Quantifying the atomistic free-volume morphology of materials with graph theory

• Published in: Computational materials science Vol. 213
• Main Authors: Chapman, James, Goldman, Nir
• Format: Journal Article
• Language: English
• Published: United States Elsevier 06.07.2022
• Subjects: Atomistic simulations; CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; Defect characterization; Free volume defects; Graph theory; MATERIALS SCIENCE; Molecular dynamics; Voids
• ISSN: 0927-0256; 1879-0801

Here, we introduce a new computational methodology for the identification and characterization of free volume within/around atomistic configurations. This scheme employs a three-stage workflow, by which spheres are iteratively grown inside of voxels, and ultimately converted to planar graphs, which are then characterized via a graph-based order parameter. Our approach is computationally efficient, physically intuitive, and universally transferable to any material system. Validation of our methodology is performed on several sets of materials problems: (1) classification of unique free volumes in various crystal phases, (2) autonomous detection and classification of complex surface defects during epitaxial growth simulations, (3) characterization of free volume defects in metals/alloys, and (4) quantification of the spatio-temporal behavior of nano-scale free volume morphologies as a function of both temperature and free-volume size. Our method accurately identifies and characterizes unique free volumes over a multitude of systems and length scales, indicating its potential for future use in understanding the relationship between free volume morphology and material properties under both static and dynamic conditions.