Self-consistent double-hybrid density-functional theory using the optimized-effective-potential method.

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• Theoretical Chemistry

Background:

• Density-functional theory (DFT) is a powerful tool for electronic structure calculations.
• Double-hybrid (DH) methods offer improved accuracy over standard DFT functionals.
• Achieving accurate orbital energies and electron affinities remains a challenge.

Purpose of the Study:

• To introduce and implement an orbital-optimized double-hybrid (DH) scheme using the optimized-effective-potential (OEP) method.
• To investigate the impact of self-consistency in the OEP-based DH scheme.
• To evaluate the performance of the new method for atomic and molecular properties.

Main Methods:

• Development of a self-consistent DH scheme with orbitals optimized by a local potential.
• Inclusion of the second-order Møller-Plesset (MP2) correlation contribution in the OEP.
• Implementation of a one-parameter OEP-based self-consistent DH scheme with BLYP functional.
• Comparison with non-self-consistent DH calculations for closed-shell systems.

Main Results:

• OEP-based self-consistency did not improve ground-state total energies or ionization potentials.
• Accuracy of electron affinities was enhanced by the self-consistent OEP-based DH scheme.
• The lowest unoccupied molecular orbital (LUMO) energy was correctly linked to neutral excitation energies.
• Reasonably accurate exchange-correlation potentials and correlated densities were obtained.

Conclusions:

• The orbital-optimized OEP-based self-consistent DH scheme offers specific advantages over non-self-consistent methods.
• This approach provides a more accurate description of electron affinities and LUMO energies.
• The method yields reliable potentials and densities for theoretical chemistry applications.