Linear Response Selected Configuration Interaction

Area of Science:

• Computational chemistry
• Quantum chemistry
• Theoretical chemistry

Background:

• Selected configuration interaction (SCI) methods approximate full configuration interaction (FCI) energies efficiently.
• Conventional SCI determinant selection primarily optimizes energy, potentially omitting crucial determinants for wave function response.
• Accurate computation of molecular response properties is vital for understanding chemical phenomena.

Purpose of the Study:

• To extend selected configuration interaction (SCI) methods to compute molecular response properties.
• To introduce a linear response (LR) framework for SCI, enabling the calculation of properties beyond energies.
• To develop new determinant selection criteria for improved response property calculations.

Main Methods:

• Introduction of a linear response (LR) framework for SCI methods.
• Development of two novel determinant selection criteria motivated by linear response theory.
• Application of a damped LR formulation for computing spectra and coupling constants.

Main Results:

• LR-SCI systematically converges to FCI limit for static polarizabilities.
• Accurate computation of water K-edge X-ray absorption spectrum in large active spaces.
• Achieved superior accuracy for NMR spin-spin coupling constants in water compared to CCSDT methods.

Conclusions:

• LR-SCI provides a powerful method for calculating molecular response properties with near-FCI accuracy.
• This approach extends the applicability of SCI methods to systems previously inaccessible to exact FCI calculations.
• LR-SCI represents a significant advancement in computational quantum chemistry for response property prediction.