Lattice dynamics and hyperfine interactions of intercalation compounds: A single crystal study of TaS2⋅Sn

Abstract

An oriented single crystal sample of the dichalcogen layer intercalation compound, TaS2⋅Sn, has been examined by 119Sn Mössbauer effect spectroscopy both at room temperature and over the temperature range 4.2⩽T⩽295 °K. From the angular dependence of the intensity ratio of the two components of the doublet spectrum at room temperature, as well as from the insensitivity of this ratio as a function of temperature at a fixed observational angle, it is concluded that there is a single lattice site for the tin atom in the layer structure. Comparison of the single crystal Mössbauer data with that obtained for a polycrystalline, (nearly) randomly oriented sample shows that even in the latter, there is a small residual orientation effect which must be corrected for in determining the anisotropy of the tin atom motion. From the isomer shift data it is clear that the tin atom is formally Sn2+ and acts as an electron donor to the TaS2 lattice. From the temperature dependence of the isomer shift parameter, it is inferred that the motion as probed by the Mössbauer resonance technique is that of a bare tin atom, in contrast to comparable data for SnS, in which appreciable participation of the nearest neighbor atoms in the motional behavior of the tin atom may be deduced. The high temperature region dependence of the recoil-free fraction leads to 119Sn Mössbauer temperatures of ϑm∼176±5 and 190±5 °K for TaS2⋅Sn and SnS, respectively.