cosmological zoom-in simulation, including radiative transfer post-processing with the code K RAMSES-RT at z = 6.5. We find that the CII/NII122 ratio is sensitive to the temperature and density of photodissociation regions. It might therefore be a useful tool for tracing the properties of this gas phase in galaxies. We also find that NII/NIII is a good tracer of the temperature and that OIII52/OIII88 is a good tracer of the gas density of HII regions. Emission line ratios containing the OIII λ 88 μm line are sensitive to high-velocity outflowing gas.
Electron systems with strong geometrical frustrations have flat bands, and their unusual band dispersions are expected to induce a wide variety of physical properties. However, for the emergence of ...such properties, the Fermi level must be pinned within the flat band. In this study, we performed first-principles calculations on pyrochlore oxide Pb2Sb2O7 and theoretically clarified that the self-doping mechanism induces pinning of the Fermi level in the flat band in this system. Therefore, a very high density of states is realized at the Fermi level, and the ferromagnetic state transforms into the ground state via a flat band mechanism, although the system does not contain any magnetic elements. This compound has the potential to serve as a new platform for projecting the properties of flat band systems in the real world.
In this
Feature Article
, we highlight our recent efforts toward stable open-shell singlet diradicaloids and polyradicaloids. A brief review on the historical works in the area is introduced first, ...followed by discussion on the fundamental electronic and physical properties of open-shell singlet diradicaloids. Then, the structure-diradical character relationships based on our recently developed diradicaloids are presented. Next, the challenges and solutions toward stable polyradicaloids and 3D π-conjugated diradicaloids are discussed. Finally, their preliminary material applications are introduced and a perspective view of the area is given.
We highlight our recent studies on stable open-shell singlet diradicaloids and polyradicaloids, originating from Chichibabin's hydrocarbon reported 110 years ago.
The experimental and theoretical realization of two-dimensional (2D) materials is of utmost importance in semiconducting applications. Computational modeling of these systems with satisfactory ...accuracy and computational efficiency is only feasible with semilocal density functional theory methods. In the search for the most useful method in predicting the band gap of 2D materials, we assess the accuracy of recently developed semilocal exchange–correlation (XC) energy functionals and potentials. Though the explicit forms of exchange–correlation (XC) potentials are very effective against XC energy functionals for the band gap of bulk solids, their performance needs to be investigated for 2D materials. In particular, the LMBJ J. Chem. Theory Comput. 2020, 16, 2654 and GLLB-SC Phys. Rev. B 82, 2010, 115106 potentials are considered for their dominance in bulk band gap calculation. The performance of recently developed meta generalized gradient approximations, like TASK Phys. Rev. Res. 1, 2019, 033082 and MGGAC Phys. Rev. B. 100, 2019, 155140 , is also assessed. We find that the LMBJ potential constructed for 2D materials is not as successful as its parent functional, i.e., MBJ Phys. Rev. Lett. 102, 2009, 226401 in bulk solids. Due to a contribution from the derivative discontinuity, the band gaps obtained with GLLB-SC are in a certain number of cases, albeit not systematically, larger than those obtained with other methods, which leads to better agreement with the quasi-particle band gap obtained from the GW method. The band gaps obtained with TASK and MGGAC can also be quite accurate.
The first divalent-metal iodate-phosphate, Pb2(IO3)(PO4), has been prepared via the strategy of introducing (IO3)− into phosphate. The structure features a unique 3D network where Pb(IO3)∞+ and ...Pb(PO4)∞− layers are alternatively interconnected. The birefringence of Pb2(IO3)(PO4) is greatly increased to 0.060 at 1064 nm.
The use of biochar as a soil amendment had been increasingly advocated for its effects on carbon sequestration and greenhouse gas emission mitigation as well as on improvement of soil fertility. ...However, lack of a general assessment of biochar effects on soil physical properties made it difficult for the recommendations for its practical use for soil quality improvement in global agriculture. In this study, we performed a meta-analysis of literature data published by October 2015 and quantified biochar effects on selected soil physical properties. The literature data covered a range of feedstocks, pyrolysis temperature, soil and experimental conditions. Results showed that biochar amendment significantly improved all the soil physical properties tested. On average, soil bulk density was significantly reduced by 7.6% whereas soil porosity significantly increased by 8.4%, aggregate stability by 8.2%, available water holding capacity (AWC) by 15.1% and saturated hydraulic conductivity by 25.2%. Furthermore, the changes in soil bulk density were negatively correlated to porosity and AWC. In addition, these effects were greater in coarse textured soils than in fine textured soils. While the size of biochar effect on soil physical properties varied with the amount of biochar added, changes in bulk density only was correlated to application rates of crop residue and wood biochar. Overall, biochar amendments could likely improve soil hydrological properties though varying with biochar and soil conditions. Use of biochar thus could offer a viable option to improve moisture storage and water use efficiency for soils poor in organic carbon in arid/semiarid zones. More studies on dynamics of soil hydrological behaviors following biochar amendment should be deserved in field conditions for a sound understanding of biochar's potential in world agriculture.
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•Biochar effect on soil physical properties was quantified using meta-analysis.•Biochar exerted significant improvements on soil physical properties.•Greater effect size was found for Ksat and AWC than on bulk density, porosity and MWD.•Greater effect size was exhibited in coarse-textured soils than in fine-textured soils.•Application rate and bulk density change correlated for crop residue and wood biochar.
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