Interface dynamics is an important issue to understand the hot spot formation mechanism in high energy explosives. We have studied the interface between octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) and graphite. The former is a good performance explosive but has high sensitivity. The latter is the desensitizer for the former. Two kinds of dynamic processes have been investigated: breaking and slipping. The structure evolution, energy variation, and breaking/slipping stresses were calculated. We found that different interface processes lead to different energy dissipation ways. For breaking, it is by surface relaxation. For slipping, it is by interface friction. Both the two ways contribute to the hot spot formation and shock sensitivity of explosives. (C) 2011 Elsevier B.V. All rights reserved.