Abstract
In this study, first-principles calculation within the density-functional perturbation theory was performed to investigate the change of electromechanical coupling factor of LiNbO3 with substitutional elements; Na, K, Rb, Cs. As ionic radius of the dopant is increased, electromechanical coupling factor is found to be increased, although crystal was found to be mechanically unstable when Cs was substituted. In addition, it was found that the changes of the piezoelectric constants are originated in the changes of the elastic response along the polarization axis, which is thought to be induced by the electrostatic repulsion between dopants and surrounding cation.
