The structures of anorthite and albite melts.

The structures of anorthite and albite melts have been investigated with the X-ray diffraction method. The scattered intensities were measured at 1600°C and 1200°C on the anorthite and albite melts, respectively. The radial distribution function reveals that the basic structural units of the two melts are the TO4 (T=Si, Al) tetrahedra. From least-squares fitting of the observed S·i(S) values to those of model structures, it was found that the framework of the tetrahedra in the anorthite melt has close similarity to that in the anorthite structure at high temperature within the short of r≤5Å, based mainly on the four-membered rings, and the framework in the albite melt to the low-tridymite structure where the six-membered rings predominate.