Calculation of Mossbauer spectrum model curves accounting for 57Fe paramagnetic hyperfine structure (PHS) of paramagnetic iron ions requires the
consideration of the combined effect of the nuclear- and the electronic spin Hamiltonian on the nuclear- and electronic states of the ion. As the latter are influenced by the crystal field the ion is situated in,
corresponding terms appear in the combined Hamiltonian. When a powder sample is measured in conjunction with the application of an external magnetic field,
the calculation of corresponding Mossbauer spectrum models requires the implementation of a spherical integral over all possible orientations of the external magnetic field with respect to the Hamiltonian reference frame that is
considered to be fixed to the individual molecules/crystallites. This spherical integral can in general be carried out only numerically, which makes the calculation of PHS theory based model curves a rather time consuming process for powders.
In MossWinn 4.0 57Fe PHS models have been implemented by making use of parallel computing techniques for the calculation of this spherical integral, which can (in comparison with traditional serial algorithms) result in a considerably enhanced
calculation speed on today's higher-end multi-core processor based computers. Together with the MossWinn Internet Database and the global search method of MossWinn that may both be especially useful in finding a reasonable starting parameter set
for PHS models, the corresponding newly developed routines of MossWinn 4.0 are expected to make the work with 57Fe PHS theories considerably more efficient and less complicated than it was possible before.
Given the computing power one has available, the calculation of PHS spectrum models in general requires balancing between accuracy and calculation time. Spectrum models calculated according to the same Hamiltonian and associated parameters may depend on one's choice concerning this balance.
On account of this potential variability of 57Fe PHS spectra, it appears to be instructive to compare calculations of MossWinn with those in selected literature examples, among others to demonstrate the concordance of MossWinn's calculations with those of earlier works. Such comparisons
are given below for different spin states of iron. Parameter values given in the listed literature examples are used to recreate the corresponding PHS model curves in MossWinn with high accuracy. The resulted theoretical curves are then displayed here together with the list of the associated parameters as
they should be set in MossWinn. Consult with the referenced papers in order to compare the results produced by MossWinn with the associated curves in the literature. Whenever the referenced work gives a parameter value in a unit different from that default in MossWinn, we also give the conversion factors
needed to arrive at the parameter value that should be set in MossWinn.
On the basis of the comparisons given below, the PHS model curves calculated by MossWinn are in general truly concordant with corresponding literature curves.
Even in the case of works published as early as in the 1970s usually minor differences can be detected only, which may easily follow from the use of different numerical integration algorithms,
as well as from differences concerning the accuracy up to which the curves were calculated. Noteworthy deviations of literature curves from those produced by MossWinn were found in one case (#1),
which we also associate with the lower-accuracy numerical integration applied in the work in question.
In contrast, the agreement with more recent works (#1, #2, #3) is typically excellent. Among the examples given here, there appears to be a perfect agreement between published model curves and those produced by MossWinn in three non-trivial cases
(#1, #2, #3).
The model spectra displayed below can be downloaded as a zipped TPF project group file: link.
After extraction of the TPF file from the zip file, in the main menu of MossWinn turn to the menu option MPD → Import Project... to import the spectra from the extracted tpf file.
For a detailed description of the PHS models included in MossWinn see the latest version of the manual.