The improved Bardeen-Cooper-Schrieffer method in polymers

It is shown that in the framework of the improved Bardeen-Cooper-Schrieffer (IBCS) theory the correlation energy per unit cell of a periodic polymer c an be computed. Furthermore, a new concept of effective correlated pairs is introduced and the coefficient kappa modifies now the correlated term in t he occupation number arised. The occupation numbers are expressed by means of quantities, which satisfy a trigonometric relation to warrant the nonide mpontent condition. As a consequence a variational method can be introduced , which involves only an unconstrained minimization which may be performed using a conjugated gradient technique. Some results of calculations on nucl eotide bases and the corresponding periodic polymers are presented. (C) 200 0 American Institute of Physics. [S0021-9606(00)50918-0].