The manual says：
For the fix ttm and fix ttm/mod commands, the corresponding atomic temperature for atoms in each grid cell can be computed and output by the fix ave/chunk command using the compute chunk/atom command to create a 3d array of chunks consistent with the grid used by this fix.
I have a question as to whether the grid used includes the vacuum layer of the grid. If 40 grids are divided along the X-axis, the first 20 grids have atoms and the last 20 are vacuums. I calculate the lattice temperature, so do I divide it into 20 blocks or 40 blocks？