Inspect a system

The following methods report basic properties without modifying the system.

energy	Total energy.
enthalpy	Total enthalpy.
forces	Forces on ions.
stress	Stress tensor.
pressure	Pressure.
volume	Box volume.
box_vectors	Box vectors (lattice vectors).
ions_xyz_coords	Cartesian coordinates of ions.
electron_density	Electron density on the grid.
grid_shape	Grid size along all three dimensions.
energy_cutoff	Plane wave energy cutoff for the current box vectors and grid.