Cell Parameters and Macroscopic Thermal Expansion and Compression

Abstract

Cell parameters of homogeneous feldspars at a given temperature and pressure are determined principally by the bulk composition and the distribution of M and T atoms among the sites. As the variations are systematic, it is possible to use them, or some simple function of them, to estimate bulk composition and degree of order (structural state). It is also possible to interpret cell- parameter variations in structural terms involving bond lengths and angles. The regular variation of the cell parameters with pressure, temperature, composition and order and its analysis in terms of various macroscopic trends (Brown et al. 1984) suggests that the integrated response of the framework is more important than individual bond lengths or angles. This can be inferred from the pattern common to all feldspars of deviations from the ideal values (Chap. 4).