TUNNELING CURRENTS IN LONG-DISTANCE ELECTRON-TRANSFER REACTIONS - III- MANY-ELECTRON FORMULATION

Many-electron formulation of the method of interatomic tunneling curre nts introduced in our earlier work [J. Chem. Phys. 104, 8424 (1996); 1 05, 10819 (1996)] for the description of long-range electron tunneling in large molecules such as proteins or DNA is proposed. The tunneling currents can be used both for calculation of the tunneling matrix ele ment and for the description of the spatial distribution of tunneling pathways at the atomic level of resolution. It is shown that the tunne ling currents can be expressed as a matrix element of a certain (curre nt) operator evaluated between two diabatic nonorthogonal one- or mult ideterminant wave functions of the initial and final states of the ele ctrons in the system. These states can be found in the standard ground state energy minimization calculations. Explicit expressions for the currents in terms of the atomic basis functions and the transformation matrices to molecular orbitals of the donor and acceptor states are g iven. Thus, the proposed theory provides a method that allows ordinary electronic structure calculations to be utilized for studies of tunne ling dynamics in many-electron systems. All electron-electron interact ions are included in the expressions for currents at the Hartree-Fock level, so that electron polarization effects arising due to interactio n of the tunneling electron and other electrons in the system are take n into account in such a description. (C) 1998 American Institute of P hysics. [S0021-9606(98)00320-1]