INFRARED SPECTRA OF NACRITE AT A ROOM AND A LOW TEMPERATURES

Abstract

The OH stretching bands of nacrite were resolved into four bands with decreasingtemperature. These bands were assigned to 3 inner surface OHs and one inner OH from the OD bands of the nacrite after selective deuteration. The 3 inner surface OH stretching bands shifted toward lower frequency with decreasing temperature, which indicated an decrease in the length of the hydrogen bond in the interlayer of nacrite at low temperature. This shorter hydrogen bond was estimated also from the increasing frequencies of the OH in-plane bending bands at a low temperature. From the unit cell parameters of the nacrite, some structural deformations were estimated as increases of the layer shift along X-axis and the tetrahedral SiO₄ rotation angle at low temperature.