Measurement and simulation of nuclear inelastic-scattering spectra of molecular crystals

H. Paulsen, H. Winkler, A. X. Trautwein, H. Grünsteudel, V. Rusanov, H. Toftlund

86 Citations (Scopus)


A procedure is presented that allows us to simulate from first principles the normalized spectra of nuclear inelastic scattering (NIS) of synchrotron radiation by molecular crystals containing a Mössbauer isotope. Neglecting intermolecular vibrations the NIS spectrum is derived from the normal modes of the free molecule, that are calculated with the density-functional method B3LYP. At low temperatures the inelastic part of the calculated NIS spectrum is a superposition of peaks that correspond to the individual vibrational modes of the molecule. The area of each peak is proportional to that part of the mean-square displacement of the Mössbauer isotope that is due to the corresponding vibrational mode. Angular-dependent NIS spectra have been recorded for a guanidinium nitroprusside single crystal and temperature-dependent NIS spectra for the spin-crossover system (Formula presented) [tpa=tris(2-pyridylmethyl)amine]. Qualitative agreement is achieved between measured and simulated spectra for different crystal orientations of guanidinium nitroprusside. A remarkable increase of the iron-ligand bond stretching upon spin crossover has unambiguously been identified by comparing the measured NIS spectra of (Formula presented) with the theoretical simulations.

Original languageEnglish
JournalPhysical Review B - Condensed Matter and Materials Physics
Issue number2
Pages (from-to)975-984
Number of pages10
Publication statusPublished - 01.01.1999


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