**Free energy of grain boundary phases: Atomistic calculations for Sigma
5(310) 001 grain boundary in Cu**

R Freitas and RE Rudd and M Asta and T Frolov, PHYSICAL REVIEW MATERIALS, 2, 093603 (2018).

DOI: 10.1103/PhysRevMaterials.2.093603

Atomistic simulations are employed to demonstrate the existence of a
well-defined thermodynamic phase transformation between grain boundary
(GB) phases with different atomic structures. The free energy of
different interface structures for an embedded-atom-method model of the
Sigma 5(310)**001** symmetric tilt boundary in elemental Cu is computed
using the nonequilibrium Frenkel-Ladd thermodynamic integration method
through molecular dynamics simulations. It is shown that the free-energy
curves predict a temperature-induced first-order interfacial phase
transition in the GB structure in agreement with computational studies
of the same model system. Moreover, the role of vibrational entropy in
the stabilization of the high-temperature GB phase is clarified. The
calculated results are able to determine the GB phase stability at
homologous temperatures less than 0.5, a temperature range particularly
important given the limitation of the methods available hitherto in
modeling GB phase transitions at low temperatures. The calculation of GB
free energies complements currently available 0 K GB structure search
methods, making feasible the characterization of GB phase diagrams.

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