Studies on the spin-Hamiltonian parameters of CuN6 clusters and their tetragonal distortions due to Jahn-Teller effect for Cu2+ in trigonal M(1-propyltetrazole)6(BF4)2 (MÂ =Â Zn, Fe) crystals

This paper reports the theoretical calculations for the anisotropic and isotropic spin-Hamiltonian parameters (g factors and the hyperfine structure constants) of tetragonal CuN6 octahedral clusters due, respectively, to the static and dynamic Jahn-Teller effects for Cu2+ ion in the trigonal M(=Zn, Fe) sites of M(1-propyltetrazole)6(BF4)2 crystals. The calculations are carried out using the high-order perturbation formulas based on a two-mechanism model, in which besides the contributions to spin-Hamiltonian parameters due to the crystal-field mechanism concerning the crystal-field excited states in the extensively used crystal-field theory, the contributions due to charge-transfer mechanism concerning the charge-transfer excited states (which are neglected in the crystal-field theory) are included. The calculated results are in reasonable agreement with the experimental values. From the calculations the tetragonal elongations ΔR = R// − R⊥ (where R// and R⊥ denote the Cu-N distances parallel with and perpendicular to the C4 axis) of CuN6 octahedral clusters due to Jahn-Teller effect are obtained. The results are discussed.