The aim of this work is the investigation of the detailed mechanisms for the initiation reaction leading to the spontaneous combustion of lignite. To carry this out we have used the ReaxFF reactive force field to perform a series of molecular dynamics (MD) simulations on a unimolecular model compound. The initiation reaction observed in the ReaxFF MD simulations involves hydrogen abstraction from phenolic hydroxyl groups by O-2 followed by the formation of HO2. The main products observed in our simulations include H2O2, H2O, CH2O, and CO2. In addition, hydrogen abstraction reactions are responsible for the formation of H2O2 and H2O. The reaction products and the mechanisms involved in the initial stage of spontaneous combustion are consistent with previous results. The agreement of these results with available experimental observations demonstrates that ReaxFF MD simulations can provide an atomistic description of the initiation mechanism for spontaneous combustion and provide useful insights into the complicated reaction processes involved. (C) 2013 Elsevier Ltd. All rights reserved.