title: Atomic Velocity Projection Method: A New Analysis Method for Vibrational Spectra in Terms of Internal Coordinates for a Better Understanding of Zeolite Nanogrowth.
abstract: An efficient protocol is presented to identify signals in vibrational spectra of silica oligomers based on theoretical molecular dynamics (MD) simulations. The method is based on the projection of the atomic velocity vectors on the tangential directions of the trajectories belonging to a predefined set of internal coordinates. In this way only contributions of atomic motions along these internal coordinates are taken into consideration. The new methodology is applied to the spectra of oligomers and rings, which play an important role in zeolite synthesis. A suitable selection of the relevant internal coordinates makes the protocol very efficient but relies on intuition and theoretical insight. The simulation data necessary to compute vibrational spectra of relevant silica species are obtained through MD using proper force fields. The new methodology-the so-called velocity projection method-makes a detailed analysis of vibrational spectra possible by establishing a one-to-one correspondence between a spectral signal and a proper internal coordinate. It offers valuable perspectives in understanding the elementary steps in silica organization during zeolite nanogrowth. The so-called velocity projection method is generally applicable on data obtained from all types of MD and is a highly valuable alternative to normal-mode analysis which has its limitations due to the presence of many local minima on the potential energy surface. In this work the method is exclusively applied to inelastic neutron scattering, but extension to the infrared power spectrum is apparent.
authors.affiliation: Center for Molecular Modeling, QCMM Alliance Ghent-Brussels, Ghent University , Technologiepark 903, B-9052 Zwijnaarde, Belgium.
authors.forename: Marc
authors.initials: M
authors.lastname: Van Houteghem
authors.affiliation: Center for Molecular Modeling, QCMM Alliance Ghent-Brussels, Ghent University , Technologiepark 903, B-9052 Zwijnaarde, Belgium.
authors.forename: Toon
authors.initials: T
authors.lastname: Verstraelen
authors.affiliation: Center for Molecular Modeling, QCMM Alliance Ghent-Brussels, Ghent University , Technologiepark 903, B-9052 Zwijnaarde, Belgium.
authors.forename: Dimitri
authors.initials: D
authors.lastname: Van Neck
authors.affiliation: Center for Surface Chemistry and Catalysis, Leuven University , Kasteelpark Arenberg 23, B-3001 Heverlee, Belgium.
authors.forename: Christine
authors.initials: C
authors.lastname: Kirschhock
authors.affiliation: Center for Surface Chemistry and Catalysis, Leuven University , Kasteelpark Arenberg 23, B-3001 Heverlee, Belgium.
authors.forename: Johan
authors.initials: J
authors.lastname: A Martens
authors.affiliation: Center for Molecular Modeling, QCMM Alliance Ghent-Brussels, Ghent University , Technologiepark 903, B-9052 Zwijnaarde, Belgium.
authors.forename: Michel
authors.initials: M
authors.lastname: Waroquier
authors.affiliation: Center for Molecular Modeling, QCMM Alliance Ghent-Brussels, Ghent University , Technologiepark 903, B-9052 Zwijnaarde, Belgium.
authors.forename: Veronique
authors.initials: V
authors.lastname: Van Speybroeck