Effect Of Crystal Field Splitting Research Articles

Mechanism analysis on manipulation of long afterglow luminescence properties of Y3Al5-xGaxO12:Ce3+, Cr3+ phosphors

Blue-light activated long afterglow luminescence phosphors have attracted much attention because of their potential application in many fields. Herein, the influence of trap depth and the quantity of electrons captured by the traps on the long afterglow luminescence properties were systematically revealed through a comparative analysis of the long afterglow luminescence performance of the series of Y3Al5-xGaxO12(YAGG):Ce3+, Cr3+ (x = 0, 1, 2, 3, 4, 5) phosphors. To achieve long afterglow luminescence, it requires that the traps can effectively capture electrons, and possess an appropriate trap depth. Additionally, it is discovered that the quantity of electrons captured by the traps is the main factor affecting the duration of long afterglow luminescence. The more electrons are captured, the longer the afterglow lasts. The quantity of trapped electrons is inversely proportional to the energy differences between CBM-Ce5d and trap depth. The sample exhibits the high quantity of trapped electrons attributable to its small energy differences which allows electrons to be directly captured by traps through the tunneling effect. On this basis, the effects of crystal field splitting (εcfs), centroid shift (εc), and the degree of dodecahedral distortion (D (YO)) on trap depth (ET) were discussed to manipulate the trap depth, demonstrating there is a significant positive correlation between εc-εcfs(2(1-10D(YO))) and ET values for the garnet structure A3B2C3O12, when the ion doped at the A-position remains constant and the ions at the B and C positions vary. Notably, A larger D (YO) value corresponds to a deeper trap depth. This study provides a new perspective toward the development and design of long afterglow materials with superior afterglow emission.

Homoleptic Rare-Earth-Metal Sandwiches with Dibenzo[a,e]cyclooctatetraene Dianions.

A family of rare-earth complexes [RE(III) = Y, La, Gd, Tb, Dy, and Er] with doubly reduced dibenzo[a,e]cyclooctatetraene (DBCOT) has been synthesized and structurally characterized. X-ray diffraction analysis confirms that all products of the [RE(DBCOT)(THF)4][RE(DBCOT)2] composition consist of the anionic sandwich [RE(DBCOT)2]- and the cationic counterpart [RE(DBCOT)(THF)4]+. Within the sandwich, two elongated π decks are slightly bent toward the metal center (avg. 7.3°) with a rotation angle of 35.9-37.6°. The RE(III) ion is entrapped between the central eight-membered rings of DBCOT2- in a η8 fashion. The trends in the RE-COT bond lengths are consistent with the variations of the ionic radii of RE(III) centers. The 1H NMR spectra of the diamagnetic Y(III) and La(III) analogues illustrate the distinct solution behavior for the cationic and anionic parts in this series. Magnetic measurements for the Dy analogue reveal single-molecule magnetism, which was rationalized by considering the effect of crystal-field splitting for both building units analyzed by electronic structure calculations.

Tunable emission of Ce3+ in (K, Rb)3GdSi2O7 phosphors toward broadband cyan luminescence

AbstractIn an effort to obtain a novel cyan‐emitting phosphor, the [K1‐xRbx]3GdSi2O7: yCe3+ materials (x = 0, 0.1, 0.2, 0.3, 0.4, y = 0, 0.005, 0.01, 0.02, 0.03, 0.04) are synthesized via a solid‐state reaction pathway, and their crystal structure and luminescence behaviors are studied systematically. The chemical substitution of Rb+ in the K+ sites can enlarge the K3GdSi2O7 host lattice and help to the blue‐shifting of emission band of Ce3+ ions due to the decreased crystal field splitting effect. It is also confirmed that the Ce3+ ions tend to enter [Gd1O6] and [Gd2O6] polyhedrons simultaneously. Consequently, the [K0.7Rb0.3]3GdSi2O7: Ce3+ phosphor yields a broadband cyan emission centered at 492 nm with the full width at half maximum (FWHM) of ∼115 nm upon 365 nm excitation. The optimal concentration of Ce3+ dopant is determined to be 0.01, and the concentration quenching effect can be attributed to the dipole−dipole interactions. The white light emitting diode (WLED) device fabricated by employing the discovered [K0.7Rb0.3]3GdSi2O7: 0.01Ce3+ phosphor displays a high color rendering index (Ra = 91.7) and a low correlated color temperature (CCT = 3749 K). This work may promote the development of cyan phosphors for near ultraviolet‐converted WLEDs with high performance.

