Linear complex polarization propagator in a four-component Kohn-Sham framework.

Area of Science:

• Computational chemistry
• Quantum mechanics
• Spectroscopy

Background:

• Linear response theory is crucial for understanding molecular properties.
• Existing methods face challenges with complex frequency arguments and relaxation channels.
• Polarization propagator approaches require robust equation solvers.

Purpose of the Study:

• To present a novel algorithm for solving linear response equations in the random phase approximation.
• To enable calculations involving complex frequency arguments and nonstimulated relaxation.
• To validate the algorithm's stability and robustness in spectroscopic applications.

Main Methods:

• Developed a complex-valued algorithm for linear response equations.
• Implemented the algorithm within a four-component relativistic, noncollinear, density functional theory framework.
• Applied the method to calculate electric dipole dispersion coefficients (C(6)) for diatomic molecules.

Main Results:

• Demonstrated the algorithm's stability and robustness across visible, ultraviolet, and X-ray spectroscopies.
• Successfully computed C(6) coefficients for rubidium (Rb2) and cesium (Cs2) dimers.
• Obtained highly accurate C(6) values: 14.0x10^3 a.u. for Rb2 and 21.9x10^3 a.u. for Cs2.

Conclusions:

• The presented algorithm is a stable and robust solver for complex linear response equations.
• The method accurately determines electric dipole dispersion coefficients for molecular dimers.
• This work advances computational methods for spectroscopic analysis and intermolecular interactions.