Origin of Water-Induced Deactivation of MnO2-Based Catalyst for Room-Temperature NO Oxidation: A First-Principles Microkinetic Study

ACS Catalysis ◽  
2021 ◽  
pp. 6835-6845
Author(s):  
Haiyang Yuan ◽  
Huagui Yang ◽  
P. Hu ◽  
Haifeng Wang
Keyword(s):  
First Principles ◽  
Room Temperature ◽  
No Oxidation

Intrinsic doping limit and defect-assisted luminescence in Cs4PbBr6

2019 ◽  
Author(s):  
Young-Kwang Jung ◽  
Joaquin Calbo ◽  
Ji-Sang Park ◽  
Lucy D. Wahlley ◽  
Sunghyun Kim ◽  
...  
Keyword(s):  
First Principles ◽  
Room Temperature ◽  
Stokes Shift ◽  
Green Luminescence ◽  
Counter Ions ◽  
Self Consistent ◽  
Deep Ultraviolet ◽  
Halide Perovskite ◽  
Related Compounds ◽  
Level Analysis

Cs<sub>4</sub>PbBr<sub>6 </sub>is a member of the halide perovskite family that is built from isolated (zero-dimensional) PbBr<sub>6</sub><sup>4-</sup> octahedra with Cs<sup>+</sup> counter ions. The material exhibits anomalous optoelectronic properties: optical absorption and weak emission in the deep ultraviolet (310 - 375 nm) with efficient luminescence in the green region (~ 540 nm). Several hypotheses have been proposed to explain the giant Stokes shift including: (i) phase impurities; (ii) self-trapped exciton; (iii) defect emission. We explore, using first-principles theory and self-consistent Fermi level analysis, the unusual defect chemistry and physics of Cs<sub>4</sub>PbBr<sub>6</sub>. We find a heavily compensated system where the room-temperature carrier concentrations (< 10<sup>9</sup> cm<sup>-3</sup>) are more than one million times lower than the defect concentrations. We show that the low-energy Br-on-Cs antisite results in the formation of a polybromide (Br<sub>3</sub>) species that can exist in a range of charge states. We further demonstrate from excited-state calculations that tribromide moieties are photoresponsive and can contribute to the observed green luminescence. Photoactivity of polyhalide molecules is expected to be present in other halide perovskite-related compounds where they can influence light absorption and emission. <br>

Intrinsic doping limit and defect-assisted luminescence in Cs4PbBr6

2019 ◽  
Author(s):  
Young-Kwang Jung ◽  
Joaquin Calbo ◽  
Ji-Sang Park ◽  
Lucy D. Wahlley ◽  
Sunghyun Kim ◽  
...  
Keyword(s):  
First Principles ◽  
Room Temperature ◽  
Stokes Shift ◽  
Green Luminescence ◽  
Counter Ions ◽  
Self Consistent ◽  
Deep Ultraviolet ◽  
Halide Perovskite ◽  
Related Compounds ◽  
Level Analysis

Cs<sub>4</sub>PbBr<sub>6 </sub>is a member of the halide perovskite family that is built from isolated (zero-dimensional) PbBr<sub>6</sub><sup>4-</sup> octahedra with Cs<sup>+</sup> counter ions. The material exhibits anomalous optoelectronic properties: optical absorption and weak emission in the deep ultraviolet (310 - 375 nm) with efficient luminescence in the green region (~ 540 nm). Several hypotheses have been proposed to explain the giant Stokes shift including: (i) phase impurities; (ii) self-trapped exciton; (iii) defect emission. We explore, using first-principles theory and self-consistent Fermi level analysis, the unusual defect chemistry and physics of Cs<sub>4</sub>PbBr<sub>6</sub>. We find a heavily compensated system where the room-temperature carrier concentrations (< 10<sup>9</sup> cm<sup>-3</sup>) are more than one million times lower than the defect concentrations. We show that the low-energy Br-on-Cs antisite results in the formation of a polybromide (Br<sub>3</sub>) species that can exist in a range of charge states. We further demonstrate from excited-state calculations that tribromide moieties are photoresponsive and can contribute to the observed green luminescence. Photoactivity of polyhalide molecules is expected to be present in other halide perovskite-related compounds where they can influence light absorption and emission. <br>

Room-temperature Ferromagnetism in Two-dimensional Transition Metal Borides: A First-principles Investigation

