Chromium (Cr) is one of the few transition metals whose body-centered cubic (bcc) structure remains stable over a wide pressure range, but its high-temperature stability and melting behavior at terapascal pressures are still elusive. Here, we use large-scale molecular dynamics simulations based on machine-learning interatomic potentials (MLIPs) to investigate the phase stability and melting of Cr at pressures up to 2 TPa. Gibbs free energies calculation and direct transformation simulations place the bcc-hcp boundary at 1393 GPa at 0 K and in the 1.4–2.0 TPa range at finite temperature. The melting temperature of Cr rises from 2135 K at ambient pressure to $12925\pm 25\mathrm{K}$ at 2 TPa. Above $\sim 50\mathrm{GPa}$ and at temperatures approaching melting, bcc-Cr enters a dynamic regime in which atoms undergo collective jumps while the bcc lattice remains intact, which closely resembles the behaviors that have been reported for other bcc metals, such as Fe under Earth's inner-core conditions and Ti near its ambient-pressure melting point. Finite-temperature phonon calculations reveal pronounced softening of the transverse acoustic branch along the Γ-N direction with increasing temperature, together with the defect-assisted fast diffusion along the $\langle 111\rangle$ direction, provide the microscopic origin of the cooperative displacements. These results identify Cr as a useful high-pressure bcc system for examining the connection between anharmonic lattice dynamics, shear softening, and cooperative atomic transport under extreme compression.

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• Diffusion
• High-pressure studies
• Liquid-solid phase transition
• Solid-solid transformations
• Elemental metals
• Density functional calculations
• Molecular dynamics