Specific propagation directions for media of rhombic symmetry

TL;DR

This paper investigates the existence and determination of acoustic axes in media with rhombic and monoclinic symmetry, providing new methods and examples for piezoelectric and non-piezoelectric materials.

Contribution

It introduces a method to determine acoustic axes in piezoelectric media of arbitrary symmetry, expanding understanding of wave propagation in such materials.

Findings

Non-piezoelectric rhombic media can have 4 or 8 acoustic axes.

Examples of monoclinic media without acoustic axes are provided.

A new method for determining acoustic axes in piezoelectric media is presented.

Abstract

We reanalyze the problem of existence of longitudinal normals inside symmetry planes of piezoelectric crystals belonging to the symmetry class mm2. The equations determining components of longitudinal normals situated outside symmetry planes for media of this symmetry are discussed. It is proven that non-piezoelectric media of rhombic symmetry could have 4 or 8 distinct acoustic axes. Examples of non-piezoelectric elastic media of monoclinic symmetry without acoustic axes are given. The method of determination of components of acoustic axes for piezoelectric media of arbitrary symmetry is presented. With the help of this method we discuss the problem of acoustic axes for piezoelectric media of the symmetry class mm2.