title: Density matrix purification with rigorous error control.
abstract: Density matrix purification, although being a powerful tool for linear scaling construction of the density matrix in electronic structure calculations, has been limited by uncontrolled error accumulation. In this article, a strategy for the removal of small matrix elements in density matrix purification is proposed with which the forward error can be rigorously controlled. The total forward error is separated into two parts, the error in eigenvalues and the error in the occupied invariant subspace. We use the concept of canonical angles to measure and control differences between exact and approximate occupied subspaces. We also analyze the conditioning of the density matrix construction problem and propose a method for calculation of interior eigenvalues to be used together with density matrix purification.
authors.affiliation: Department of Theoretical Chemistry, School of Biotechnology, Royal Institute of Technology, Stockholm, Sweden. emanuel@theochem.kth.se
authors.forename: Emanuel H
authors.initials: EH
authors.lastname: Rubensson
authors.forename: Elias
authors.initials: E
authors.lastname: Rudberg
authors.forename: Paweł
authors.initials: P
authors.lastname: Sałek
mesh_terms: D000465:Algorithms; D003198:Computer Simulation; D008956:Models, Chemical; D008958:Models, Molecular; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity