Quasiaperiodic grain boundary phases of E5 tilt grain boundaries in refractory metals

EZ Chen and T Frolov, PHYSICAL REVIEW B, 112, L060101 (2025).

DOI: 10.1103/vsgc-gkdx

We report ground-state structures and phase transitions in E5001 tilt grain boundaries (GBs) in bodycentered-cubic (bcc) refractory metals Nb, Ta, Mo, and W. E5 tilt GBs have been extensively investigated over the past several decades, with their ground-state structure-composed of kite-shaped structural units-previously thought to be well understood. By performing a rigorous GB structure search that optimizes the number of atoms in the boundary core, we predict different quasiaperiodic "split kite" phases analogous to those previously found in GBs in face- centered-cubic metals. Our results suggest that complex aperiodic phases of GBs appear to be a general phenomenon, as validated through density functional theory calculations. Moreover, the atoms in the split kite phase demonstrate distinct collective diffusion dynamics. Phase-contrast image simulations of split kites show better agreement with experimental observations, offering an alternative explanation for previous microscopy results and motivating future atomically resolved imaging of the GB structure.

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