First-principles study of the difference in permittivity between Ba(Mg1 / 3Ta2 / 3)O3 and Ba(Mg1 / 3Nb2 / 3)O3

This paper discusses the difference in permittivity at infrared frequencies between Ba(Mg1/3Ta2/3)O3 (BMT) and Ba(Mg1/3Nb2/3)O3 (BMN) based on a first-principles calculation. The permittivity, far-infrared and Raman spectra are successfully computed. Analysis of these results shows that the smaller amplitude of O in the low frequency mode Eu2 (BMT), which is caused by the larger polarizability of Ta5+, is the origin of the smaller permittivity of BMT.