Based on the fact that the Lagrangian bulk moduli of many materials can be expressed as a second order expansion with respect to pressure,a four-parameter equation of state has been proposed which,in comparison with the three-parameter equation of state,can be applied to a wider pressure range and has higher fitting accuracy and good extrapolation behavior.The parameters in the equation are dependent on the first,second and third order derivatives,hence,by using the derivative relations of the Hugoniot and ...