MP2-based composite extrapolation schemes can predict core-ionization energies for first-row elements with coupled-cluster level accuracy
arxiv(2024)
摘要
X-ray photoelectron spectroscopy (XPS) measures core-electron binding
energies (CEBEs) to reveal element-specific insights into chemical environment
and bonding. Accurate theoretical CEBE prediction aids XPS interpretation but
requires proper modeling of orbital relaxation and electron correlation upon
core-ionization. This work systematically investigates basis set selection for
extrapolation to the complete basis set (CBS) limit of CEBEs from ΔMP2
and ΔCC energies across 94 K-edges in diverse organic molecules. We
demonstrate that an alternative composite scheme using ΔMP2 in a large
basis corrected by ΔCC-ΔMP2 difference in a small basis can
quantitatively recover optimally extrapolated ΔCC CEBEs within 0.02 eV.
Unlike ΔCC, MP2 calculations do not suffer from convergence issues and
are computationally cheaper, and, thus, the composite ΔMP2/ΔCC
scheme balances accuracy and cost, overcoming limitations of solely using
either method. We conclude by providing a comprehensive analysis of the choice
of small and large basis sets for the composite schemes and provide practical
recommendations for highly accurate (within 0.10-0.15 eV MAE) ab initio
prediction of XPS spectra.
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