Local electric fields and molecular properties in heterogeneous environments through polarizable embedding

Area of Science:

• Computational chemistry
• Spectroscopy
• Quantum mechanics

Background:

• The local field experienced by molecules in condensed phases differs from the external field, affecting their properties.
• The polarizable embedding (PE) model approximates direct molecule-environment coupling effects on molecular response properties.
• Existing models may not fully capture the influence of environment polarization induced by external fields.

Purpose of the Study:

• To extend the PE model to incorporate effective external field effects.
• To enable calculations of molecular properties defined with respect to the external field.
• To investigate the impact of these effects on spectroscopic properties.

Main Methods:

• Developed an extended polarizable embedding (PE) model.
• Calculated one- and two-photon absorption (1PA and 2PA) properties using a response framework.
• Studied PRODAN-methanol clusters and the fluorescent protein DsRed.

Main Results:

• Accounting for both dynamical reaction field and effective external field contributions is necessary for accurate calculations.
• Effective external field effects significantly reduced 1PA and 2PA cross-sections for DsRed's lowest π→π* transition.
• The influence of the effective external field varies with the environment's heterogeneity, causing screening or enhancement.

Conclusions:

• The extended PE model accurately reproduces quantum chemical calculations.
• Effective external field effects are critical for understanding molecular spectroscopy in condensed phases.
• Environmental heterogeneity plays a key role in modulating these effects.