  High-throughput approaches for producing approximate vibrational spectral
data for molecules of astrochemistry interest rely on scaled harmonic frequency
calculations. However, level of theory and basis set pair recommendations for
these calculations are not yet available and thus benchmarking against
comprehensive benchmark databases is needed. Here, we present a new database
for vibrational frequency calculations (VIBFREQ1295) storing 1,295 experimental
fundamental frequencies and CCSD(T)(F12*)/cc-pVDZ-F12 ab initio harmonic
frequencies from 141 molecules. VIBFREQ1295's experimental data was complied
through a comprehensive review of contemporary experimental data while the ab
initio data was computed here. The chemical space spanned by the molecules
chosen is considered in depth and shown to have good representation of common
organic functional groups and vibrational modes.
  Scaling factors are routinely used to approximate the effect of anharmonicity
and convert computed harmonic frequencies to predicted fundamental frequencies.
With our experimental and high-level ab initio data, we find that a global
scaling factor of 0.9617 results in median errors of 15.9 cm-1. Far superior
performance with a median error of 7.5 cm-1 can be obtained, however, by using
separate scaling factors for three regions: frequencies less than 1000 cm-1
(0.987), between 1000 and 2000 cm-1 (0.9727) and above 2000 cm-1 (0.9564). This
sets a lower bound for the performance of level of theory and basis set pairs
in scaled harmonic frequency calculations.
  VIBFREQ1295's most important purpose is to provide a robust benchmarking
database for vibrational frequency calculations. The database can be found as
part of the supplemental material for this paper, or in the Harvard DataVerse
at https://doi.org/10.7910/DVN/VLVNU7.
