The Feller-Peterson-Dixon (FPD) composite method is based on complete basis set (CBS) extrapolations, typically at the CCSD(T) level of theory, using correlation consistent Gaussian basis sets with additional contributions of outer-core electron correlation, scalar and spin-orbit relativistic effects, and often higher order electron correlation. This methodology is typically used for high accuracy thermochemistry, i.e., from chemical accuracy (~1 kcal/mol) to even kJ/mol accuracy, but is just as amenable to accurate ab initio spectroscopy by carrying out the same set of calculations on many points of the near-equilibrium potential energy surface. The present talk will compare and contrast FPD calculations of the ro-vibrational spectra of several coinage metal triatomic molecules, namely cyanides and nitroxides, MCN and MNO (M= Cu, Ag, Au). The former utilized explicitly correlated CCSD(T) in order to facilitate the estimation of the complete basis set (CBS) limits, whereas the metal nitrosyls employed Brueckner coupled cluster in order to overcome difficulties encountered with the standard CCSD(T) approach.

Ab initio spectroscopy using composite coupled cluster methods: Coinage metal cyanides and nitroxides

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ACS Fall 2022

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