Frequency-dependent nonlinear optical properties with explicitly correlated coupled-cluster response theory using the...

Area of Science:

• Computational chemistry
• Quantum chemistry
• Theoretical chemistry

Background:

• Coupled-cluster (CC) methods are essential for accurate electronic structure calculations.
• Explicitly correlated methods, like R12, accelerate basis set convergence.
• Response theory describes molecular properties under external perturbations.

Purpose of the Study:

• To combine infinite-order response theory with explicitly correlated coupled-cluster singles and doubles (CCSD(R12)) model.
• To derive and analyze the additional terms and computational costs of linear-r(12) corrections.
• To implement and apply the method for calculating higher-order optical properties.

Main Methods:

• Integration of infinite-order response theory with CCSD(R12).
• Derivation and analysis of linear-r(12) contributions.
• Implementation of cubic response function for one-electron perturbations.
• Calculation of electronic polarizabilities and second hyperpolarizabilities.

Main Results:

• The CCSD(R12) method retains the improved basis set convergence for higher-order optical properties.
• Electronic polarizabilities and second hyperpolarizabilities were computed for BH, N(2), and formaldehyde.
• Frequency-dependent second hyperpolarizability results for N(2) were presented.
• The study discusses the computational overhead associated with R12 corrections.

Conclusions:

• Explicitly correlated coupled-cluster methods significantly enhance the efficiency of basis set convergence for response properties.
• The developed CCSD(R12) response theory provides accurate predictions for molecular optical properties.
• This approach is valuable for studying frequency-dependent electronic and optical characteristics of molecules.