(a) General representative of states of the impurity atom, and and of single impurity doped (rutile) and (b) , , and are energy states of two different impurities. The occupied and unoccupied states are shown by black and white boxes, respectively. (c) Schematic diagram of relaxed geometry of Fe- and Mo-doped . Ti, O, and Fe atoms are shown as larger gray, smaller black, and larger black balls, respectively. Three different substitutional sites for Mo (named as 1, 2, and 3 in the figure) have been selected. Based on total energy calculations, Mo is likely to be located at site 1. The energy differences between Mo in sites 2 and 3, and 1 are 0.127 and 0.164 eV, respectively.
Partial DOS of , , , and of (a) and , (b) and , and (c) and are shown. The up and down arrow indicate the majority and minority spin states. The strong hybridization between the Ti or impurities with oxygen atoms are also seen from this figure.
Pseudo-spin-density contours (similar intervals) for (a) and (b) . The continuous and dotted contours mean the up- and down-spin components. The impurities states overlapping with the Ti conduction band are clearly depicted the presence of larger spin-density contours around Ti in .
The energy separation between CBM and the highest occupied impurity states ( and , and nature of system (NS) are given for double-impurities-doped (rutile). The metallic, half-metallic, and semiconducting nature are shown as M, H, and S, respectively. “a” means all states are unoccupied.
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