RAMAN-SPECTRA OF THE UNIDIMENSIONAL ALUMINOPHOSPHATE MOLECULAR-SIEVESALPO(4)-11, ALPO(4)-5, ALPO(4)-8, AND VPI-5

Laser Raman scattering spectra of the unidimensional molecular sieves AlPO4-11, AlPO4-5 (with and without Pr3N template), AlPO4-8, and VPI-5 are reported. The lattice deformation region, ca. 300-500 cm(-1), was observed to become increasingly complex as the contents of the Bravai s cell increased and the factor group symmetry was reduced. Bands at c a. 400 and ca. 500 cm(-1), absent in the Raman spectrum of alpha-AlPO4 (berlinite), were attributed to the presence of four T-atom rings in the above molecular sieve structures. Bands at ca. 260-310 cm(-1) were ascribed to ''pore-breathing'' framework vibrational modes. The frequ ency (v) of these bands displayed a linear relationship of v(2) propor tional to cos theta, where theta is dependent on the average Al-O-P an gle around the unidimensional channel of each of these molecular sieve materials.