SYMMETRY AND THE STABILITY OF BINARY SOLID-SOLUTION OF LINEAR-MOLECULES

Kitaigorodskii's rather straightforward rules for the formation of sta ble solid solutions, based on crystal symmetries of pure components an d relative molecular volumes, arc found to be effective for the descri ption of binary phase behavior in n-paraffins and cholesteryl esters. Electron diffraction data from the paraffins reveal that the layer pac king and methylene subcell symmetry are more important than formal uni t cell symmetry for the prediction of continuous solution in the solid state. Relative molecular volumes tolerated in stable solutions fall well within Kitaigorodskii's previously-defined limits. For cholestery l esters, on the other hand, the total unit cell symmetry of each comp onent is the primary condition for the stability of a resulting solid solution. Stable solid solutions are found within the defined volume c onstraints if the symmetry criterion is met.