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Updated: Jun 3, 2026
08:55
Methods of Ex Situ and In Situ Investigations of Structural Transformations: The Case of Crystallization of Metallic Glasses
Published on: June 7, 2018
Magnetic phase transformations of face-centered cubic and hexagonal close-packed Co at zero Kelvin.
James E Saal1, ShunLi Shang, Yi Wang
1Department of Materials Science and Engineering, The Pennsylvania State University, University Park, PA 16802, USA. jes531@psu.edu
Summary
First-principles calculations reveal pressure-induced magnetic phase transformations in cobalt (Co) at 0 K. These findings align with experimental data, predicting key transformation pressures for FCC and HCP cobalt structures.
Area of Science:
- Condensed Matter Physics
- Materials Science
- Computational Materials Science
Background:
- Understanding pressure-induced phase transformations in magnetic materials like cobalt (Co) is crucial for materials science.
- Previous studies have explored cobalt's phase diagram, but detailed 0 K magnetic transformations under pressure require further investigation.
- First-principles calculations offer a robust method for predicting material behavior under extreme conditions.
Purpose of the Study:
- To investigate the 0 K pressure-induced magnetic phase transformations of face-centered cubic (FCC) and hexagonal close packed (HCP) cobalt.
- To develop a physically meaningful equation of state fitting scheme for energy-volume data involving magnetic transitions.
- To compare theoretical predictions with experimental phase equilibria and extrapolate existing pressure-temperature phase diagrams to 0 K.
Main Methods:
- Utilized first-principles calculations to simulate cobalt's behavior under varying pressure.
- Developed and applied a novel fitting scheme to energy-volume data, focusing on regions with linearly decreasing magnetic moments.
- Analyzed magnetic and structural phase transitions, determining their order and associated pressure thresholds.
Main Results:
- Identified ferromagnetic to nonmagnetic transitions at 77 GPa for FCC Co (first order) and 123 GPa for HCP Co (second order).
- Predicted an HCP/FCC structure transformation at 99 GPa and a novel transformation at negative pressure (-31 GPa).
- The proposed fitting scheme provides physically meaningful equations of state for metastable volumes.
Conclusions:
- The calculated 0 K magnetic and structural phase transitions for FCC and HCP cobalt are consistent with experimental phase diagram extrapolations.
- The study provides precise pressure values for key transformations, enhancing the understanding of cobalt's phase behavior.
- The developed fitting methodology offers a reliable approach for analyzing phase transitions in first-principles calculations.
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