Superionic-like diffusion in an elemental crystal: bcc Titanium

Abstract

Recent theoretical investigations [Belonoshko et al. Nature Geoscience 10, 312 (2017)] revealed occurrence of concerted migration of several atoms in bcc Fe at inner-core temperatures and pressures. Here, we combine first-principles and semi-empirical atomistic simulations to show that a diffusion mechanism analogous to the one predicted for bcc iron at extreme conditions is also operative and of relevance for the high-temperature bcc phase of pure Ti at ambient pressure. The mechanism entails a rapid collective movement of numerous (from two to dozens) neighbors along tangled closed-loop paths in defect-free crystal regions. We argue that this phenomenon closely resembles the diffusion behavior of superionics and liquid metals. Furthermore, we suggest that concerted migration is the atomistic manifestation of vanishingly small w-mode phonon frequencies previously detected via neutron scattering and the mechanism underlying anomalously large and markedly non-Arrhenius self-diffusivities characteristic of bcc Ti.

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Cited by in corpus (7)

• Elinvar effect in $\beta -$Ti simulated by on-the-fly trained moment tensor potential
• Defects from phonons: Atomic transport by concerted motion in simple crystalline metals
• Phonon-assisted diffusion in bcc phase of titanium and zirconium from first-principles
• Vibrational entropy of crystalline solids from covariance of atomic displacements
• Phase stability of Fe from first-principles: atomistic spin dynamics coupled with ab initio molecular dynamics simulations and thermodynamic integration
• Understanding the role of anharmonic phonons in diffusion of bcc metal
• Non-Linear Arrhenius Behavior of Self-Diffusion in $\beta$-Ti and Mo