Suppression of intervalley scattering and enhanced phonon anharmonic interactions in 2D Bi2TeSe2: Crystal-field symmetry and band convergence

The electron-phonon (el-ph) and phonon-phonon interactions play a key role in determining electronic and thermal transport properties, respectively, in promising two-dimensional (2D) semiconductor devices. In this study, we investigated el-ph interactions using Wannier-Fourier interpolation method and renormalized phonon scattering considering finite-temperature effects in Bi2TeSe2 monolayer. The results show that the optical phonon modes dominate the carrier scattering, where level repulsion induced by crystal field splitting and spin-orbit coupling (SOC) effect effectively suppresses intervalley scattering, leading to high hole mobility. Moreover, the strong anharmonicity in Bi2TeSe2 monolayer results in the temperature-dependent softening of its optical phonons, along with a corresponding variation in interatomic force constants (IFCs). As a result, the lattice thermal conductivity is remarkably low and exhibits weak temperature dependence. Finally, the predicted dimensionless thermoelectric figure of merit exceeds unity in the range of 200–800 K, indicating the potential of Bi2TeSe2 monolayer for thermoelectric applications. This work provides new insights into the elimination of intervalley scattering by crystal field splitting and SOC effects, and paves the way for the evaluation of thermoelectric properties of materials with complex scattering mechanisms and strong anharmonicity.

Adjustment of Bi3+ Luminescence and Thermal Quenching Properties by B'-Site Ion Substitution Strategy in Double Perovskite CaLaMgSb/TaO6:Bi3+ Phosphor.

Thermal quenching has always been one of the most difficult issues in creating high-quality phosphor conversion light-emitting diodes (pc-LED), and a family of strategies are urgently needed to improve the luminescence performance of phosphors at high temperatures. In this contribution, a novel B'-site substitution CaLaMgSbxTa1-xO6:Bi3+ phosphor was constructed using an ion substitution strategy in the matrix with a green activator Bi3+ and a novel double perovskite material. When Sb5+ replaces Ta5+, a surprising increase in luminescence intensity occurs and the thermal quenching properties are greatly improved. The shift of the Raman characteristic peak to a smaller wavenumber and the reduction of the Bi-O bond length confirm that the crystal field environment around Bi3+ changes, which has a substantial effect on the crystal field splitting and nepheline effect of Bi3+ ions, affecting the crystal field splitting energy (Dq). This results in a corresponding increase of the band gap and the thermal quenching activation energy (ΔE) of the activator Bi3+. From the perspective of Dq, the intrinsic relationships among the activator ion band gap, bond length, and Raman characteristic peak changes were analyzed, and a mechanism for regulating luminescence thermal quenching properties was constructed, which provides an effective strategy for improving the promising new materials such as double perovskite.

Universal scaling between on-site Coulomb repulsion and numbers of core and valence electrons in transition metal trichalcogenides

Electron correlations that determine a broad spectrum of the physical properties of transition metal compounds are largely manifested by the on-site Coulomb repulsion U, which so far has been mainly evaluated on a case-by-case basis. Here we employ a linear response method based on constrained local density approximation to systematically investigate U in representative classes of transition metal trichalcogenides, with the transition metals covering all the unfilled 3d, 4d, and 5d orbitals. We uncover a characteristic scaling dependence of U on two elemental physical parameters, namely, the numbers of the core and valence electrons. Such a universal scaling law reflects the intuition that more unfilled d electrons residing on a smaller spherical core will feel stronger Coulomb repulsion. Next, by using the artificial intelligence-based SISSO (Sure Independence Screening and Sparsifying Operator) approach, we identify a more sophisticated descriptor that not only further refines the scaling law, but also captures the crystal-field splitting effect as pictorially reflected by invoking an elliptical core instead of a spherical core. The approach developed in this study should find transferability in other classes of transition metal compounds.

Photoluminescence Properties of Cyan-Emitting Lu3GaxAl5-xO12: Ce3+ Garnet Phosphors Synthesized in Nonreducing Atmosphere and at Different Temperature for High Quality w-LEDs.

