Detailed Atomistic Investigation of Fe-Doped Rutile Phases

We have investigated iron-doped rutile TiO₂ in great detail by density functional theory (DFT) calculations. The influence of the Fe dopants on the structural and electronic properties are calculated. Three different dopant models are considered in this study, where iron is present in Fe­(II), Fe­(III), and Fe­(IV) oxidation states. Our results indicate that the configuration of Fe­(III), where two neighboring Ti sites are replaced by Fe dopants and an O vacancy locates in between, is the lowest-energy structure. The resulting Mößbauer signatures are in excellent agreement with the available experimental literature data, thus supporting the proposed structural model. Although the crystal structure of doped rutile is not significantly altered, even for larger concentrations of dopant atoms, the local structure around Fe atoms can be strongly distorted, especially due to the presence of oxygen vacancies. Fe doping lowers the band gap and introduces midgap states

Density Functional Theory and Beyond for Band-Gap Screening: Performance for Transition-Metal Oxides and Dichalcogenides

The performance of a wide variety of commonly used density functionals, as well as two screened hybrid functionals (HSE06 and TB-mBJ), on predicting electronic structures of a large class of en vogue materials, such as metal oxides, chalcogenides, and nitrides, is discussed in terms of band gaps, band structures, and projected electronic densities of states. Contrary to GGA, hybrid functionals and GGA+<i>U</i>, both HSE06 and TB-mBJ are able to predict band gaps with an appreciable accuracy of 25% and thus allow the screening of various classes of transition-metal-based compounds, i.e., mixed or doped materials, at modest computational cost. The calculated electronic structures are largely unaffected by the choice of basis functions and software implementation, however, might be subject to the treatment of the core electrons

Hyper-Cross-Linked Organic Microporous Polymers Based on Alternating Copolymerization of Bismaleimide

A novel type of hyper-cross-linked organic microporous polymer (HOMP) has been successfully prepared based on the radical copolymerization of bismaleimides and divinylbenzene. In comparison with the HOMPs prepared with cross-linking techniques, the new radical strategy circumvents some intractable problems, such as low atom economy, structure irregularity and corrosive byproducts. The obtained HOMPs have defined molecular structures due to the intrinsic alternating copolymerization properties of the two monomers. A maximum BET surface area of 841 m² g^–1 and high gas capture capacity (CO₂, 11.22 wt %, 273 K/1.0 bar; H₂, 0.82 wt %, 77.3 K/1.0 bar; benzene, 545 mg g^–1, room temperature/0.6 bar; and cyclohexane, 1736 mg g^–1, room temperature/0.6 bar) were achieved. In addition, the polymers also displayed good chemical and thermal stability, which is critical for the practical application

Porosity-Enhanced Polymers from Hyper-Cross-Linked Polymer Precursors

Hyper-cross-linked polymers (HCPs) have aroused great interest because of their potential applications in adsorbing greenhouse gases and volatile organic compounds. However, the selection of raw materials and the postcontrol of the porosity of HCPs remain a challenge. Here, we developed new porosity-enhanced materials by chemically creating additional pores in polymer-based HCPs. The as-prepared material presents a high surface area (1201 m² g^–1), large microporous volume, and high chemical stability even in concentrated acid, thus demonstrating potential in gas capture and storage (CO₂: 15.31 wt % at 273 K/1.0 bar; selectivity for CO₂ against N₂: 36.6; and large adsorption capacity for six organic vapors). This method of creating additional pores in polymer-based HCPs may open doors to the creation of novel porosity-enhanced materials suitable for high-performance adsorbents

Biochar derived from corn straw affected availability and distribution of soil nutrients and cotton yield

<div><p>Biochar application as a soil amendment has been proposed as a strategy to improve soil fertility and increase crop yields. However, the effects of successive biochar applications on cotton yields and nutrient distribution in soil are not well documented. A three-year field study was conducted to investigate the effects of successive biochar applications at different rates on cotton yield and on the soil nutrient distribution in the 0–100 cm soil profile. Biochar was applied at 0, 5, 10, and 20 t ha^-1 (expressed as Control, BC5, BC10, and BC20, respectively) for each cotton season, with identical doses of chemical fertilizers. Biochar enhanced the cotton lint yield by 8.0–15.8%, 9.3–13.9%, and 9.2–21.9% in 2013, 2014, and 2015, respectively, and high levels of biochar application achieved high cotton yields each year. Leaching of soil nitrate was reduced, while the pH values, soil organic carbon, total nitrogen (N), and available K content of the 0–20 cm soil layer were increased in 2014 and 2015. However, the changes in the soil available P content were less substantial. This study suggests that successive biochar amendments have the potential to enhance cotton productivity and soil fertility while reducing nitrate leaching.</p></div

Soil NH₄⁺−Nin 0–100 cm soil after cotton harvested in 2013, 2014and 2015.

<p>Soil NH₄⁺−Nin 0–100 cm soil after cotton harvested in 2013, 2014and 2015.</p

Soil pH values after cotton harvested in 2013, 2014 and 2015.

<p>Soil pH values after cotton harvested in 2013, 2014 and 2015.</p

Soil available K contents after cotton harvested in 2013, 2014 and 2015 (mg kg^-1).

<p>Soil available K contents after cotton harvested in 2013, 2014 and 2015 (mg kg^-1).</p

Fiber quality in response to biochar application at different rates.

<p>Fiber quality in response to biochar application at different rates.</p

Soil available P contents after cotton harvested in 2013, 2014 and 2015 (mg kg^-1).

<p>Soil available P contents after cotton harvested in 2013, 2014 and 2015 (mg kg^-1).</p