Fast and accurate quantum Monte Carlo for molecular crystals

Computer simulation plays a central role in modern-day materials
science. The utility of a given computational approach depends
largely on the balance it provides between accuracy and computational
cost. Molecular crystals are a class of materials of great
technological importance which are challenging for even the most
sophisticated ab initio electronic structure theories to accurately
describe. This is partly because they are held together by a balance
of weak intermolecular forces but also because the primitive
cells of molecular crystals are often substantially larger than those
of atomic solids. Here, we demonstrate that diffusion quantum
Monte Carlo (DMC) delivers subchemical accuracy for a diverse
set of molecular crystals at a surprisingly moderate computational
cost. As such, we anticipate that DMC can play an important role
in understanding and predicting the properties of a large number
of molecular crystals, including those built from relatively
large molecules which are far beyond reach of other high-accuracy
methods.