Variable Valence State of Trace Elements Regulating Toxic Potencies of Inorganic Particulate Matter

Trace element is known to be one major component in determining particulate matter (PM) toxicities. However, there is still no accurate assessment of the toxic potency of the mixed valences. Here, we reported the oxidative stress and cytotoxicity potencies of 14 trace elements in their various valence states and estimated the toxic gaps of inorganic PM resulting from variations in element valences. Substantial discrepancies of up to 3 orders of magnitude in toxic potencies were observed among their different valences. When considering their abundance in PM, the toxicity gaps are estimated to range from 5 to 6 times between the greatest and weakest toxic valence states in the inorganic PM emitted from industrial sources, with iron contributing to 65.5%–91.0% of the overall gaps. Furthermore, the relative toxic variation of inorganic PM shows a significant correlation with the additive toxicities of Fe(II) and Fe(III) ions during aging process. The finding highlights that the multiple coexisting valence states of trace elements in PM need to be taken into account when estimating their toxic potencies

Novel Boron-rich Phosphides with High Hardness, Large Strain, and Magnetism

Boron-rich compounds have attracted much attention due to their interesting structures and excellent properties. Here, we performed an extensive study on the different B–P stoichiometries under pressure by combining a particle swarm optimization method with first-principles calculations. At 1 atm, BP and B6P are thermodynamically stable, while other stoichiometries are metastable. Under pressure, BP and B6P remain stable relative to constituent pure solids up to 80 GPa, while other stoichiometries become unstable at relatively low pressures. A new Cmca B6P is predicted with the lowest energy at 1 atm and shows higher shear strain than the R3̅m structure, which is known to be more resistant to brittle fracture than B4C. Moreover, the predicted Pm B8P is a magnetic semiconductor with a magnetic moment of 1 μB. All these boron-rich phosphides are hard materials. The present results enrich the B–P phase diagram and promote extensive research on their excellent properties

High-Pressure Phase Transitions and Structures of Topological Insulator BiTeI

Being a giant bulk Rashba semiconductor, the ambient-pressure phase of BiTeI was predicted to transform into a topological insulator under pressure at 1.7–4.1 GPa [Nat. Commun. 2012, 3, 679]. Because the structure governs the new quantum state of matter, it is essential to establish the high-pressure phase transitions and structures of BiTeI for better understanding its topological nature. Here, we report a joint theoretical and experimental study up to 30 GPa to uncover two orthorhombic high-pressure phases of <i>Pnma</i> and <i>P</i>4/<i>nmm</i> structures named phases II and III, respectively. Phases II (stable at 8.8–18.9 GPa) and III (stable at >18.9 GPa) were first predicted by our first-principles structure prediction calculations based on the calypso method and subsequently confirmed by our high-pressure powder X-ray diffraction experiment. Phase II can be regarded as a partially ionic structure, consisting of positively charged (BiTe)⁺ ladders and negatively charged I^– ions. Phase III is a typical ionic structure characterized by interconnected cubic building blocks of Te–Bi–I stacking. Application of pressures up to 30 GPa tuned effectively the electronic properties of BiTeI from a topological insulator to a normal semiconductor and eventually a metal having a potential of superconductivity