Atomic dipole moments calculated using analytical molecular second-moment gradients

Area of Science:

• Computational chemistry
• Quantum chemistry

Background:

• Accurate calculation of atomic properties is crucial for understanding molecular behavior.
• Existing methods for partitioning molecular properties into atomic contributions have limitations.

Purpose of the Study:

• To implement and compare analytical second-moment gradients for Hartree-Fock and multiconfigurational self-consistent-field wave functions.
• To evaluate the performance of the generalized atomic polar tensor (GAPT) and Dinur-Hagler (DH) formalisms for calculating atomic multipole moments.
• To assess the suitability of these methods for analyzing electron density and intermolecular interactions.

Main Methods:

• Implementation of analytical second-moment gradients for electronic structure calculations.
• Application of GAPT and DH formalisms to compute atomic dipole and multipole moments.
• Basis-set convergence analysis and comparison of results for various molecular properties.

Main Results:

• Both GAPT and DH methods show good basis-set convergence and capture electron correlation effects.
• GAPT fails to accurately predict molecular quadrupole moments for some molecules.
• DH exactly reproduces molecular quadrupole moments but is limited to planar systems.
• Both methods yield poor results for higher-order multipoles (octupole, hexadecapole).

Conclusions:

• Atomic quadrupole moments are necessary for accurate molecular charge distribution analysis.
• The DH approach is superior for reproducing molecular quadrupole moments but lacks general applicability.
• Further development is needed for methods applicable to arbitrary molecular shapes and higher-order multipoles.