The equation of state of tantalum to 433 GPa

Abstract

The volume compression of body-centered cubic tantalum has been measured to 433 GPa in the standard bevel and toroidal diamond anvil cell (DAC) using synchrotron-based angle-dispersive powder x-ray diffraction. Six experiments were carried out achieving a maximum pressure of 433(6) GPa. Pressures were estimated using an equation of state (EoS) of Cu or Bi for all experiments. We additionally calculated the elastic constants of Ta and Bi and used our previously calculated values for Cu to inform the stress state of the sample and an EoS of Ta for comparison to our experimental data. Our experimental pressure–volume data for Ta was fit with a fourth-order Vinet EoS, resulting in parameters K0 = 192(5) GPa, η  = 6.4(6), β = −35(5), and Ψ  = 141(13). This Ta EoS is consistent within uncertainty with the ultrasonically derived ambient isothermal bulk modulus, with existing DAC data up to 100 GPa, and with Ta ramp EoS measurements that exceed the pressures of the current study.