Constrained Multipole Moment Density Functional Theory for the Frozen Contribution in Non-Covalent Complexes.

Area of Science:

• Quantum Chemistry
• Computational Chemistry
• Theoretical Chemistry

Background:

• Constrained dipole moment density functional theory (CDMDFT) enables control over molecular dipole moments.
• Accurate description of intermolecular interactions is crucial in chemistry and materials science.

Purpose of the Study:

• To develop a variational and nonempirical methodology for controlling dipole, quadrupole, and octupole moments.
• To estimate individual and combined multipole contributions to the ground state of molecular complexes.
• To approximate the variational frozen state and its contribution to complex formation.

Main Methods:

• Implementation of a variational and nonempirical method to control multipole moments.
• Calculation of individual and combined multipole contributions (dipole, quadrupole, octupole).
• Analysis of 24 noncovalent complexes across four literature sets.

Main Results:

• The methodology successfully controls dipole, quadrupole, and octupole moments.
• Individual and combined multipole contributions were estimated for ground state formation.
• Fast convergence of the multipole expansion was observed.
• The dipole, quadrupole, and octupole moments were sufficient to describe the frozen state well.

Conclusions:

• The developed method provides accurate control and estimation of molecular multipole moments.
• Multipole contributions are key to understanding the nature of interactions in noncovalent complexes.
• The multipole expansion converges rapidly, simplifying the description of frozen states.