Molecular dynamics simulations of the defect evolution in tungsten on successive collision cascades
Abstract
Molecular dynamics (MD) simulations of successive collision cascades within the same simulation domain were performed using two different inter-atomic potentials (IAP) in tungsten, one EAM based and the other a `quantum accurate' machine learning potential, SNAP. The micro-structural changes are analyzed as a function of displacements per atom (dpa) for primary knock-on atom (PKA) energies of 20 keV and 50 keV, reaching up-to irradiation dose of 0.1 and 0.2 dpa, respectively. Five sample simulations are carried out for each case for observing stochastic differences in the evolution of damage. A detailed defect analysis is carried out to observe changes in different parameters such as the number of surface defects, defect density, defect morphology and size distribution etc., as a function of dpa. We explore the properties that are sensitive to the IAP used and those that are sensitive to the PKA energy and note their similarities with experimental results at various dpa values. The SNAP potential shows better agreement with the experiments for swelling and number of surface defects. However, it also predicts presence of high number of small sessile defects which may have definite affect on the processes of microstructural evolution and material properties.
AI-Generated Overview
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Research Focus: The study investigates defect evolution in tungsten subjected to successive collision cascades through molecular dynamics simulations, utilizing two different inter-atomic potentials.
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Methodology: Molecular dynamics simulations were performed for primary knock-on atom (PKA) energies of 20 keV and 50 keV, analyzing micro-structural changes as a function of displacements per atom (dpa) and using two inter-atomic potentials: EAM (Embedded Atom Method) and a quantum-accurate machine learning potential (SNAP).
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Results: The SNAP potential demonstrated better correlation with experimental results regarding swelling and surface defects, while both potentials indicated differences in defect morphology, particularly in the formation of smaller, stable defects and larger dislocation loops.
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Key Contribution(s): The research highlights the impact of different inter-atomic potentials on the microstructural evolution of tungsten under ion irradiation, emphasizing that surface defects correlate well with experimental data regardless of PKA energy or potential used.
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Significance: This work provides insights into the understanding of radiation-induced damage mechanisms in tungsten, which is critical for materials used in nuclear applications and for designing better materials.
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Broader Applications: Findings may inform the development and optimization of materials for radiation resistance in nuclear reactors and aerospace applications, as well as improve models predicting material behavior under irradiation.