2021 ◽  
Author(s):  
Fang Wu ◽  
Min Dou ◽  
Huan Li ◽  
Yunfei Liu ◽  
Qingnian Yao ◽  
...  
Keyword(s):  
Transition Metal ◽  
First Principles ◽  
Room Temperature ◽  
Room Temperature Ferromagnetism ◽  
Ferromagnetic Materials ◽  
Information Storage ◽  
Two Dimensional ◽  
Storage Media ◽  
Metal Borides ◽  
Generation Information

It is important to predict new two-dimensional (2D) ferromagnetic materials for next-generation information storage media. However, discovered 2D ferromagnetic materials are still rare. Here, we explored that 2D transition metal...

scholarly journals Room-temperature multiferroicity and diversified magnetoelectric couplings in 2D materials

2019 ◽  
Vol 7 (2) ◽  
pp. 373-380 ◽  
Author(s):  
Tingting Zhong ◽  
Xiaoyong Li ◽  
Menghao Wu ◽  
Jun-Ming Liu
Keyword(s):  
First Principles ◽  
Room Temperature ◽  
2D Materials ◽  
Magnetoelectric Coupling ◽  
Alternative Possibility ◽  
Practical Applications ◽  
Layer Structures ◽  
Curie Temperatures ◽  
Ultrathin Layer ◽  
Ferroelectric Switching

Abstract Multiferroics are rare in nature due to the mutual exclusive origins of magnetism and ferroelectricity. The simultaneous coexistence of robust magnetism/ferroelectricity and strong magnetoelectric coupling in single multiferroics is hitherto unreported, which may also be attributed to their potential conflictions. In this paper, we show the first-principles evidence of such desired coexistence in ultrathin-layer CuCrS2 and CuCrSe2. The vertical ferroelectricity is neither induced by an empty d shell nor spin-driven, giving rise to an alternative possibility of resolving those intrinsic exclusions and contradictions. Compared with their bulk phases, the ferromagnetism in the thin-layer structures (two–six layers) can be greatly stabilized due to the enhanced carrier density and orbital shifting by vertical polarization, and the Curie temperatures of both ferromagnetism and ferroelectricity can be above room temperature. Moreover, a considerable net magnetization can be reversed upon ferroelectric switching, where the change in spin-resolved band structure also renders efficient ‘magnetic reading + electrical writing’. The thickness-different layers may even exhibit diversified types of magnetoelectric coupling, which both enriches the physics of multiferroics and facilitates their practical applications.

scholarly journals The first-principles study of the adsorption of NH3, NO, and NO2 gas molecules on InSe-like phosphorus carbide

2020 ◽  
Vol 44 (22) ◽  
pp. 9377-9381 ◽  
Author(s):  
Andrey A. Kistanov
Keyword(s):  
Gas Sensors ◽  
First Principles ◽  
Room Temperature ◽  
First Principles Study ◽  
Gas Molecules

Novel γ-PC is a promising reversible material for room-temperature gas sensors.

scholarly journals Dimer rattling mode induced low thermal conductivity in an excellent acoustic conductor

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Ji Qi ◽  
Baojuan Dong ◽  
Zhe Zhang ◽  
Zhao Zhang ◽  
Yanna Chen ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Single Crystals ◽  
Layered Structure ◽  
First Principles ◽  
Sound Speed ◽  
Lattice Dynamics ◽  
Room Temperature ◽  
Lattice Thermal Conductivity ◽  
Atomic Structures ◽  
Order Of Magnitude

Abstract A solid with larger sound speeds usually exhibits higher lattice thermal conductivity. Here, we report an exception that CuP2 has a quite large mean sound speed of 4155 m s−1, comparable to GaAs, but single crystals show very low lattice thermal conductivity of about 4 W m−1 K−1 at room temperature, one order of magnitude smaller than GaAs. To understand such a puzzling thermal transport behavior, we have thoroughly investigated the atomic structures and lattice dynamics by combining neutron scattering techniques with first-principles simulations. This compound crystallizes in a layered structure where Cu atoms forming dimers are sandwiched in between P atomic networks. In this work, we reveal that Cu atomic dimers vibrate as a rattling mode with frequency around 11 meV, which is manifested to be remarkably anharmonic and strongly scatters acoustic phonons to achieve the low lattice thermal conductivity.

scholarly journals First-principles prediction of magnetically ordered half-metals above room temperature

2019 ◽  
Vol 5 (3) ◽  
pp. 404-412 ◽  
Author(s):  
Muhammad Atif Sattar ◽  
S. Aftab Ahmad ◽  
Fayyaz Hussain ◽  
Claudio Cazorla
Keyword(s):  
First Principles ◽  
Room Temperature ◽  
Half Metals ◽  
Magnetically Ordered
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