We present an ab initio transient analysis of acoustic wave generation in piezoelectric materials, which takes into account second-order effects ( e.g., bulk wave generation and interaction between surface waves and bulk waves). The computer program we have developed for this purpose solves the fundamental differential equations in two space dimensions with the corresponding mechanical displacements and the electrical potential as dependent variables using a semi-implicit finite difference scheme rather than by wave approximations. This has become possible with acceptable usage of computer resources only by introducing a novel form of boundary conditions for the quasi-infinite sagittal plane to avoid reflection phenomena. We present numerical results for YX LiNbO 3.