SHORT-RANGE ORDER OF CATIONS IN NATURAL DOUBLE-CHAIN SILICATES. MARKOV-CHAIN MODELS

Abstract

We investigated double chain silicates (amphiboles), whose structures contain three octahedral positions. A shift in the frequency of the IR vibrations of the hydroxyl group at one vertex of these octahedra was used to determine the cation population of the polyhedra, which carries information on short-range order in the unit cells of the structure. For statistical description of the sequence of cations in amphiboles we used the technique of stationary and nonstationary Markov chains of various order. The resulting statistically modeled chains represent a rather wide array of 'texts' that differ in their symbol sequences.