Chain Conformation, Molecular Dynamics, and Thermal Properties of Poly(n-methylene 2,5-furanoates) as a Function of Methylene Unit Sequence Length

2019 ◽  
Vol 52 (17) ◽  
pp. 6533-6546 ◽  
Author(s):  
George Papamokos ◽  
Theodoros Dimitriadis ◽  
Dimitrios N. Bikiaris ◽  
George Z. Papageorgiou ◽  
George Floudas
2000 ◽  
Vol 307 (1-2) ◽  
pp. 1-9 ◽  
Author(s):  
Kazuhiro Yamada ◽  
Ken Kurosaki ◽  
Msayoshi Uno ◽  
Shinsuke Yamanaka

Author(s):  
Wei Ning ◽  
Yang Chen ◽  
Kun Cai ◽  
Yingyan Zhang ◽  
Qingxiang Pei ◽  
...  

Author(s):  
Majid S. al-Dosari ◽  
D. G. Walker

Yttrium Aluminum Garnet (YAG, Y3Al5O12) and its varieties have applications in thermographic phosphors, lasing mediums, and thermal barriers. In this work, thermal properties of crystalline YAG where aluminum atoms are substituted with gallium atoms (Y3(Al1−xGax)5O12) are explored with molecular dynamics simulations. For YAG at 300K, the simulations gave values close to experimental values for constant-pressure specific heat, thermal expansion, and bulk thermal conductivity. For various values of x, the simulations predicted no change in thermal expansion, an increase in specific heat, and a decrease in thermal conductivity for x = 50%. Furthermore, the simulations predicted a decrease in thermal conductivity with decreasing system size.


Author(s):  
Keivan Esfarjani ◽  
Gang Chen ◽  
Asegun Henry

Based on first-principles density-functional calculations, we have developed and tested a force-field for silicon, which can be used for molecular dynamics simulations and the calculation of its thermal properties. This force field uses the exact Taylor expansion of the total energy about the equilibrium positions up to 4th order. In this sense, it becomes systematically exact for small enough displacements, and can reproduce the thermodynamic properties of Si with high fidelity. Having the harmonic force constants, one can easily calculate the phonon spectrum of this system. The cubic force constants, on the other hand, will allow us to compute phonon lifetimes and scattering rates. Results on equilibrium Green-Kubo molecular dynamics simulations of thermal conductivity as well as an alternative calculation of the latter based on the relaxation-time approximation will be reported. The accuracy and ease of computation of the lattice thermal conductivity using these methods will be compared. This approach paves the way for the construction of accurate bulk interatomic potentials database, from which lattice dynamics and thermal properties can be calculated and used in larger scale simulation methods such as Monte Carlo.


2018 ◽  
Vol 8 (12) ◽  
pp. 2380 ◽  
Author(s):  
Miaocao Wang ◽  
Fulong Zhu ◽  
Yixin Xu ◽  
Sheng Liu

Silicon carbide (SiC), especially 4H-SiC, is an ideal semiconductor in power electronics due to its outstanding electrical and thermal properties. It has high hardness and brittleness, which makes it difficult to machine. To understand the nanomachining characteristics of off-axis 4H-SiC and provide suggestions on 4H-SiC substrate thinning, the nanocutting process of 4 ∘ off-axis 4H-SiC was simulated by molecular dynamics. The results showed that the stacking fault induced by cutting propagates in the basal plane, and propagates deep into the SiC workpiece when the angle between the cutting direction and the c-axis is smaller than 90 ∘ . Bond reconstruction is found near the slip plane. The cutting depth is also a key parameter in nanocutting. With smaller cutting depth, machining is more like scratching than cutting. With larger cutting depth, more atoms are involved in the cutting, cutting force and workpiece temperature are higher, and more defects exist.


2015 ◽  
Vol 1727 ◽  
Author(s):  
M. Rifu ◽  
K. Shintani

ABSTRACTThe thermal conductivities of pillared-graphene nanostructures (PGNSs) are obtained using nonequilibrium molecular-dynamics simulation. It is revealed their thermal conductivities are much smaller than the thermal conductivities of carbon nanotubes (CNTs). This fact is explained by examining the density of states (DOS) of the local phonons of PGNSs. It is also found the thermal conductivity of a PGNS linearly decreases with the increase of the inter-pillar distance.


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