| Abstrakt: |
Inelastic neutron scattering spectra of the zeolites natrolite Na[sub 2]Al[sub 2]Si[sub 3]O[sub 10] 2H[sub 2]O, wairakite CaAl[sub 2]Si[sub 4]O[sub 12] 2H[sub 2]O, scolecite CaAl[sub 2]Si[sub 3]O[sub 10] 3H[sub 2]O, and bikitaite Li[sub 2]Al[sub 2]Si[sub 4]O[sub 12]. 2H[sub 2]O, together with the sheet silicate apophyllite KCa[sub 4]Si[sub 8]O[sub 20](F, OH) 8H[sub 2]O, are shown here. We show clear trends across these minerals, illustrating the relative influence of hydrogen bonding and cation bonding. For some of these spectra, the bands are clearly separated, permitting a discussion of their assignments. In particular, we can identify librational bands (L) or librational edge (LE) and translational (cation-water stretch) bands (C), and by elimination can tentatively assign bands as hydrogen-bond stretch bands (H), as follows (frequencies given in meV): Natrolite: 13,18 (C) 26 (H), 64,68,87 (L); Apophyllite 17,26 (C), 35 (H) 64,79,98 (L); Scolecite 10 (C), 22,29,36,41 (H), 46 (LE); Wairakite 12 (C), 30 (LE); Bikitaite 13 (C), 22 (H), 34 (LE), 70(L). The results are compared with those for ice and are explained in terms of the nearest-neighbor environment of the water molecule. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR] |
