title: On the full exploitation of symmetry in periodic (as well as molecular) self-consistent-field ab initio calculations.
abstract: Use of symmetry can dramatically reduce the computational cost (running time and memory allocation) of self-consistent-field ab initio calculations for molecular and crystalline systems. Crucial for running time is symmetry exploitation in the evaluation of one- and two-electron integrals, diagonalization of the Fock matrix at selected points in reciprocal space, reconstruction of the density matrix. As regards memory allocation, full square matrices (overlap, Fock, and density) in the Atomic Orbital (AO) basis are avoided and a direct transformation from the packed AO to the symmetry adapted crystalline orbital basis is performed, so that the largest matrix to be handled has the size of the largest sub-block in the latter basis. Quantitative examples, referring to the implementation in the CRYSTAL code, are given for high symmetry families of compounds such as carbon fullerenes and nanotubes.
authors.affiliation: Dipartimento di Chimica, Università di Torino and NIS, Nanostructured Interfaces and Surfaces, Centre of Excellence, Via P. Giuria 7, 10125 Torino, Italy.
authors.forename: Roberto
authors.initials: R
authors.lastname: Orlando
authors.affiliation: Dipartimento di Chimica, Università di Torino and NIS, Nanostructured Interfaces and Surfaces, Centre of Excellence, Via P. Giuria 7, 10125 Torino, Italy.
authors.forename: Marco
authors.initials: M
authors.lastname: De La Pierre
authors.affiliation: Facultad de Ciencias, Universidad Autónoma del Estado de Morelos, Av. Universidad, 1001, Col. Chamilpa, 62209 Cuernavaca (Morelos), Mexico.
authors.forename: Claudio M
authors.initials: CM
authors.lastname: Zicovich-Wilson
authors.affiliation: Dipartimento di Chimica, Università di Torino and NIS, Nanostructured Interfaces and Surfaces, Centre of Excellence, Via P. Giuria 7, 10125 Torino, Italy.
authors.forename: Alessandro
authors.initials: A
authors.lastname: Erba
authors.affiliation: Dipartimento di Chimica, Università di Torino and NIS, Nanostructured Interfaces and Surfaces, Centre of Excellence, Via P. Giuria 7, 10125 Torino, Italy.
authors.forename: Roberto
authors.initials: R
authors.lastname: Dovesi