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The European Physical Journal B
ISSN: 1434-6028 (printed version)
ISSN: 1434-6036 (electronic version)
Abstract Volume 3 Issue 3 (1998) pp 349-352
Possible reaction coordinates in the metastable states of sodiumnitroprusside $\mathsf{Na_2 [Fe(CN)_5 NO] 2H_2O}$: a discussion based on neutron diffraction- and spectroscopic measurements
J. Schefer (1) (a), T. Woike (2), M. Imlau (2), B. Delley (3)
(1) Laboratory for Neutron Scattering ETH Zürich and Paul Scherrer Institute, 5232 Villigen PSI, Switzerland
(2) Institute for Crystallography, University at Cologne, 50764 Köln, Germany
(3) Department for Condensed Matter Research Using Large Facilities (F3A), Theory Group, Paul Scherrer Institute, 5232 Villigen PSI, Switzerland
Received: 23 June 1997 / Accepted: 13 October 1997
Abstract: The metastable states of sodiumnitroprusside $\rm Na_2[Fe(CN)_5NO]2H/D_2O$ are extremely stable at temperatures below 200 K. It is possible to allocate structural changes measured by neutron diffraction to measured spectroscopic parameters, but the amount of the structural change is relatively small for a reaction co-ordinate as the metastable states have an extremely long lifetime. New hypotheses for related systems try to explain such a phenomena in two ways: The first way is a $90^\circ$ bending of the NO-bond in the metastable state, the second one an exchange of the oxygen and nitrogen atoms in the NO-bond (which can be regarded as an $180^\circ$ bending). As such changes would be possible also from our density functional calculations, we re-investigated our neutron diffraction data using the new models. However, our results are not compatible with one of these models. On the contrary, the neutron diffraction data show partially opposite tendencies. We compare both models with EXAFS measurements, with vibrational spectroscopic results and the data found by Mössbauer spectroscopy. We propose a potential scheme for all three states (GS, $\rm MS_I$ and $\rm MS_{II}$) extracted from absorption and thermodynamic data to explain the electronic and energetic rearrangement, and the population dynamics.
PACS. 61.80.Hg Neutron radiation effects - 61.50.Lt Crystal binding; cohesive energy - 33.45.+x Mössbauer spectra
(a) email: jurg.schefer@psi.ch
Article in PDF-Format (222 KB)
Online publication: July 14, 1998
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