title: Numerical and exact kinetic energy operator using Eckart conditions with one or several reference geometries: Application to HONO.
abstract: For the computation of rovibrational levels and their spectroscopic intensities, the Eckart conditions are essential to achieve the optimal separation between rotation and vibration. Dymarsky and Kudin [J. Chem. Phys. 122, 124103 (2005)] proposed a procedure for a simplified calculation of the Eckart rotation matrix. In the present work, we have adapted their approach to obtain a kinetic energy operator in curvilinear coordinates using a numerical but exact procedure without resorting to finite differences. Furthermore, we have modified this approach for the study of molecular systems with several minima, for which several Eckart reference geometries are required. The HONO molecular system has been used to show the efficiency of our implementation. Using the Eckart conditions with multi-reference geometries allows for a calculation of the rotational levels as well as frequencies and intensities of the infrared spectra of both HONO isomers with a single calculation.
authors.affiliation: Laboratoire de Chimie Physique, Bâtiment 349, CNRS, UMR8000, Orsay F-91405, France and University of Paris-Sud, Orsay F-91405, France.
authors.forename: David
authors.initials: D
authors.lastname: Lauvergnat
authors.affiliation: Institut de Química Computacional and Departament de Química, Universitat de Girona, Campus Montilivi, 17071 Girona, Catalonia, Spain.
authors.forename: Josep M
authors.initials: JM
authors.lastname: Luis
authors.affiliation: Department of Chemistry and Biochemistry, University of California, Santa Barbara, California 93106, USA.
authors.forename: Bernard
authors.initials: B
authors.lastname: Kirtman
authors.affiliation: Department of Chemistry, Faculty of Natural Sciences, Matej Bel University, Tajovského 40, 97400 Banska Bystrica, Slovakia.
authors.forename: Heribert
authors.initials: H
authors.lastname: Reis
authors.affiliation: Laboratoire de Chimie Physique, Bâtiment 349, CNRS, UMR8000, Orsay F-91405, France and University of Paris-Sud, Orsay F-91405, France.
authors.forename: André
authors.initials: A
authors.lastname: Nauts