Computation of NMR shieldings at the CASSCF level using gauge-including atomic orbitals and Cholesky decomposition

TL;DR

This paper introduces a new computational method combining CP-CASSCF theory with gauge-including atomic orbitals and Cholesky decomposition to efficiently calculate NMR chemical shifts, enabling analysis of larger molecular systems.

Contribution

The authors develop and implement a CP-CASSCF approach with gauge-including atomic orbitals and Cholesky decomposition for NMR shielding calculations, improving efficiency and scalability.

Findings

Efficient computation demonstrated on systems with up to 1300 basis functions.

The implementation provides insights into computational efficiency and limitations.

Numerical tests validate the method's accuracy and performance.

Abstract

We present an implementation of coupled-perturbed complete active space self-consistent field (CP-CASSCF) theory for the computation of nuclear magnetic resonance chemical shifts using gauge-including atomic orbitals and Cholesky decomposed two-electron integrals. The CP-CASSCF equations are solved using a direct algorithm where the magnetic Hessian matrix-vector product is expressed in terms of one-index transformed quantities. Numerical tests on systems with up to about 1300 basis functions provide information regarding both the computational efficiency and limitations of our implementation.