ZHANG, X; ONG, CK; STONEHAM, AM; (1994) STABILITY OF A SELF-TRAPPING HOLE IN ALPHA-QUARTZ. J PHYS-CONDENS MAT , 6 (29) 5647 - 5656. 10.1088/0953-8984/6/29/007.

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Abstract

Previous calculations of self-trapping in quartz adopt quantum chemical methods. However, for certain purposes, for example, when more than a few atoms are involved in a defect process, it would be helpful to use instead the shell model methods which work well for halides. We present the first calculation of the self-trapped hole (STH) in alpha-quartz and other forms of silicon dioxide using the classic defect simulation technique. The calculation suggests that the hole can be self-trapped on oxygen atom with a binding energy of 0.41 eV. The self-trapping is accompanied by a large network distortion, in which the O- ion on which the hole is self-trapped shifts 0.14 angstrom and the nearest-neighbour silicon atoms move 0.4-0.6 angstrom away from the O- ion. These results are similar to those obtained from the ab initio HF Calculation of STH in amorphous SiO2. We have also estimated the effective activation energy of a STH to be 0.12 eV at 180 K though there will also be a significant component of conduction from excitation of the small polaron to the delocalized large-polaron state.

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