Finite lifetime effects on the polarizability within time-dependent density-functional theory

Area of Science:

• Computational Chemistry
• Quantum Mechanics
• Theoretical Physics

Background:

• Linear-response theory is crucial for understanding molecular properties.
• Time-dependent density-functional theory (TD-DFT) is a powerful tool for electronic structure calculations.
• Finite lifetimes of excited states can significantly impact observable properties.

Purpose of the Study:

• To implement a method that incorporates finite excited-state lifetimes into TD-DFT.
• To enable the calculation of frequency-dependent polarizabilities over a wide range of energies.
• To study linear-response properties in both resonant and non-resonant regimes.

Main Methods:

• Introduced a phenomenological damping factor to account for excited-state lifetimes.
• Extended linear-response TD-DFT to calculate real and imaginary frequency-dependent polarizabilities.
• Applied the method to investigate photoabsorption properties of small alkali clusters.

Main Results:

• Successfully calculated real and imaginary polarizabilities for alkali clusters in the 1-4 eV range.
• Demonstrated the method's ability to study properties in resonance and non-resonance cases.
• Obtained results showing good agreement with previous theoretical and experimental data.

Conclusions:

• The developed method provides a valuable complement to standard excitation energy calculations.
• This approach allows for a more comprehensive study of photoabsorption and other linear-response properties.
• The findings validate the utility of incorporating finite excited-state lifetimes in TD-DFT for accurate predictions.