MP2-Based Composite Extrapolation Schemes Can Predict Core-Ionization Energies for First-Row Elements with...

Area of Science:

• Computational Chemistry
• Spectroscopy
• Quantum Chemistry

Background:

• X-ray photoelectron spectroscopy (XPS) provides element-specific chemical information.
• Accurate theoretical prediction of core-electron binding energies (CEBEs) is essential for interpreting XPS data.
• Modeling core-ionization effects like orbital relaxation and electron correlation is critical for accurate CEBE predictions.

Purpose of the Study:

• To systematically investigate basis set selection for extrapolating CEBEs to the complete basis set limit.
• To develop and validate a cost-effective composite computational scheme for accurate CEBE prediction.
• To provide practical recommendations for ab initio XPS data prediction.

Main Methods:

• ΔMP2 and ΔCC (Coupled Cluster) energy calculations were performed.
• Basis set extrapolation techniques were applied to obtain complete basis set (CBS) limit energies.
• A composite ΔMP2/ΔCC scheme was developed and evaluated.

Main Results:

• The composite ΔMP2/ΔCC scheme accurately recovers extrapolated ΔCC CEBEs (within 0.02 eV).
• MP2 calculations offer computational advantages over CC methods, avoiding convergence issues and reducing cost.
• The proposed scheme balances accuracy and computational expense for CEBE prediction.

Conclusions:

• The composite ΔMP2/ΔCC scheme provides a practical and accurate method for predicting XPS CEBEs.
• Recommendations for basis set selection in composite schemes are provided.
• The study enables highly accurate (0.10-0.15 eV MAE) ab initio prediction of XPS data.