The existence of so-called blue-green cavities in the luminescence spectrum has been a hindrance to the improvement in the performance of traditional phosphor-converted white light emitting diodes. The commercial phosphors synthesized in reducing atmospheres can also cause problems such as equipment complexity, increased cost, and environmental pollution. Herein, a series of cyan-emitting Lu3GaxAl5−xO12: Ce3+ (x = 0, 1, 2, 3, 4) garnet phosphors were synthesized by a traditional solid-state reaction in a nonreducing atmosphere at different temperatures. The crystal structure, grain morphology, optical properties, and thermal quenching behavior were used to analyze the optical properties of the as-prepared phosphors. The luminescence intensity of samples is affected by the synthesis temperature and energy gap between the conduction band and the lowest energy of the 5d excited state of the host lattice. With the substitution of Al3+ by Ga3+, the regularity of the excitation and emission band movement is determined by the combined effects of crystal field splitting (CFS) and the nephelauxetic effect (NE). The temperature dependence of luminescence was studied. The thermal quenching mechanism was clarified by the thermal ionization model. Finally, by employing Lu2.94Ga2Al3O12: Ce3+0.06 as a cyan component, a w-LED with a high color rendering index of 93.2 and low correlation color temperature of 3880 K based on a blue chip and commercial red phosphors were fabricated in order to explore its possible application in high quality w-LED.

LaVO3 : A true Kugel-Khomskii system

We show that the $t_{2g}^2$ perovskite LaVO$_3$, in its orthorhombic phase, is a rare case of a system hosting an orbital-ordering Kugel-Khomskii phase transition, rather than being controlled by the Coulomb-enhanced crystal-field splitting. We find that, as a consequence of this, the magnetic transition is close to (and even above) the super-exchange driven orbital-ordering transition, whereas typically magnetism arises at much lower temperatures than orbital ordering. Our results support the experimental scenario of orbital-ordering and G-type spin correlations just above the monoclinic-to-orthorhombic structural change. To explore the effects of crystal-field splitting and filling, we compare to YVO$_3$ and $t_{2g}^1$ titanates. In all these materials the crystal-field is sufficiently large to suppress the Kugel-Khomskii phase transition.

Band engineering and improved thermoelectric performance in p-type SmMg2Sb2: A first-principles study

The thermoelectric properties of p-type SmMg2Sb2 are investigated by using the density functional theory and the Boltzmann transport equation method. It is found that SmMg2Sb2 shows a narrow band gap characteristic, and the crystal field splitting and spin-orbital coupling effect result in a singly degenerate valence band maximum. Meanwhile, SmMg2Sb2 exhibits an intrinsic low lattice thermal conductivity owing to the obvious phonon softening in the low-frequency acoustic branches. Based on a careful analysis of the band structure, we propose a scheme of metallic dopant at Sm site to promote the valence band convergence and improve the Seebeck coefficient. The improved thermoelectric properties are numerically confirmed in the Ba-doped p-type SmMg2Sb2, where a significantly improved ZT of 1.6 at 750 K is predicted with the synergistical effects of band engineering and enhanced phonon scattering.

Non-equilibrium synthesis of stacking faults-abundant Ru nanoparticles towards electrocatalytic water splitting

Metallic nanomaterials with multidimensional defects are promising for electrocatalysis, whereas exploring facile approaches to synthesize such materials with peculiar structure remains challenging. Here, we firstly synthesized Ru nanoparticles with abundant stacking faults (SFs) combining ultrafast heating with rapid quenching. The close-packed planes of perfect hexagonal closed-packed partially transform into face-centered cubic in the SFs region. It requires 196 mV and 35 mV to drive hydrogen evolution reaction and oxygen evolution reaction under 10 mA/cm2 current density, prominently expedites overall water splitting with 1.51 V in acid. Theoretical calculations demonstrate the performance is originated from synergistic effect of the SFs and induced continuous strain field, among which the dominant compressive strain attenuates crystal field splitting effect of Ru sites, thus enhancing the electron transfer of Ru sites. The excellent inter-orbital p-d transfers determine strong electronic activities for boosting OER performance. This work provides insights for rational design of catalysts with defective structures.

