First-principles calculations of solid-phase enthalpy of formation of energetic materials.

The solid-phase enthalpy of formation (∆Hf, solid) of energetic materials was generally predicted from the gas-phase enthalpy of formation (∆Hf, gas) and sublimation enthalpy (∆Hsub). Here, the standard ∆Hf, solid of energetic materials is directly obtained from density functional theory (DFT) calculations by computing the enthalpy difference between the solid-phase energetic material and its constituent elements in their reference states. To reduce the errors in DFT calculations, a concept of isocoordinated reaction is introduced, i.e., the reference states are selected based on the coordination numbers of all atoms in the energetic material. This DFT method for ∆Hf, solid calculation does not require experimental input, data fitting, or machine learning. For more than 150 energetic materials collected from the literature, the mean absolute error (MAE) of ∆Hf, solid for the DFT method is 39 kJ mol-1 (or 9.3 kcal mol-1) referring to the literature. Our demonstration raises prospects for first-principles prediction of the properties of energetic materials, and the proposed method for ∆Hf, solid calculation is also promising for other materials.