The MD simulations were run using the LAMMPS software and the KOKKOS package . The ReaxFF potential with the parameters described by Ashraf et al. was used as the reactive interatomic potential. Simulations were initialized with either 64 molecules of isobutane (C 4 H 10 ), 125 molecules of ethane (C 2 H 6 ), 160 molecules of methane (CH 4 ) or 36 molecules of octane (C 8 H 18 ). These numbers were chosen to have between 800 and 1,000 atoms in the simulations. Each simulation was initialized at 111 K and 1,013 hPa and ramped up to the desired temperature (between 2,900 K and 5,000 K) and a pressure of 40.53 GPa using a Nosé-Hoover chain thermostat and barostat with chain length 3 and damping parameter of 2.4 fs for temperature and 60 fs for pressure. . The ramping process was spread over 24 ps with a timestep duration of 0.12 fs. The temperature and pressure were then kept constant using the same thermostat, with a barostat with damping parameter of 14.4 fs, and a timestep of 0.12 fs. The duration of the second part of the simulation was between 120 ps and 1,200 ps depending on the starting molecule and the temperature of the simulation. During the constant temperature and pressure part of the simulation, the atom coordinates were output every 12 fs and all the analyses described below were performed using these atom coordinates.