Studies on the spin-Hamiltonian parameters of CuN(6) clusters and their tetragonal distortions due to Jahn-Teller effect for Cu2+ in trigonal M(1-propyltetrazole)6(BF4)2 (M=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.

Spin-Hamiltonian parameters and angular distortion for the trigonal Nd(3+) center in congruent LiNbO(3).

The 52x52 energy matrix related to the ground multiplet (4)I(9/2) and the first to third excited multiplets (4)I(11/2), (4)I(13/2) and (4)I(15/2) for 4f(3) ions in trigonal crystal field under an external magnetic field is established. By diagonalizing the energy matrix, the spin-Hamiltonian parameters (g factor g(parallel), g(perpendicular) and hyperfine structure constants (143)A(parallel), (143)A( perpendicular), (145)A(parallel), (145)A( perpendicular)) of the trigonal Nd(3+) center in congruent LiNbO(3) crystal are calculated. The calculated results are in reasonable agreement with the experimental values. From the calculations, the negative signs of hyperfine structure constants are suggested and the angular distortion of the trigonal Nd(3+) center in LiNbO(3), which is unable to be determined by EXAFS measurement, is obtained. The results are discussed.