DFT calculation of electron tunneling currents: Real-space (grid) molecular orbitals vs. Gaussian-type molecular orbitals

Long-range electron tunneling occurs in many biological systems. Detailed q uantitative information about the tunneling process can be obtained from th e analysis of electron tunneling currents. However, ab initio tunneling cur rent calculation is a challenging problem since it demands an accurate spat ial representation of molecular orbitals. Conventional Gaussian-type molecu lar orbitals give relatively inaccurate results according to continuity equ ation for current. We have applied a newly developed grid-based numerical m ethod for the density functional theory (DFT) calculation of molecular orbi tals that describes the tunneling electron in the medium. The method yields Excellent results for the spatial distribution of tunneling currents and f or the tunneling matrix element. The method employs the full approximation scheme of multigrid technique to solve both the Kohn-Sham equations and the Poisson equation. (C) 2000 John Wiley & Sons, Inc.