Charged Oxygen Defects inSiO2: Going beyond Local and Semilocal Approximations to Density Functional Theory

Abstract

The long-standing problem of the oxygen self-diffusion mechanism in silicon dioxide, a prototypical oxide, both in the crystalline and in the amorphous phase, is studied from first principles. We demonstrate that the widely used local-density approximation to density functional theory (DFT) predicts a kinetic behavior of oxygen in strong disagreement with available experiments. Applying a recently developed scheme that combines DFT with quasiparticle energy calculations in the G0W0 approximation considerably improves defect energetics and gives gratifying agreement with experiment.

Band-edge levels in semiconductors and insulators: Hybrid density functional theory versus many-body perturbation theory

“…The GW approximation has also successfully been applied to band-offset [7][8][9] and defect [10][11][12][13][14] calculations. However, its widespread application is still hampered by the high computational cost involved.…”

Point charges and atomic multipole moments of Si and O in amorphous SiO2 for the estimation of the electrostatic field and potential

“…However, on the other hand, a model of charged vacancy diffusion over interstices was one of the consequences of the use of DFT in the LDA approximation, as showed the authors of [10]. The work [10] in the LDA/G 0 W 0 approximation confirms a more possible mechanism of diffusion of oxygen atoms in SiO 2 through neutral defects in the interstices whereas the formation energy of the charged vacancy becomes high. An important advantage of the employment of EC methods is a more ample opportunity to use the Hartree-Fock (HF) exchange term that is rarely applied in a variant with boundary conditions, but without which the DFT exchange results in a structure of charged oxygen vacancies with two Si atoms nearby.…”

“…Periodic conditions in a wide range of the rearrangement lead to costly solutions, and even at a cell [34] with a size of about 15 Å the system does not reach the relaxed state in vicinity of the defect, which results in overestimated values for the formation energy of a charged oxygen vacancy [11,12]. However, on the other hand, a model of charged vacancy diffusion over interstices was one of the consequences of the use of DFT in the LDA approximation, as showed the authors of [10]. The work [10] in the LDA/G 0 W 0 approximation confirms a more possible mechanism of diffusion of oxygen atoms in SiO 2 through neutral defects in the interstices whereas the formation energy of the charged vacancy becomes high.…”

“…Widespread approaches are as follows: (a) DFT or Hartree-Fock methods using periodic boundary conditions and the choice of a supercell (SC) [6][7][8][9][10]; (b) methods of the type of embedded cluster (EC) [11][12][13]. Within the methods of the first group the authors have discussed oxidation mechanisms through the introduction of an O atom or ion [6], one О 2 molecule with different charges [7,8], or Н 2 О [8] along the Si-Si bond.…”

SiO2 in density functional theory and beyond

“…Defect levels (donor or acceptor) and formation energies of charged defects are difficult to describe quantitatively within DFT 35. Indeed, they are related to ionization potentials ( N − 1 excitation)/electron affinities ( N + 1 excitation) of the defect state 36, 37. Some attempts have been made to try to circumvent the need of going beyond DFT 38, 39.…”