A Real-Time Time-Dependent Density Functional Tight-Binding Implementation for Semiclassical Excited State...

Area of Science:

• Computational chemistry and physics
• Quantum dynamics simulations
• Spectroscopy

Background:

• Simulating ultrafast quantum dynamics in photoexcited systems requires efficient computational tools.
• Existing methods often struggle with low computational cost and describing quantum effects accurately.

Purpose of the Study:

• To develop an efficient real-time time-dependent DFTB (TD-DFTB) implementation for simulating subpicosecond dynamics.
• To enable the study of nuclear motion effects in photoinduced charge transfer and enhance computational spectroscopies.

Main Methods:

• Combining the Density Functional Tight-Binding (DFTB) method with the semiclassical Ehrenfest method.
• Implementing a real-time TD-DFTB code with novel features for static and time-resolved spectroscopies.
• Utilizing corrections like "LDA+U" and "pseudo SIC" for improved optical property calculations.

Main Results:

• The TD-DFTB implementation accurately simulates nuclear motion effects in photoinduced charge transfer.
• It handles optical properties of periodic materials and improves calculations with "LDA+U" and "pseudo SIC" corrections.
• Efficient simulation of time-resolved transient absorption and impulsive vibrational spectra is now feasible.

Conclusions:

• The developed TD-DFTB method provides an efficient tool for studying ultrafast quantum dynamics.
• It opens new avenues for investigating nonequilibrium phenomena and vibrational coherences in various materials.
• This advancement facilitates the exploration of photochemical mechanisms and material properties.