The missing parameters in the COMPASS force fields for Ho(III) aqua-tris(dibenzoylmethane), which is a seven-coordinate complex with a water molecule and three dibenzoylmethane ligands, were developed as a fitting route for establishing a crystalline structure using AIMD data. The lattice constant and atomic distances around Ho observed in SC-XRD data were found to be well reproduced by CMD using the developed force-field parameters. This route will be extended to other metal complexes with high-molecular-weight ligands and seven-or eight-coordinate complexes.