title: Adaptive vibrational configuration interaction (A-VCI): A posteriori error estimation to efficiently compute anharmonic IR spectra.
abstract: A new variational algorithm called adaptive vibrational configuration interaction (A-VCI) intended for the resolution of the vibrational Schrödinger equation was developed. The main advantage of this approach is to efficiently reduce the dimension of the active space generated into the configuration interaction (CI) process. Here, we assume that the Hamiltonian writes as a sum of products of operators. This adaptive algorithm was developed with the use of three correlated conditions, i.e., a suitable starting space, a criterion for convergence, and a procedure to expand the approximate space. The velocity of the algorithm was increased with the use of a posteriori error estimator (residue) to select the most relevant direction to increase the space. Two examples have been selected for benchmark. In the case of H2CO, we mainly study the performance of A-VCI algorithm: comparison with the variation-perturbation method, choice of the initial space, and residual contributions. For CH3CN, we compare the A-VCI results with a computed reference spectrum using the same potential energy surface and for an active space reduced by about 90%.
authors.affiliation: HiePACS project-team, Inria Bordeaux Sud-Ouest, 200, Avenue de la Vieille Tour, F-33405 Talence Cedex, France.
authors.forename: Romain
authors.initials: R
authors.lastname: Garnier
authors.affiliation: IPREM, Université de Pau et des Pays de l'Adour, 2, Avenue du Président Pierre Angot, F-64053 Pau Cedex 9, France.
authors.forename: Marc
authors.initials: M
authors.lastname: Odunlami
authors.affiliation: IPREM, Université de Pau et des Pays de l'Adour, 2, Avenue du Président Pierre Angot, F-64053 Pau Cedex 9, France.
authors.forename: Vincent
authors.initials: V
authors.lastname: Le Bris
authors.affiliation: IPREM, Université de Pau et des Pays de l'Adour, 2, Avenue du Président Pierre Angot, F-64053 Pau Cedex 9, France.
authors.forename: Didier
authors.initials: D
authors.lastname: Bégué
authors.affiliation: IPREM, Université de Pau et des Pays de l'Adour, 2, Avenue du Président Pierre Angot, F-64053 Pau Cedex 9, France.
authors.forename: Isabelle
authors.initials: I
authors.lastname: Baraille
authors.affiliation: HiePACS project-team, Inria Bordeaux Sud-Ouest, 200, Avenue de la Vieille Tour, F-33405 Talence Cedex, France.
authors.forename: Olivier
authors.initials: O
authors.lastname: Coulaud