jp9b11474_si_002.pdf (538.94 kB)
Accuracy of the PM6 and PM7 Methods on Bare and Thiolate-Protected Gold Nanoclusters
journal contribution
posted on 2020-03-20, 19:17 authored by Joani Mato, Emilie B. GuidezSemiempirical
quantum mechanical (SEQM) methods offer an attractive
middle ground between fully ab initio quantum chemistry and force-field
simulations, allowing for a quantum mechanical treatment of the system
at a relatively low computational cost. However, SEQM methods have
not been frequently utilized in the study of transition metal systems,
mostly due to the difficulty in obtaining reliable parameters. This
paper examines the accuracy of the PM6 and PM7 semiempirical methods
to predict geometries, ionization potentials, and HOMO–LUMO
energy gaps of several bare gold clusters (Aun) and thiolate-protected gold nanoclusters (AuSNCs). Contrary to
PM6, the PM7 method can predict qualitatively correct geometries and
ionization potentials when compared to DFT. PM6 fails to predict the
characteristic gold core and gold–sulfur ligand shell (staple
motifs) of the AuSNC structures. Both the PM6 and PM7 methods overestimate
the HOMO–LUMO gaps. Overall, PM7 provides a more accurate description
of bare gold and gold–thiolate nanoclusters than PM6. Nevertheless,
refining the gold parameters could help achieve better quantitative
accuracy.