title: New General Tools for Constrained Geometry Optimizations.
abstract: A modification of the constrained geometry optimization method by Anglada and Bofill (Anglada, J. M.; Bofill, J. M. J. Comput. Chem. 1997, 18, 992-1003) is designed and implemented. The changes include the choice of projection, quasi-line-search, and the use of a Rational Function optimization approach rather than a reduced-restricted-quasi-Newton-Raphson method in the optimization step. Furthermore, we show how geometrical constrains can be implemented in an approach based on nonredundant curvilinear coordinates avoiding the inclusion of the constraints in the set of redundant coordinates used to define the internal coordinates. The behavior of the new implementation is demonstrated in geometry optimizations featuring single or multiple geometrical constraints (bond lengths, angles, etc.), optimizations on hyperspherical cross sections (as in the computation of steepest descent paths), and location of energy minima on the intersection subspace of two potential energy surfaces (i.e. minimum energy crossing points). In addition, a novel scheme to determine the crossing point geometrically nearest to a given molecular structure is proposed.
authors.affiliation: Department of Theoretical Chemistry, Lund University, Chemical Centre, P.O. Box 124, S-221 00 Lund, Sweden.|Dipartimento di Chimica, Università di Siena, via A. De Gasperi 2, I-53100 Siena, Italy, and Centro per lo Studio dei Sistemi Complessi, Via Tommaso Pendola 37, I-53100 Siena, Italy.|Department of Chemical Physics, Lund University, Chemical Centre, P.O. Box 124, S-221 00 Lund, Sweden.
authors.forename: Luca
authors.initials: L
authors.lastname: De Vico
authors.affiliation: Department of Theoretical Chemistry, Lund University, Chemical Centre, P.O. Box 124, S-221 00 Lund, Sweden.|Dipartimento di Chimica, Università di Siena, via A. De Gasperi 2, I-53100 Siena, Italy, and Centro per lo Studio dei Sistemi Complessi, Via Tommaso Pendola 37, I-53100 Siena, Italy.|Department of Chemical Physics, Lund University, Chemical Centre, P.O. Box 124, S-221 00 Lund, Sweden.
authors.forename: Massimo
authors.initials: M
authors.lastname: Olivucci
authors.affiliation: Department of Theoretical Chemistry, Lund University, Chemical Centre, P.O. Box 124, S-221 00 Lund, Sweden.|Dipartimento di Chimica, Università di Siena, via A. De Gasperi 2, I-53100 Siena, Italy, and Centro per lo Studio dei Sistemi Complessi, Via Tommaso Pendola 37, I-53100 Siena, Italy.|Department of Chemical Physics, Lund University, Chemical Centre, P.O. Box 124, S-221 00 Lund, Sweden.
authors.forename: Roland
authors.initials: R
authors.lastname: Lindh