Computational Study of Vertical Ionization Potentials Using Density Functional Theory and Green's Function Methods

摘要

Over one hundred vertical ionization potentials (VIPs) were computed using density functional theory (DFT) and Green's function (GF) based methods. The DFT approaches include the unrestricted transition state (uTS) and unrestricted diffuse ionization (uDI) approximations using the Becke88-Perdew86-exchange-correlation functional. Green's function methods include the outer-valence GF (OVGF) approach, the parametrized GF2 (pGF2), and the parametrized GF2 times screended intraction (pGW2) approximations. DFT computations of IPs using the uTS approximation was found to the nearly as accurates as those predicted using the elaborate OVGF method. The much more computationally efficient uDI approximation provides predictions of moderate accuarcy and is recommended for computing IPs for larger molecules. We have observed that the average absolute deviations from a uDI calculaiton using poorer basis set (DZVP) and poorer geometry (AM1 optimization) is only slightly larger.