arXiv subjects

Guilherme da Silva Lopes Fabris

Publications and source records attributed to Guilherme da Silva Lopes Fabris.

7 recordsLinked to original sources

arXiv2026

Diamond-to-graphite transformation under hypersonic impact

Diamond to graphite transformation is a complex kinetically driven process which has been studied under various conditions for its fundamental importance. We report the transformation of diamond embedded ceramic matrix composites during hypersonic impact. Diamond particles embedded in cubic boron nitride matrix provide a superhard composite that was subjected to high impact collisions of metal projectiles travelling at speeds reaching Mach 8.45. Our observations suggest that the energy absorption and fracture of the composite is primarily enabled via the phase change of diamond into graphite. Characterization of the impact-fractured composite shows transformed diamond particles and provides details of the shock-induced phase transformation and the nature of diamond-graphite interfaces formed during rapid phase change. The study provides new understanding of phase transformation of diamond under extreme conditions.

cond-mat.mtrl-sci↗

arXiv2026

High-Entropy Nitride Photocatalysts for Visible-Light Antibiotic Degradation: Structural Stability, In Situ Interfacial Visualization, and Molecular-Level Mechanistic Insights

High-entropy nitrides (HENs) have emerged as a promising class of advanced materials with tunable electronic structures, high stability, and abundant active sites. The incorporation of nitrogen enhances visible-light absorption, promotes efficient charge separation, and improves structural robustness, making these materials highly suitable for photocatalytic applications. In this study, (MnFeCoNiCu)N-based HEN nanoparticles (NPs) were synthesized as visible-light-assisted photocatalysts for the degradation of antibiotics, including sulfamethoxazole (SME) and tetracycline (TCL). The catalyst exhibited excellent performance, achieving 96% degradation of SME and 94% removal of TCL within 2 h of visible-light irradiation. The photocatalytic activity was systematically evaluated under varying operational parameters, including solution pH, catalyst dosage, pollutant concentration, and the presence of coexisting ions. Notably, the catalyst maintained high efficiency in real water matrices, demonstrating its practical applicability. The entropy-stabilized nitride framework exhibited negligible metal leaching, excellent thermal and structural stability as confirmed by temperature-dependent synchrotron angle-dispersive X-ray diffraction, and stable performance over multiple reuse cycles. Furthermore, in situ liquid-cell transmission electron microscopy provided real-time insight into catalyst-pollutant interactions, while complementary molecular simulations revealed the structural stability of the HEN NPs during molecular adsorption and the distinct interaction modes of the two antibiotics. Phytotoxicity tests using Vigna radiata confirmed the effective detoxification of treated solutions. Overall, this work establishes (MnFeCoNiCu)N HENs as efficient and durable visible-light-driven photocatalysts for the removal of antibiotics from complex aqueous environments.

cond-mat.mtrl-sci↗

arXiv2025

Nanoscale mechanics and ultralow Friction of natural 2D silicates: Biotite and Rhodonite

Two-dimensional (2D) silicates have emerged as a promising class of ultrathin materials, expanding the landscape of 2D systems beyond conventional van der Waals crystals. Their unique crystal chemistries and structural anisotropies make them attractive for applications ranging from sensors and flexoelectric devices to drug delivery and catalysis. To unlock their full potential, it is critical to understand their thickness-dependent mechanical properties within the family of 2D silicates. In this study, we investigate the nanomechanical and frictional behaviors of two structurally distinct natural silicates: layered Biotite and chain-structured Rhodonite. Using atomic force microscopy (AFM), we found that Rhodonite exhibits nearly ten times higher adhesion force and modulus response compared to Biotite. Despite this, Biotite demonstrates superior frictional performance, with ultrathin (5 nm) flakes showing a remarkably low coefficient of friction ($\sim 0.6 \times 10^{-3}$) versus Rhodonite ($\sim 3.6 \times 10^{-3}$). To further elucidate interlayer adhesion, density functional theory (DFT) calculations with Hubbard correction were employed. These findings offer valuable insights into the design and selection of 2D silicates for advanced mechanical and tribological applications.

cond-mat.mtrl-sci↗

arXiv2025

Unraveling Mn intercalation and diffusion in NbSe$_2$ bilayers through DFTB simulations

Understanding transition metal atoms' intercalation and diffusion behavior in two-dimensional (2D) materials is essential for advancing their potential in spintronics and other emerging technologies. In this study, we used density functional tight binding (DFTB) simulations to investigate the atomic-scale mechanisms of manganese (Mn) intercalation into NbSe$_2$ bilayers. Our results show that Mn prefers intercalated and embedded positions rather than surface adsorption, as cohesive energy calculations indicate enhanced stability in these configurations. Nudged elastic band (NEB) calculations revealed an energy barrier of 0.68 eV for the migration of Mn into the interlayer, comparable to other substrates, suggesting accessible diffusion pathways. Molecular dynamics (MD) simulations further demonstrated an intercalation concentration-dependent behavior. Mn atoms initially adsorb on the surface and gradually diffuse inward, resulting in an effective intercalation at higher Mn densities before clustering effects emerge. These results provide helpful insights into the diffusion pathways and stability of Mn atoms within NbSe$_2$ bilayers, consistent with experimental observations and offering a deeper understanding of heteroatom intercalation mechanisms in transition metal dichalcogenides.

