Theoretical Investigations on the Spin Hamiltonian Parameters and Local Structures for Cu ²⁺ in xNaI‐(30–x)Na ₂ O‐70B ₂ O ₃ (5 ≤  <i>x</i>  ≤ 25) Glasses

The spin Hamiltonian parameters (SHPs) (g factors g_// and g_⊥ and hyperfine structure constants A_// and A_⊥) and their concentration (x) dependences for Cu²⁺ in xNaI·(30-x)·Na₂O·70B₂O₃ (5 ≤ x ≤ 25) glasses are theoretically investigated in a consistent way. The [CuO₆]^10- complexes are subject to the Jahn-Teller effect, leading to the relative elongations of about 7%. The concentration dependences of the SHPs are suitably attributed to the nonmonotonic piecewise relationships of cubic field parameter, covalency factor, relative tetragonal elongation ratio, and core polarization constant with NaI concentration x due to the modifications of local crystal fields and electron cloud distribution around impurity Cu²⁺. The calculated cubic field splittings E₁, g factors, and A_// at various concentrations x agree well with the measured results, and the values of corresponding A_⊥ are also predicted. The properties of optical and EPR spectra are discussed, and the microscopic mechanisms of the concentration dependences of the related quantities are also analyzed.