Unravel the effect of lattice distortion on the 4f-5d excitation of Ce3+ in garnet phosphors

To increase the red component and improve the color rendering index, the emission redshift of Ce-doped garnet phosphors was extensively studied by a vast amount of researches. But surprisingly, there are still some fuzzy parts in the luminescence mechanism based on the classic configuration coordinate model, which makes some peculiar situations difficult to explain, e.g., the counterintuitive trends of excitation shift in M 2+ -Si 4+ (M 2+ = Mg 2+ , Ca 2+ , Sr 2+ , Ba 2+ ) doped Ce: YAG. To figure out the origin of contradiction and reveal the concrete luminescence dynamics, a series of Ce-doped garnet ceramic phosphors were fabricated and characterized in this work. Combined with historical data and current research, it is analyzed that the effects of crystal field splitting and structural rigidity on the luminescent properties of Ce 3+ share the same changing trend with the distortion of cubic symmetry. When the distortion of cubic symmetry is strengthened, the e g splitting and the electron-phonon coupling will be strengthened simultaneously, which leads to the downward and rightward shift of the 5d 1 parabola curve. This effect can well explain the remaining problems in previous researches, and also provides a guideline for future studies on Ce-doped garnet phosphors.

Effects of reduced dimensionality, crystal field, electron-lattice coupling, and strain on the ground state of a rare-earth nickelate monolayer

Motivated by the potential for cuprate-like superconductivity in monolayer rare-earth nickelate superlattices, we study the effects of crystal field splitting, lattice distortions and strain on the charge, magnetic, and orbital order in undoped two-dimensional (2D) nickelate monolayers $R$NiO$_3$. We use a two-band Hubbard model to describe the low-energy electron states, with correlations controlled by a effective Hubbard $U$ and Hund's $J$. The electrons are coupled to the octahedral breathing-mode lattice distortions. Treating the lattice semiclassically, we apply the Hartree-Fock approximation to obtain the phase diagram for the ground-state as a function of the various parameters. We find that the 2D confinement leads to strong preference for the planar $d_{x^2-y^2}$ orbital even in the absence of a crystal-field splitting. The $d_{x^2-y^2}$ polarization is enhanced by adding a crystal field splitting, whereas coupling to breathing-mode lattice distortions weakens it. However, the former effect is stronger, leading to $d_{x^2-y^2}$ orbital and antiferromagnetic (AFM) order at reasonable values of $U,J$ and thus to the possibility to realize cuprate-like superconductivity in this 2D material upon doping. We also find that the application of tensile strain enhances the cuprate-like phase and phases with orbital polarization in general, by reducing the $t_2 / t_1$ ratio of next-nearest to nearest neighbour hopping. On the contrary, systems with compressive stress have an increased hopping ratio and consequently show a preference for ferromagnetic (FM) phases, including, unexpectedly, the out-of-plane $d_{3z^2-r^2}$ FM phase.

Quantitative assessing of crystal field, nephelauxetic, and Stokes shift effects on the blue luminescence of Eu2+ ions incorporated in ZnS films

A quantitative study of the crystal field, nephelauxetic, and Stokes shift effects on the 5d → 4 f levels of Eu2+ ions incorporated in ZnS films is presented. The magnitude of the crystal effect was calculated using the simplest point charge model to express the crystal field splitting of Eu2+ 5d orbitals surrounded by four S2− ligands in tetrahedral coordination symmetry. The shift of the centroid of the 5d levels by nephelauxetic effect was analyzed using a model that involves the polarizability of the anion ligands, similar to that used to investigate this effect for Ce3+ in many inorganic compounds. The Stokes shift was evaluated according to the Frank-Condon principle, under the idealized situation where the Stokes shift and the emission bandwidth can be expressed in terms of the Huang-Rhys parameter. We found that the redshift of the 5d → 4 f transition for the free Eu2+ ion, due to crystal field splitting was half of the redshift due to the nephelauxetic effect. This result is consistent with the large size, large polarizability, and low electronegativity of the sulfide ions. We also found a relatively large Stokes shift which can be attributed to the autoionization of the 5d electrons to the conduction band levels. The total redshift of the 5d and 4 f energy levels with respect to the 5d and 4 f energy gap for a free Eu2+ in vacuum fits quite well with the blue luminescence peaked at 2.73 eV for Eu2+ ions incorporated in the ZnS films. Based on the experimental results and the calculations for the crystal field splitting, nephelauxetic, and Stokes shift effects, we also propose a simplified energy band and levels diagram which helps to explain the excitation-emission mechanisms of the blue luminescence of the Eu2+ ions incorporated in the ZnS films.

