Abstract
THE preceding communication by Dr. Nagendra Nath is one of a series attempting to defend Raman's interpretation of the diffuse spots in X-ray photographs of crystals by discrediting the thermal theory accepted by other investigators of this phenomenon. Raman insists that not only is this application of lattice dynamics to X-ray scattering wrong, but also the foundations of lattice dynamics itself. He questions in particular the method of the 'cyclic boundary conditions', which consists in the following : The vibrations of a finite piece of the crystal depend in principle on the shape of the surface and the dynamical conditions prevailing on it. But if the dimensions of the piece are large compared with the single cell, it is plausible that the dependence on the boundary conditions will be inessential, so that these can be replaced by simpler ones (periodicity). The same assumption is made in the theory of radiant heat (black body radiation) and of the electrons in metals. It has never been doubted in these applications, and whoever rejects it would have to reconstruct these extended theories without this simplification.
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BORN, M. Density of Frequencies in Lattice Dynamics. Nature 151, 197 (1943). https://doi.org/10.1038/151197a0
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DOI: https://doi.org/10.1038/151197a0
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