This result is consistent with the experimentally observed features of short - life . that shows our model is reasonable . the parameters of the extended bbv model are as follows : the near neighbor interaction intension f = 0 . 75ev and the coefficient of the hubbard term u = 1 . 5ev 我们的模型参量为:近邻格点电子相互作用强度作0 . 75ev ,同一格点的电子相互作用强度卜1 . 5ev 。