Variational computation of a vibrating lithium niobate rectangular plate
  Electrically-excited electroelastic extensional vibrations of an arbitrarily cut three-dimensional piezocrystal resonator are analyzed variationally. A set of trigonometric trial functions applicable to a waveguide behavior of the resonator partly covered by metal electrodes is proposed. The dependence of the content of the vibration modes sustained by the resonator on the electrode configuration is found. The frequency spectra taken in 128-Y-rotated lithium niobate rectangular plates exhibit a good correspondence with the computed resonator eigenfrequencies. 
O. I. Polovina, V. V. Kurylyuk and O. A. Korotchenkov