Linear-Response Time-Dependent Density Functional Theory with Stochastic Range-Separated Hybrids.

Area of Science:

• Computational Chemistry
• Quantum Mechanics
• Materials Science

Background:

• Generalized Kohn-Sham density functional theory (GKS-DFT) is vital for studying electronic ground states.
• Range-separated hybrid (RSH) functionals accurately model long-range electronic interactions but are computationally expensive.
• Stochastic methods reduce computational cost for ground-state RSH-DFT calculations.

Purpose of the Study:

• Extend stochastic RSH methods to calculate excited states.
• Develop a computationally efficient approach for excited-state calculations in large systems.
• Investigate the impact of defects on excited-state properties.

Main Methods:

• Linear-response generalized Kohn-Sham time-dependent density functional theory (GKS-TDDFT) with a plane-wave basis.
• Stochastic representation of the density matrix and Coulomb convolution.
• Validation using N2 and CO molecules, followed by application to a MoS2 sheet.

Main Results:

• Accurate excitation energies for N2 and CO compared to deterministic methods.
• Demonstrated computational efficiency for a large MoS2 system (approx. 1500 electrons).
• Calculated exciton charge density and geometric relaxation for the MoS2 sheet.

Conclusions:

• The stochastic GKS-TDDFT method is a viable and efficient approach for excited-state calculations.
• This method enables the study of excited-state properties in large, complex systems.
• The approach can be used to investigate defect effects on material properties.