XRD, TDPAC and LAPW study of Hf¹⁰B₂ under high pressure

The crystallographic structure and electronic properties of Hf ¹⁰B₂ were studied as a function of pressure by combining X-ray diffraction measurements with full potential linearized augmented plane wave (LAPW) calculations. No phase transition was observed up to a pressure of 30.8 GPa, with a total volume contraction of V/V ₀ = 0.85 and a bulk modulus value of B ₀ = 232 ±13 GPa. The calculated V _zz value at the hafnium site is linearly increasing as a function of the pressure induced volume reduction, while the V _zz value at the boron site stays almost zero. The major contribution to the V _zz value at the hafnium site comes from a p-p contribution next to the probe nucleus, with a relatively large d-d contribution of about 25%. This unusual large d-d contribution arises from the hafnium p-d electrons coupling.