Graphene phonons lifetime and mean free path using ab initio molecular dynamics and spectral energy density analysis

2021 ◽  
Author(s):  
Morteza Mafakheri ◽  
Amir Abbas Sabouri Dodaran
Keyword(s):  
Molecular Dynamics ◽  
Energy Density ◽  
Ab Initio ◽  
Free Path ◽  
Mean Free Path ◽  
Ab Initio Molecular Dynamics ◽  
Spectral Energy ◽  
Spectral Energy Density ◽  
Density Analysis

Comparison of Spectral Energy Density Methods for Predicting Phonon Properties

2012 ◽  
Author(s):  
Jason M. Larkin ◽  
Alexandre D. Massicotte ◽  
Joseph E. Turney ◽  
Alan J. H. McGaughey ◽  
Cristina H. Amon
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulation ◽  
Energy Density ◽  
Lattice Dynamics ◽  
Dynamics Simulation ◽  
Spectral Energy ◽  
Spectral Energy Density ◽  
Lennard Jones ◽  
Density Methods ◽  
Phonon Properties

To predict the thermal conductivity of a dielectric or insulating material requires the phonon frequencies and lifetimes. Techniques for predicting these quantities have been proposed based in molecular dynamics simulation and lattice dynamics calculations. Here, two expressions for the phonon spectral energy density are described and applied to two test systems: Lennard-Jones argon and Stillinger-Weber silicon. One spectral energy density expression is derived from lattice dynamics theory, while the other uses only the atomic velocities from molecular dynamics simulation. We find that while the spectral energy density using only atomic velocities can predict the phonon frequencies, it is not generally able to predict the lifetimes due to terms omitted in the derivation.

Predicting Phonon Properties From Molecular Dynamics Simulations Using the Spectral Energy Density

2011 ◽  
Author(s):  
Joseph E. Turney ◽  
John A. Thomas ◽  
Alan J. H. McGaughey ◽  
Cristina H. Amon
Keyword(s):  
Molecular Dynamics ◽  
Energy Density ◽  
Molecular Dynamics Simulations ◽  
Lattice Dynamics ◽  
Relaxation Times ◽  
Mode Analysis ◽  
Spectral Energy ◽  
Spectral Energy Density ◽  
Dynamics Simulations ◽  
Phonon Properties

Using lattice dynamics theory, we derive the spectral energy density and the relation between the spectral energy density and the phonon frequencies and relaxation times. We then calculate the spectral energy density and phonon frequencies and relaxation times for a test system of Lennard-Jones argon using velocities obtained from molecular dynamics simulations. The phonon properties, which can be used to calculate thermal conductivity, are compared to predictions made using (i) anharmonic lattice dynamics calculations and (ii) a technique that performs normal mode analysis on the positions and velocities obtained from molecular dynamics simulations.

Combustion Driven by Fragment-based Ab Initio Molecular Dynamics Simulation

2019 ◽  
Author(s):  
Liqun Cao ◽  
Jinzhe Zeng ◽  
Mingyuan Xu ◽  
Chih-Hao Chin ◽  
Tong Zhu ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Ab Initio ◽  
Large Scale ◽  
Methane Combustion ◽  
Combustion Method ◽  
Dynamics Simulation ◽  
Ab Initio Molecular Dynamics ◽  
Computational Time ◽  
Combustion Mechanism ◽  
Daily Lives

Combustion is a kind of important reaction that affects people's daily lives and the development of aerospace. Exploring the reaction mechanism contributes to the understanding of combustion and the more efficient use of fuels. Ab initio quantum mechanical (QM) calculation is precise but limited by its computational time for large-scale systems. In order to carry out reactive molecular dynamics (MD) simulation for combustion accurately and quickly, we develop the MFCC-combustion method in this study, which calculates the interaction between atoms using QM method at the level of MN15/6-31G(d). Each molecule in systems is treated as a fragment, and when the distance between any two atoms in different molecules is greater than 3.5 Å, a new fragment involved two molecules is produced in order to consider the two-body interaction. The deviations of MFCC-combustion from full system calculations are within a few kcal/mol, and the result clearly shows that the calculated energies of the different systems using MFCC-combustion are close to converging after the distance thresholds are larger than 3.5 Å for the two-body QM interactions. The methane combustion was studied with the MFCC-combustion method to explore the combustion mechanism of the methane-oxygen system.

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