Dipole Moment Calculations Using Multiconfiguration Pair-Density Functional Theory and Hybrid Multiconfiguration...

Area of Science:

• Quantum Chemistry
• Computational Chemistry
• Molecular Spectroscopy

Background:

• Molecular polarity, indicated by dipole moments, is crucial for understanding chemical properties.
• Accurate dipole moment prediction relies on high-quality electron density calculations.
• Single-reference methods struggle with strongly correlated systems, leading to inaccurate dipole moments.

Purpose of the Study:

• Derive an analytical expression for electric dipole moments using multiconfiguration pair-density functional theory (MC-PDFT).
• Assess the accuracy of MC-PDFT for predicting dipole moments at various geometries.
• Evaluate MC-PDFT's performance against established methods for challenging molecules.

Main Methods:

• Derivation of analytical expressions for electric dipole moments within MC-PDFT.
• Application of MC-PDFT to a dataset of transition-metal diatomics and main-group polyatomics.
• Comparison of MC-PDFT results with CASSCF, CASPT2, and MRCISD+Q.

Main Results:

• MC-PDFT provides dipole moment curves with reasonable behavior even for stretched geometries.
• MC-PDFT significantly improves upon CASSCF by incorporating more electron correlation.
• MC-PDFT and HMC-PDFT show performance comparable to CASPT2 and MRCISD+Q with lower computational cost.
• Recommended optimal functional and active space choices yield mean unsigned deviations of ~0.24-0.29 D.

Conclusions:

• MC-PDFT offers a computationally efficient and accurate method for predicting dipole moments, particularly for systems with multireference character.
• The method shows significant improvement over CASSCF and competitive accuracy with higher-cost methods.
• MC-PDFT represents a valuable advancement for computational chemistry studies requiring precise molecular polarity data.