抄録
Pressure induced phase transformation of the diatom frustule composed of hydrous amorphous silica was investigated by Raman spectroscopic analysis. At 0.3 GPa, it can be readily crystallized into a mixture of quartz and moganite. At 5.7 GPa, it is crystallized into coesite. The first-principles calculations revealed that the Si-O-Si bridging unit with trans configuration is twisted 60° and changed into the cis configuration with a close approach of water molecule, which would be responsible for the readily crystallization of hydrous amorphous silica.
