Publikacje

Abstract:

The existence conditions of zero electric fields E and zero electric displacements D are studied for bulk acoustic waves in piezoelectric crystals. General equations are derived for lines of zero electric fields, E(m)=0, and for specific points m(0) of vanishing electric displacements, D(m(0))=0, on the unit sphere of propagation directions m(2)=1. The obtained equations are solved for a series of examples of particular crystal symmetry. It is shown that the vectors D-alpha(m) being generally orthogonal to the wave normal m are characterized by definite orientational singularities in the vicinity of m(0) and can be described by the Poincare indices n=0, +/- 1 or +/- 2. The algebraic expressions for the indices n are found both for unrestricted anisotropy and for a series of particular cases.

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Non-piezoactivity in piezoacoustics: basic properties and topological features