Angular dispersion of phonons in biaxial crystals

Bonilla, I.R. and Rutt, H.N. (1975) Angular dispersion of phonons in biaxial crystals. Physica Status Solidi (b), 69, 395-398.


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The angular dispersion (kph ↫ ω/c) of polar phonons in the region of the ν3,-states of the SO42−-ions in biaxial MgSO4, · 7 H2O has been observed with Raman-scattering experiments at T = 300 K and T = 1.9 K. The agreement of the experimental data with the existing theories of angular dispersion is very satisfying. Some accidental degeneracies of transverse with longitudinal states of different symmetry could be observed. This degeneracy, where the two branches cross with equal slopes of opposite signs, can be lifted due to the temperature dependence of the frequencies. This behaviour is also interpreted theoretically and some simple relations are derived for the slopes and the curvature of dispersion branches, which relate these data to the effective charges and the dielectric function ε(ω), and which characterize the critical points occuring on the dispersion branches.

Item Type: Article
Divisions: Faculty of Physical Sciences and Engineering > Electronics and Computer Science
ePrint ID: 258462
Date Deposited: 05 Nov 2003
Last Modified: 30 Jun 2015 16:59
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