Institute of Physics of Materials AS CR, v. v. i. > Projects > Calculation of the Peierls barrier in bcc metals and its dependence on stress
Calculation of the Peierls barrier in bcc metals and its dependence on stress
| Investigator | doc. Ing. Roman Gröger, Ph.D. |
| Number of Project | P204/10/0255 |
| Agency | Grantová agentura České republiky |
| Duration | 2009-12-31 - 2012-12-30 |
Anotace |
| Plastic deformation of bcc metals is governed by motion of 1/2<111> screw dislocations that possess a high lattice fiction (Peierls) stress. At finite temperatures and strain rates, the dislocation moves by overcoming the Peierls barrier that is a crucial ingredient of thermodynamic description of the dislocation glide. However, atomistic simulations provide only the maximum slope of the Peierls barrier and, therefore, its shape is generally unknown. In this project, we will develop a novel computational method that utilizes the Nudged Elastic Band method to calculate the entire shape of the Peierls barrier and its variation under stress. The interactions between atoms are described by the state-of-the-art Bond Order Potentials that capture the mixed metallic and covalent character of bonds in bcc transition metals. The main advantage of our model, that distinguishes it from other methods, is that we calculate directly the position of the dislocation in the perpendicular {111} plane. This allows for both a self-consistent use of boundary conditions along the transition path of the dislocation and an unambiguous identification of the positions of the dislocation. This work forms a basis for the development of physically justified macroscopic flow criteria for bcc metals. |
