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Manuscript Title: Program for optimal computation of EPR spin-Hamiltonian parameters for ions in tetragonal symmetry.
Authors: A.S. Stefanescu
Catalogue identifier: ACKI_v1_0
Distribution format: gz
Journal reference: Comput. Phys. Commun. 11(1976)257
Programming language: Fortran.
Computer: IBM 360/168.
Operating system: OS.
RAM: 14K words
Word size: 32
Keywords: Solid state physics, Epr spin hamiltonian Parameters, Tetragonal environment, Least squares fit, Field magnetic, Paramagnetic ion, Fourth order Perturbation, Experiment.
Classification: 7.4.

Nature of problem:
The program computes the EPR spin-hamiltonian parameters for the paramagnetic ions in a tetragonal environment and an external magnetic field H. Its purpose is to optimize the computation of these spin- hamiltonian parameters with respect to the experimental errors. It can be used also for paramagnetic ions in cubic environment or in the absence of any of the parameters, D,A,B,a,F.

Solution method:
Performing a fourth-order perturbation expansion for the above spin- hamiltonian in the cases when the applied magnetic field is parallel and perpendicular, respectively, with respect to the axis of highest symmetry, one obtains a set of nonlinear equations for the spin- hamiltonian parameters. In the case when the number of available equations is greater than the number of parameters, a least squares minimization by an iterative procedure is carried out. The external magnetic field H was assumed to be sufficiently large to to make the electronic Zeeman term dominant with respect to any other terms in the hamiltonian.

The expressions used for the transition fields are valid only for hamiltonians with tetragonal or cubic symmetry and for a dominant Zeeman term. The nuclear and the quadrupole terms are neglected.

Running time:
The time required for the test run of Mn**2+ in NH4Cl is 7.55 s on a IBM 370/168 computer, of which 6.72 s are needed for compiling.