Are we assuming the objects retain form? If I smash two iron cubes together and apply enough gravity, eventually I'll get fusion of the atom cores. As the highl

Are we assuming the objects retain form? If I smash two iron cubes together and apply enough gravity, eventually I'll get fusion of the atom cores. As the highly-compressed charged particles start to collide more-and-more, some will repel, some will fuse. As long as the 2nd law is in play, I could see the two objects as being passed through each other. One side you have particlesA[cub1_particles, new_fusion_particles] and on the other side you have particlesB[cube2_particles, new_fusion_particles]. Both of these would sum to the same thermodynamic energy of [cube1, cube2]. Right?