Response of low quartz SiO2 to the presence of an external static electric field: A density functional theory study.
Résumé
We present a systematic theor. study of response properties of α-quartz SiO2 to an external static elec. field in the framework of the d. functional theory. The distortions of the electron d. and cryst. structure by the application of the field are investigated and compared to x-ray scattering intensity variations obtained by Guillot et al. when a macroscopic elec. field of 28.8 kV/cm is applied along the crystallog. a axis. Our calcns. show that the exptl. macroscopic field produces mainly at. displacements, with a negligible electronic contribution. The calcd. displacements along the a axis are in good agreement with the exptl. data obtained from structure factors while the perpendicular displacements are found to be smaller, as well as the rotations of the Si-O bonds in the two independent tetrahedra around the a axis. In this work, the direct gap, the high-frequency dielec. const. as well as the elastic and piezoelec. tensors are also computed in order to confirm the accuracy of our calcns.