Compression and Shear of Tantalum to 64 GPa

It has been reported that the $\beta $-phase (body-centered-cubic) of tantalum (Ta) is stable to pressures over mega-bar under hydrostatic compression.[1] However, the shock compression clearly indicates its transformation to the $\omega $-phase (hexagonal) at 45 GPa.[2] Theoretical work suggests that the shear might have played an important role in inducing this phase transformation.[3] Here we report our experimental results on the effects of pressure and shear by use of a rotational diamond anvil cell and the synchrotron X-ray diffraction. The results indicate that under extensive shear and pressures over 60 GPa, Ta remains stable in the $\beta $ phase. \\[4pt] [1] H. Cynn and C.-S. Yoo, ``Phy. Rev. B'' \textbf{59}, 8526 (1999)\\[0pt] [2] L. M. Hsiung and D. H. Lassila, ``Scr. Mater.'' \textbf{38}, 1371 (1998)\\[0pt] [3] D. Mukherjee, K. D. Joshi, S. C. Gupta, ``J. Phys. Conf. Ser.'' 377, 012072 (2012)