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Efficient and accurate determination of lattice-vacancy diffusion coefficients via non equilibrium ab initio molecular dynamics

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Alling,  Björn
Adaptive Structural Materials (Simulation), Computational Materials Design, Max-Planck-Institut für Eisenforschung GmbH, Max Planck Society;
Department of Physics, Chemistry and Biology (IFM), Thin Film Physics Division, Linköping University, Linköping, Sweden;

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Citation

Sangiovanni, D. G., Hellman, O., Alling, B., & Abrikosov, I. A. (2016). Efficient and accurate determination of lattice-vacancy diffusion coefficients via non equilibrium ab initio molecular dynamics. Physical Review B, 93(9): 094305. doi:10.1103/PhysRevB.93.094305.


Cite as: http://hdl.handle.net/21.11116/0000-0001-B854-1
Abstract
We revisit the color-diffusion algorithm [Aeberhard, Phys. Rev. Lett. 108, 095901 (2012)10.1103/PhysRevLett.108.095901] in non equilibrium ab initio molecular dynamics (NE-AIMD) and propose a simple efficient approach for the estimation of monovacancy jump rates in crystalline solids at temperatures well below melting. Color-diffusion applied to monovacancy migration entails that one lattice atom (colored atom) is accelerated toward the neighboring defect site by an external constant force F. Considering bcc molybdenum between 1000 and 2800 K as a model system, NE-AIMD results show that the colored-atom jump rate kNE increases exponentially with the force intensity F, up to F values far beyond the linear-fitting regime employed previously. Using a simple model, we derive an analytical expression which reproduces the observed kNE(F) dependence on F. Equilibrium rates extrapolated by NE-AIMD results are in excellent agreement with those of unconstrained dynamics. The gain in computational efficiency achieved with our approach increases rapidly with decreasing temperatures and reaches a factor of 4 orders of magnitude at the lowest temperature considered in the present study. © 2016 American Physical Society.