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The Adiabatic Bond Charge Model of Phonons

The dispersion relation between frequency and wavevector of atomic vibrations, or phonons, can be succinctly described by the adiabatic bond charge model, first developed by Weber. The model 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 wavevector 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.

Identiferoai:union.ndltd.org:wpi.edu/oai:digitalcommons.wpi.edu:etd-dissertations-1179
Date26 April 2012
CreatorsKassebaum, Paul Gregory
ContributorsL. Ramdas Ram-Mohan, Advisor, Padmanabhan K. Aravind, Committee Member, Richard D. Sisson, Jr., Committee Member
PublisherDigital WPI
Source SetsWorcester Polytechnic Institute
Detected LanguageEnglish
Typetext
Formatapplication/pdf
SourceDoctoral Dissertations (All Dissertations, All Years)

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