A modified definition of the zeroth-order Hamiltonian in multiconfigurational perturbation theory (CASPT2)

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A modified definition of the zeroth-order Hamiltonian in multiconfigurational perturbation theory (CASPT2). / Ghigo, Giovanni; Roos, Björn; Malmqvist, Per-Åke.

I: Chemical Physics Letters, Vol. 396, Nr. 1-3, 2004, s. 142-149.

Forskningsoutput: TidskriftsbidragArtikel i vetenskaplig tidskrift

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TY - JOUR

T1 - A modified definition of the zeroth-order Hamiltonian in multiconfigurational perturbation theory (CASPT2)

AU - Ghigo, Giovanni

AU - Roos, Björn

AU - Malmqvist, Per-Åke

N1 - The information about affiliations in this record was updated in December 2015. The record was previously connected to the following departments: Theoretical Chemistry (S) (011001039)

PY - 2004

Y1 - 2004

N2 - A new shifted zeroth-order Hamiltonian is presented, which will be used in second-order multiconfigurational perturbation theory (CASPT2). The new approximation corrects for the systematic error of the original formulation, which led to an relative overestimate of the correlation energy for open shell system, resulting in too small dissociation and excitation energies. Errors in the D, values for 49 diatomic molecules have been reduced with more than 50%. Calculations on excited states of the N-2 and benzene molecules give a similar improvement. (C) 2004 Elsevier B.V. All rights reserved.

AB - A new shifted zeroth-order Hamiltonian is presented, which will be used in second-order multiconfigurational perturbation theory (CASPT2). The new approximation corrects for the systematic error of the original formulation, which led to an relative overestimate of the correlation energy for open shell system, resulting in too small dissociation and excitation energies. Errors in the D, values for 49 diatomic molecules have been reduced with more than 50%. Calculations on excited states of the N-2 and benzene molecules give a similar improvement. (C) 2004 Elsevier B.V. All rights reserved.

U2 - 10.1016/j.cplett.2004.08.032

DO - 10.1016/j.cplett.2004.08.032

M3 - Article

VL - 396

SP - 142

EP - 149

JO - Chemical Physics Letters

JF - Chemical Physics Letters

SN - 0009-2614

IS - 1-3

ER -