Charge traps in crystalline and amorphous SiO₂ are of great technological importance for the design of reliable and radiation tolerant metal oxide silicon devices.
We performed ab initio Hartree - Fock calculations of the electronic structure of the Frenkel defect (Si-Si-O-O-) in SiO₂. All calculations were made in cluster model. Fragments of crystalline -quartz were used for calculations. Broken Si-O bonds on the cluster boundaries were saturated with H atoms. For simulating SiO₂ bulk we used a Si₅O₁₆H₁₂ cluster including 3 correct coordinated spheres. In this cluster the Si-O bond length was  ~ 1.63Å the Si-O-Si angle ~ 145, and the O-Si-O angle  ~ 109.5. The Hartree - Fock molecular orbitals were constructed using double-zeta basis with polarization 3d- and s-, p- diffuse functions for all atoms (standard basis 6-31+G). On the first step the positions of all Si and O atoms have been fully optimized and position of terminal H atoms have been fixed to represent embedding in solid.
For evaluating whether the given cluster has ability to capture electrons or holes we calculate its total energy in different charged states and find the energy gain. Our results show that the electron capture by Frenkel pair is energetically unfavorable but the energy gain for hole capture is -2.43 eV. I.e. our calculation predicts that this defective center is a hole trap in SiO₂.
From the calculated result, the Frenkel defect is 7.7 eV less stable than the regular structure.
From the comparative analysis the density of states of the neutral regular and Frenkel structures we assert that two states corresponding Frenkel pair appear inside the energy gap of -SiO2. This is antibonding and bonding molecular orbitals with eigenvalues -11.8 eV and -11.31 eV respectively.

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