Raman, FTIR, Photoacoustic-FTIR and Inelastic Neutron Scattering Spectra of Alkaline Earth and Lanthanide Salts of Hexahydridoruthenate(II), A₂RuH₆, (A = Ca, Sr, Eu) and Their Deuterides

Abstract

The vibrational spectra (Raman, photoacoustic and Fourier transform infrared and inelastic neutron scattering) of the calcium, strontium and europium salts of hexahydrido- and hexadeuteridoruthenate(II) have been analyzed. All observed fundamental modes and overtone and combination bands are assigned. Density functional theory calculations of the vibrational frequencies assist in the analysis.

Structural and vibrational properties of Ca2FeH6 and Sr2RuH6

“…3 strong bands are observed for Ca 2 FeH 6 at 924, 1442 and 1570 cm À 1 , while only two IR active fundamentals (u 3 and u 4 ) are expected. The band at 1442 cm À 1 can be assigned to the combination of u 6 +libration (ca 900+ 540 cm À 1 ), which is enhanced by Fermi resonance, in agreement with previous results for Ca 2 RuH 6 and Sr 2 RuH 6 [8]. In the case of Mg 2 FeH 6 , this combination mode is not observed.…”

“…2 presents the Raman spectrum below 1000 cm À 1 of Sr 2 RuH 6 . Besides the previously reported T 2g bending mode (u 5 ) at 851 cm À 1 [5,8], the translational T 2g mode at 134 cm À 1 is observed for the first time.…”

“…Thus noticeably different values were predicted at the LDA and GGA levels for the librational frequency of Ca 2 RuH 6 [7]. This explains the discrepancy observed between experiment and theory for the librational frequency of Sr 2 RuH 6 , which is calculated at 478 cm À 1 and was observed at 561 cm À 1 by Barsan et al [8].…”

“…We have previously [5] attempted to correlate Ru-H stretching frequencies with Ru-H bond length using Badger's rule, however the correlation was not very satisfactory. Using both experimental [4][5][6][7][8][9][10] and theoretical results from the literature and from this study, we have plotted IR and Raman active stretching modes against the M-H bond length in Fig. 3.…”

“…Later, however, it was shown to be of interest as a material in thermal heat energy storage systems [3]. As to the vibrational properties of the A 2 TH 6 series several members have been studied in the past, such as Mg 2 FeH 6 or Ca 2 RuH 6 [4][5][6][7][8][9]. A recent review [10] summarizes the data available so far.…”