First-principles study on visible light absorption of defected SrNbO3

In the present work, electronic states and light absorption spectra of d(1) metallic strontium niobate, SrNbO3, are numerically investigated to gain a further insight into the controversial origin of its visible light absorption observed at (similar to)1.9 eV optical gap experimentally. Our numerical results show that this optical gap corresponds to the inter-band CB -> B-1 transition. Furthermore, it turns out that the photocatalysis of d(1) type such as SrNbO3 is a special case where the optical contributions from the low symmetric k points on the fermi surface are larger than those from the more symmetric k points. A comparative study of the well-researched Sr1-xNbO3 having only Sr defects and the Sr1-xNbO3-x. having both Sr defects and O vacancies implies that the latter reproduces the experimental dependence of an optical gap on the amount of Sr defects and that the light absorption intensity of the latter is larger than that of the former.