Improved Semi-experimental Equilibrium Structure Determination And Theoretical Prediction Of Hydrazoic Acid (<span Class="roman">hn</span>_{<span Class="roman">3</span>})

We conducted multiple high-level \textit{ab initio} calculations to obtain improved semi-experimental equilibrium structures ($r_{e}$$^{SE}$) of hydrazoic acid (\chem{HN_3}) using previously reported experimental data and to obtain improved, purely theoretical predictions of the structure. For the $r_{e}$$^{SE}$ structures, we used the isotopologue-dependent vibrational corrections to the ground rotational constants obtained from anharmonic VPT2 calculations at CCSD(T) using cc-pV$X$Z and cc-pCV$X$Z basis sets (where $X = D, T, Q, 5$), as well as the isotopologue-dependent electron-mass corrections at the same level of theory, to carry out nonlinear least-squares fits of the experimentally determined rotational constants for all but two of the \chem{HN_3} isotopologues. The extent of corrections that were calculated allowed for extrapolation of the $r_{e}$$^{SE}$ structure to the complete basis set limit. To achieve an improved theoretical prediction, we obtained a CCSD(T)/cc-pCV6Z optimization and included corrections for extrapolation to the complete basis set limit, for effects of electron correlation, for relativistic effects, and for the Born-Oppenheimer approximation. The parameters of the resulting theoretical structure agrees to within the $2\sigma$ uncertainties of the $r_{e}$$^{SE}$