Ab initio and finite-temperature molecular dynamics studies of lattice resistance in tantalum

TL;DR

This study uses ab initio and finite-temperature molecular dynamics to investigate the lattice resistance in tantalum, revealing a higher zero-temperature Peierls stress than previously estimated and suggesting other mechanisms influence low-temperature slip.

Contribution

First ab initio calculation of zero-temperature Peierls stress in tantalum using periodic boundary conditions, and analysis of temperature dependence of lattice resistance.

Findings

Ab initio Peierls stress is over five times larger than experimental extrapolations.

Common extrapolation techniques underestimate zero-temperature Peierls stress by 10-20%.

Other mechanisms besides Peierls stress may influence low-temperature slip.

Abstract

This manuscript explores the apparent discrepancy between experimental data and theoretical calculations of the lattice resistance of bcc tantalum. We present the first results for the temperature dependence of the Peierls stress in this system and the first ab initio calculation of the zero-temperature Peierls stress to employ periodic boundary conditions, which are those best suited to the study of metallic systems at the electron-structure level. Our ab initio value for the Peierls stress is over five times larger than current extrapolations of experimental lattice resistance to zero-temperature. Although we do find that the common techniques for such extrapolation indeed tend to underestimate the zero-temperature limit, the amount of the underestimation which we observe is only 10-20%, leaving open the possibility that mechanisms other than the simple Peierls stress are important in controlling the process of low temperature slip.