Biradical states of oxygen- vacancy defects in alpha-quartz: centers E ''(2) and E ''(4)

作者：Mashkovtsev Rudolf I^*; Pan Yuanming

来源：Physics and Chemistry of Minerals, 2011, 38(8): 647-654.

DOI：10.1007/s00269-011-0437-0

• Quartz
• EPR
• Radiation-induced centers
• Spin triplet states
• Oxygen vacancies

Several new radiation defects with total electron spin S = 1 occurring in electron-irradiated, synthetic alpha-quartz have been observed by using electron paramagnetic resonance spectroscopy. These defects are considered to be biradicals, i.e., pairs of S = 1/2 species. The concentration of these centers depends on the condition of the fast-electron irradiation. They have different decay behaviors that allow measurements of any individual species especially when it predominates over the others. The primary spin Hamiltonian parameter matrices g (1), g (2), D have now been determined for two similar defects, which herein are labeled E-2('') and E-4(''). Inter-electron distances estimated by using the magnetic dipole model, suggest that the structures of centers E-2('') and E-4(''). both involve the unpaired electrons each located in orbitals of two silicon atoms next to a common oxygen vacancy but which have slightly different Si-Si distances at 0.90 and 0.79 nm, respectively. This model is consistent with previous DFT calculations of the triplet configurations with local energetic minima. Observed decay behaviors suggest a transformation of centers E-2,4('') to the analoguous E-1('').center. These triplet centers in quartz provide new insights into the structures of analogous defects in amorphous silica.

• 出版日期2011-9