Deallocate the memory allocated for the grid.
subroutine destroy_grid()
!< Deallocate the memory allocated for the grid.
!-----------------------------------------------------------
implicit none
call dmsg(1, 'grid', 'destroy_memory')
call dealloc(grid_x)
call dealloc(grid_y)
call dealloc(grid_z)
! call dealloc(sphere_indices)
end subroutine destroy_grid