Silicon clathrates exhibit cagelike host lattices formed by 46 or 136
silicon atoms in which alkali atoms M are trapped. The Raman spectra o
f the silicon clathrates K8Si46, Na1Si136, Na6Si136, and Na10Si136 are
observed and compared with theoretical predictions determined from gr
oup theory and density of vibrational states simulations. These experi
mental results demonstrate the need of improved simulations of vibrati
onal spectra. [S0163-1829(98)51116-2].