Accurate or Fast Prediction of Solid-State Formation Enthalpies Using Standard Sublimation Enthalpies Derived From Geometrical Fragments

In view of its success in predicting sublimation enthalpies of molecular crystals near triple point conditions [Ind. Eng. Chem. Res. 2012, 51, 2814], the geometrical fragment (GF) approach is presently used to estimate standard values Δ_subH⁰ adjusted to the reference temperature of 298.15 K. The resulting GF⁰ scheme is fitted against theoretically confirmed Δ_subH⁰ data for 185 high nitrogen compounds and validated using organic compounds not used in the fitting process. It is subsequently used to predict the solid-state formation enthalpy Δ_fH⁰(cr) of 40 energetic materials, combined with either correlated ab initio methods or simple models to estimate the gas-phase contribution. The combination of GF⁰ with ab initio data yields Δ_fH⁰(cr) values with state-of-the-art accuracy. Combined with the simple atom pair contribution model, this procedure predicts Δ_fH⁰(cr) with better accuracy and stronger physical grounds than alternative low-cost methods.