Effect of Pressure on Molecular and Transition-State Geometries

Area of Science:

• Computational Chemistry
• Molecular Modeling
• High-Pressure Science

Background:

• High pressure profoundly impacts molecular behavior, influencing geometries and energy landscapes.
• Computational methods for studying isolated molecules under extreme pressure are a recent development.

Purpose of the Study:

• To investigate the geometric response of isolated molecules under high pressure (up to 5 GPa).
• To evaluate the reliability of perturbative and full geometry optimization methods using the extreme-pressure polarizable continuum model (XP-PCM).

Main Methods:

• Utilized the extreme-pressure polarizable continuum model (XP-PCM) with perturbative and full geometry optimization approaches.
• Examined seven molecules (covalent, metal-ligand, nonbonded) and six transition states.
• Performed mode-by-mode analysis to understand pressure effects on molecular vibrations.

Main Results:

• Observed that most molecular bonds shorten under pressure, as expected.
• Identified counterintuitive bond elongation in some transition states under pressure.
• Rationalized geometric changes based on bond strength, volume changes, and structural type (minimum vs. transition state).

Conclusions:

• XP-PCM perturbative and full optimization methods agree well and offer complementary insights into high-pressure molecular geometries.
• Experimental data validate the computational methods, confirming their accuracy.
• These approaches provide a framework for exploring pressure-induced chemical reactivity and properties.