Exploring structures and energetics of large OCS clusters by correlated methods

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• Molecular Modeling

Background:

• Carbonyl sulfide (OCS) clusters are crucial for understanding intermolecular forces.
• Accurate binding energy calculations are essential for predicting cluster stability and properties.

Purpose of the Study:

• To perform an extensive minima search for (OCS)n clusters (n=2-5).
• To accurately estimate binding energies using high-level computational methods.
• To assess the feasibility of ab initio calculations on large clusters with limited hardware.

Main Methods:

• Utilized MP2 and CCSD(T) levels of theory for binding energy estimation.
• Employed Molecular Tailoring Approach (MTA) for calculating energies at the Complete Basis Set (CBS) limit.
• Performed geometry optimization using MP2/aug-cc-pvTZ basis set.
• Conducted benchmark calculations with dispersion-corrected B2PLYPD functional.

Main Results:

• Geometrical parameters obtained show excellent agreement with experimental findings.
• A substantial blue shift in asymmetric C-O stretch vibrational frequency was observed with increasing cluster size.
• Calculated binding energies provide insights into the stability of (OCS)n clusters.

Conclusions:

• The study validates the accuracy of the employed computational methods for OCS clusters.
• Ab initio calculations on large clusters are feasible on limited hardware with minimal loss of accuracy.
• The findings contribute to a better understanding of non-covalent interactions in molecular clusters.