cond-mat.mtrl-sci↗

arXiv2025

Electronic and Optical Properties of the Recently Synthesized 2D Vivianites (Vivianenes): Insights from First-Principles Calculations

Vivianite (Fe$_3$(PO$_4$)$_2$8H$_2$O) is a naturally occurring layered material with significant environmental and technological relevance. This work presents a comprehensive theoretical investigation of its two-dimensional (2D) counterpart, Vivianene, focusing on its structural, electronic, and optical properties. Using density functional theory (DFT) calculations and ab initio molecular dynamics (AIMD) simulations, we evaluate its thermodynamic stability, band structure, density of states, and optical response. Our results confirm that Vivianene retains the main structural features of bulk Vivianite while exhibiting enhanced thermodynamic stability at room temperature. The electronic structure analysis reveals an indirect bandgap of 3.03 eV for Vivianene, which is slightly lower than the 3.21 eV observed for bulk Vivianite, deviating from the expected quantum confinement trend in 2D materials. The projected density of states (PDOS) analysis indicates that Fe d orbitals predominantly contribute to the valence and conduction bands. Optical calculations demonstrate that Vivianene exhibits a higher optical band gap (3.6 eV) than bulk Vivianite (3.2 eV), with significant absorption in the ultraviolet region. The refractive index and reflectivity analyses suggest that most of the incident light is absorbed rather than reflected, reinforcing its potential for optoelectronic applications. These findings provide valuable insights into the fundamental properties of Vivianene and highlight its potential for advanced applications in sensing, optoelectronics, and energy-related technologies.

cond-mat.mtrl-sci↗

arXiv2025

Emamectin benzoate sensing using vivianenes (2D vivianites)

The excessive application of pesticides, particularly the overreliance on insecticides for the protection of desirable crops from pests, has posed a significant threat to both ecological systems and human health due to environmental pollution. This research outlines a comprehensive approach to recognizing and quantifying the presence of insecticides through the application of spectroscopic and electrochemical sensing methods. The detection of Emamectin benzoate (EB), a commonly used insecticide, was performed utilizing vivianenes, a 2D phosphate that has been mechanically exfoliated from the naturally occurring vivianite minerals. This investigation examined the structural and compositional characteristics of vivianenes, utilizing a range of characterization methods. The spectroscopic analyses reveal the molecular interactions and structural modifications that take place during the interaction of EB with the 2D template. Electrochemical investigations employing cyclic voltammetry were performed for different concentrations of EB to enable real-time monitoring of the pesticide. The modified sensing electrode using vivianene demonstrated a linear range of from 50 mg/L to 10 micro g/L, effectively detecting EB molecules at levels significantly below the hazardous threshold. Fully atomistic molecular dynamics simulations were also carried out to obtain further insights into the interaction mechanisms of the EB with the vivianites, and the results corroborate the adsorption mechanism. Our results highlight the potential application of 2D phosphate minerals as advanced sensors to enhance agricultural monitoring and promote sustainable development.

physics.chem-ph↗

arXiv2023

Theoretical insights into the chemical bonding, electronic structure, and spectroscopic properties of the lanarkite Pb$_2$SO$_5$ structure

This article provides a comprehensive investigation on the chemical bonding, electronic structure, and spectroscopic properties of the lanarkite-type PSO structure from a computational perspective. Thus, different functionals in the field of DFT (e.g., PBE, PBE0, PBESOL, PBESOL0, BLYP, WC1LYP and B3LYP) using a triple-zeta valence plus polarization basis set were assessed to accurate prediction their fundamental properties. Among all DFT functionals tested in this study, in particular, the PBE was the one that showed the best agreement with the experimental data available in the literature. Our results also reveal that the [PbO$_5$] clusters are formed with three different Pb--O bond lengths, with values of about 2.32, 2.59 and 2.84Å, respectively, and the [SO$_4$] clusters have the same S--O bond length of 1.57Å. We then performed a complete topological analysis of this system to better understand these structural differences. Additionally, the PSO structure has an indirect band gap energy of 2.9 eV and an effective mass ratio of about 0.415 (using PBE calculations) which may, in principle, indicate a low recombination of electro-hole pairs in the lanarkite structure. Therefore, we believe that a detailed understanding of their electronic structure and spectroscopic properties as well as their chemical bonding is critically important for developing new technologies based on PSO.

cond-mat.mtrl-sci↗