AN EFFICIENT GENERAL ALGORITHM FOR THE SIMULATION OF MAGNETIC-RESONANCE SPECTRA OF ORIENTATIONALLY DISORDERED SOLIDS

We present an efficient and general algorithm for the simulation of EPR powder spectra. The method is based on the accumulation of a large number of single-crystal spectra. Only 2-10% of these spectra are computed by exact diagonalization of the spin-Hamiltonian matrix, whereas the other spectra are obtained by separate bicubic spline interpolation procedures for the spectral positions and intensities of all relevant transitions. The energy-level tracking scheme required for the correct interpolation of the resonance position uses the inproduct matrix of the eigenvectors of the spin-Hamiltonian matrices calculated for two subsequent orientations of the magnetic field. The procedure can be easily included in any general spin-Hamiltonian program. The merits of the method are demonstrated with the simulation of the spectrum of Re(IV) in TiO (S = 3 2, I = 5 2, two isotopes Dzz = 40,000 × 10-4cm-1) at X band. The computing time as compared to that of an algorithm without interpolation was reduced by a factor of 10 without deterioration of the resulting simulated powder spectrum. © 1990.