ON THE DETERMINATION OF EFFECTIVE ONE-ELECTRON HAMILTONIANS TO BE USED FOR STUDYING LARGE MOLECULES

We studied the possibility of defining a one-electron effective Hamiltonian in the form of a Huckel-type matrix, taking into account the effect of the environment of the atoms in different molecules (the E2HT). It is found that the appropriate basis set in which this Hamiltonian is defined can be determined by using diatomic fragments. Concerning the matrix elements themselves, the appropriate information can be taken in fragments with a size similar to that of ethane. (C) 1994 John Wiley & Sons, Inc.