Generalized Gradient Approximation Exchange Energy Functional with Near-Best Semilocal Performance.

Area of Science:

• Quantum Chemistry
• Computational Physics
• Materials Science

Background:

• Density Functional Theory (DFT) is a cornerstone of modern computational chemistry and physics.
• Accurate exchange-correlation functionals are crucial for reliable predictions of molecular properties.
• Existing functionals often struggle with accurately describing asymptotic potential behavior and derivative discontinuities.

Purpose of the Study:

• Develop and validate a new nonempirical generalized gradient approximation (GGA) exchange (X) density functional.
• Improve the accuracy of Kohn-Sham eigenvalues for Density Functional Theory (DFT) ionization potential theorem.
• Enable reliable time-dependent DFT (TD-DFT) calculations for molecular response properties.

Main Methods:

• Construction of the NCAP functional by reconsidering asymptotic potential constraints.
• Inclusion of derivative discontinuity and approximate integer self-interaction correction.
• First-principles determination of the effective second-order gradient expansion coefficient.

Main Results:

• NCAP achieves performance comparable to SCAN meta-GGA on standard thermochemistry tests.
• NCAP yields Kohn-Sham eigenvalues approximating DFT ionization potential theorem values.
• NCAP enables high-quality TD-DFT calculations of polarizabilities, hyper-polarizabilities, and excited states without ad hoc modifications.

Conclusions:

• The NCAP functional represents a significant advancement over previous functionals like CAP.
• NCAP offers improved atomic exchange potential behavior and accurate long-range properties.
• NCAP provides a robust and versatile tool for various quantum chemical calculations.