Double-hybrid density functional theory for g-tensor calculations using gauge including atomic orbitals.

Area of Science:

• Quantum Chemistry
• Computational Chemistry
• Spectroscopy

Background:

• Accurate calculation of magnetic properties like the electronic g-tensor is crucial in chemistry and materials science.
• Existing methods for g-tensor calculation can be computationally expensive or suffer from gauge dependency.
• Second-order Møller-Plesset perturbation theory (MP2) and double-hybrid density functional theory (DHDFT) are advanced quantum chemical methods.

Purpose of the Study:

• To develop and present an efficient computational implementation for calculating the electronic g-tensor.
• To incorporate the resolution of identity (RI) approximation for efficient integral treatment.
• To include gauge-including atomic orbitals (GIAO) to address gauge dependence issues.

Main Methods:

• Implementation of electronic g-tensor calculations at the MP2 level of theory.
• Application of the resolution of identity (RI) approximation for two-electron integrals.
• Inclusion of gauge-including atomic orbitals (GIAO) to resolve gauge problems.
• Integration of double-hybrid density functional theory (DHDFT) methods, specifically B2PLYP and DSD-PBEP86.
• Study of computational performance using RIJK and RIJCOSX approximations for analytic second derivatives.

Main Results:

• The study presents an efficient RI-MP2 and DHDFT implementation for g-tensor calculations.
• Calculated g-shifts were compared against experimental and other theoretical data, showing good agreement.
• The computational performance was evaluated for medium to large molecular systems, demonstrating efficiency gains.

Conclusions:

• The developed RI-MP2 and DHDFT approach provides an efficient and accurate method for electronic g-tensor calculations.
• The implementation effectively handles gauge dependence and improves computational performance.
• This method is valuable for studying magnetic properties in various molecular systems.