What Electronic Structure Method Can Be Used in the Global Optimization of Nanoclusters?

Area of Science:

• Computational chemistry
• Materials science
• Nanotechnology

Background:

• Determining the spatial structure of nanoclusters is complex due to numerous potential energy surface minima (isomers).
• Global optimization methods often use low-level energy calculations followed by high-level refinement, but lower-level results may not match higher-level outcomes.
• Validating the reliability of lower-level methods in global optimization for nanocluster structures is crucial.

Purpose of the Study:

• To benchmark coupled cluster calculations at the complete basis set limit for various isomers of third-row element clusters.
• To assess the hypothesis that lower-level computational methods can reliably guide global optimization of nanocluster structures.
• To develop a methodology for comparing minima obtained at different computational levels.

Main Methods:

• Performed benchmark coupled cluster calculations at the complete basis set limit.
• Developed a methodology to compare a large number of minima obtained at different calculation levels.
• Assessed density functional theory (DFT) functionals and scaled variants of the MP2 method.

Main Results:

• Most tested DFT functionals proved reliable for global optimization if the method identifies the global minimum and a few low-lying structures, with TPSSh showing particular promise.
• Scaled MP2 variants outperformed standard MP2 and DFT methods for most systems.
• One system with numerous van der Waals structures presented an exception where scaled variants were not superior.

Conclusions:

• The study provides a more solid foundation for using lower-level methods in global nanocluster optimization.
• The findings offer guidance for selecting appropriate computational methods in global optimization studies.
• DFT and scaled MP2 methods are recommended for reliable nanocluster structure determination, with specific considerations for systems dominated by van der Waals interactions.