**Possible origin of the discrepancy in Peierls stresses of fcc metals:
First-principles simulations of dislocation mobility in aluminum**

I Shin and EA Carter, PHYSICAL REVIEW B, 88, 064106 (2013).

DOI: 10.1103/PhysRevB.88.064106

Dislocation motion governs the strength and ductility of metals, and the
Peierls stress (sigma(p)) quantifies dislocation mobility. sigma(p)
measurements carry substantial uncertainty in face-centered cubic (fcc)
metals, and sigma(p) values can differ by up to two orders of magnitude.
We perform first-principles simulations based on orbital-free density
functional theory (OFDFT) to calculate the most accurate currently
possible sigma(p) for the motion of 1/2 < 110 >*111* dislocations in fcc
Al. We predict the sigma(p)s of screw and edge dislocations (dissociated
in their equilibrium state) to be 1.9 x 10(-4)G and 4.9 x 10(-5)G,
respectively (G is the shear modulus). These values fall within the
range of measurements from mechanical deformation tests
(10(-4)-10(-5)G). OFDFT also finds a new metastable structure for a
screw dislocation not seen in earlier simulations, in which a
dislocation core on the glide plane does not dissociate into partials.
The corresponding sigma(p) for this undissociated dislocation is
predicted to be 1.1 x 10(-2)G, which agrees with typical Bordoni peak
measurements (10(-2)-10(-3)G). The calculated sigma(p)s for dissociated
and undissociated screw dislocations differ by two orders of magnitude.
The presence of undissociated, as well as dissociated, screw
dislocations may resolve the decades-long mystery in fcc metals
regarding the two orders of magnitude discrepancy in sigma(p)
measurements.

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