Anna Maria Ferrari

In this study, we perform density functional theory (DFT) simulations to investigate the Raman spectra of the bulk and surface phases of β-Li₃PS₄ (LPS) and Li₂S, as well as their interfaces at varying compositional ratios. This analysis is relevant given the widespread application of these materials in Li–S solid-state batteries, where Li₂S functions not only as a cathode material but also as a protective layer for the lithium anode. Understanding the interfacial structure and how compositional variations influence its chemical and mechanical stability is therefore crucial. Our results demonstrate that the LPS/Li₂S interface remains stable regardless of the compositional ratio. However, when the content of both materials is low, the Raman-active vibrational mode associated with the [PS₄]³⁻ tetrahedral cluster dominates the interface spectrum, effectively obscuring the characteristic peaks of Li₂S and other interfacial features. Only when sufficient amounts of both LPS and Li₂S are present does the coupling between their vibrational modes become sufficiently pronounced to alter the Raman profile and reveal distinct interfacial fingerprints.

Alloys, solid solutions, and doped systems are essential in technologies such as energy generation and catalysis, but predicting their properties remains challenging because of compositional disorder. As the concentration of components changes in a binary solid solution A ( 1 − x ) B x , the number of possible configurations becomes computationally intractable. Algorithms used in classical optimization methods cannot avoid assessing high-energy states where, for example, simulated annealing is designed to initially spend computational effort. We introduce a scalable, practical, and accurate approach using quantum annealing to efficiently sample low-energy configurations of disordered materials, avoiding the need for excessive high-energy calculations. Our method includes temperature and simulates large unit cells, producing a Boltzmann-like distribution to identify thermodynamically relevant structures. We demonstrate this by predicting bandgap bowing in Al 1 − x Ga x N and bulk modulus variations in Ta 1 − x W x , with results in excellent agreement with experiments.

This Account traces the scientific journey of Gianfranco Pacchioni, a pioneer in the theoretical understanding of catalysis and materials chemistry. From his early contributions to the study of metal clusters and organometallic compounds to his groundbreaking work on surface defects and single-atom catalysis, Gianfranco has profoundly shaped our understanding of the electronic structure and reactivity of catalytic materials. A defining feature of his career has been his ability to translate chemical complexity into comprehensive and powerful theoretical models, often anticipating experimental findings and guiding the design of catalytic systems. His work on defect engineering, oxide-supported metal clusters, and ultrathin films has laid foundational principles in surface science. At the same time, his more recent contributions have elevated the field of single-atom catalysis through a unique blend of coordination chemistry, solid-state physics, and computational rigor. Gianfranco’s legacy extends beyond his scientific output: he has fostered international collaborations, mentored generations of researchers, and played a pivotal role in shaping the landscape of theoretical chemistry in Italy and beyond.

In this study, we present a combined experimental and theoretical study of point defects in MoS₂ monolayers supported on Au(111). By tuning the experimental conditions, we achieved selective defect formation, paving the way for advanced defect engineering. Density functional theory (DFT) simulations were performed to model both the perfect Moiré superstructure and a variety of defect configurations. This allowed us to precisely identify the experimentally created single- and multiatom vacancies, interpret their contrast in scanning tunneling microscopy (STM), and characterize their electronic properties and effects on the valence band (VB). Our results show that tuning the kinetics of ion bombardment and the chemical environment during annealing treatments can produce different combinations of simple and complex defects. Additionally, we find that the Moiré modulation has minimal impact on the geometric and electronic properties of the surface, suggesting that the defect-engineered MoS₂/Au surface could serve as a rather general model system to further investigate the electronic and catalytic properties of MoS₂-based nanomaterials.

Lithium-titanium-sulfur cathodes have garnered interest due to their distinctive properties and potential applications in lithium-ion batteries. They present various benefits, including lower cost, enhanced safety, and greater energy density compared to the commonly used transition metal oxides. The current trend in lithium-ion batteries is to move to all-solid-state chemistries in order to improve safety and energy density. Several chemistries for solid electrolytes have been studied, tested, and characterized to evaluate the applicability in energy storage system. Among those, sulfur-based Argyrodites have been coupled with cubic rock-salt type Li₂TiS₃ electrodes. In this work, Li₂TiS₃ surfaces were investigated with DFT methods in different conditions, covering the possible configurations that can occur during the cathode usage: pristine, delithiated, and overlithiated. Interfaces were built by coupling selected Li₂TiS₃ surfaces with the most stable Argyrodite surface, as derived from a previous study, allowing us to understand the (electro)chemical compatibility between these two sulfur-based materials.

The interaction of water with solid surfaces is crucial for a wide range of disciplines, including catalysis, environmental science, corrosion, geology, and biology. In this study, we present a combined experimental and theoretical investigation that elucidates the interaction of water with a model iron oxide surface under near ambient conditions (i.e., room temperature and water vapor in the mbar range). Our findings reveal that surface hydroxylation can be controlled at the nanoscale by the local properties of the oxide film, such as local rumpling and electrostatic potential. The iron oxide surface presents alternating hydrophilic and hydrophobic domains, creating after water exposure a hexagonal pattern with a pitch of approximately 3 nm, where the highly hydroxylated regions act as nucleation centers for nanoconfined water molecule clusters.

In the roadmap toward designing new and improved materials for Lithium ion batteries, the ability to estimate the diffusion coefficient of Li atoms in electrodes, and eventually solid-state electrolytes, is key. Nevertheless, as of today, accurate prediction through computational tools remains challenging. Its experimental measurement does not appear to be much easier. In this work, we devise a computational protocol for the determination of the Li-migration energy barrier and diffusion coefficient, focusing on a common cathode material such as LiNiO₂, which represents a prototype of the widely adopted NMC (LiNi_1-x-y Mn _x Co _y O₂) class of materials. Different methodologies are exploited, combining ab initio metadynamics, path sampling, and density functional theory. Furthermore, we propose a novel, fast, and simple 1D approximation for the estimation of the effective frequency. The outlined computational protocol aims to be generally applicable to Lithium diffusion in other materials and components for batteries, including anodes and solid electrolytes.

Specific features of the three high-symmetry domains of the FeO/Au moiré superstructure (surface electrostatic potential, work function, local film rumpling, interface distance and charge transfer) are identified thanks to VASP-DFT calculations.

DFT was applied to study the LiIn surfaces' formation and structural stability in interfaces with β-Li ₃ PS ₄ . The stable interfaces established with the β-Li ₃ PS ₄ featured favorable adhesion energy, low strain energy, and little reconstruction.