arXiv subjects

Luiz A. Ribeiro Junior

Publications and source records attributed to Luiz A. Ribeiro Junior.

At least 19 recordsLinked to original sources

arXiv2026

Hopping-Mediated Charge Transport in Graphene Beyond the Ballistic Regime

We present a trajectory-resolved framework for charge transport in graphene and related two-dimensional carbon systems beyond the ideal ballistic and fully coherent limits. Transport is described by kinetic Monte Carlo hopping on a predefined atomic lattice, allowing the combined treatment of disorder, thermal activation, and external fields. Current and effective transmittance are extracted directly from stochastic carrier trajectories, without phenomenological transport coefficients. We apply the method to graphene under bias voltage (0-0.10 V), temperature (300-900 K), magnetic field (0-10 T), in-plane strain (2-10%, uniaxial and biaxial), and vacancy concentration (0-10%). Pristine graphene shows an almost ohmic response, with currents of about 7-8 uA, effective transmittance near 0.98-1.00, and conductance of about (5.8-7.8) x 10^-5 S at 0.10 V, depending on direction. Vacancies strongly suppress transport, reducing transmittance to about 0.45-0.75 at 10% vacancy. Higher temperature accelerates hopping and partly restores transport, but cannot overcome severe connectivity loss. Magnetic fields further reduce transport, especially in disordered networks. The framework provides a unified computational scheme for realistic two-dimensional carbon materials and also yields diffusion coefficients and effective mobilities from carrier displacements and transit times.

cond-mat.mes-hall↗

arXiv2026

Endohedral Derivatives of the Recently Synthesized Two-Dimensional Fullerene Networks: Electronic and Optical Insights from First-Principles Calculations

The quasi-hexagonal phase of the two-dimensional fullerene network (qHPC$_{60}$), recently synthesized, has emerged as a stable carbon-based material with distinct structural and electronic features. In this work, we employed density functional theory (DFT) calculations to investigate the electronic and optical properties of its endohedral derivatives. The encapsulation of nitrogen, cerium, and strontium atoms inside fullerene cages was systematically analyzed at different concentrations. Our results show that encapsulation preserves the semiconducting backbone of pristine qHPC$_{60}$ while introducing localized electronic states that alter the bandgap and enable new transition channels. Nitrogen encapsulation produces intragap states with potential relevance for discrete optical emission, whereas cerium and strontium generate intraband states near the conduction edge. These modifications induce a red shift of the absorption onset into the visible spectrum, accompanied by enhanced refractive and absorptive responses. The robustness of the electronic structure under reduced concentrations indicates that the fully encapsulated limit adequately represents the system. Overall, the findings highlight impurity-endowed qHPC$_{60}$ as a promising platform for optoelectronic and light-harvesting applications.

cond-mat.mtrl-sci↗

arXiv2025

Sodium-Decorated Ennea-Graphene: A Novel 2D Carbon Allotrope for High-Capacity Hydrogen Storage

The development of safe, efficient, and reversible hydrogen storage materials is critical for advancing hydrogen-based energy technologies and achieving carbon-neutral goals. Ennea-Graphene, a new 2D carbon allotrope made of 4-, 5-, 6-, and mainly 9-membered carbon rings (nonagons), is introduced via Density Functional Theory (DFT) calculations. Phonon dispersion and ab initio molecular dynamics demonstrate that the monolayer is mechanically and dynamically stable at 300 K, as no imaginary modes are detected. The pristine system further exhibits metallic-like electronic behavior. The material exhibits high in-plane stiffness (Young modulus of 255 N/m). Sodium adsorption at the centers of the nonagonal rings is energetically favorable, with a binding energy of approximately -1.56 eV, leading to the formation of the Na@Ennea-Graphene complex. The calculated H2 adsorption energies range from -0.15 eV to -0.18 eV. The Na-decorated structure demonstrates excellent hydrogen storage performance, reversibly adsorbing up to four H2 molecules per Na atom (8.8 wt\% H2). This capacity surpasses the U.S. Department of Energy's 2025 target for onboard hydrogen storage materials. The adsorbed H2 remains molecular (H-H bond of 0.76~Å) and can be released under near-ambient conditions, as verified by 300 K ab initio molecular dynamics simulations. These findings position sodium-decorated Ennea-Graphene as a promising nanomaterial for next-generation hydrogen storage technologies.

