Charge states of point defects in plutonium oxide: A first-principles study

Phase Segregation, Transition, or New Phase Formation of Plutonium Dioxide: The Roles of Transition Metals

“…Here, we adopt its 2 × 2 × 2 supercell containing 32 Pu atoms and 64 O atoms (i.e., Pu 32 O 64 ) as the parent structure to build the TM-doped models, as shown in Figure . It is worth pointing out that the 2 × 2 × 2 supercell size has been validated for the calculation of dilute dopants by our previous work and other researchers’ works. − The lattice Pu site for TM doping is the exclusive consideration because the relatively large size of TMs and electron mismatch between TMs and O result in the instability of TMs at interstitial and lattice O sites. Other complicated defects, such as Frenkel defects, Schottky defects, defect complexes, and extended defects ,which might be the favorable sites for TMs are not considered since the present works aim to find the general trends of TM doping.…”

“…An effective Hubbard U ( U eff = U – J ; i.e., the difference between Coulomb U and exchange J values, hereafter denoted as U ) value of 4 eV is selected for the localized 5f electrons of Pu. This value has been validated by ourselves and other research groups to be reasonable in reproducing the experimental ground-state properties of PuO 2 and, more importantly, in characterizing PuO 2 -related reaction energies or defect formation energies mainly due to the fortunate errors cancellation which holds for other selections of calculation parameters such as spin–orbit coupling and weak interaction corrections. − ,− For the magnetic orders of PuO 2 , we use the commonly accepted collinear 1 – k antiferromagnetic (AFM) state along the (100) directio,n which is generally energetically more favorable than nonmagnetic (NM) and ferromagnetic (FM) states. Complete relaxation without symmetry constraints is employed, which is particularly necessary for the defective systems due to the potential of more or less lattice distortion.…”

“…The total and projected density of states (TDOS and PDOS) of Pu 31 TMO 64 are plotted in Figure . On the whole, TM-doped PuO 2 maintains the semiconducting ground state of the host with the typical feature of well-separated valence band (VB) and conduction band (CB), − and the band gaps vary in a small range; this is primarily because the very low concentration TMs have a relatively weak effect on the main behaviors of the host. Notwithstanding, the differences in the detailed DOS profiles are noticeable.…”

Thermodynamics Study of Dehydriding Reaction on the PuO2(110) Surface from First Principles

“…Attributed to underestimating the strong on-site Coulomb repulsion of 5f electrons in plutonium, standard exchange-correlation approximations in density functional theory (DFT) fail to provide correct electronic structure and magnetic properties of PuO 2 . − Previous works have shown that the DFT + U approach allow us to achieve a reliable description of the interactions of strongly correlated 5f electrons. By addition of an energy term of the effective Hubbard parameter, the antiferromagnetic Mott insulator feature and electronic as well as structural properties of PuO 2 bulk material are well-described. − Jomard and Bottin applied the DFT + U method to investigate the influence of electronic correlations on thermodynamic stability of PuO 2 surfaces and obtained a proper description of the electronic features of the insulating PuO 2 surfaces, which is a prerequisite for exploring chemical reactions on the PuO 2 surfaces . Sun et al systematically studied the effects of thickness and oxygen vacancy concentration on the stability and chemical activity of the PuO 2 surfaces and showed that the surface stability is affected by the oxygen environment .…”

Dissociation Mechanism of Water Molecules on the PuO2(110) Surface: An Ab Initio Molecular Dynamics Study

“…The DFT + U approach is one of the most popular methods that allow correct treatment of systems containing strongly correlated electrons. By addition of an energy term of the effective Hubbard parameter, the antiferromagnetic Mott insulator feature and structural parameters of PuO 2 are well described. − Several previous studies had focused on the properties of plutonium-oxide surfaces. − Jomard and Bottin investigated the influence of electronic correlations on thermodynamic stability of PuO 2 surfaces in ref and also pointed out that the electronic structure of the insulating PuO 2 surfaces can be well described within the DFT + U method, which is a prerequisite to explore chemical reactions on the PuO 2 surfaces. Sun et al further reported the effects of thickness and oxygen vacancy on the stability and chemical activity of the PuO 2 surfaces, where the spin–orbit coupling (SOC) interaction was considered .…”