  Achieving kJ/mol accuracy in the cohesive energy of molecular crystals, as
necessary for crystal structure prediction and the resolution of polymorphism,
is an ongoing challenge in computational materials science. Here, we evaluate
the performance of second-order M{\o}ller-Plesset perturbation theory (MP2),
including its spin-component scaled models, by calculating the cohesive
energies of the 23 molecular crystals contained in the X23 dataset. Our
calculations are performed with periodic boundary conditions and Brillouin zone
sampling, and we converge results to the thermodynamic limit and the complete
basis set limit to an accuracy of about 1 kJ/mol (0.25 kcal/mol), which is
rarely achieved in previous MP2 calculations of molecular crystals. Comparing
to experimental cohesive energies, we find that MP2 has a mean absolute error
of 12.9 kJ/mol, which is comparable to that of DFT using the PBE functional and
TS dispersion correction. Separate scaling of the opposite-spin and same-spin
components of the correlation energy, with parameters previously determined for
molecular interactions, reduces the mean absolute error to 9.5 kJ/mol, and
reoptimizing the spin-component scaling parameters for the X23 set further
reduces the mean absolute error to 7.5 kJ/mol.
