EQUATION OF STATE FOR EXTRAPOLATION OF HIGH-PRESSURE SHOCK HUGONIOT DATA - COMMENT

Oh and Persson [J. Appl. Phys. 65, 3852 (1989)] proposed an equation o f state to extrapolate high-pressure shock Hugoniot data to other high -pressure and high-temperature states and compared it to data. The req uirement that F=-(partial derivative E/partial derivative V)(p)/(parti al derivative E/partial derivative V)(H) approximate to 1 (E is specif ic internal energy, V is specific volume, P is the constant pressure p ath and H is the constant Hugoniot path) needed to establish the equat ion of state appears to be in error. I have found F to vary from 0.16 to 3.59 for fifteen common materials of interest to shock physicists. Oh and Persson's [J. Appl. Phys. 65, 3852 (1989)] comparison of their equation of state to data gives the impression of a better agreement t han actually occurs because of possible errors in the transcription of data, and the use of an inappropriate Hugoniot for water. When data a re correctly plotted and an appropriate water Hugoniot is used, the co mparison of data to theory indicates that the equation of state loses accuracy with increasing pressure or decreasing porous initial density .