title: New Formulation and Implementation of Vibrational Self-Consistent Field Theory.
abstract: A new implementation of the vibrational self-consistent field (VSCF) method is presented on the basis of a second quantization formulation. A so-called active terms algorithm is shown to be a significant improvement over a standard implementation reducing the computational effort by one order in the number of degrees of freedom. Various types of screening provide even further reductions in computational scaling and absolute CPU time. VSCF calculations on large polyaromatic hydrocarbon model systems are presented. Further, it is demonstrated that in cases where distant modes are not directly coupled in the Hamiltonian, down to linear scaling of the required CPU time with respect to the number of vibrational modes can be obtained. This is illustrated with calculations on simple model systems with up to 1 million degrees of freedom.
authors.affiliation: The Lundbeck Foundation Center for Theoretical Chemistry, Center for Oxygen Microscopy and Imaging, Department of Chemistry, University of Aarhus, Langelandsgade 140, DK 8000 Aarhus C, Denmark, and Department of Chemistry, Middle East Technical University, 06531 Ankara, Turkey.
authors.forename: Mikkel B
authors.initials: MB
authors.lastname: Hansen
authors.affiliation: The Lundbeck Foundation Center for Theoretical Chemistry, Center for Oxygen Microscopy and Imaging, Department of Chemistry, University of Aarhus, Langelandsgade 140, DK 8000 Aarhus C, Denmark, and Department of Chemistry, Middle East Technical University, 06531 Ankara, Turkey.
authors.forename: Manuel
authors.initials: M
authors.lastname: Sparta
authors.affiliation: The Lundbeck Foundation Center for Theoretical Chemistry, Center for Oxygen Microscopy and Imaging, Department of Chemistry, University of Aarhus, Langelandsgade 140, DK 8000 Aarhus C, Denmark, and Department of Chemistry, Middle East Technical University, 06531 Ankara, Turkey.
authors.forename: Peter
authors.initials: P
authors.lastname: Seidler
authors.affiliation: The Lundbeck Foundation Center for Theoretical Chemistry, Center for Oxygen Microscopy and Imaging, Department of Chemistry, University of Aarhus, Langelandsgade 140, DK 8000 Aarhus C, Denmark, and Department of Chemistry, Middle East Technical University, 06531 Ankara, Turkey.
authors.forename: Daniele
authors.initials: D
authors.lastname: Toffoli
authors.affiliation: The Lundbeck Foundation Center for Theoretical Chemistry, Center for Oxygen Microscopy and Imaging, Department of Chemistry, University of Aarhus, Langelandsgade 140, DK 8000 Aarhus C, Denmark, and Department of Chemistry, Middle East Technical University, 06531 Ankara, Turkey.
authors.forename: Ove
authors.initials: O
authors.lastname: Christiansen