Correlated electronic structure and chemical bonding of cerium pnictides and $\gamma$-Ce

We present calculated spectral properties and lattice parameters for cerium pnictides (CeN, CeP, CeAs, CeSb, CeBi) and $\gamma$-Ce, within the LDA/GGA+DMFT (local density approximation/generalized gradient approximation+dynamical mean field theory) approach. The effective impurity model arising in the DMFT is solved by using the spin-polarized $T$-matrix fluctuation-exchange (SPTF) solver for CeN compound and the Hubbard I (HI) solver for CeP, CeAs, CeSb, and CeBi. For all the addressed compounds, the calculated spectral properties are in reasonable agreement with measured photoelectron spectra at high binding energies. At low binding energies, the HI approximation does not manage to capture the Kondo-like peak observed for several of the Ce pnictides. Nevertheless, the calculated lattice constants are in a good agreement with available experimental data, showing that the such a peak does not play a major role on the bonding properties. Furthermore, the HI calculations are compared to a simpler treatment of the Ce $4f$ electron as corelike in LDA/GGA for CeP, CeAs, CeSb, and CeBi, and the two approaches are found to give similar results.

Figure 1

Experimental and calculated lattice constants of Ce pnictides. The theoretical values for CeN are obtained with the SPTF solver and the AM05 DFT functional. The Hubbard I solver together with the AM05 DFT functional was used for all other pnictides.

Figure 2

Calculated lattice constants of Ce pnictides. The theoretical values for CeN are obtained with the SPTF solver and two DFT parametrizations, AM05 and PW91. The Hubbard I solver with both the AM05 and PW91 DFT functionals was used for all other pnictides. These data are compared to calculations using localized $4f$ (core) states with the AM05 and PW91 functional. For CeN, the plain AM05 DFT results with $4f$ valence electrons are also reported, emphasizing how such a description is much better than the assumption of localized core states for this material.

Figure 3

Experimental and calculated spectra of CeN. The blue points label the XPS data and the red points mark the BIS spectrum from Ref. 69, where the relative intensities of the XPS and BIS spectra have been tentatively adjusted. The factor ($\times 10$) comes directly from Ref. 69, and we have kept it to make a better comparison between the experimental XPS data and the theoretical curve. The solid line denotes the total spectral function using the SPTF solver for the Ce $4f$ states.

Figure 4

Experimental and calculated spectral properties of the $4f$ states for CeP. The XPS data from Ref. 16 are marked as blue circles. The red circles label the resonant spectrum of CeP, while the red dashed line labels the extracted photoemission spectrum of $4f$ states from Ref. 17. The black solid line is the calculated spectral function of the Ce $4f$ states with the Hubbard I solver.

Figure 5

Total spectral function calculated with the Hubbard I solver (black solid line) compared with experimental data from Ref. 17. We also present the projections for the Ce $5d$ and $4f$ states, and the P $3p$ states (dashed lines). The vertical arrow labels the $pd$ peak, which is close to the experimental nonresonant photoemission data taken at $h\nu =112$ eV (red solid line).

Figure 6

Experimental and calculated spectral properties using Hubbard I approximation of CeAs. The total spectral function is labeled by the black solid line, the Ce $4f$ projection is marked by the black dashed line, while the red dashed line marks the experimental resonant $4f$ emission from Ref. 17. The red solid line represents the experimental data from nonresonant emission (formed by As $4p$ and Ce $5d$ states).

Figure 7

Total spectral function of CeSb calculated with the Hubbard I solver (black solid line) compared with the experimental data from Ref. 16. We also present projections for the Ce $4f$ and $5d$ states, and the Sb $5p$ states (dashed lines). The $pd$ peak is close to the experimental data from nonresonant photoemission (red circles).

Figure 8

Experimental and calculated spectral properties of CeBi using the Hubbard I approximation. The total spectral function is labeled by the black solid line, while the Ce $4f$ contribution is marked by the black dashed line. The red dashed line and the red solid line respectively mark the experimental resonant $4f$ emission from Ref. 17 and the nonresonant emission, formed by the Bi $6p$ and Ce $5d$ states. The blue dashed line labels the resonant $4f$ emission from Ref. 18.