Pressure dependence of the elastic moduli of body-centered-cubic transition metals

Abstract

The single-crystal elastic moduli, Cij, and their pressure derivatives, dCij/dP, have been measured ultrasonically at 25°C for body-centered-cubic Ti-V-Cr, Nb-Mo, and Ta-W solid solutions. The rigid-band model for the alloy electronic structure is known to work fairly well for these metals in predicting the density of states at the Fermi energy and related properties. The results of this study show that changes in the composition dependence of the Cij and, particularly, the dCij/dP appear to be related to topological changes in the Fermi surface which occur as the electron population varies in the rigid-band model. The relationship between the band structure and the Cij is discussed and a qualitative explanation is given for the correlations between the moduli and the Fermi surface. Sources of error in the ultrasonic measurements are considered in detail. It is found that compression of the pressure medium can cause significant errors in the dCij/dP values under certain experimental conditions, and methods for minimizing these errors are suggested. The results are also compared to other ultrasonic measurements and to X-ray and shock-wave compression experiments. Possible sources of disagreement, where it exists, are discussed.