The problem of assessing the stability of molecular crystals is of great interest in science and technology.
The quantity considered is the lattice energy, that is the energy gained by a molecule in the crystal form with respect to vacuum; it ranges from just a few, to hundreds of kJ/mol, while to distinguish between different polymorphs is often necessary to go beyond the chemical accuracy.
Theoretical approaches are of great interest to complement experimental investigations, as these are difficult, indirect and potentially incur large error bars.
Many approaches are available already, but those capable to reach subchemical accuracy are thought to have an enormous computational cost which limits their applicability.
We highlight here, via a representative set of eight diverse molecular crystals, the exceptional achievements of quantum Monte Carlo approaches, which is able of high accuracy while being computationally feasible.
Thus, a wider future application of quantum Monte Carlo is expected in the screening of lots of systems, of use for crystal structure determination, predicting crystal properties, furthering crystal engineering to design novel pharmaceutical compounds with desired physical and mechanical properties.