Quasiparticle spectra from a nonempirical optimally tuned range-separated hybrid density functional.

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• Materials Science

Background:

• Accurate calculation of outer-valence quasiparticle excitation energies is crucial for understanding molecular properties.
• Many-body perturbation theory, particularly the GW approximation, provides high accuracy but is computationally expensive.
• Developing efficient and accurate methods for these calculations is essential for studying larger systems.

Purpose of the Study:

• To present a novel density-functional theory (DFT)-based method for calculating outer-valence quasiparticle excitation energies.
• To achieve accuracy comparable to the GW approximation but with reduced computational cost.
• To provide a viable alternative for studying large-scale molecular systems.

Main Methods:

• Utilized a range-separated hybrid density functional with asymptotically exact and short-range fractional Fock exchange.
• Determined the two functional parameters (range separation and short-range Fock fraction) nonempirically based on physical constraints.
• Applied the method to benchmark organic molecules: perylene, pentacene, 3,4,9,10-perylene-tetracarboxylic-dianhydride (PTCDA), and 1,4,5,8-naphthalene-tetracarboxylic-dianhydride (NTCDA).

Main Results:

• The DFT-based method achieves accuracy comparable to the GW approximation for outer-valence quasiparticle excitation energies.
• The nonempirical determination of functional parameters ensures system-specific accuracy.
• Demonstrated reliable performance on a set of relevant organic molecules.

Conclusions:

• The proposed DFT method offers a computationally inexpensive yet accurate alternative to GW calculations for outer-valence excitation spectra.
• This approach enables the study of large-scale molecular systems previously inaccessible.
• Opens new avenues for computational investigations in materials science and molecular electronics.