TEMPERATURE DEPENDENCE OF INFRARED DISPERSION IN NaF AND $CaF_{2}$
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Date
1968
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Ohio State University
Abstract
By defining a ``pseudo unit cell'' one is able to describe the lattice vibrations of a mixed crystal. The theory can determine the existence or non-existence of local or gap modes and their independence of the phonon wave vector. In describing the zone center optic phonons, the virtual crystal model or the MREI model can be shown to be special cases of the present theory, which can also describe the zone boundary phonons. Given the properties of the ``pure'' end members AB and AC, the theory can predict the concentration dependence of the TO and LO modes of the mixed system, $AB_{x}C_{1-x}$. A large number of examples will be given.
Description
Present address of I. F. Chang: Components Division, IBM, Fishkill, New York.
Author Institution: Department of Electrical Engineering, University of Rhode Island; Components Division, IBM, Fishkill
Author Institution: Department of Electrical Engineering, University of Rhode Island; Components Division, IBM, Fishkill