AB-INITIO QUANTUM-CHEMICAL CALCULATION OF ELECTRON-TRANSFER MATRIX-ELEMENTS FOR LARGE MOLECULES

Using a diabatic state formalism and pseudospectral numerical methods, we have developed an efficient ab initio quantum chemical approach to the calculation of electron transfer matrix elements for large molecu les. The theory is developed at the Hartree-Fock level and validated b y comparison with results in the literature for small systems. As an e xample of the power of the method, we calculate the electronic couplin g between two bacteriochlorophyll molecules in various intermolecular geometries. Only a single self-consistent field (SCF) calculation on e ach of the monomers is needed to generate coupling matrix elements for all of the molecular pairs. The largest calculations performed, utili zing 1778 basis functions, required similar to 14 h on an IBM 390 work station. This is considerably less cpu time than would be necessitated with a supermolecule adiabatic state calculation and a conventional e lectronic structure code. (C) 1997 American Institute of Physics.