Single-Pole Polarization Models: Rapid Evaluation of Electron Affinities of Solvated-Electron and Superatomic Molecular Anionic States

We propose a single-parameter effective
one-particle potential,
termed the single-pole exchange-correlation (1p-XC), to rapidly evaluate
electron affinities (EAs) of nonvalence electronic states of molecular
clusters and nanoassemblies. The model combines exact-exchange and
the random phase approximation (RPA) correlation potential with a
single-pole approximation to model the frequency-dependent polarization
function. It captures long-range static and dynamic-frequency effects
in the correlation potential, with mean absolute errors of 0.06 eV
for EAs of hydrated- and ammoniated-electron clusters with EA values
in the range 0.24–1.77 eV. The 1p-XC approximation enables
EA estimation with a computational wall-time similar to that of hybrid
functionals. The model also provides a compressed-basis, which significantly
reduces the rank of higher-level parameter-free one-particle Hamiltonians
and further simplifies the computation of EAs. The compressed-basis
approach is used to model the hybridization of superatomic molecular
states of (C60)2– and (C60)3–, thereby verifying previous
model Hamiltonian studies.