Metal-insulator transition in a ternary model with long range correlated disorder

We study the metal - insulator transition of the one- dimensional diagonal Anderson ternary model with long range correlated disorder. The starting point of the model corresponds to a ternary alloy ( i. e. with three possible on- site energies), and shows a metal - insulator transition when the random distribution of site energies is assumed to have a power spectrum S(k) proportional to 1/k((2 alpha-1)). In this paper, we define a purity parameter for the ternary alloy which adjusts the occupancy probability of site potentials, and for any given alpha we calculate the critical purity parameter for which extended states are obtained. In this way, we show that the ternary alloy requires weaker correlations than the binary alloy to present a phase transition from localized to extended states. A phase diagram which separates the extended regime from the localized one for the ternary alloy is presented, obtained as the critical purity parameter in terms of the corresponding correlation exponent.