title: Exploiting space-group symmetry in fragment-based molecular crystal calculations.
abstract: Recent developments in fragment-based methods make it increasingly feasible to use high-level ab initio electronic structure techniques to molecular crystals. Such studies remain computationally demanding, however. Here, we describe a straightforward algorithm for exploiting space-group symmetry in fragment-based methods which often provides computational speed-ups of several fold or more. This algorithm does not require a priori specification of the space group or symmetry operators. Rather, the symmetrically equivalent fragments are identified automatically by aligning the individual fragments along their principle axes of inertia and testing for equivalence with other fragments. The symmetry operators relating equivalent fragments can then be worked out easily. Implementation of this algorithm for computing energies, nuclear gradients with respect to both atomic coordinates and lattice parameters, and the nuclear hessian is described.
authors.affiliation: Department of Chemistry, University of California, Riverside, California, 92521.
authors.forename: Yonaton
authors.initials: Y
authors.lastname: Heit
authors.forename: Gregory J O
authors.initials: GJ
authors.lastname: Beran
mesh_terms: D000081:Acetamides / Q000737:chemistry*; D019342:Acetic Acid / Q000737:chemistry*; D000465:Algorithms; D003460:Crystallization; D005559:Formamides / Q000737:chemistry*; D007093:Imidazoles / Q000737:chemistry*; D015394:Molecular Structure; D011789:Quantum Theory
chemical_list: D000081:Acetamides; D005559:Formamides; D007093:Imidazoles; C031066:formamide; C029899:imidazole; C030686:acetamide; D019342:Acetic Acid
keywords: electronic structure theory; fragment methods; molecular crystals; space-group symmetry