Analytical Model for the Molecular Ionization Energy in an External Electric Field

Area of Science:

• Physical Chemistry
• Theoretical Chemistry
• Computational Chemistry

Background:

• The Poole-Frenkel model is widely used for conductivity in electric fields.
• Understanding molecular ionization energy in applied electric fields is crucial for electronic processes.
• Previous methods often require computationally intensive quantum chemical calculations.

Purpose of the Study:

• To develop an analytical model for molecular ionization energy in an applied electric field.
• To assess the model's accuracy against established methods like constrained density functional theory.
• To provide a computationally efficient alternative for simulating electronic processes.

Main Methods:

• A perturbation expansion of molecular ionization energy in the applied electric field.
• Utilizing the Frenkel approach as the leading term in the expansion.
• Testing the model on a set of representative molecules.

Main Results:

• The Frenkel term is identified as dominant and sufficient at low electric fields.
• Molecular dipole and polarizability terms contribute significantly only at high fields and for larger molecules.
• The model's results show comparable quality to constrained density functional theory calculations.

Conclusions:

• The analytical model effectively predicts molecular ionization energy in electric fields.
• The model avoids complex quantum chemical calculations, enabling direct application in coarse-grained simulations.
• This approach facilitates the study of electronic processes in dielectric condensed phases.