ESTIMATION OF THE STRUCTURE OF AN ANHYDROUS 2:1-NA LAYER SILICATE SYNTHESIZED FROM TALC BY INTERCALATION PROCEDURE

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The structure of an anhydrous 2:1-Na layer silicate (NLS), which was synthesized by heating a mixture of talc and Na_2SiF_6 at 800℃ for 2 h, was estimated by MD simulation besed on a 1 M mica structure (C2/m). The results of MD simulation showed that the top and bottom silicate layers moved in mutually opposite direction along the a- and b-axes, and the silicate layer stacking of NSL was similar to that of talc structure. The trajectory of the Na^+ ions in the NLS structure from the MD simulation clearly shows two different movements as follows: one Na^+ ion near the Mg^<2>+ vacant site inthe octahedral sheet was especially localized in the upper silicate layers, but the other Na^+ ion apart from the Mg^<2+> vacant site in the octahedral sheet was placed in the middle position beteen the silicate layers. The ^<23>Na MAS NMR spectra of the NLS and Mg^<2+> ion-exchanged NLS also showed that the NLS had two different kinds of Na^+ ions, one was exchangeable and the other was non-exchangeable. However, the MD simulation could not explain quantitatively the mass balance of the exchangeable and non-exchangeable Na^+ ions in the NLS structure.
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