SIMPLE-MODEL FOR COMPLEX STRUCTURES

The complex structures of the low-temperature phases of light actinide s are analyzed in terms of a simple model involving Pettifor's structu ral energy difference theorem in combination with an estimate of the s tructural dependence of the electrostatic interaction in the solid. Wi th this simple model the complex structures of the actinides are contr asted to the simpler ones of the transition metals, and in agreement w ith observations we find that at ambient conditions the f-electron ele ments favor distorted structures, whereas d-electron metals ''prefer'' cubic or hcp structures.