Date of Award

8-2014

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Legacy Department

Physics

Advisor

Dr. Murray S. Daw

Committee Member

Dr. Bradley Meyer

Committee Member

Dr. Catalina Marinescu

Committee Member

Dr. Sumanta Tewari

Abstract

A new method (second moment approximation method) of calculating mode lifetimes of materials has been proposed by Dickel and Daw [14, 15]. The method was tested on an anharmonic lattice model, and it shows consistency with results from using traditional method (molecular dy-namics with Green-Kubo [2]) at high temperatures, but deviates at low temperatures. Based on this method, we developed the fourth moment approximation method, and tested it on various models from 1D anharmonic chain to the FCC cube with Lennard-Jones potential. Calculations showed that the fourth moment approximation method provides a fast and reliable scheme to calculate mode lifetimes at wide range of temperatures, and this scheme can be used on many different materials.

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