Abstract
The relationship of the cell volume to the composition of humite solid solution, xMg(OH)2·(1−x)MgF2·nMg2SiO4 (0≤x≤1 and n=1, 2, 3 and 4) was formulated on the basis of the following model: The crystal of the humites is composed of small elastic blocks consisting of end member units, which have the different volume in the pure end members. Each block is constrained to have the same volume in the solid solution, and the strain energy is then stored in each block. The minimization criterion of the total strain energy is introduced to determine the equilibrium cell volume of the solid solution. The calculated cell volumes on this model agree with the observed values up to four figures for all the data available. Application of the present solid solution model is extended to cover the cation substitution in the humites and also to the solid solutions of alkali halide.
