Electronic Structure of Hole-Doped Transition Metal Cyanides

Abstract

Electronic structures of hole-doped transition metal cyanides, Na 0:84Àx Co[Fe(CN) 6 ] 0:71 . 3.8H 2 O (NCF71), Na 0:72Àx Ni[Fe(CN) 6 ] 0:68 . 5.1H 2 O (NNF68) and Na 1:60Àx Co[Fe(CN) 6 ] 0:90 . 2.9H 2 O (NCF90),were investigated by means of the x-ray absorption spectroscopy and the valence differential spectroscopy. The x-ray absorption spectroscopy revealed that the holes are introduced on the Fe, Fe, and Co sites for the NCF71, NNF68 and NCF90 films, respectively. Owning to the valence differential spectroscopy, we unambiguously assigned the spectral components to the respective optical transitions. We further found that an ab initio band calculation based on the local density approximation with the onsite Columbic repulsion (LDA+U) semi-quantitatively explains the optical transitions.

Synchrotron-Radiation X-Ray Investigation of Li+/Na+Intercalation into Prussian Blue Analogues

“…Figure 11(a) shows the XAS spectra of LCF90 films around the Co K-edge against . The XAS spectrum at = 0.0 coincides with that of LS Co 3+ , while the spectrum at 1.6 coincides with that of HS Co 2+ [30]. The electronic configuration at = 0.00 becomes Co 3+ -Fe .…”

“…Figure 4(a) shows the XAS spectra of LMF83 films around the Fe K-edge against . The peak energy at = 1.32 coincides with that of low-spin (LS) Fe 2+ [30]. The blue-shift with decrease in indicates partial formation of LS Fe 3+ .…”

Concentration dependence of Li+/Na+ diffusion in manganese hexacyanoferrates

“…The Fe K-edge spectra at x Na = 0.0 and 1.3 coincide with those of Fe 2+ (S = 1/2) and Fe 2+ (S = 0). 51) Under the charge neutrality condition, the electronic configura-…”

In situ observation of macroscopic phase separation in cobalt hexacyanoferrate film

“…In the green phase, the intense absorption observed around 380 nm is ascribed to the electron transfer from Fe 2+ to the neighboring Co 2+  17. In the black phase, the broad absorption observed around 540 nm is ascribed to the electron transfer from Fe 2+ to the neighboring Co 3+  17. The absorption intensity at 540 nm shows significant change in the phase transformation from the green to black phases.…”

“…Roughly speaking, the spectra at x  = 1.6 and 1.0 corresponds to the green and black phases, respectively. In the green phase, the intense absorption observed around 380 nm is ascribed to the electron transfer from Fe 2+ to the neighboring Co 2+  17. In the black phase, the broad absorption observed around 540 nm is ascribed to the electron transfer from Fe 2+ to the neighboring Co 3+  17.…”