Flexible Ab initio boundary conditions: simulating isolated dislocations in bcc Mo and Ta

Area of Science:

• Materials Science
• Condensed Matter Physics
• Computational Materials Science

Background:

• Dislocations are fundamental crystal defects influencing material properties.
• Understanding dislocation core structure and mobility is crucial for predicting mechanical behavior.
• Previous atomistic studies of <111> screw dislocations in bcc metals have limitations.

Purpose of the Study:

• To perform the first ab initio density-functional theory (DFT) study on <111> screw dislocations in bcc Mo and Ta.
• To investigate the strain field and Peierls stress of these dislocations.
• To accurately model the interplay between local and long-range elastic fields.

Main Methods:

• Utilizing ab initio density-functional theory (DFT) for electronic structure calculations.
• Employing a flexible boundary condition method to couple local and long-range elastic fields.
• Performing mesoscopic atomistic calculations focused on the dislocation core region.

Main Results:

• The predicted equilibrium core structure for Mo differs significantly from previous atomistic results.
• Significant non-Schmid behavior was observed in the Peierls stress for both Mo and Ta.
• The flexible boundary condition method effectively reduced computational complexity.

Conclusions:

• Ab initio DFT provides accurate insights into dislocation core structures and Peierls stress in bcc metals.
• The findings highlight the importance of accurate core modeling for understanding plastic deformation.
• The study establishes a robust computational framework for future dislocation studies in refractory metals.