Effects of Eu2+ substitution on structural and optical properties with blue light emission in pollucite CsAlSi2O6 phosphor

A series of Eu2+ substituted pollucite [(Cs1-xEu1-2x)AlSi2O6 (CASO:xEu) (x = 0.001–0.08)] phosphors were synthesized by a high-temperature solid-state reaction method in a reducing atmosphere and characterized by X-ray diffraction, photoluminescence (PL), and PL excitation (PLE) measurements. Under excitation at 275 nm, CASO:xEu phosphors exhibit an emission band that shifts from the bright blue region with color coordinates of (0.159, 0.247) to the bright blue-green region with color coordinates of (0.225, 0.421) with increasing x. Such tunable luminescence color was attributed to the crystal field splitting effect of Eu2+ ions because the substitution of Eu2+ created vacancies at Cs sites, and fluctuations occurred at the positions occupied by the Eu2+ ions. Studies on the temperature dependence of luminescence for x = 0.01, 0.03 0.05, and 0.07 in CASO:xEu reveal that 92.5%, 85.3%, 74.9%, and 79.8% of the initial value of the luminescence intensity at 300 K are retained at 400 K, respectively. Tuning the emission spectra was possible by varying the value of x while maintaining a high thermal stability.

Nickelate superconductors: Multiorbital nature and spin freezing

Superconductivity with a remarkably high $T_c$ has recently been found in Sr-doped NdNiO$_2$ thin films. While this system bears strong similarities to the cuprates, some differences, such as a weaker antiferromagnetic exchange coupling and possible high-spin moments on the doped Ni sites have been pointed out. Here, we investigate the effect of Hund coupling and crystal field splitting in a simple model system and argue that a multiorbital description of nickelate superconductors is warranted, especially in the strongly hole-doped regime. We then look at this system from the viewpoint of the spin-freezing theory of unconventional superconductivity, which provides a unified understanding of unconventional superconductivity in a broad range of compounds. Sr$_{0.2}$Nd$_{0.8}$NiO$_2$ falls into a parameter regime influenced by two spin-freezing crossovers, one related to the emergent multi-orbital nature in the strongly doped regime and the other related to the single-band character and square lattice geometry in the weakly doped regime.

Tunable luminescence in co-doped Zn3Al2Ge2O10:Cr3+ by controlling crystal field splitting and nephelauxetic effect

Ce3+/Dy3+/Tb3+/Eu3+/Mn2+ and Cr3+ ions co-doped Zn3Al2Ge2O10 phosphor were prepared by a high-temperature solid-state method. X-ray diffraction patterns prove the cubic phase structure of prepared Zn3Al2Ge2O10 phosphor. Emission, excitation spectra and decay curves confirm the tunable luminescence. Different degrees of the decrease of emission FWHM in Zn3Al2Ge2O10:0.02Cr3+,RE (RE = Ce3+, Dy3+, Tb3+, Eu3+) and Zn3Al2Ge2O10:0.02Cr3+,Mn2+ are observed. The reason of variable FWHM is the effect of crystal field splitting and nephelauxetic effect, and the nephelauxetic effect is dominant. Therefore, the emission FWHM decreases with the increasing concentration of Mn2+/Tb3+/Eu3+ in Zn3Al2Ge2O10:0.02Cr3+, and for Zn3Al2Ge2O10:0.02Cr3+,Ce3+ and Zn3Al2Ge2O10:0.02Cr3+,Dy3+, it is a constant. The variation of Zn3Al2Ge2O10:0.02Cr3+,Tb3+ is more obvious than that of Zn3Al2Ge2O10:0.02Cr3+,Eu3+, because Tb3+ ion has smaller electronegativity. Thus, the tunable luminescence of Cr3+ can be realized by co-doping different ions. And these phosphors have potential applications in light-emitting diodes for plant growth.

Structures and Spectral and Magnetic Properties of a Series of Carbacylamidophosphate Pentanuclear Lanthanide(III) Hydroxo Complexes.

A series of pentanuclear lanthanide complexes Ln5L6(μ-L)4(μ3-OH)4(μ4-OH) (LnIII = Nd, Dy, Ho, Er, Yb; L- = dimethyl N-benzoylamidophosphate ion, [C6H5C(O)-N-P(O)(OCH3)2]-) was obtained by the reaction of sodium dimethyl N-benzoylamidophosphate with the corresponding lanthanide nitrates. The pentanuclear cores formed as a result of self-arrangement and their composition did not depend on the lanthanide ion. The complexes and sodium dimethyl N-benzoylamidophosphate have been characterized by single-crystal X-ray diffraction. The absorption spectra of the complexes were measured at 300 and 4 K. The dysprosium and ytterbium complexes exhibited weak emission in the visible and IR regions, respectively. Temperature dependences of magnetic susceptibility (χM) of the dysprosium, holmium, and erbium compounds were studied. It was found that χM vs T dependences were governed by the crystal field splitting effects with the Δ parameter being in the range 5-17 cm-1. Slow magnetic relaxation was found for the dysprosium complex by ac magnetic measurements, while no significant out-of-phase signals were detected for holmium and erbium complexes.

