RAMAN-SCATTERING STUDIES OF LITHIUM-INTERCALATED NIPS3

We report on the vibrational properties of lithium-intercalated NiPS3 microcrystalline samples. Raman scattering spectra of LixNiPS3 (0 less than or equal to x less than or equal to 1.16) compounds have been re corded as a function of temperature in the wavenumber range 50-700 cm( -1). The new peak located at 313 cm(-1) is interpreted as a stretching mode due to vibration of lithium atoms located in the van der Waals g ap against the nearest neighbouring sulphur atoms. Results are analyze d in terms of stretching vibrations of LiS6 entities. It is concluded that lithium ions are more likely to occupy octahedral sites in the li thium-rich phase. Using a simple model of lattice dynamics, the coupli ng force constants are determined and compared with those in the prist ine material.