Charge transfer, double and bond-breaking excitations with time-dependent density matrix functional theory

Area of Science:

• Quantum chemistry
• Computational physics
• Theoretical chemistry

Background:

• Adiabatic time-dependent density functional theory (TDDFT) has known limitations.
• These include incorrect excited state surfaces during bond breaking, absence of doubly excited configurations, and underestimated charge transfer excitation energies.
• These failures are evident in simple two-electron systems like H2 and HeH+.

Purpose of the Study:

• To investigate the performance of time-dependent density matrix functional theory (TDMDFT) for prototype two-electron systems.
• To address the known failures of adiabatic TDDFT.
• To develop an improved adiabatic approximation within TDMDFT.

Main Methods:

• Application of time-dependent density matrix functional theory.
• Utilizing simple adiabatic approximations.
• Formulating a new adiabatic approximation to include double excitations.

Main Results:

• TDMDFT with simple adiabatic approximations accurately describes excited state surfaces and charge transfer excitations.
• These approximations do not capture double excitations.
• A novel adiabatic approximation within TDMDFT successfully accounts for double excitations.

Conclusions:

• Time-dependent density matrix functional theory offers a promising alternative to TDDFT for describing electronic excitations.
• The developed adiabatic approximation overcomes critical limitations of current TDDFT methods.
• This advancement is crucial for accurate modeling of chemical processes involving excited states.