Optical transitions and EPR properties of two-coordinated Si, Ge, Sn and related H ( I ) , H ( II ) , and H ( III ) centers in pure and doped silica from ab initio calculations

摘要: The photoabsorption and photoluminescence properties of two-coordinated Si, Ge, Sn defect centers the magnetic interactions corresponding $[=\mathrm{S}\mathrm{i}\ensuremath{-}\mathrm{H}{]}^{\ifmmode\bullet\else\textbullet\fi{}},$ $[=\mathrm{G}\mathrm{e}\ensuremath{-}\mathrm{H}{]}^{\ifmmode\bullet\else\textbullet\fi{}},$ $[=\mathrm{S}\mathrm{n}\ensuremath{-}\mathrm{H}{]}^{\ifmmode\bullet\else\textbullet\fi{}}$ structures, $H(\mathrm{I}),$ $H(\mathrm{II}),$ $H(\mathrm{III})$ centers, respectively, have been studied by means ab initio quantum-chemical methods. Using cluster models configuration interaction wave functions, we determined transition energies to lowest singlet triplet states emissions lifetimes. computed optical are in close agreement with those proposed for pure doped silica. hyperfine paramagnetic using unrestricted Hartree-Fock density-functional theory approaches. Also, this case, assignments consistent calculations. results provide strong theoretical support proposal Si as origin one component 5.0 eV ${B}_{2}$ absorption band amorphous