| Popis: |
The Raman spectra of crystalline α′-P 4 Se 3 I 2 , β-P 4 Se 3 I 2 , α-P 4 S 3 I 2 , and β-P 4 S 3 I 2 have been measured as a function of temperature in the range 80–370 K at ambient pressure. In general, the internal and external first-order Raman-active phonons vary smoothly in wavenumber over this temperature interval, a behaviour typical of a molecular solid. Mode softening ( d v d T positive) of the 179.6 cm −1 phonon of β-P 4 Se 3 I 2 is attributed to intra-intermolecular coupling, similar to that observed for the parent molecule P 4 Se 3 . |
