First-principles modeling of the infrared spectrum of antigorite

Abstract. The infrared absorption spectrum of a natural antigorite sample from New Caledonia is compared to its theoretical counterpart computed for the pristine m=17 polysome within density functional perturbation theory framework. model reproduces most bands related Si-O stretching in 800–1300 cm−1 range, OH libration, hindered translation and SiO4 bending 400–800 3500–3700 range. Most observed have composite nature involving several vibrational modes contributing their intensity, except apical one basal whose intensity carried by single mode. peculiarity structure favors localization specific regions unit cell. Weaker experimentally at 1205 1130 are occurrence 6- 8-reversals structure, respectively. distribution bond lengths leads an asymmetric frequencies consistent with width shape band. It also strong libration ranging 600 830 explaining asymmetry band 648 spectrum.