arXiv subjects

Abrar Faiyad

Publications and source records attributed to Abrar Faiyad.

6 recordsLinked to original sources

arXiv2026

Machine Learning Interatomic Potentials Enable Molecular Dynamics Simulations of Doped MoS2

Dopants can tune the performance of MoS2 in various applications, but use of molecular dynamics simulations for doped MoS2 materials discovery is limited by the lack of multi-dopant interatomic potentials. Universal machine learning interatomic potentials (MLIPs) could be a solution, but the accuracy of these potentials must first be evaluated. Here, we evaluate the accuracy of a recently developed MLIP, META's Universal Model for Atoms (UMA), for 25 different MoS2 dopants spanning metals, non-metals, and transition metals in Mo substitution, S substitution, and intercalated positions by benchmarking the MLIP-predicted formation energy and the dopant-induced structural change against density functional theory calculations. The computational framework for MLIP validation and simulations are described in detail and the source code is made open source. The MLIP is then demonstrated by performing heating-cooling simulations of MoS2 supercells with all 25 dopants. These simulations capture complex phenomena including dopant clustering, MoS2 layer fracturing, interlayer diffusion, and chemical compound formation at orders-of-magnitude reduced computational cost compared to density functional theory. This work provides a computational workflow for application-oriented design of doped-MoS2, enabling high-throughput screening of dopant candidates and optimization of compositions for targeted tribological, electronic, and optoelectronic performance. Github Repo Link: https://github.com/AbrarFaiyad/Machine-Learning-Interatomic-Potential-UMA-Enables-MD-Simulations-of-MoS2-Doped

cond-mat.mtrl-sci↗

arXiv2026

Deriving effective electrode-ion interactions from free-energy profiles at electrochemical interfaces

Understanding ion adsorption at electrified metal-electrolyte interfaces is essential for accurate modeling of electrochemical systems. Here, we systematically investigate the free energy profiles of Na$^+$, Cl$^-$, and F$^-$ ions at the Au(111)-water interface using enhanced sampling molecular dynamics with both classical force fields and machine-learned interatomic potentials (MLIPs). Our classical metadynamics results reveal a strong dependence of predicted ion adsorption on the Lennard-Jones parameters, highlighting that -- without due care -- standard mixing rules can lead to qualitatively incorrect descriptions of ion-metal interactions. We present a systematic methodology for tuning the cross-term LJ parameters to control adsorption energetics in agreement with more accurate models. As a surrogate for an ab initio model, we employed the recently released Universal Models for Atoms (UMA) MLIP, which validates classical trends and displays strong specific adsorption for chloride, weak adsorption for fluoride, and no specific adsorption for sodium, in agreement with experimental and theoretical expectations. By integrating molecular-level adsorption free energies into continuum models of the electric double layer, we show that specific ion adsorption substantially alters the interfacial ion population, the potential of zero charge, and the differential capacitance of the system. Our results underscore the critical importance of force field parameterization and advanced interatomic potentials for the predictive modeling of ion-specific effects at electrified interfaces and provide a robust framework for bridging molecular simulations and continuum electrochemical models.

physics.chem-ph↗

arXiv2023

The Impact of Cooling Rate on the Tensile and Cyclic Stress-Strain Characteristics of Different Solder Alloys at Nanoscale

In recent years, lead-free solder alloys based on tin, silver, or copper have gained popularity over lead-based solder alloys due to their improved mechanical and electrical properties and their non-toxic nature. In our previous studies, we examined the stress-strain behavior of SAC305 under varying cooling rates. This study extends our investigation to various lead-free solder materials, including Sn, Sn-Ag, and SAC305, to compare their relative mechanical and cyclic properties. We employed molecular dynamics to model the atomistic behavior. Initially, the models were melted at a constant rate and then cooled at various rates, including 2.5 K/ps, 10 K/ps, 50 K/ps, and 100 K/ps. Additionally, exponential cooling was used to replicate real-world cooling scenarios.. We utilized a set of modified embedded atomic model (MEAM) interatomic potentials for the tensile test and cyclic loading. The tensile test has been conducted until fracture occurs at a constant strain rate. Furthermore, we investigated the cyclic loading behavior within a strain range of -10% to 10% for 10 cycles. The results indicated that cooling rates significantly influenced mechanical properties, with slower rates (2.5 K/ps and 10 K/ps) showing substantial differences, while the differences between higher rates (50 K/ps and 100 K/ps) were less pronounced. The ultimate strength, Young's modulus, modulus of resilience, and coefficient of thermal expansion exhibited a negative correlation with increasing cooling rates, while the modulus of toughness increased, indicating improved impact resistance. To assess energy dissipation during cyclic loading, we examined the hysteresis loop area and stress amplitude. After a certain number of cycles, the energy lost during each cycle reached a stable level.

