docs: def bm3_p(v, v0, k0, k0p, p_ref=0.0):
      """
      calculate pressure from 3rd order Birch-Murnathan equation
  
      :param v: volume at different pressures
      :param v0: volume at reference conditions
      :param k0: bulk modulus at reference conditions
      :param k0p: pressure derivative of bulk modulus at different conditions
      :param p_ref: reference pressure (default = 0)
      :return: pressure
      """
      return cal_p_bm3(v, [v0, k0, k0p], p_ref=p_ref)