Mössbauer Investigation of the Single Crystal and Powder Sample of Barium Nitroprusside Ba[Fe(CN)₅NO]⋅3H₂O (BNP)

Angle-dependent Mössbauer investigation on single crystals of barium nitroprosside (BNP) using a-, b- and c-crystal cuts has been performed. The EFG tensor has been fully determined by the orientation between the main EFG component V_ZZ and the b-crystal axis (α=±6(2)°) and by the asymmetry parameter (η=0.04(2)). Mössbauer spectra of powder samples have been recorded at 293 K and at liquid helium temperature in an external magnetic field. In spite of the negligible Goldanskii-Karyagin effect observed in the powder sample a remarkable vibrational anisotropy was found in the crystal. The Lamb–Mössbauer factors along the main crystallographic directions are: f_LM^(a)=0.36(1); f_LM^(b)=0.23(1) and f_LM^(c)=0.50(1). The relative orientation of the main component of the MSD tensor with respect to the b-crystal axis is ω=±36(5)°.