scholarly journals Quantitative Evaluations of Hydrogen Diffusivity in V-X (X = Cr, Al, Pd) Alloy Membranes Based on Hydrogen Chemical Potential

Membranes ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 67
Author(s):  
Asuka Suzuki ◽  
Hiroshi Yukawa
Keyword(s):  
Nearest Neighbor ◽  
Chemical Potential ◽  
Hydrogen Permeability ◽  
First Principle ◽  
Hydrogen Diffusivity ◽  
Hydrogen Atoms ◽  
First Principle Calculations ◽  
Blocking Effects ◽  
Pd Alloy ◽  
Quantitative Evaluations

Vanadium (V) has higher hydrogen permeability than Pd-based alloy membranes but exhibits poor resistance to hydrogen-induced embrittlement. The alloy elements are added to reduce hydrogen solubility and prevent hydrogen-induced embrittlement. To enhance hydrogen permeability, the alloy elements which improve hydrogen diffusivity in V are more suitable. In the present study, hydrogen diffusivity in V-Cr, V-Al, and V-Pd alloy membranes was investigated in view of the hydrogen chemical potential and compared with the previously reported results of V-Fe alloy membranes. The additions of Cr and Fe to V improved the mobility of hydrogen atoms. In contrast, those of Al and Pd decreased hydrogen diffusivity. The first principle calculations revealed that the hydrogen atoms cannot occupy the first-nearest neighbor T sites (T1 sites) of Al and Pd in the V crystal lattice. These blocking effects will be a dominant contributor to decreasing hydrogen diffusivity by the additions of Al and Pd. For V-based alloy membranes, Fe and Cr are more suitable alloy elements compared with Al and Pd in view of hydrogen diffusivity.

Lattice Monte Carlo Simulations of Vacancy-Mediated Diffusion and Aggregation using Ab-Initio Parameters

1997 ◽  
Vol 469 ◽  
Author(s):  
Marius M. Bunea ◽  
Scott T. Dunham
Keyword(s):  
Monte Carlo ◽  
Monte Carlo Method ◽  
Nearest Neighbor ◽  
First Principle ◽  
High Concentration ◽  
Lattice Monte Carlo ◽  
First Principle Calculations ◽  
System Energy ◽  
Concentration Diffusion ◽  
Nearest Neighbor Distances

The lattice Monte Carlo method with parameters from recent first-principle calculations1,2 are used to investigate dopant diffusion in silicon. In the simulations, vacancy hopping on a silicon lattice is biased by changes in system energy, including interactions up to the sixth-nearest neighbor. We find that vacancy-mediated diffusivity increases dramatically above 1020 cm−3, in agreement with experimental observations3 and previous calculations.4 However, for very long simulation times, arsenic diffusivity is reduced due to formation of AsxV complexes, with clustering more pronounced at high doping levels. As suggested by Ramamoorthy and Pantelides,5 we find that As2V complexes are mobile, and although they diffuse much more slowly than AsV pairs, they appear likely to have a significant role in high concentration diffusion due to their much higher numbers. We also investigated dopant fluxes in a vacancy gradient. For dopants like As for which pair diffusion is limited by the dissociation to third-nearest neighbor distances, the dopant flux is less than that predicted by pair diffusion models, with greater difference at higher temperatures. In contrast, for phosphorus/vacancy pairs, whose diffusion is limited by dopant/vacancy exchange, the dopant flux is close to the predictions of pair diffusion.

Lattice Vibration, Heat Capacity and Vibration Entropy of Single-Layer Hexagonal-BN

2013 ◽  
Vol 669 ◽  
pp. 138-143
Author(s):  
Man Zhao ◽  
Fei Ma ◽  
Hai Bing Zheng ◽  
Dong Yang ◽  
Ke Wei Xu
Keyword(s):  
Heat Capacity ◽  
Lattice Vibration ◽  
Single Layer ◽  
Vibration Modes ◽  
First Principle ◽  
Frequency Range ◽  
Phonon Modes ◽  
Hydrogen Atoms ◽  
First Principle Calculations ◽  
Narrow Frequency Range

Abstract. The phonon spectrum of zigzag h-BN nanoribbons with the edges passivated by hydrogen atoms under tensile strain along the axis direction were calculated by first-principle calculations. It is found that the uniaxial strain can lead to a narrow frequency range of lattice vibration modes. But it hardly affects the two highest frequency modes due to the vibration of B-H or N-H bonds. In particular, the strain usually promotes the softening of phonon modes. It means that more phonons should be activated at a given temperature. This may result in the changes of thermal properties, such as, heat capacity and vibration entropy.

