  We use density functional theory within the generalized gradient
approximation to characterize the dielectric response of rare earth oxides:
(La,Sc)2 O3 bixbyite, and LaScO3 perovskite. We focus on the role of strain on
the phonon contribution of the dielectric constant and find that, contrary to
the classical expectation based on the Clausius-Mossotti relation, tensile
volumetric strain and volume-conserving bi- axial strain on the order of +/-1%
can lead to an increase in dielectric constant of up to 20%. The insight into
the atomic mechanisms responsible for these effects and the quantitative
results in this paper can contribute to the development and understanding of
high-{\kappa} materials.
