Effective Fragment Potentials for Microsolvated Excited and Anionic States

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• Physical Chemistry

Background:

• The effective fragment potential (EFP) approach offers a parameter-free hybrid method to incorporate solvation effects in condensed-phase studies.
• Accurately modeling solvation in electronically excited states, especially for diffuse states, remains a challenge for traditional electronic structure methods.

Purpose of the Study:

• To evaluate the performance of the EFP method for microsolvation in electronically excited states of neutral and anionic species.
• To assess EFP's accuracy for both localized valence and diffuse nonvalence states.

Main Methods:

• Utilized equation-of-motion coupled cluster with singles and doubles (EOM-XX-CCSD) for quantum chemical calculations.
• Employed mixed quantum mechanics/EFP (QM/EFP) calculations for microsolvated clusters.
• Compared QM/EFP results with full quantum mechanical calculations for various excited states.

Main Results:

• QM/EFP calculations show minimal average differences compared to full quantum results when averaging over multiple microsolvated cluster configurations.
• Individual configurations may exhibit larger errors, and diffuse states show slightly increased, though not significant, errors.
• State ordering can be affected in QM/EFP due to the close proximity of states, potentially reducing accuracy.
• Properties like photoelectron spectra and metastable state lifetimes are well-reproduced for monohydrated clusters.

Conclusions:

• The EFP method provides a reliable and computationally efficient way to study microsolvation effects in excited electronic states.
• QM/EFP is particularly effective for localized states and shows reasonable performance for diffuse states, with potential limitations in state ordering.
• The method accurately predicts properties like photoelectron images and lifetimes for simple microsolvated systems.