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.

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.

scholarly journals Lattice Dynamics of Gd1−xYxMn2O5 Investigated by Infrared Spectroscopy

2017 ◽  
Vol 2017 ◽  
pp. 1-7 ◽  
Author(s):  
Javed Ahmad ◽  
Jawaria Mansoor ◽  
Mehr Khalid Rehmani ◽  
M. Tufiq Jamil ◽  
Syed Hamad Bukhari
Keyword(s):  
Infrared Spectroscopy ◽  
Optical Conductivity ◽  
Lattice Dynamics ◽  
Lattice Vibration ◽  
Systematic Investigation ◽  
Structural Distortion ◽  
Frequency Range ◽  
Phonon Modes ◽  
Frequency Shifts ◽  
The Real

We present infrared (IR) reflectivity of Gd1-xYxMn2O5 with x = 0, 0.2, 0.4, 0.6, 0.8, and 1 in the frequency range 30–1000 cm−1. A total of 18 IR active phonons were observed for GdMn2O5 (x=0) and three additional phonons have been observed with increasing x, marking a total of 21 phonons in YMn2O5 (x=1). A systematic investigation was performed to map out the structural distortion through the lattice vibration and discuss the consequences of frequency shifts in phonon modes. In addition, we have calculated the real part of optical conductivity (σ1(ω)) which reflects the semiconducting nature of Gd1-xYxMn2O5.

Quantifying Thermal Transport of High-Temperature Ceramics From First Principle Calculations

2011 ◽  
Author(s):  
Babak Kouchmeshky ◽  
Peter Kroll
Keyword(s):  
Thermal Transport ◽  
Dynamics Simulation ◽  
Ab Initio Molecular Dynamics ◽  
First Principle ◽  
Anisotropic Behavior ◽  
Phonon Modes ◽  
Virtual Testing ◽  
Crystalline Materials ◽  
First Principle Calculations ◽  
Refractory Ceramics

We provide virtual testing capabilities of materials at temperatures where actual testing encounters many and severe technical difficulties. Combining ab-initio molecular dynamics simulation and kinetic theory we compute and analyze thermal transport of refractory ceramics at (ultra-) high temperatures ranging from 1000K to 2200 K. Most of our results are agreeable with available experimental data, though we find and examine discrepancies in selected cases. Our approach also catches the anisotropic behavior in thermal transport of some (single crystalline) materials. Since contributions of individual phonon modes on thermal transport are quantified, we suggest avenues for control and design of thermal conductivity in these materials.

scholarly journals Structural stability of single-layer PdSe2 with pentagonal puckered morphology and its nanotubes

2020 ◽  
Vol 22 (16) ◽  
pp. 8289-8295 ◽  
Author(s):  
Artem V. Kuklin ◽  
Hans Ågren ◽  
Pavel V. Avramov
Keyword(s):  
Structural Stability ◽  
2D Materials ◽  
Single Layer ◽  
First Principle ◽  
First Principle Calculations ◽  
Stability And Instability

Based on first-principle calculations, we demonstrate structural stability and instability of several recently proposed 2D materials with pentagonal morphology including the experimentally exfoliated single-layer PdSe2.

Improved Dreiding force field for single layer black phosphorus

2019 ◽  
Vol 21 (30) ◽  
pp. 16804-16817 ◽  
Author(s):  
Lijun Deng ◽  
Nian Zhou ◽  
Shan Tang ◽  
Ying Li
Keyword(s):  
Molecular Dynamics ◽  
Particle Swarm Optimization ◽  
Force Field ◽  
Particle Swarm Optimization Algorithm ◽  
Single Layer ◽  
Md Simulations ◽  
Black Phosphorus ◽  
First Principle ◽  
Swarm Optimization ◽  
First Principle Calculations

We present an improved Dreiding force field for single layer black phosphorus (SLBP) obtained by first-principle calculations in conjunction with the particle swarm optimization algorithm and molecular dynamics (MD) simulations.

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.

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