THE OPTICAL-ABSORPTION SPECTRUM OF THE OCTAHEDRAL RHCL63- COMPLEX - AB-INITIO CALCULATIONS OF EXCITATION-ENERGIES AND THE EFFECT OF SPIN-ORBIT-COUPLING

The spin-orbit states of octahedral RhCl63- in the three lattices NaCl , Cs2NaYCl6 and water solution have been investigated theoretically wi th multiconfigurational self-consistent field (SCF) type procedure (CA SSCF), followed by a second order perturbation correlation treatment ( CASPT2). The spin-orbit effects for the ground state (1)A(1g) and the lowest excited states T-3(1g), T-3(2g), T-1(1g) and T-1(2g) were calcu lated with an effective one-electron operator and shifts of more than 1000 cm(-1) were found. Different basis sets were tried: the presence off functions on Rh and d functions on Cl is important for both excita tion energies and equilibrium distances. There is agreement between co mputed excitation energies and the available experimental data that in dicate a redshift of the T-1(1g,2g) <-- (1)A(1g) transitions as the Rh -Cl distance increases. (C) 1998 American Institute of Physics. [S0021 -9606(98)30532-2]