New constraints on gruneisen parameters applications to equations of state for pressure markers

Abstract

“Regular” linear relations between shock and particle velocities, u_s = u_s0, + c · u_p, imply a divergence of the Hugoniot pressure p_H at a critical compression V _c/V _o = (c-1)/c, where the thermal pressure Δp _th = (γ/V)· ΔU _th = p _H-p _T becomes very large with respect to the cold (isothermal) pressure p _T at this compression. The Hugoniot relation for the total internal energy U _H results in this case in the relation γ_c = 2(c- 1) for the Grüneisen parameter in this region. Experimental data for the zero pressure value Γ_o and its derivative Γ_o together with theoretical data for the limiting value γ_∞ = 2/3, and the additional expenmental value γ_c are then used to determine the thermal (phonon) pressure with the common Mie-Grüneisen assumption.

Key Words:

• Grüneisen parameters
• high pressure
• shock waves