arXiv subjects

Iwnetim I. Abate

Publications and source records attributed to Iwnetim I. Abate.

4 recordsLinked to original sources

arXiv2026

Many-Body Destabilization of Intermediate Oxygen-Hole States

Oxygen holes in transition-metal oxides can appear as localized polarons, symmetry-delocalized ligand holes, or intermediate states whose stability is controlled by subtle electron-correlation effects. In layered Na$_{2-x}$Mn$_3$O$_7$, hybrid density functional theory (DFT) predicts an unusual bond-centered split oxygen-hole polaron stabilized near ordered Mn vacancies. Here we resolve the nature of this state using diffusion Quantum Monte Carlo (QMC). Although hybrid DFT favors the split configuration, QMC reverses the energetic ordering and identifies the localized oxygen polaron as the lower-energy state. The result is robust to the class of trial wavefunctions used, including hybrid and generalized-gradient DFT wavefunctions. Many-body spin densities further show that the nominal split state partially collapses toward a localized polaron. Because localized and split configurations produce similar O K-edge spectral features, this qualitative failure is not resolved by conventional X-ray absorption signatures alone. These findings identify Na$_{2-x}$Mn$_3$O$_7$ as a stringent benchmark for oxygen-hole polarons and reveal a failure mode of hybrid functionals in correlated oxides.

cond-mat.mtrl-sci↗

arXiv2025

Grotthuss-type oxygen hole polaron transport in desodiated Na$_{2}$Mn$_3$O$_7$

Polarons are quasiparticles that arise from the coupling of electrons or holes with ionic vibrations in polarizable materials. Typically, they are either localized at a single atomic site or delocalized over multiple sites. However, after the desodiation of Na$_{2}$Mn$_{3}$O$_{7}$, we identify a rare split-hole polaron, where a single hole is shared between two adjacent oxygen atoms rather than fully localized or delocalized. We present a density functional theory (DFT) study on the migration and transport properties of these oxygen hole polarons in NaMn$_{3}$O$_{7}$ and Na$_{1.5}$Mn$_{3}$O$_{7}$. Our calculations reveal that the split polaron configuration near a sodium vacancy is the ground state, while the localized polaron acts as the transition state. Migration occurs via a stepwise charge transfer mechanism along the $b$-axis, where the split-hole polaron transitions through a localized hole state. This transport behavior closely resembles the Grotthuss mechanism, which describes proton transport in H$_{2}$O. We compute the polaron mobility as $μ$ = 1.37 $\times$ 10$^{-5}$ cm$^2$/(V$\cdot$s) with an energy barrier of 242 meV. Using the Mulliken-Hush theory, we determine the electronic coupling parameter $V_{AB}$ = 0.87 eV. A similar migration mechanism is observed in Na$_{1.5}$Mn$_{3}$O$_{7}$, where the split polaron remains more stable than in the localized state. This study provides the first theoretical investigation of split-hole polaron migration, offering new insights into the charge transport of exotic polaronic species in materials with implications for a wide range of functional materials including battery cathodes, thermoelectrics, photocatalysts, and next-generation optoelectronic devices.

cond-mat.mtrl-sci↗

arXiv2025

Electrochemically induced switching from antiferromagnetic spin-chain to frustrated spin-glass state in maple-leaf lattice Na2Mn3O7

We report the electrochemical tuning of magnetic properties in the Na2Mn3O7 maple-leaf lattice (MLL) through ion deintercalation, revealing a switch from the 1D antiferromagnetic (AFM) spin-chain behavior of the S=3/2 MLL structure to frustrated magnetism spin-glass behavior. By utilizing Na deintercalation, we stabilize ferromagnetic (FM) short-range interactions within the original short-range AFM system, creating magnetic frustration within the system beyond that induced from the MLL geometrically frustrated structure, leading to a spin-glass state. Magnetic and structural analyses, combined with density functional theory (DFT) calculations, demonstrate the near-degeneracy between AFM and FM configurations in Na2Mn3O7, suggesting that the altered lattice distortions and disorder introduced via deintercalation are responsible for the frustrated magnetism. Our findings provide a novel platform for studying low-dimensional magnetism, spin glass behavior, and potential applications in spintronics and computing technologies. This study represents the first observation of an induced spin glass state in MLL materials and is a rare example of electrochemically induced spin glass state, highlighting the critical role of ion intercalation in tuning magnetic interactions.

cond-mat.mtrl-sci↗

arXiv2020

Coulombically-stabilized oxygen hole polarons enable fully reversible oxygen redox

Stabilizing high-valent redox couples and exotic electronic states necessitate an understanding of the stabilization mechanism. In oxides, whether they are being considered for energy storage or computing, highly oxidized oxide-anion species rehybridize to form short covalent bonds and are related to significant local structural distortions. In intercalation oxide electrodes for batteries, while such reorganization partially stabilizes oxygen redox, it also gives rise to substantial hysteresis. In this work, we investigate oxygen redox in layered Na2-XMn3O7, a positive electrode material with ordered Mn vacancies. We show that coulombic interactions between oxidized oxide-anions and the interlayer Na vacancies can disfavor rehybridization and stabilize hole polarons on oxygen at 4.2 V vs. Na/Na+. These coulombic interactions provide thermodynamic energy saving as large as O-O covalent bonding and enable ~ 40 mV voltage hysteresis over multiple electrochemical cycles with negligible voltage fade. Our results establish a complete picture of redox energetics by highlighting the role of coulombic interactions across several atomic distances and suggest avenues to stabilize highly oxidized oxygen for applications in energy storage and beyond.

cond-mat.mtrl-sci↗