physics.app-ph↗

arXiv2025

A Concise Review of Recently Synthesized 2D Carbon Allotropes: Amorphous Carbon, Graphynes, Biphenylene and Fullerene Networks

Two-dimensional (2D) carbon allotropes have received considerable attention due to their unique properties and potential applications in several fields, including electronics, catalysis, energy storage, and sensing. Following the experimental realization of graphene, numerous other 2D carbon structures have been proposed and, in some cases, successfully synthesized. This work presents a concise review of the recently experimentally realized 2D carbon allotropes, including graphynes, biphenylene-based networks, fullerene networks, and monolayer amorphous carbon. For each class, we discuss structural characteristics, theoretical predictions, and synthesis methods, with emphasis on the interplay between theory and experiment. We also highlight instances where experimental studies overlooked relevant theoretical contributions. Finally, we identify theoretically predicted structures that remain unexplored experimentally, suggesting opportunities for synthesis-driven investigations.

cond-mat.mtrl-sci↗

arXiv2025

Sodium-Decorated P-C3N: A Porous 2D Framework for High-Capacity and Reversible Hydrogen Storage

The development of reversible hydrogen storage materials has become crucial for enabling carbon-neutral energy systems. Based on this, the present work investigates the hydrogen storage on the sodium-decorated P-C$_3$N (Na@P-C$_3$N), a porous carbon nitride monolayer recently proposed as a stable semiconductor. First-principles calculations reveal that Na atoms preferentially adsorb with an adsorption energy of -4.48~eV, effectively suppressing clusterization effects. Upon decoration, the system becomes metallic, while \textit{ab initio} molecular dynamics simulations confirm the thermal stability of Na@P-C$_3$N at 300~K. Hydrogen adsorption on Na@P-C$_3$N occurs through weak physisorption, with energies ranging from -0.18 to -0.28~eV, and desorption temperatures between 231 and 357~K. The system can stably absorb 16 H$_2$ molecules per unit cell, corresponding to a gravimetric storage capacity of 9.88~wt\%, surpassing the U.S. Department of Energy target. These results demonstrate that Na@P-C$_3$N is a promising candidate for lightweight, stable, and reversible hydrogen storage.

cond-mat.mtrl-sci↗

arXiv2025

Alpha-, Beta-, and Gamma-TODD-G: Novel 2D Planar Carbon Allotropes

We present a comprehensive first-principles investigation of three novel two-dimensional carbon allotropes: alpha-, beta-, and gamma-TODD-Graphene (TODD-G), composed of 3-8-12-16, 3-8-12-16, and 3-4-8-12 interconnected carbon rings with sp/sp2 hybridization, respectively. Structural optimization, phonon spectra, and ab initio molecular dynamics simulations confirm their thermal and dynamical stability. All phases exhibit metallic electronic behavior, with distinct Dirac-like features and tilted Dirac cones that suggest anisotropic charge transport. Mechanical analysis reveals tunable anisotropy: alpha-TODD-G is strongly anisotropic, beta-TODD-G shows moderate anisotropy, and gamma-TODD-G displays an almost isotropic mechanical response. Optical spectra further differentiate the phases, with gamma-TODD-G showing strong absorption in the infrared region, while alpha- and beta-TODD-G mainly absorb in the visible and ultraviolet ranges.

cond-mat.mtrl-sci↗

arXiv2025

$β$-Irida-Graphene: A New 2D Carbon Allotrope for Sodium-Ion Battery Anodes

The quest for sustainable and efficient energy storage has driven the exploration of sodium-ion batteries (SIBs) as promising alternatives to lithium-ion systems. However, the larger ionic radius of sodium poses intrinsic challenges such as slow diffusion and structural strain in conventional electrode materials. As a contribution to addressing these limitations, the \b{eta}-Irida-graphene ($β$-IG) is herein introduced, a novel two-dimensional (2D) carbon allotrope derived from Irida-graphene, featuring a diverse polygonal lattice of 3-, 4-, 6-, 8-, and 9-membered carbon rings. Through density functional theory and ab initio molecular dynamics simulations, $β$-IG demonstrated remarkable thermal, dynamical, and mechanical stability, coupled with intrinsic conductive character and efficient sodium-ion mobility (energy barriers < 0.30 eV). Furthermore, the adsorption of sodium ions was energetically favorable, delivering an impressive predicted specific capacity of 554.5 mAh/g. The reported findings highlight $β$-IG as a good potential anode candidate for next-generation SIBs, offering high-rate performance and structural robustness, and expanding the functional design space for advanced carbon-based electrode materials.

