calculate static pressure at 300 K.

        :param v: unit-cell volume in A^3
        :return: static pressure at t_ref (=300 K) in GPa

def cal_pst(self, v):
        """
        calculate static pressure at 300 K.

        :param v: unit-cell volume in A^3
        :return: static pressure at t_ref (=300 K) in GPa
        """
        p_h = self._hugoniot_p(v)
        p_th_h = self._hugoniot_pth(v)
        p_st = p_h - p_th_h
        return p_st