Structural phase transitions of a 3d transition element, titanium, have been investigated at pressures up to 220 GPa at room temperature using a monochromatic synchrotron x-ray diffraction technique. At 140 GPa, the hexagonal $\left(\omega \right)$ phase was transformed into an orthorhombic $\left(\delta \right)$ phase with a distorted bcc structure via an intermediate $\left(\gamma \right)$ phase, which has recently been proposed by Vohra and Spencer [Phys. Rev. Lett. 86, 3068 (2001)]. Both the δ and the γ phases had a unique zigzag-chain-like structure, which resulted from an orthorhombic distortion. The δ-γ transition could be explained as a rearrangement of the packing between the zigzag chains.

• Received 7 June 2001

DOI:https://doi.org/10.1103/PhysRevLett.87.275503