Multilayer acoustic-surface-wave program. Computer-program description

A computer program is described for calculating the acoustic velocity and related field quantities for planar multilayer structures of arbitrary anisotropy and piezoelectricity. The solution method is based on a matrix approach wherein each layer is characterised by a transfer matrix relating the mechanical and electrical variables at the boundary planes. By choosing the system variables to be those quantities which must be continuous at material interfaces, formulating boundary conditions for planar multilayers is equivalent to cascading multipart networks. Thus, the transfer matrix across a multilayer is obtained by chain-multiplying the transfer matrices of successive layers. The chain-multiplication aspect, which is a fundamental consequence of this approach, guarantees that, irrespective of the number of layers, the setting of at most a 5×5 determinant to zero is all that is required to satisfy the boundary conditions. The program also calculates the mechanical and electrical field profiles as a function of depth, and metallic shorting planes can be located at any arbitrary location in the multilayer. The main program consists of four packages: a package for reading, initiating and preparing data; a package for generating the system matrices, evaluating transfer matrices, and setting up the boundary determinant for the required problem; a co-ordinate rotation package; and a mathematical package for carrying out complex eigenanalysis and function minimisation.