| Summary: | <p>This thesis is concerned with the application of lattice dynamical theories to problems of current physical interest. The first sort is a calculation of the lattice dynamics of calcium fluoride, with a detailed discussion of the various types of model which may be used. On the basis of this discussion the Bern model is used in the numerical calculation and the results are presented in the form of dispersion curves and density-of-states curves.</p> <p>The second part of the thesis deals with the theory of the vibrations of crystal lattices perturbed by the introduction of defects. The object is to develop the theory into a form such that it becomes easy to perform numerical calculations, using existing lattice dynamical calculations, so that physical properties of defects which involve changes of force constants as well as mass changes may be computed.</p> <p>The third part deals with such a defect which has received some experimental attention recently, namely, the hydrogenation in calcium fluoride crystals. This is an interesting theoretical problem as not only is the theory of defects in crystal lattices concerned, but also that of anharmonicity. From the optical observations it is possible to calculate some of the anharmonic force constants involved.</p>
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