We extend the equation of state and phase stability of body-centered cubic (bcc) antimony (Sb) into the multimegabar regime using both first-principles calculations up to 436 GPa and experimental synchrotron x-ray diffraction in the diamond-anvil cell up to 258(6) GPa using Ne as a soft pressure-transmitting medium. We observe the complete sequence of pressure-induced phase transitions from Sb's A7 rhombohedral phase through the intermediate pressure incommensurate structures, including evidence for Sb-IV, and identify the onset of the bcc phase between 28.9(5) and 30.3(6) GPa. The high-pressure volumetric response of the bcc phase was fit to a third-order Vinet equation of state with parameters of $V_0=26.28\left(32\right){\AA }^3/\mathrm{atom}, K_0=66.50\left(47\right)\mathrm{GPa}$, and $K^{\prime }=4.97\left(2\right)$. Density-functional theory confirms the stability and characterizes the elastic properties of bcc Sb up to 436 GPa. A Comparison with bcc As and Bi highlights the systematic trends in compressibility and electronic structure across these group-15 elements.

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• Elastic modulus
• Equations of state
• High-pressure studies
• Pressure effects
• Structural phase transition
• Metalloids
• Metals
• Density functional theory
• Pressure techniques
• X-ray diffraction