Wave function methods for fractional electrons.

Area of Science:

• Quantum chemistry
• Materials science
• Computational physics

Background:

• Accurate chemical potentials are crucial for understanding molecular and material properties.
• Current methods like density functional theory and GW computations are computationally demanding.
• Calculating chemical potentials requires defining ground state energy for fractional charges.

Purpose of the Study:

• To extend wave function theories to handle fractional charges for chemical potential determination.
• To investigate ionization potential and electron affinity as energy derivatives concerning electron number.
• To enable chemical potential calculations within correlated wave function methods for bulk materials.

Main Methods:

• Exploration of wave function theories extended to fractional electron charges.
• Analysis of ionization potential and electron affinity as energy derivatives.
• Application of perturbation theory and coupled-cluster approaches.

Main Results:

• Second-order perturbation theory shows improvement over Hartree-Fock and density functionals for fractional charge errors.
• Higher-order perturbation theory and coupled-cluster methods offer greater accuracy and robustness.
• Post-Hartree-Fock methods enhance accuracy by improving integer values and Coulomb correlation.

Conclusions:

• The developed approach provides a unified method for calculating fundamental gaps, relative energies, and geometries.
• Wave function methods extended to fractional charges become applicable to solid-state materials.
• This work bridges molecular and solid-state chemistry by offering an integrated computational approach.