XAFQAZ was a more challenging system. The experimentally observed crystal structure is reproduced by the global energy minimum in space group P 2 1 /c. The QR-BH and pure QR methods generated similar energy landscapes in P 2 1 /c (see Fig. ). However, the pure QR method had difficulty locating several low-energy structures, including the global minimum, which was first hit after 30,315 minimizations. The 3000 K, 1:1 QR-BH search located the P 2 1 /c global minimum in 2 of 3 searches, both in significantly fewer steps than QR. Increasing the seed:step ratio to 2:1 or 10:1 led to more consistent success of QR-BH: the P 2 1 /c was located in all searches with these higher seed:step ratios, with fewer mean steps than QR. Lowering the temperature to 500 K gave less consistent results in P 2 1 /c; at each seed:step ratio, only one of three repeats located the global minimum in 50,000 minimizations.