cond-mat.mtrl-sci↗

arXiv2025

First-Principles and Machine Learning Investigation of the Structural and Optoelectronic Properties of Dodecaphenylyne: A Novel Carbon Allotrope

We report the computational discovery and characterization of Dodecaphenylyne (DP), a novel carbon allotrope with a distinctive geometric arrangement. DP structural, thermodynamic, mechanical, electronic, and optical properties were evaluated using density functional theory and a machine learning interatomic potential trained explicitly for this material. The formation energy of -7.98 eV/atom indicates high thermodynamic stability, further supported by the absence of imaginary phonon modes and the preservation of structural integrity up to 1000 K in ab initio molecular dynamics simulations. Mechanical analysis reveals high in-plane stiffness with directional dependence: Young's modulus values of 469.09 GPa and 600.41 GPa along the x and y directions, respectively. Electronic band structure and projected density of states analyses confirm the DP semiconducting character. Calculations of carrier mobility using the deformation potential theory reveal pronounced anisotropy, with maximum values reaching up to $30.6 \times 10^4$ cm$^2$/V$\cdot$s (electrons, e) and $8.4 \times 10^4$ cm$^2$/V$\cdot$s (holes, h), much higher than the observed for other 2D materials. DP also exhibits anisotropic optical absorption in the visible and ultraviolet spectrum, highlighting its potential for optoelectronic applications.

cond-mat.mtrl-sci↗

arXiv2025

Potassium Decoration on Graphenyldiene Monolayer for Advanced Reversible Hydrogen Storage

Potassium-decorated graphenyldiene (K@GPD) is investigated as a promising two-dimensional material for reversible hydrogen storage using first-principles density functional theory calculations. Potassium atoms bind strongly to the GPD monolayer, and ab initio molecular dynamics (AIMD) simulations confirm the thermal stability of the functionalized system at 300 K. Hydrogen adsorption energies range from -0.11 to -0.14 eV per H$_2$, denoting reversible storage. At full coverage (18 H$_2$ molecules), the system reaches a storage capacity of 8.82 wt\%, exceeding the U.S. DOE target. AIMD simulations reveal spontaneous H$_2$ desorption at ambient temperature, demonstrating excellent reversibility.

cond-mat.mtrl-sci↗

arXiv2025

Athos-Graphene: Computational Discovery of an Art-Inspired 2D Carbon Anode for Lithium-Ion Batteries

Two-dimensional (2D) carbon allotropes have attracted growing interest for their structural versatility and potential in energy storage and nanoelectronics. We propose Athos-Graphene (AG), a novel 2D carbon allotrope inspired by the geometric patterns of Brazilian artist Athos Bulcão. Designed using density functional theory, AG features a periodic structure with high thermodynamic and thermal stability, as evidenced by a low cohesive energy of -7.96 eV/atom, the absence of imaginary phonon modes, and robust performance in ab initio molecular dynamics simulations up to 1000 K. It exhibits anisotropic mechanical properties, with Young's modulus values of 585 GPa and 600 GPa along the x- and y-directions, and Poisson's ratios of 0.19 and 0.17, respectively. Electronic structure analyses confirm its metallic behavior, while optical studies reveal anisotropic absorption in the visible and UV regions. For lithium-ion storage, Athos-Graphene shows strong Li adsorption (-2.3 to -1.0 eV), a high theoretical capacity of 836.78 mAh/g, and a low average open-circuit voltage of 0.54 V. Lithium diffusion barriers are as low as 0.3 eV on the surface and 0.66 eV between layers, with a high diffusion coefficient greater than 6x10^-6 cm^2/s. These features highlight AG as a promising anode material for high-performance lithium-ion batteries.

