We present density-functional results of $\delta$-Pu obtained from three electronic-structure methods. These methods have their individual strengths and are used in combination to investigate the magnetic and crystal stability of $\delta$-Pu. An all-electron, full potential linear muffin-tin orbitals (FPLMTO) method, that includes corrections for spin-orbit coupling and orbital-polarization effects, predicts $\delta$-Pu to be an antiferromagnet at zero temperature with a volume and a bulk modulus in very good agreement with experiment. The site-projected magnetic moment is smaller than expected $\left(\sim 1.5{\mu }_B\right)$ due to large cancellation of spin and orbital moments. These calculations also predict a mechanical instability of antiferromagnetic (AF) $\delta$-Pu. In addition, techniques based on the Korringa-Kohn-Rostoker (KKR) method within a Green’s-function formalism and a projector augmented wave (PAW) method predict the same behavior of $\delta$-Pu. In order to study disordered magnetism in $\delta$-Pu, the KKR Green’s-function technique was used in conjunction with the disordered local-moment model, whereas for the FPLMTO and PAW methods this was accomplished within the special quasirandom structure model. While AF $\delta$-Pu remains mechanically unstable at lower temperatures, paramagnetic $\delta$-Pu is stabilized at higher temperatures where disordered magnetic moments are present and responsible for the crystal structure, the low density, and the low bulk modulus of this phase.

• Received 26 July 2002

DOI:https://doi.org/10.1103/PhysRevB.66.205109