# Unraveling the Intrinsic Mechanisms Controlling the Variations in Density, Sensitivity, and Thermal Decomposition of Typical Nitroguanidine Derivatives

## TL;DR

This study explores how structural changes in nitroguanidine compounds affect their density, sensitivity, and thermal decomposition, offering insights for optimizing energetic materials.

## Contribution

The paper reveals intrinsic mechanisms linking molecular structure to macro-level properties in nitroguanidine derivatives.

## Key findings

- ANGN has higher density due to stronger hydrogen bonding from enhanced electrostatic and inductive interactions.
- Weaker electrostatic interactions in ANQ lead to lower density and different sensitivity behavior.
- A strong linear correlation (R2 = 0.92) exists between N–NO2 bond dissociation energy and NO2 mass spectral intensity.

## Abstract

Nitroguanidine-type energetic materials have broad application prospects in the propellant field, and their derivative structures are numerous, with intricate changes in macro-level properties. However, due to the unclear inherent evolution mechanisms of these macro-level properties, the structural optimization of compounds and the iteration of application systems face difficulties. This work systematically investigates the variations in density, thermal decomposition, and sensitivity among nitroguanidine (NQ), 1-amino-2-nitroguanidine (ANQ), and 1-amino-2-nitroguanidinium nitrate (ANGN). Hirshfeld surface and bond dissociation energy analyses reveal that strengthened electrostatic and inductive interactions enhance the hydrogen bonding network in ANGN, leading to its higher density compared to NQ. In contrast, weakened electrostatic interactions in ANQ result in a less robust hydrogen bonding network and a correspondingly lower density. The sensitivity trend is consistently explained from both molecular and crystalline perspectives: an increasingly inhomogeneous electrostatic potential distribution, coupled with a higher frequency of O···O contacts, provides a coherent explanation for the experimental observations. Furthermore, the electron-withdrawing -NH3+ group in ANGN weakens the N–NO2 bond, reducing its bond dissociation energy and leading to the most intense NO2 mass spectral signal during thermal decomposition. ANQ exhibits the opposite behavior. A linear correlation (R2 = 0.92) is observed between the N–NO2 BDE and NO2 mass spectral intensity across NQ, ANQ, and ANGN. This study provides unique insights into the intrinsic mechanisms governing variations in the properties of nitroguanidine derivatives.