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A combination of density functional theory and the dynamical mean-field theory (DMFT) is used to calculate the magnetic susceptibility, heat capacity, and the temperature dependence of the valence band photoemission spectra for -Pu. We predict that -Pu has a Pauli-like magnetic susceptibility near ambient temperature, as in experiment, indicating that electronic coherence causes the absence of local moments. Additionally, we show that volume expansion causes a crossover from incoherent to coherent electronic behavior at increasingly lower temperatures.Pu embodies a forefront of both technology and theoretical condensed-matter physics. Elemental Pu displays exotic physical behavior that continues to defy explanation. For example, it exhibits six allotropic phases at ambient pressure, the low-density fcc phase has a negative coefficient of thermal expansion, and the volume expands by more than 25% when the system is heated from the high-density monoclinic phase to the phase. Regarding the pure phase, a complicating factor is that it is only stable in the temperature range 580 K < T < 700 K. However, the phase can be stabilized at low temperatures by a variety of alloying elements such as Ga and Am. This allows for the experimental exploration of the phase at low temperatures, with the caveat that it is not clear what changes the alloying element may be inducing.Lashley et al.[1] have measured the magnetic susceptibility to be Pauli-like in both the and phases, and hence detect no presence of localized magnetic moments. Similarly, Heffner et al. [2 -4] have used SR and showed that there are no ordered magnetic moments in Pu nor in -stabilized Pu (i.e., 4.3% Ga) for temperatures down to 4 K. Nuclear magnetic resonance (NMR) measurements by Curro and Morales [5] also show an absence of magnetic moments.The linear coefficient of the specific heat for -stabilized Pu has been measured by various groups and the resulting values are 42 mJ mol K 2 for alloying with 2% of Ga [1], 64 mJ mol K 2 for 5% of Al [6], and 35-55 mJ mol K 2 for 8%-20% of Am [7]. The large variation among these measurements may be due to the fact that the phase has been stabilized by a different alloying element in each study.Several previous studies have applied a combination of density functional theory and the dynamical mean-field theory (DFT DMFT) [8] to Pu. DMFT requires a solution of an auxiliary quantum impurity problem, and for the corresponding impurity model of Pu, no exact method was available in the past. Savrasov et al. [9] used an interpolative solver to calculate the energy and the photoemission spectra of Pu. The approach yielded a significant improvement for the volume of the phase of Pu compared to DFT. Shick et al.[10] computed the photoemission spectra using the Hubbard I impurity solver and were successful in predicting the three-peak structure in the photoemission spectra. Pourovskii et al. [11] computed the photoemission spectra and the heat capacity using the Fluctuation Exchange Approximation (FLEX) as an impurity solver. Th...

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Plutonium possesses the most complicated phase diagram in the periodic table, driven by the complexities of overlapping 5f electron orbitals. Despite the importance of the 5f electrons in defining the structure and physical properties, there is no experimental evidence that these electrons localize to form magnetic moments in pure Pu. Instead, a large temperature-independent Pauli susceptibility indicates that they form narrow conduction bands. Radiation damage from the ␣-particle decay of Pu creates numerous defects in the crystal structure, which produce a significant temperature-dependent magnetic susceptibility, (T), in both ␣-Pu and ␦-Pu (stabilized by 4.3 atomic percent Ga). This effect can be removed by thermal annealing above room temperature. By contrast, below 35 K the radiation damage is frozen in place, permitting the evolution in (T) with increasing damage to be studied systematically. This result leads to a two-component model consisting of a Curie-Weiss term and a short-ranged interaction term consistent with disorder-induced local moment models. Thus, it is shown that self-damage creates localized magnetic moments in previously nonmagnetic plutonium.disorder ͉ magnetism ͉ radiation damage A mong the interesting properties of plutonium is a complex phase diagram, which at ambient pressure exhibits six distinct solid-state phases below the melting temperature. These phases are narrowly spaced in energy, with the five lowest-energy phases separated by Ͻ2 mRyd, placing them on a molecularenergy scale as compared with the more typical 10-20 mRyd scale typical of metals such as neighboring Np and Am (1). Although there is no theoretical consensus as to the origin of the low-density fcc ␦-phase of Pu (1-7), there is an understanding that the organization of the spin and orbital moments play a key role in stabilizing this phase. The lack of significant magnetic moments is a central issue among theorists and inspired a recent experimental review (8) painstakingly describing the evidence against the existence of magnetic moments in plutonium. Recent SR ϩ studies for ␣-and ␦-phase Pu further support this absence of magnetic moments, placing the upper bound on frozen moments at 0.001 Bohr magneton ( B ) (9). However, all solid Pu phases possess large magnetic susceptibilities, suggesting they border on becoming magnetic. Consistent with this observation and general predictions of narrow 5f bands in plutonium are large electronic contributions to the specific heat in both ␣-Pu and alloy-stabilized ␦-Pu, qualifying each as a highly correlated electron system (10).Often, local magnetic moments can be induced in nearly magnetic systems by imposing a suitable perturbation. One such method is to increase disorder by introducing a low concentration of impurities via chemical substitution. For example, when very dilute quantities of Fe, Co, or Ni are doped into nonmagnetic Pd, they induce remarkably large magnetic moments by polarizing the surrounding lattice (11,12). Similarly, one-half atomic percent (at. %) Pu do...