Abstract
Density functional perturbation theory is used to study the mechanism of the piezoelectric response in α-GeO2 and to estimate its magnitude. To date, its piezoelectric-stress elements have never been calculated using this level of theory nor measured on a high-quality water-free single crystal. Our calculations predict that the value of e11 piezoelectric-stress is about 50% higher than in α-quartz. This enhancement is due to larger tetrahedra distortions and/or a lower frequency of the dominant polar E-mode. In contrast to α-quartz, α-GeO2 has also a sizable e14 value that reaches 0.169 C/m2.