Density Functional Theory with Complex Absorbing Potentials: A Fast and Accurate Way of Modeling Metastable Anions.

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• Theoretical Chemistry

Background:

• Complex Absorbing Potentials (CAP) are established for describing temporary anions.
• Previous CAP applications in Kohn-Sham Density Functional Theory (DFT) were restricted to the local density approximation.
• A need exists for advanced DFT methods to accurately model metastable molecular anions.

Purpose of the Study:

• To implement and validate a Complex Absorbing Potential DFT (CAP-DFT) method.
• To extend CAP-DFT to generalized gradient approximations and hybrid functionals.
• To accurately calculate energies and lifetimes of metastable molecular anions.

Main Methods:

• Implementation of CAP with generalized gradient approximations and hybrid functionals.
• Application to various molecular systems, including N2, CH2O, CH2O2, C2H4, and pyrene anions.
• Comparison with Hartree-Fock and equation-of-motion coupled-cluster methods.

Main Results:

• Pure DFT approximations inaccurately predict anion energies and decay widths.
• Hartree-Fock theory exhibits opposite inaccuracies compared to pure DFT.
• Hybrid functionals provide a balanced approach, yielding results comparable to high-level coupled-cluster theory.

Conclusions:

• The developed CAP-DFT method accurately computes energies and lifetimes of metastable molecular anions.
• Advanced DFT functionals, particularly hybrid functionals, are crucial for reliable anion descriptions.
• This method offers a computationally efficient alternative to traditional high-accuracy methods for studying temporary anions.