Complex absorbing potentials with Voronoi isosurfaces wrapping perfectly around molecules.

Area of Science:

• Computational Chemistry
• Quantum Mechanics
• Electronic Structure Theory

Background:

• Complex absorbing potentials (CAPs) are used to adapt bound-state methods for unbound systems in quantum mechanics.
• In electronic structure theory, the box-CAP is commonly used due to its facile integral evaluation in Gaussian basis sets.
• The box-CAP suffers from symmetry breaking and inefficiency in describing large molecules or clusters with significant 'dead space'.

Purpose of the Study:

• To introduce and evaluate two novel CAP formulations: Voronoi-CAP and smooth Voronoi-CAP.
• To address the limitations of the traditional box-CAP in electronic structure calculations.
• To explore the applicability of these new CAPs for studying larger, asymmetric molecular systems and clusters.

Main Methods:

• Development of Voronoi-CAP and smooth Voronoi-CAP, defined within atomic Voronoi cells.
• Numerical computation of integrals, as analytical solutions are not feasible for these new CAPs.
• Systematic exploration and comparison of the new CAPs against the standard box-CAP.

Main Results:

• Voronoi-CAPs exhibit the same symmetry as the molecular system, overcoming a key limitation of the box-CAP.
• These new CAPs demonstrate improved treatment for larger molecules with asymmetric side chains and molecular clusters.
• The isosurfaces of Voronoi-CAPs resemble cavities used in solvation modeling.

Conclusions:

• Voronoi-CAPs and smooth Voronoi-CAPs represent a significant advancement over the box-CAP for specific computational chemistry applications.
• They offer enhanced symmetry properties and better applicability to complex molecular systems.
• Despite the need for numerical integration, these novel CAPs facilitate the study of challenging molecular structures.