Author Affiliations
1Laboratory of Micro-Nano Optoelectronic Materials and Devices, Key Laboratory of High-Power Laser Materials, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800, China2Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing 100049, China3e-mail: yhang@siom.ac.cnshow less
Fig. 1. (a) Supercell structure of Al2O3. (b) Four kinds of Ti3+−Ti3+ ion pair models. (c) 3Ti4+−VAl3− model. (d)–(f) Three kinds of Ti3+−3Ti4+−VAl3− models.
Fig. 2. Experimental absorption spectrum of Ti:sapphire sample with a doping concentration less than 0.16% (mass fraction) (on the left) and the simulated absorption spectrum of substitutional Ti-doped model with a theoretical doping concentration more than 3.6% (mass fraction) (on the right). There is a step at 860 nm on the experimental absorption spectrum, which is caused by the test system. The calculated PDOS distribution of Ti_3d is inserted into the simulated absorption spectrum.
Fig. 3. Band structure (on the left) and polarized absorption spectrum of line-contact Ti3+−Ti3+ ion pair model (on the right).
Fig. 4. The DOS of the supercell Ti2Al46O72, the LDOS of Al, O and Ti, and the PDOS of s, p, d electrons of line-contact Ti3+−Ti3+ ion pair model.
Fig. 5. Optimized charge distributions of HOMO, LUMO, and LUMO+i (i=1,2,3,4) of line-contact Ti3+−Ti3+ ion pair model. HOMO is the highest occupied molecule orbital. LUMO is the lowest unoccupied molecule orbital, while LUMO+1 means the first adjacent orbital above it, and so on for LUMO+i in a similar fashion. The blue-shaded area is the probability distribution of electrons in space, and the green spheres covered by it represent Ti ions.
Fig. 6. Band structure, Ti_3d_PDOS, and polarized absorption spectrum of 3Ti4+−VAl3− model.
Fig. 7. Band structure, Ti_3d_PDOS, and polarized absorption spectrum of face-contact Ti3+−Ti4+ ion pair model.
Fig. 8. Optimized charge distributions of HOMO, LUMO, and LUMO+j (j=1, 2, 3, 10) of face-contact Ti3+−Ti4+ ion pair model (see caption of Fig. 5 for details).
| Distance (Optimized) | Magnetic Coupling | Band Gap | Total Energy |
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Face-contact | 2.448 Å | Antiferromagnetic | 0.659 eV | −37453.6827 eV | Line-contact | 2.563 Å | Antiferromagnetic | 0.770 eV | −37453.8375 eV | Point-contact 2 | 3.034 Å | Ferrimagnetic | 0.543 eV | −37453.1967 eV | Point-contact 1 | 3.471 Å | Ferromagnetic | 0.299 eV | −37453.0835 eV |
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Table 1. Main Parameters and Calculation Results for Four Kinds of Ion Pair Models
| Band Gap | Total Energy |
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Face-contact | 0.610 eV | −40487.4271 eV | Line-contact | 0.436 eV | −40487.5264 eV | Point-contact | 0.218 eV | −40487.3425 eV |
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Table 2. Band Gap and Total Energy for Three Kinds of Ion Pair Models