arXiv subjects

Mohammad Jane Alam Khan

Publications and source records attributed to Mohammad Jane Alam Khan.

3 recordsLinked to original sources

arXiv2026

Peripheral Nitrogen Topology as a Defect-Chemical Switch for Electronic and Magnetic States in Graphene: A First-Principles Study of Pyridinic, Pyridazinic, Pyrrolic, and Pyrazolic Configurations

Defect and heteroatom engineering offer powerful routes for tuning the electronic and magnetic properties of graphene, yet the role of specific peripheral nitrogen topologies around graphene voids remains insufficiently understood. Here, spin-polarized first-principles calculations were performed to investigate how four heterocyclic -- like peripheral nitrogen configurations -- pyridinic, pyridazinic, pyrrolic, and pyrazolic modify the structural stability, charge redistribution, electronic structure, and magnetic response of graphene containing a central void. Among the four peripheral N configurations, the pyridinic N provides the most favorable structural-energetic balance among the investigated motifs. Bond-length analysis reveals that nitrogen topology strongly controls local lattice reconstruction. Charge-density, charge-density-difference, and Bader analyses demonstrate that the peripheral N atoms act as electron-accumulating centers and reshape the local electronic environment around the vacancy rim. Spin-resolved band structures show that pyridinic, pyridazinic, and pyrrolic configurations retain metallic or near-metallic defect-state character, whereas pyrazolic graphene opens a narrow band gap. Magnetic analysis further reveals that pyrazolic graphene is spin-compensated, with zero net magnetization, unlike the other systems, which possess finite spin-polarized moments. Spin-density and SPDOS analyses indicate that the magnetism originates from N-modulated vacancy-edge states involving both N 2p and neighboring C 2p orbitals. These findings establish peripheral nitrogen topology not merely as a structural defect descriptor, but as a deterministic defect-chemical switch, offering a metal-free route to pattern active spintronic and semiconducting domains directly into the graphene lattice through controlled vacancy-edge nitrogen coordination.

cond-mat.mtrl-sci↗

arXiv2025

Impact of Nitrogen Atom Clusters and Vacancy Defects on Graphene: A Molecular Dynamics Investigation

Graphene's exceptional mechanical properties are crucial for its integration into advanced technological applications. However, real-world synthesis and functionalization processes introduce structural modifications that can compromise its mechanical integrity. Nitrogen doping, while beneficial for electronic property tuning, often results in atomic clustering rather than uniform distribution, while concurrent vacancy defect formation represents another common structural alteration during processing. This study systematically investigates the comparative effects of nitrogen atom clusters and equivalent sized vacancy defects on the mechanical behavior of graphene sheets through molecular dynamics simulations. The Nitrogen clustering significantly degraded mechanical performance almost similarly to random doping. In comparison, systems with equivalent-sized vacancy defects showed higher stiffness and lower ductility than those with clusters. The study revealed distinct failure mechanisms between doped and defective configurations, with nitrogen clusters showing modified crack propagation patterns while vacancies acted as pronounced stress concentrators, leading to premature failure. However, this study also showed that defect morphology critically influences mechanical properties. These findings provide important insights for optimizing graphene synthesis and processing protocols, highlighting the differential mechanical risks associated with dopant clustering versus vacancy formation. The results inform defect-tolerant design strategies for graphene-based nanoelectronics, composites, and sensors, where mechanical reliability is paramount for device performance and longevity.

cond-mat.mtrl-sci↗

arXiv2024

A Molecular Dynamics Study of Mechanical Properties of Vertically Stacked Silicene/MoS2 van der Waals Heterostructure

Silicene is an intriguing silicon allotrope with a honeycomb lattice structure similar to graphene with slightly buckled geometry. Molybdenum disulfide (MoS2), on the other hand, is a significant 2D transition metal dichalcogenide that has demonstrated promise in a variety of applications. Van der Waals heterostructures, which are created by stacking distinct 2D crystals on top of each other, are becoming increasingly important due to their unique optoelectronic and electromechanical properties. Using molecular dynamics simulations, the mechanical characteristics of vertically stacked Silicene/MoS2 van der Waals heterostructures are examined in this study. The response and structural stability of the heterostructures at various loading orientations and temperatures are given particular attention. The research findings highlight that the fracture strength of the Silicene/MoS2 heterostructure decreases by 40% in both armchair and zigzag orientations when the temperature is raised from 100K to 600K. Furthermore, a linear decrease in Young's modulus is observed as temperature rises. It is noteworthy that the Rule of Mixture (ROM) predictions for Young's Moduli are observed to be marginally lower than the simulation results. The analyses reveal that the silicene layer fractures first under both loading directions shows crack propagation at +-60°in the armchair and predominantly perpendicular in zigzag, followed by subsequent MoS2 layer failure. The study also shows that the MoS2 layer largely determines the elastic properties of the heterostructure, whereas the silicene layer primarily dictates the failure of the heterostructure. These findings offer an in-depth understanding of the mechanical properties of Silicene/MoS2 heterostructures, with significant implications for their use in cutting-edge nanoelectronics and nanomechanical systems.

cond-mat.mtrl-sci↗