cond-mat.mtrl-sci↗

arXiv2025

A Novel Graphyne-Like Carbon Allotrope: 2D Dewar-Anthracyne

Anthracyne (2DDA). 2DDA consists of chains of Dewar-anthracenes connected by acetylenic linkages. DFT-based simulations show that 2DDA is thermally stable and exhibits no imaginary phonon modes, confirming its dynamic stability. 2DDA is metallic with Dirac-like features near the Fermi level, dominated by C pz orbitals. It shows marked mechanical anisotropy, with Young's modulus of 176.24 N/m (x) and 31.51 N/m (y), shear modulus up to 69.14 N/m, and Poisson's ratio varying from 0.27 to 0.87. The material also exhibits strong anisotropic optical absorption in the visible and ultraviolet ranges. Raman and IR spectra reveal intense bands at 648 cm-1 (Raman) and 1292 cm-1 (Infrared). Nanoribbon structures derived from 2DDA exhibit diverse electronic behaviors, from metals up to bandgap values of up to 0.42 eV, depending on the edge-type terminations and width. These findings demonstrate the 2DDA potential for nanoelectronic and optoelectronic applications.

cond-mat.mtrl-sci↗

arXiv2025

Petal-Graphyne: A Novel 2D Carbon Allotrope for High-Performance Li and Na Ion Storage

Using density functional theory simulations, this study introduces Petal-Graphyne (PLG), a novel multi-ring metallic structure composed of 4-, 8-, 10-, and 16-membered rings. Its structural, electronic, and lithium/sodium storage properties were comprehensively investigated. PLG exhibits a high theoretical capacity of 1004 mAh/g for Li, Na, and mixed Li/Na ions, surpassing conventional graphite anodes. The material remains metallic, with multiple band crossings at the Fermi level. The optimal energy barriers for Li (0.28 eV) and Na (0.25 eV) on PLG and favorable diffusion coefficients in both monolayer and multilayer configurations are unveiled. The open circuit voltages are 0.47 V for Li, 0.51 V for Na, and 0.54 V for mixed-ion storage, suggesting stable electrochemical performance. These results highlight PLG as a promising candidate for next-generation lithium and sodium-ion batteries, combining high storage capacity and efficient ion transport.

cond-mat.mtrl-sci↗

arXiv2025

Computational Characterization of the Recently Synthesized Pristine and Porous 12-Atom-Wide Armchair Graphene Nanoribbon

Recently synthesized Porous 12-Atom-Wide Armchair Graphene Nanoribbons Nano Lett. 2024, 24, 10718-10723 exhibit tunable properties through periodic porosity, enabling precise control over their electronic, optical, thermal, and mechanical behavior. This work presents a comprehensive theoretical characterization of pristine and porous 12-AGNRs based on density functional theory (DFT) and molecular dynamics (MD) simulations. DFT calculations reveal substantial electronic modifications, including band gap widening and the emergence of localized states. Analyzed within the Bethe-Salpeter equation (BSE) framework, optical properties highlight strong excitonic effects and significant absorption shifts. Thermal transport simulations indicate a pronounced reduction in conductivity due to enhanced phonon scattering at nanopores. At the same time, MD-based mechanical analysis shows decreased stiffness and strength while maintaining structural integrity. Despite these modifications, porous 12-AGNRs remain mechanically and thermally stable. These findings establish porosity engineering as a powerful strategy for tailoring graphene nanoribbons' functional properties, reinforcing their potential for nanoelectronic, optoelectronic, and thermal management applications.

cond-mat.mtrl-sci↗

arXiv2025

Exploring Novel 2D Analogues of Goldene: Electronic, Mechanical, and Optical Properties of Silverene and Copperene

Two-dimensional (2D) materials have garnered significant attention due to their unique properties and broad application potential. Building on the success of goldene, a monolayer lattice of gold atoms, we explore its proposed silver and copper analogs, silverene and copperene, using density functional theory calculations. Our findings reveal that silverene and copperene are energetically stable, with formation energies of -2.3 eV/atom and -3.1 eV/atom, closely matching goldene's -2.9 eV/atom. Phonon dispersion and ab initio molecular dynamics simulations confirm their structural and dynamical stability at room temperature, showing no bond breaking or structural reconfiguration. Mechanical analyses indicate isotropy, with Young's moduli of 73 N/m, 44 N/m, and 59 N/m for goldene, silverene, and copperene, respectively, alongside Poisson's ratios of 0.46, 0.42, and 0.41. These results suggest comparable rigidity and deformation characteristics. Electronic band structure analysis highlights their metallic nature, with variations in the band profiles at negative energy levels. Despite their metallic character, these materials exhibit optical properties akin to semiconductors, pointing to potential applications in optoelectronics.

