Calculations of positron binding and annihilation in polyatomic molecules

Area of Science:

• Computational Chemistry
• Quantum Mechanics
• Atomic and Molecular Physics

Background:

• Positron-molecule interactions are crucial for understanding annihilation processes.
• Existing ab initio methods are limited to strongly polar molecules.
• A generalized approach is needed for broader applicability.

Purpose of the Study:

• Develop a versatile model-potential method for calculating positron-molecule binding energies.
• Extend calculations to weakly polar and nonpolar molecular systems.
• Investigate positron annihilation rates in these systems.

Main Methods:

• Calculated molecular electrostatic potential at the Hartree-Fock level.
• Incorporated a model potential for short-range correlations and long-range polarization.
• Solved the Schrödinger equation for the positron in the effective potential.
• Applied the method to hydrogen cyanide (HCN) as a test case.

Main Results:

• The model-potential approach accurately predicts positron binding energies for HCN.
• Results align with existing ab initio calculations for strongly polar systems.
• Predicted annihilation rates for the positron bound state in HCN range from 0.1-0.2 × 10^9 s^-1.

Conclusions:

• The developed model-potential method offers a robust and broadly applicable tool for positron-molecule interaction studies.
• This methodology expands the scope beyond strongly polar molecules.
• The findings provide valuable insights into positron binding and annihilation dynamics.