Self-consistent field calculations of excited states using the maximum overlap method (MOM)

Area of Science:

• Quantum Chemistry
• Computational Physics

Background:

• Accurate calculation of excited-state properties is crucial for understanding molecular behavior.
• Traditional methods often suffer from variational collapse to the ground state during self-consistent field (SCF) calculations.

Purpose of the Study:

• To introduce a novel algorithm, the maximum overlap method (MOM), for efficiently obtaining excited-state solutions.
• To provide a robust method that prevents variational collapse and facilitates excited-state energy derivative calculations.

Main Methods:

• The maximum overlap method (MOM) is proposed, which differs from the Aufbau principle.
• MOM maximizes orbital overlap between successive SCF iterations to guide the calculation towards excited states.
• The method allows excited-state solutions to be treated similarly to ground-state solutions.

Main Results:

• MOM successfully finds excited-state solutions by preventing collapse to the ground state.
• The algorithm directs the SCF process to the nearest energy solution, not necessarily the lowest.
• Demonstrated applicability to excitation energies, charge-transfer states, and excited-state properties.

Conclusions:

• The maximum overlap method (MOM) offers a simple yet effective approach for calculating excited states.
• This method simplifies the computation of excited-state properties and energy derivatives.
• MOM provides a reliable alternative for exploring excited-state electronic structures.