Fingerprint plots of Hirshfeld surfaces were used to locate and analyze the deficiencies in various methodologies employed in the determination of the relative energies of five polymorphs of 1,8-dihydroxyanthraquinone. Nine crystallographically independent molecules were characterized by X-ray crystallography and Hirshfeld surfaces were derived from the X-ray structures. The space groups and number of independent molecules (Z′) for each of the polymorphs (1-5) is as follows: (1) P4 1 (or P4 3 ), Z′ ) 1; (2) Pca2 1 , Z′ ) 2; (3) P1 j , Z′ ) 4; (4) P2 1 /n, Z′ ) 1; (5) P4 1 2 1 2 (or P4 3 2 1 2), Z′ ) 0.5. Form 1 is the most thermodynamically stable among the reproducible structures, as established by competitive solubility tests, followed by 2 and then 4. The unrestrained structures of the five polymorphs were computed using the CVFF and COMPASS force fields as well as with the density functional code, SIESTA.

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