In situ synchrotron X-ray diffraction study of the formation of TaB 2 from the elements in a laser heated diamond anvil cell

In situ synchrotron X-ray diffraction was used to observe the reaction induced by laser heating of a mixture of tantalum and boron in a diamond anvil cell. Laser heating at pressures of 12 and 24 GPa resulted in the formation of TaB₂. The bulk modulus of TaB₂ (B₀ = 341(7) GPa) was determined from a fit of a second-order Birch-Murnaghan equation of state to the p-V data. Density functional theory based calculations complemented the experimental observations and were used to obtain the full tensor of elastic stiffness coefficients. The choice of the most appropriate exchange-correlation functional for the description of elastic properties is discussed.