Quantum-chemical modeling of the structure, stability, and IR spectra of tellurium-containing defects in amorphous selenium

The incorporation of Te atoms into the continuous random network (CRN) of a-Se was modeled by quantum-chemical methods. The structure with the two-coordinate impurity atom Te-2(0) is the most stable. However, hypervalent configurations in which the coordination number of Te exceeds 2 do not require considerable expenditures of energy and are considerably lower on the energy scale than analogous defects in "pure" a-Se. In particular, the Te, defect with the four-coordinate impurity atom is nearly as stable as the major structure and can have a rather high concentration in the CRN. The presence of defects with participation of Te atoms leads to the emergence of extra peaks in the vibrational spectra both in low-frequency and high-frequency regions. The contributions of each of the defects to the IR spectrum are rather characteristic, so that a defect with a noticeable concentration in the CRN of a-Se is expected to be experimentally identified.