The method has been tested on a set of single-component molecular crystals, for which we find that the QR-BH algorithm improves on the sampling efficiency of the pure Table : Comparison of steps required to locate the global energy minima with QR-BH using on-the-fly clustering in space groups P 1, P 2 1 and P 2 1 /c and the experimentally observed structure in P 2 1 for PYRPMA, and XAFQAZ in space groups P 2 1 /c, F dd2 and I4 1 /a. The QR-BH results are compared to a pure QR search. QR searching in locating the global energy minimum more quickly than pure quasi-random searching and leads to better sampling of the lowest energy structures in each space group. We also find that the combined QR-BH method maintains the desirable feature from QR search methods of reliably locating important high-energy crystal structures; this is illustrated using the molecule TTBI as an extreme example, where experimentally observable crystal structures occupy a very wide range in lattice energies. Surprisingly, QR-BH located even the highest energy observed structures more quickly that a pure QR search.