Oxidation-Induced Redshifts in the Energy Gap of Silicon Quantum Dots

2013 ◽  
Vol 562-565 ◽  
pp. 852-857 ◽  
Author(s):  
Jie Qiong Zeng ◽  
Hong Yu
Keyword(s):  
Quantum Dots ◽  
Porous Silicon ◽  
Software Package ◽  
Energy Gap ◽  
Slight Reduction ◽  
First Principle ◽  
Hydrogen Atoms ◽  
Silicon Quantum Dots ◽  
First Principle Calculations ◽  
Oxidized Porous Silicon

To investigate the effects of Si/O bond at the surface of silicon quantum dots (Si QDs) on the electronic properties of Si QDs, first principle calculations have been performed for Si QDs consisting of 10-87 Si atoms (0.6-1.5 nm in diameter) by using the CASTEP software package. In these calculations the Si dangling bonds on the surface of Si QDs are passivated by hydrogen atoms and oxygen. Four different oxygen configurations have been studied, they are double-bonded, backbonded, bridge-bonded and inserted, respectively. We find that a significant reduction of energy gap is caused by the presence of double-bonded oxygen, whereas for other three oxygen configurations there is just a slight reduction on energy gap. As a result, the model which contains Si=O bond is considered the most appropriate to explain the photoluminescence redshifts in oxidized porous silicon.

scholarly journals A First-Principle Study of Monolayer Transition Metal Carbon Trichalcogenides

2021 ◽  
Author(s):  
Muhammad Yar Khan ◽  
Yan Liu ◽  
Tao Wang ◽  
Hu Long ◽  
Miaogen Chen ◽  
...  
Keyword(s):  
Phonon Dispersion ◽  
Magnetic Ordering ◽  
Dimensional Structure ◽  
First Principle ◽  
Two Dimensional ◽  
Biaxial Strain ◽  
Half Metallic ◽  
First Principle Calculations ◽  
Potential Applications ◽  
External Strain

AbstractMonolayer MnCX3 metal–carbon trichalcogenides have been investigated by using the first-principle calculations. The compounds show half-metallic ferromagnetic characters. Our results reveal that their electronic and magnetic properties can be altered by applying uniaxial or biaxial strain. By tuning the strength of the external strain, the electronic bandgap and magnetic ordering of the compounds change and result in a phase transition from the half-metallic to the semiconducting phase. Furthermore, the vibrational and thermodynamic stability of the two-dimensional structure has been verified by calculating the phonon dispersion and molecular dynamics. Our study paves guidance for the potential applications of these two mono-layers in the future for spintronics and straintronics devices.

scholarly journals Growth of sillenite Bi12FeO20 single crystals: structural, thermal, optical, photocatalytic features and first principle calculations

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Durga Sankar Vavilapalli ◽  
Ambrose A. Melvin ◽  
F. Bellarmine ◽  
Ramanjaneyulu Mannam ◽  
Srihari Velaga ◽  
...  
Keyword(s):  
Single Crystal ◽  
Single Crystals ◽  
Photoelectron Spectroscopy ◽  
Diffraction Method ◽  
Lattice Parameter ◽  
First Principle ◽  
X Ray Diffraction ◽  
X Ray ◽  
First Principle Calculations ◽  
Photodegradation Efficiency

AbstractIdeal sillenite type Bi12FeO20 (BFO) micron sized single crystals have been successfully grown via inexpensive hydrothermal method. The refined single crystal X-ray diffraction data reveals cubic Bi12FeO20 structure with single crystal parameters. Occurrence of rare Fe4+ state is identified via X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS). The lattice parameter (a) and corresponding molar volume (Vm) of Bi12FeO20 have been measured in the temperature range of 30–700 °C by the X-ray diffraction method. The thermal expansion coefficient (α) 3.93 × 10–5 K−1 was calculated from the measured values of the parameters. Electronic structure and density of states are investigated by first principle calculations. Photoelectrochemical measurements on single crystals with bandgap of 2 eV reveal significant photo response. The photoactivity of as grown crystals were further investigated by degrading organic effluents such as Methylene blue (MB) and Congo red (CR) under natural sunlight. BFO showed photodegradation efficiency about 74.23% and 32.10% for degrading MB and CR respectively. Interesting morphology and microstructure of pointed spearhead like BFO crystals provide a new insight in designing and synthesizing multifunctional single crystals.

scholarly journals Author Correction: Growth of sillenite Bi12FeO20 single crystals: structural, thermal, optical, photocatalytic features and first principle calculations

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Durga Sankar Vavilapalli ◽  
Ambrose A. Melvin ◽  
F. Bellarmine ◽  
Ramanjaneyulu Mannam ◽  
Srihari Velaga ◽  
...  
Keyword(s):  
Single Crystals ◽  
First Principle ◽  
First Principle Calculations

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

scholarly journals The thermal stability of FAPbBr3 nanocrystals from temperature-dependent photoluminescence and first-principles calculations

RSC Advances ◽  
2020 ◽  
Vol 10 (72) ◽  
pp. 44373-44381
Author(s):  
Xiaozhe Wang ◽  
Qi Wang ◽  
Zhijun Chai ◽  
Wenzhi Wu
Keyword(s):  
First Principles ◽  
First Principle ◽  
First Principles Calculations ◽  
Temperature Dependent ◽  
Time Resolved ◽  
First Principle Calculations ◽  
Steady State Time ◽  
Time Resolved Photoluminescence ◽  
Thermal Stability Of ◽  
Temperature Dependent Photoluminescence

The thermal properties of FAPbBr3 perovskite nanocrystals (PNCs) is investigated by use of temperature-dependent steady-state/time-resolved photoluminescence and first-principle calculations.

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