cond-mat.mtrl-sci↗

arXiv2023

Atomistic study on cooling rate induced nanoindentation properties of Additively Manufactured Inconel-718

Inconel-718's compatibility with additive manufacturing (AM) has made it a center of attention for researchers. This paper focuses on how cooling rates affect the hardness of AM Inconel-718. To study the AM process, monocrystalline and polycrystalline Inconel-718 layers were added to a pristine substrate and equilibrated at 2000 K before being cooled to 300 K using cooling rates ranging from 5 K/ps to 100 K/ps, as well as an exponential cooling rate. The layers were then subjected to atomistic nanoindentation simulation to analyze the nanomechanical response, including hardness, dislocation density, microstructure, and surface imprints, at different cooling rates. Load-displacement (P-h) curves were plotted for each cooling rate. The findings of this study provide crucial insights into the effect of cooling rate on the nanoindentation-based response of additively manufactured Inconel-718. These insights can aid in the design of high-performance components for various applications

cond-mat.mtrl-sci↗

arXiv2021

MEAM parameterization for cyclic and tensile deformations of Gold-Silver core-shell systems

Gold-Silver (Au-Ag) core-shell nanostructures are gaining importance in stretchable electronics where high tensile and fatigue resistance is of paramount importance. This work proposes the parameterization of a modified embedded atomic model (MEAM) interatomic potential through density functional theory (DFT) calculations for investigating the role of dislocations and defect interaction governing the mechanical behavior of Au-Ag and Ag-Au Core-shell nanostructures under tensile and fatigue loading using molecular dynamics (MD) simulations. A comparative analysis between the Core-shell structures and their pristine counterparts is also conducted. Throughout this work, pseudo-potential and all-electron full potential DFT schemes are used for parameterizing MEAM by calculating cohesive energy, lattice parameter, and bulk modulus of pure Au, Ag and their alloy. Using the new force-field for MD simulations, the tensile behavior of pristine and core-shell nanowires is explored for temperatures between 300K to 600K. The fatigue properties of two pristine and two core-shell nanowires in a strain range of -15% to 15% for 10 cycles is also conducted. Our results suggest that Ag-Au Core-shell nanowire shows the best reversibility under fatigue loading among the structures examined. Moreover, Ag-Au exhibit the highest dislocation formation and complete annihilation of defects consistently. While, Au-Ag present improved fatigue properties than its pristine counterparts but have some residual defects leading to lower reversibility when compared to Ag-Au. For tensile loading, all four structures exhibited deterioration in strength with increasing temperature. Thermal softening is seen to be more prominent in Au-Ag core-shell nanowires compared to Ag-Au.

cond-mat.mtrl-sci↗

arXiv2020

Deformation mechanisms of Inconel-718 at nanoscale by molecular dynamics

Ni-based superalloy Inconel-718 is ubiquitous in metal 3D printing where high cooling rate and thermal gradient are present. These manufacturing conditions are conducive to high initial dislocation density and porosity or void in the material. This work proposes a molecular dynamics (MD) analysis method that can examine the role of dislocations, cooling rates, void, and their interactions governing the material properties and failure mechanism in Inconel-718 using Embedded Atom Method (EAM) potential. Three different structures: nanowire (NW), nanopillar, and nanoplate are used throughout this work. Initially, strain rates are varied from 10^8s^-1 to 10^10s^-1 keeping the NW diameter and temperature constant at 3.17 nm and 300K respectively. Compressive loading is applied to a 7.04 nm nanopillar by applying a constant strain rate of 109 s^-1 while temperature is varied from 100K to 700K. Different cooling rates ranging from 0.5x10^10 K/s to 1 x 10^14 K/s are applied to nanoplates (with and without a central void). The size of the central void is kept fixed at 2.12 nm. Increasing strain rates in tension not only results in strain hardening but also increase in dislocation density. Our computational method is successful to capture extensive sliding on {111} shear plane, which leads to significant necking of the alloy before fracture due to dislocation. The high cooling rates creating non-equilibrium structure leads to high strength and ductile behavior. On the other hand, the low cooling rate forming well defined crystalline structure causes low strength and brittle behavior. This brittle to ductile transition is observed solely due to cooling rate. Cooling rate may diminish the void by healing the structure during solidifications process. Subsequent mechanical properties by varying temperature and size are also presented in detail.

cond-mat.mtrl-sci↗