Publications by authors named "Michele Reticcioli"
Atomic-Scale View at the Segregation of Alkali Metals toward the KTaO(001) Perovskite Surface.
ACS Appl Mater Interfaces
December 2024
Perovskites exhibit outstanding performance in applications such as photocatalysis, electrochemistry, or photovoltaics, yet their practical use is hindered by the instability of these materials under operating conditions, specifically caused by the segregation of alkali cations toward the surface. The problem arises from the bulk strain related to different cation sizes, as well as the inherent electrostatic instability of perovskite surfaces. Here, we focus on atomistic details of the surface-driven process of interlayer switching of alkali atoms at the inorganic perovskite surface.
View Article and Find Full Text PDFIn polarizable materials, electronic charge carriers interact with the surrounding ions, leading to quasiparticle behavior. The resulting polarons play a central role in many materials properties including electrical transport, interaction with light, surface reactivity, and magnetoresistance, and polarons are typically investigated indirectly through these macroscopic characteristics. Here, noncontact atomic force microscopy (nc-AFM) is used to directly image polarons in FeO at the single quasiparticle limit.
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- Recent findings suggest that high-temperature superconducting phases in hydrides under high pressure may allow for the possibility of near-ambient superconductivity.
- The study focuses on N-doped LuH hydride, using machine learning to show that nitrogen impurities can stabilize hydrogen molecules at ambient pressure, which are crucial for achieving low-temperature superconductivity.
Article Synopsis
- * This study uses density functional theory and surface experiments to investigate how Rh, Pt, and Au metals interact with reduced TiO(110) surfaces, identifying different coupling behaviors influenced by polarons.
- * It finds that Pt and Au strongly interact with oxygen vacancy sites, resulting in charge transfer and metal reduction, while Rh has weaker interactions, indicating a complex relationship between adatoms, vacancies, and polarons essential for understanding single-atom catalysts.
Article Synopsis
- Polarizable materials, like KTaO, are important in catalysis due to their ability to modify chemical reactivity through surface properties.
- The study highlights how KTaO's surfaces, which have different terminations, create unique environments for carbon monoxide (CO) molecules, affecting their charge and binding strength.
- Results indicate that the presence of excess charge on TaO terraces leads to stronger interactions with CO, demonstrating a link between adsorption states and ferroelectric polarization.
Article Synopsis
- - The common model for describing excess charge on ionic compound surfaces, known as the two-dimensional electron gas (2DEG), is shown to be an oversimplification as it does not account for more complex electronic states on polar surfaces.
- - Research combining scanning probe microscopy with density functional theory reveals that on the TaO surface of KTaO(001), charge density waves coexist with strongly-localized electron polarons and bipolarons, leading to varied electronic behavior.
- - These complex surface electronic states are more energetically favorable than the 2DEG model and influence surface properties, resulting in distinct spectroscopy signals and a reduction in ferroelectric distortions.
Article Synopsis
- Thermoelectricity, discovered in 1821, allows the direct conversion between thermal and electrical energy using effects like Seebeck and Peltier.
- Researchers Mahan and Sofo theorized that the ideal thermoelectric material would have a specific electronic transport function, but such materials seemed theoretical until now.
- This study introduces the Anderson transition in a controlled impurity band to achieve significant changes in thermoelectric properties, demonstrating a practical way to enhance material performance.
Modeling polarons in density functional theory: lessons learned from TiO.
J Phys Condens Matter
March 2022
Article Synopsis
- Density functional theory (DFT) is widely used to analyze polarons in materials, particularly in rutile TiO, to ensure accurate predictions that match experimental results.
- The study examines how electronic correlation correction methods in the DFT + formalism influence charge localization, structural changes, and electronic features of polarons, comparing surface and subsurface layers.
- It highlights that local strain affects polaron behavior differently depending on their location, which impacts their stability and interactions, such as with CO adsorbates.
Electronic State Unfolding for Plane Waves: Energy Bands, Fermi Surfaces, and Spectral Functions.
J Phys Chem C Nanomater Interfaces
June 2021
Article Synopsis
- Present day computing allows for advanced studies using density functional theory to investigate complex physical and chemical issues, typically requiring large supercells for accurate modeling.
- However, using supercells results in small Brillouin zones that complicate the analysis of electronic properties due to folded electronic states.
- The authors introduce a new unfolding scheme embedded in the Vienna Simulation Package (VASP) that simplifies this process, enabling easier computation of band structures, Fermi surfaces, and spectral functions while being applied to various complex scenarios, like the influence of doping in superconductors and interactions on material surfaces.
Interaction of molecular oxygen with semiconducting oxide surfaces plays a key role in many technologies. The topic is difficult to approach both by experiment and in theory, mainly due to multiple stable charge states, adsorption configurations, and reaction channels of adsorbed oxygen species. Here we use a combination of noncontact atomic force microscopy (AFM) and density functional theory (DFT) to resolve [Formula: see text] adsorption on the rutile [Formula: see text](110) surface, which presents a longstanding challenge in the surface chemistry of metal oxides.
View Article and Find Full Text PDFPolaron formation plays a major role in determining the structural, electrical, and chemical properties of ionic crystals. Using a combination of first-principles calculations, scanning tunneling microscopy, and atomic force microscopy, we analyze the interaction of polarons with CO molecules adsorbed on the reduced rutile TiO_{2}(110) surface. Adsorbed CO shows attractive coupling with polarons in the surface layer, and repulsive interaction with polarons in the subsurface layer.
View Article and Find Full Text PDFBy means of first principles schemes based on magnetically constrained density functional theory and on the band unfolding technique we study the effect of doping on the conducting behaviour of the Lifshitz magnetic insulator NaOsO. Electron doping is treated within a supercell approach by replacing sodium with magnesium at different concentrations ([Formula: see text], [Formula: see text]). Undoped NaOsO is subjected to a temperature-driven Lifshitz transition involving a continuous closing of the gap due to longitudinal and rotational spin fluctuations (Kim et al 2016 Phys.
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- The stacking of charged planes in ionic crystals leads to a "polar catastrophe," causing an imbalance in electrostatic energy that needs to be addressed at the surface.
- Researchers investigated the compensation mechanisms of the potassium tantalate (KTaO) (001) surface using advanced microscopy and computational methods.
- Results showed that the surface can rapidly transition from an insulator to a metal and undergo significant structural changes, with the optimal surface state achieved after exposure to water vapor, creating a beneficial hydroxylated overlayer.