Amadon Bernard, Dorado Boris
CEA, DAM, DIF, F-91297 Arpajon, France.
J Phys Condens Matter. 2018 Oct 10;30(40):405603. doi: 10.1088/1361-648X/aadc7a. Epub 2018 Aug 23.
We show that a calculation using density functional theory (DFT) in the generalized gradient approximation (GGA) supplemented by an explicit Coulomb interaction term between correlated electrons (GGA+U), can accurately describe structural properties of (1) the room temperature phases of U, Np, Pu, Am and Cm, and (2) the α, β, γ, δ and ϵ phases of plutonium, as does the combination of GGA with dynamical mean field theory (DMFT). It thus changes the view on the role of electronic interaction in these systems and opens the way to fast calculations of structural properties in actinides metallic system. We use ab initio values of effective Coulomb interactions and underline that Hund's exchange and spin-orbit coupling are of utmost importance in these calculations. Secondly, we show that phonons properties in δ plutonium are impacted by strong interactions. The GGA+DMFT results exhibits a lattice instability for the transverse (1 1 1) phonon mode. Moreover the amplitude of this lattice instability is consistent with the experimental temperature of stability of this phase. Our calculation thus shows that when the δ phase is thermodynamically unstable (at 0 K), it is also dynamically unstable.
我们表明，在广义梯度近似（GGA）中使用密度泛函理论（DFT）并辅以相关电子之间的显式库仑相互作用项（GGA+U）进行的计算，能够准确描述（1）U、Np、Pu、Am和Cm的室温相的结构性质，以及（2）钚的α、β、γ、δ和ε相的结构性质，GGA与动态平均场理论（DMFT）的结合也能做到这一点。因此，它改变了人们对这些系统中电子相互作用作用的看法，并为快速计算锕系金属系统的结构性质开辟了道路。我们使用了有效库仑相互作用的从头算值，并强调洪德交换和自旋轨道耦合在这些计算中至关重要。其次，我们表明δ钚中的声子性质受到强相互作用的影响。GGA+DMFT结果显示横向（1 1 1）声子模式存在晶格不稳定性。此外，这种晶格不稳定性的幅度与该相的实验稳定温度一致。我们的计算因此表明，当δ相在热力学上不稳定时（在0 K时），它在动力学上也是不稳定的。
