Accelerating Prediction of Complex Molecular Crystals by Sensible Selection of Asymmetric Units

Effective crystal structure prediction (CSP) relies on thorough exploration of potential energy surfaces. For this reason, molecular CSP has historically focused on simple crystals with a single molecule in the asymmetric unit. Increasing the number of molecules in the asymmetric unit increases the degrees of freedom of the crystal structure and the burden on the crystal structure predictor. We mitigate this burden by modifying quasi-random structure searching (QRSS) with "sensible asymmetric units for crystal exploration" (SAUCE). Compared to traditional QRSS implementations, the crystal structures generated by SAUCE are denser, and in a more energetically favorable environment, leading to faster geometry optimizations and more frequent recovery of the low energy minima discovered by traditional QRSS. This will allow for structure predictors to approach more complex molecular materials and to reduce the computational cost of molecular CSP.