One-particle density matrix polarization susceptibility tensors

Area of Science:

• Quantum Chemistry
• Computational Chemistry
• Theoretical Chemistry

Background:

• Understanding how molecules respond to electric fields is crucial for predicting their behavior in condensed phases.
• Existing methods for calculating electric field effects on electron density can be computationally intensive.

Purpose of the Study:

• To develop a generalized model for predicting electric field-induced changes in one-electron density.
• To provide analytic approximate expressions for these changes based on Hartree-Fock theory.
• To enable accurate calculations of molecular properties like polarization energies, dipole, and quadrupole moments.

Main Methods:

• Expressing electric field-induced density changes as a series of one-particle density matrix susceptibilities.
• Deriving analytic approximate expressions within the Hartree-Fock framework.
• Developing a generalized model applicable to arbitrary wavefunctions and density matrices.

Main Results:

• Accurate prediction of one-electron ground-state density changes in water molecules under uniform and non-uniform electric fields.
• Quantitative description of polarization energies, dipole moments, and quadrupole moments from weak to strong fields (0.001-0.07 a.u.).
• Validation of the model for both linear and quadratic electric field effects.

Conclusions:

• The proposed model offers a fast and efficient approach for calculating molecular properties in condensed phases.
• This generalized model advances quantum chemistry calculations for systems under external electric fields.
• The findings pave the way for new computational strategies in studying molecular responses to electric fields.