Crystal structure, energy transfer and tunable luminescence of Ca8(Mg,Zn)Ce(PO4)7:Eu2+ solid solution phosphor

Here we investigated the tunable luminescence properties of Ca8(Mg1−xZnx)Ce(PO4)7:Eu2+ as a function of Zn2+ concentration. All the synthesized phosphors shared the same whitlockite-type structure and crystallized in the rhombohedral unit cell with the space group R3c (no.161). Energy can be efficiently transferred from Ce3+ to Eu2+ in Ca8(Mg1−xZnx)Ce(PO4)7:Eu2+ phosphors. Furthermore, the color of these phosphors can turn from blue to green with increasing the Zn content (x). Such tunable luminescence cannot be attributed to the effect of crystal field splitting or energy transfer between Ce3+ and Eu2+ ions. It is found that the modification of host composition via Zn substitution causes different Eu2+ sensitization efficiencies and induces the luminescence tuning. This mechanism may be general in iso-structural solid-solution phosphors and will be useful in tuning optical and other properties whose sensitization efficiency is sensitive to the host composition.

Crystal field splitting and spin states of Co ions in cobalt ferrite with composition Co1.5Fe1.5O4 using magnetization and X-ray absorption spectroscopy measurements

Structural, magnetic and electronic properties of partially inverted Cobalt Ferrite with composition Co1.5Fe1.5O4 is discussed in the present work. Single phase (SG: Fd3m) sample is synthesized by co-precipitation technique and subsequent air annealing. The values of saturation magnetization obtained from careful analysis of approach to saturation in initial M(H) curves are used to determine spin states of Co ions in tetrahedral (TH) and octahedral (OH) sites. Spin states of Co3+ ions in TH sites, which has not been reported in literature, were found to be in high spin state. Temperature variation of magnetic parameters has been studied. The sample shows magneto-crystalline anisotropy with two clearly distinct pinning centers. Oxygen K-edge and Fe as well as Co L2,3-edge X-ray absorption (XAS) spectra have been used as complementary measurements to study crystal field splitting and core hole effects on transition metal (TM) 3d orbitals. The ratio of intensities of t2g and eg absorption bands in O-K edge XAS spectrum is used to estimate the spin states of Co ions at OH and TH sites. The results are in agreement with those obtained from magnetization data, and favors Co3+ ions in TH sites in high spin states. Normalized areas of the satellite peaks in TM L2,3-edge XAS spectra have been used to estimate 3dn+1L contribution in ground state wave function and the contributions were found to be significant.

Electronic structure origin of conductivity and oxygen reduction activity changes in low-level Cr-substituted (La,Sr)MnO3.

The electronic structure of the (La(0.8)Sr(0.2))(0.98)Mn(1-x)Cr(x)O3 model series (x = 0, 0.05, or 0.1) was measured using soft X-ray synchrotron radiation at room and elevated temperature. O K-edge near-edge X-ray absorption fine structure (NEXAFS) spectra showed that low-level chromium substitution of (La,Sr)MnO3 resulted in lowered hybridisation between O 2p orbitals and M 3d and M 4sp valance orbitals. Mn L3-edge resonant photoemission spectroscopy measurements indicated lowered Mn 3d-O 2p hybridisation with chromium substitution. Deconvolution of O K-edge NEXAFS spectra took into account the effects of exchange and crystal field splitting and included a novel approach whereby the pre-peak region was described using the nominally filled t(2g) ↑ state. 10% chromium substitution resulted in a 0.17 eV lowering in the energy of the t(2g) ↑ state, which appears to provide an explanation for the 0.15 eV rise in activation energy for the oxygen reduction reaction, while decreased overlap between hybrid O 2p-Mn 3d states was in qualitative agreement with lowered electronic conductivity. An orbital-level understanding of the thermodynamically predicted solid oxide fuel cell cathode poisoning mechanism involving low-level chromium substitution on the B-site of (La,Sr)MnO3 is presented.