Absorbing Boundary Conditions for Molecular Dynamics

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Title: Absorbing Boundary Conditions for Molecular Dynamics
Author: Thirunavukkarasu, Senganal
Advisors: Dr. M. N. Guddati, Committee Chair
Dr. P. A. Gremaud, Committee Member
Dr. M. S. Rahman, Committee Member
Abstract: With the goal of minimizing the domain size for Molecular dynamics (MD) simulations, we develop a new class of absorbing boundary conditions (MD-ABC's) that can mimic the phonon absorption of an unbounded exterior. The proposed MD-ABC's are extensions of perfectly matched discrete layers (PMDL), originally developed as an absorbing boundary condition for continuous wave propagation problems. Called MD-PMDL, this extension carefully targets the absorption of phonons, the high frequency waves, whose propagation properties are completely different from continuous waves. This thesis presents the derivation of MD-PMDL for general lattice systems, followed by explicit application to one-dimensional and two-dimensional square lattice systems.The accuracy of MD-PMDL for phonon absorption is proven by analyzing reflection coefficients, and demonstrated through numerical experiments. Unlike existing ABC's that are effective for high frequency phonon absorption, MD-PMDL is local in both space and time and is thus more efficient. Based on their favorable properties, it is concluded that MD-PMDL could provide a more effective alternative to existing MD-ABC's.
Date: 2009-03-05
Degree: MS
Discipline: Civil Engineering
URI: http://www.lib.ncsu.edu/resolver/1840.16/1880

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