Electron affinities of the first-row atoms revisited. Systematic basis sets and wave functions

TLDR

The calculation of accurate electron affinities (EAs) of atomic or molecular species is one of the most challenging tasks in quantum chemistry. The authors present a reliable procedure for determining the EA of an atom and report results for hydrogen, boron, carbon, oxygen, and fluorine. The method employs correlation‑consistent basis sets augmented for diffuse anion character and a uniform expansion of the reference space for multireference singles and doubles configuration‑interaction (MRSD‑CI) calculations. The MRSD‑CI calculations give EAs of 0.740 eV (H), 0.258 eV (B), 1.245 eV (C), 1.384 eV (O), and 3.337 eV (F), all within 0.03 eV of full CI results and close to experimental values.

Abstract

The calculation of accurate electron affinities (EAs) of atomic or molecular species is one of the most challenging tasks in quantum chemistry. We describe a reliable procedure for calculating the electron affinity of an atom and present results for hydrogen, boron, carbon, oxygen, and fluorine (hydrogen is included for completeness). This procedure involves the use of the recently proposed correlation-consistent basis sets augmented with functions to describe the more diffuse character of the atomic anion coupled with a straightforward, uniform expansion of the reference space for multireference singles and doubles configuration-interaction (MRSD-CI) calculations. Comparison with previous results and with corresponding full CI calculations are given. The most accurate EAs obtained from the MRSD-CI calculations are (with experimental values in parentheses) hydrogen 0.740 eV (0.754), boron 0.258 (0.277), carbon 1.245 (1.263), oxygen 1.384 (1.461), and fluorine 3.337 (3.401). The EAs obtained from the MR-SDCI calculations differ by less than 0.03 eV from those predicted by the full CI calculations.