cond-mat.mtrl-sci↗

arXiv2024

Enhanced Elastocaloric Effects in γ-graphyne

The global emphasis on sustainable technologies has become a paramount concern for nations worldwide. Specifically, numerous sustainable methods are being explored as promising alternatives to the well-established vapor-compression technologies in cooling and heating devices. One such avenue gaining traction within the scientific community is the elastocaloric effect (eC). This phenomenon holds promise for efficient cooling and heating processes without causing environmental harm. Studies carried out at the nanoscale have demonstrated the efficiency of the eC, proving to be comparable to that of state-of-the-art macroscopic systems. In this study, we used classical molecular dynamics simulations to investigate the elastocaloric effect for γ-graphyne. Our analysis goes beyond obtaining changes in eC temperature and the coefficient of performance (COP) for two species of γ-graphyne nanoribbons (armchair and zigzag). We also explore their dependence on various conditions, including whether they are on deposited on a substrate or pre-strained. Our findings reveal a substantial enhancement in the elastocaloric effect for γ-graphyne nanoribbons when subjected to pre-strain, amplifying it by at least one order of magnitude. Under certain conditions, the change in the eC temperature and the COP of the structures reach expressive values as high as 224 K and 14, respectively. We discuss the implications of these results by examining the shape and behavior of the carbon-carbon bond lengths within the structures.

cond-mat.mes-hall↗

arXiv2023

Exploring the Elastic Properties and Fracture Patterns of Me-Graphene Monolayers and Nanotubes through Reactive Molecular Dynamics Simulations

Me-graphene (MeG) is a novel two-dimensional (2D) carbon allotrope. Due to its attractive electronic and structural properties, it is important to study the mechanical behavior of MeG in its monolayer and nanotube topologies. In this work, we conducted fully atomistic reactive molecular dynamics simulations using the Tersoff force field to investigate their mechanical properties and fracture patterns. Our results indicate that Young's modulus of MeG monolayers is about 414 GPa and in the range of 421-483 GPa for the nanotubes investigated here. MeG monolayers and MeGNTs directly undergo from elastic to complete fracture under critical strain without a plastic regime.

cond-mat.mtrl-sci↗

arXiv2023

Elastocaloric Effect in Graphene Kirigami

Kirigami, a traditional Japanese art of paper-cutting, has recently been explored for its elastocaloric effect (ECE) in kirigami-based materials (KMs), where applying strain induces temperature changes. In this study, we investigate the ECE in a nanoscale graphene kirigami (GK) monolayer, representing the thinnest possible KM, to better understand this phenomenon. Through molecular dynamics simulations, we analyze the temperature change and coefficient of performance (COP) of the nanoscale GK architecture. Our findings reveal that while GKs lack the intricate temperature changes observed in macroscopic KMs, they exhibit a substantial temperature change of approximately 9.32 K (23 times higher than that of macroscopic KMs, which is about 0.4K) for heating and -3.50 K for cooling. Additionally, they demonstrate reasonable COP values of approximately 1.57 and 0.62, respectively. It is noteworthy that the one-atom-thick graphene configuration prevents the occurrence of the complex temperature distribution observed in macroscopic KMs.

cond-mat.mtrl-sci↗

arXiv2023

On the Mechanical, Electronic, and Optical Properties of 8-16-4 Graphyne: A 2D Carbon Allotrope with Dirac Cones

Due to the success achieved by graphene, several 2D carbon-based allotropes were theoretically predicted and experimentally synthesized. We used density functional theory and reactive molecular dynamics simulations to investigate the mechanical, structural, electronic, and optical properties of 8-16-4 Graphyne. The results showed that this material exhibits good dynamical and thermal stabilities. Its formation energy and elastic moduli are -8.57 eV/atom and 262.37 GPa, respectively. This graphyne analogue is a semi-metal and presents two Dirac cones in its band structure. Moreover, it is transparent, and its intense optical activity is limited to the infrared region. Remarkably, the band structure of 8-16-4 Graphyne remains practically unchanged at even moderate strain regimes. As far as we know, this is the first 2D carbon allotrope to exhibit this behavior.

cond-mat.mtrl-sci↗