Petr Grigorev

selected publications

1. 

   Calculation of dislocation binding to helium-vacancy defects in tungsten using hybrid ab initio-machine learning methods

   Petr Grigorev, Alexandra M. Goryaeva, Mihai-Cosmin Marinica, James R. Kermode, and Thomas D. Swinburne

   Acta Materialia 247 p. 118734 (Feb 2023)

   Abstract HTML PDF Code

   Calculations of dislocation-defect interactions are essential to model metallic strength, but the required system sizes are at or beyond ab initio limits. Current estimates thus have extrapolation or finite size errors that are very challenging to quantify. Hybrid methods offer a solution, embedding small ab initio simulations in an empirical medium. However, current implementations can only match mild elastic deformations at the ab initio boundary. We describe a robust method to employ linear-in-descriptor machine learning potentials as a highly flexible embedding medium, precisely matching dislocation migration pathways whilst keeping at least the elastic properties constant. This advanced coupling allows dislocations to cross the ab initio boundary in fully three dimensional defect geometries. Investigating helium and vacancy segregation to edge and screw dislocations in tungsten, we find long-range relaxations qualitatively change impurity-induced core reconstructions compared to those in short periodic supercells, even when multiple helium atoms are present. We also show that helium-vacancy complexes, considered to be the dominant configuration at low temperatures, have only a very weak binding to screw dislocations. These results are discussed in the context of recent experimental and theoretical studies. More generally, our approach opens a vast range of mechanisms to ab initio investigation and provides new reference data to both validate and improve interatomic potentials.

2. PhysRev

   Hybrid quantum/classical study of hydrogen-decorated screw dislocations in tungsten: Ultrafast pipe diffusion, core reconstruction, and effects on glide mechanism

   Petr Grigorev, Thomas D. Swinburne, and James R. Kermode

   Phys. Rev. Materials 4 p. 023601 (Feb 2020)

   Abstract HTML PDF

   The interaction of hydrogen (H) with dislocations in tungsten (W) must be understood in order to model the mechanical response of future plasma-facing materials for fusion applications. Here, hybrid quantum mechanics/molecular mechanics (QM/MM) simulations are employed to study the ⟨111⟩ screw dislocation glide in W in the presence of H, using the virtual work principle to obtain energy barriers for dislocation glide, H segregation, and pipe diffusion. We provide a convincing validation of the QM/MM approach against full DFT energy-based methods. This is possible because the compact core and relatively weak elastic fields of ⟨111⟩ screw dislocations allow them to be contained in periodic DFT supercells. We also show that H segregation stabilizes the split-core structure while leaving the Peierls barrier almost unchanged. Furthermore, we find an energy barrier of less than 0.05 eV for pipe diffusion of H along dislocation cores. Our quantum-accurate calculations provide important reference data for the construction of larger-scale material models.

3. PhD Thesis

   Assessment of retention of plasma components in tungsten under high flux plasma exposure: multi-scale modelling approach

   Petr Grigorev

   PhD Thesis Ghent University, Faculty of Engineering and Architecture/Universidad Complutnese de Madrid, Facultad de Ciencias Fisicas (Apr 2017)

   Abstract HTML PDF

   The results of my work described in this thesis are roughly divided in three parts. (1) Analysis of ab initio data and development of the model of dislocation mediated H retention in tungsten; (2) Development of an interatomic potential for W-H-He system and performing a large number of Molecular Dynamics (MD) simulations; (3) Implementation of the model in a Rate Theory simulation tool and its validation by comparison with experimental results; This pdf file also contains the pdf versions of the most of the articles listed below. Frankly speaking I am not allowed to share those here, but lets keep it between us.