Physics Department PhD. Dissertation, "The adiabatic bond charge model of phonons" by Paul Kassebaum, WPI Physics Department Graduate Student

Science / Technology - Colloquium

Friday, April 20, 2012
4:00 PM-5:00 PM

Olin Hall

The dispersion relation between wave vector and frequency of atomic vibrations, or phonons, can be succinctly described by the adiabatic bond charge model, first developed by Werner Weber, which employs as few as four parameters to fit experiment. We investigated this model in order to better unify the description of the technologically relevant group IV elemental semiconductors (e.g. diamond, silicon, germanium, and gray tin) by replacing an ad hoc parameter introduced by Weber with one arising from quadrupolar interactions between the bond charges, and by fitting the parameters to density functional theory calculations. We also illustrate constant frequency surfaces embedded in wave vector space for the various modes of vibration for the first time. The bond charge model allows for rapid calculation of various quantities related to the interaction of phonons with electrons and photons as compared to density functional theory, especially in structures with little symmetry and for macroscopic structures, thus enabling the design of complicated electronic and photonic devices much more accurately.

Cost: Free

Suggested Audiences: College

Phone: 508-831-5258

Last Modified: April 12, 2012 at 1:59 PM

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