First-principles based analysis of the piezoelectric response in α-LiIO3

The density functional theory combined with the modern theory of polarization is used to understand the microscopic origin of the piezoelectric effect in the hexagonal lithium iodate (α-phase). Calculations show that the e33 and e14 piezoelectric-stress elements respectively have the highest and the smallest value in agreement with the experimental evidences. This e33 value is a consequence of the lone pair orbital of the IO3- group. Further insights are obtained by the separation of the piezoelectric-stress into a purely electronic and ionic contributions. The latter contribution has been also decomposed into contributions from individual atoms, as well as contributions from phonon normal modes. The full set of elastic constants was computed, by means of which the piezoelectric-strain coefficients have been derived. These are discussed and compared to experimental data reported in literature.

63