Electronic and optical properties of Ti_{1-x}Cd_xO2: A first-principles   prediction
  A first-principles study has been carried out to evaluate the electronic and optical properties of rutile Ti1-xCdxO2 as a possible photocatalytic material. It was found that Cd incorporation lead to the enhancement of p states in the top of valence band and the decrease of band gap. The optical transition between Cd p and O p enhances gradually and shifts to high energy range with increasing Cd concentration. Furthermore, optical absorption of Ti1-xCdxO2 increases in the visible range. 
X. D. Zhang, M. L. Guo, C. L. Liu, W. X. Li, and X. F. Hong
cond-mat.mtrl-sci physics.comp-ph