Vibrational states of H2O in beryl: physical aspects

Single-crystal polarized Raman spectra (3,000–4,000 cm⁻¹ at 3 ≤ T ≤ 300 K) were measured for synthetic alkali-free and natural beryl, Be₂Al₃Si₆O₁₈·xH₂O, to determine the behavior of H₂O molecules of both Type I and Type II in the cavities. At low temperature, the H₂O molecules of Type I displace from the center of cavity and give rise to very weak hydrogen bonding with the host lattice. The H₂O Type I translational motion is characterized by substantial anharmonicity and looks like a motion of “a particle in the box” with a frequency of 6.3 cm⁻¹. Water Type II is characterized by a free rotation with respect to the C ₂ molecule axis, and it makes possible the water nuclear isomers (i.e. ortho- and para-) to be observed at low temperature.

Boris KolesovEmail: