Experimental and theoretical studies on the C15 intermetallic compounds MV(sub 2) (M = Zr, Hf and Ta): Elasticity and phase stability

摘要

The phase stability of C15 HfV(sub 2) was studied by specific heat measurements. The elastic constants of C15 HfV(sub 2) were measured by the resonant ultrasound spectroscopy. Total energy and electronic structure of C15 intermetallic compounds MV(sub 2) (M = Zr, Hf and Ta) were calculated using the linear muffin tin orbital (LMTO) method. The band structures at X-point near the Fermi level were used to understand the anomalous shear moduli of the C15 HfV(sub 2) and ZrV(sub 2). It was found that the double degeneracy with a linear dispersion relation of electronic levels at the x-point near the Fermi surface is mainly responsible for the C15 anomalous elasticity at high temperatures. The densities of states at Fermi level and the geometry of the Fermi surface were used to explain the low temperature phase instability of C15 HfV(sub 2) and ZrV(sub 2) and the stability of C15 TaV(sub 2). The relationship between the anomalous elasticity and structural instability of C15 HfV(sub 2) and ZrV(sub 2) were also studied.