Time-dependent density functional theory with the orthogonal projector augmented wave method.

Area of Science:

• Computational Chemistry
• Quantum Mechanics
• Materials Science

Background:

• The projector augmented wave (PAW) method offers advantages over norm-conserving pseudopotentials (NCPP) in density functional theory (DFT) calculations.
• PAW typically requires solving for non-orthogonal wavefunctions, limiting its direct application in methods demanding orthogonal wavefunctions.
• Previous work introduced orthogonal PAW (OPAW) to address the need for orthogonal wavefunctions within DFT.

Purpose of the Study:

• To extend the applicability of OPAW beyond standard DFT to post-DFT methods.
• To implement OPAW within the real-time time-dependent DFT (TDDFT) framework.
• To assess the computational efficiency and accuracy of OPAW-TDDFT for molecular electronic properties.

Main Methods:

• Implementation of OPAW within a real-time TDDFT framework.
• Utilized fourth-order Runge-Kutta for time-propagation.
• Calculated absorption spectra for organic and biological molecules.

Main Results:

• OPAW-TDDFT successfully computed molecular absorption spectra.
• Achieved accurate results using significantly larger grid spacings (0.6-0.7 bohr) compared to traditional NCPP-TDDFT (0.4-0.5 bohr).
• Demonstrated a reduction in memory and propagation costs by approximately a factor of three.

Conclusions:

• OPAW is a viable and computationally efficient method for real-time TDDFT calculations.
• The developed OPAW-TDDFT approach significantly reduces computational resource requirements.
• This methodology is readily adaptable for other post-DFT methods involving time-dependent propagations, such as GW approximation and Bethe-Salpeter equation.