Electronic Structure Calculations on Linear Polymers Containing Transition Metal Atoms Using CNDO/2-CO Method I.Double-Decker Polymetal Sandwich Compound, Fe_nbis（polyacene）

In the present paper, we have extended the CNDO/2-CO method to perform calculations on linear polymers containing transition metal atoms.The formulas for additional matrix elements are derived and programmed for the electronic structure calculations on polymetal sandwich compounds.As an illustration, we have applied the extended CNDO/2-CO method to calculate the electronic structure and properties （such as energy bands, energy gap, bandwidths, and so forth） of Fe_nbis（polyacene）. The conclusions drawn from the results of calculations are: Fe_nbis （polyacene） should be more stable than polyacene decker, so it may exist, and it will be a semiconductor p-type doping.