Permutationally Invariant Potential Energy Surfaces.

Area of Science:

• Computational chemistry
• Theoretical chemistry
• Chemical physics

Background:

• Accurate potential energy surfaces (PESs) are crucial for understanding chemical reactions and molecular properties.
• Calculating PESs for polyatomic molecules and clusters is computationally challenging.

Purpose of the Study:

• To present and demonstrate the permutationally invariant polynomial (PIP) method for calculating PESs.
• To showcase the method's applicability to reactive and nonreactive systems, including large molecular clusters.

Main Methods:

• Utilizes the permutationally invariant polynomial (PIP) method, a general linear least-squares approach.
• Fits tens of thousands of electronic energies from quantum chemical calculations.
• Incorporates recent methodological improvements and extensions for large clusters via the many-body representation.

Main Results:

• Successfully calculated approximately 50 PESs for systems ranging from 4 to 11 atoms and for clusters.
• Demonstrated applications to the formic acid dimer, H2-H2O complex, and protonated water clusters (n=2,3,4,6).
• The formic acid dimer calculation represents a new record for reactive system size.

Conclusions:

• The PIP method is a powerful and versatile tool for generating accurate PESs for diverse chemical systems.
• The method's scalability allows for the study of increasingly complex molecular systems and clusters.