Quantifying Free-volume Topology in Atomistic Structures Through a Combination of Voxelization and Graph Theory

TL;DR

This paper presents a novel, efficient computational method combining voxelization and graph theory to identify and analyze free volume in atomistic structures across various materials and scales.

Contribution

It introduces a new three-stage workflow that converts free volume into planar graphs for characterization, applicable to diverse material systems and defect types.

Findings

Accurately classifies free volumes in crystal phases

Characterizes free volume defects in metals and alloys

Detects complex surface defects during epitaxial growth

Abstract

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) characterization of free volume defects in metals/alloys, and (3) autonomous detection and classification of complex surface defects during epitaxial growth simulations. 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.