An insight into optical and EPR properties of AgCl and AgF complexes through MS–Xα and SCCEH calculations

MS-Xα and SCCEH calculations on the Ag²⁺ complexes AgF and AgCl (displaying an elongated D_4h symmetry) have been carried out for a better understanding of their experimental optical and EPR properties. As salient features, the present work supports that the unpaired electron in AgCl spends a little more time on ligands than on Ag²⁺, in agreement with the previous analysis of EPR and optical data for KCl:Ag²⁺. Furthermore, the five experimental optical transitions observed in that case are reasonably assigned. The first transition (observed at 12,500 cm⁻¹) is assigned to a jump involving the 5a_1g orbital built mainly (∽70%) from 3p orbitals of axial ligands, a fact that reflects the distinct level scheme for AgCl when compared to that for more ionic complexes. Calculations on AgF and AgF performed as a function of the equatorial Ag²⁺ –F⁻ distance led to a reasonable understanding of experimental gyromagnetic and superhyperfine tensors displayed by Ag²⁺ in fluorides. The different relative decrease undergone by g‖– go (8%) and g ⟂ – go (28%) on passing from CsCdF₃:Ag²⁺ to RbCdF₃:Ag²⁺ is shown to be consistent with the formation of AgF and AgF complexes, respectively, related to the different substitutional position of Ag²⁺ in such lattices. The decrement of about 8.5% experienced by both g‖ – go and g⟂ – go values on going from CsCdF₃:Ag²⁺ to NaF:Ag²⁺ is pointed out to reflect the different electrostatic potential (exerted by the rest of the lattice upon the complex) seen by AgF embedded in NaCl or perovskite-type lattices. © 1994 John Wiley & Sons, Inc.