The Incoherent Inelastic Neutron Spectra of TaS2 • NH3 and TaS2(NH3)1/3(H20)2/3

The intercalation compounds of layered dichalcogenides MX2 (M = transition metal, X = S, Se) with Lewis base guest molecules have received considerable attention due to their interesting physical properties and structural anisotropy [1]. The most simple molecule that is known to intercalate is the thermodynamically stable compound NH3; extensive work has been devoted to the characterization of the intercalation reactions and the products MS2(NH3). The theoretical treatment of the interaction host lattice/guest molecules in terms of whole-complex molecular orbitals [2] or the Mulliken charge-transfer formalism [3] suggests a transfer of electron density towards the dichalcogenide layers. Recent investigations were able to demonstrate, however, that the intercalation process is correlated with redox reactions, and an ionic structure model [4] was presented that involves the presence of NH4+ ions: (NH4+)^(NH3)1_^[MS2]X-. An alternative model, suggested recently, implies hydride formation [5] with hydrogen atoms in the intralayer position as observed for HrTaS2 [6]. The basic structure schemes for the different models are given in Figure 1.