Use of a dynamic shift scheme for the levels of Brillouin states in the super-CI method
- 28 Downloads
We propose a dynamic shift method for the levels of the Brillouin states, providing reliable and sufficiently rapid convergence of the iteration process in the CASSCF method with optimization of the orbitals according to the super-CI scheme. In each step of the super-CI procedure, the shift parameters are determined automatically and individually for each Brillouin state. The proposed method is simple and easy to carry out. It also guarantees that a physically incorrect solution cannot appear. The method was carried out using the CASSCF programming package; for the example of specific calculations for the1Σ+ state of the TiO molecule, we show that the method is efficient and preferred.
KeywordsProgramming Package Iteration Process Specific Calculation Shift Parameter Rapid Convergence
Unable to display preview. Download preview PDF.
- 1.B. O. Roos, P. R. Taylor, and P. E. M. Siegbahn, “A complete active space SCF method (CASSCF) using a density matrix formulated Super-CI approach,” Chem. Phys.,48, No. 2, 157–173 (1980).Google Scholar
- 2.P. E. M. Siegbahn, A. Heiberg, B. O. Roos, and B. Levy, “A comparison of the Super-CI and the Newton-Raphson scheme in the complete active space SCF method,” Phys. Scr.,21, 323–327 (1980).Google Scholar
- 3.B. O. Roos, “The complete active space SCF method in a Fock-matrix based Super-CI formulation,” Int. J. Quantum Chem. Symp.,14, 175–189 (1980).Google Scholar
- 4.K. Ruedenberg, L. M. Cheung, and S. T. Elbert, “MC SCF optimization through combined use of natural orbitals and the Brillouin-Levy-Berthier theorem,” Int. J. Quantum Chem.,16, 1069–1101 (1979).Google Scholar
- 5.F. Grein and T. C. Chang, “Multiconfiguration wave functions obtained by application of the generalized Brillouin theorem,” Chem. Phys. Lett.,12, No. 1, 44–48 (1971).Google Scholar
- 6.B. N. Parlett, The Symmetric Eigenvalue Problem [Russian translation], Mir, Moscow (1983).Google Scholar
- 7.R. McWeeny and B. T. Sutcliffe, Methods of Molecular Quantum Mechanics [Russian translation], Mir, Moscow (1972).Google Scholar
- 8.L. V. Gurvich, I. V. Veits, V. A. Medvedev et al., Thermodynamic Properties of Pure Substances [in Russian], Nauka, Mocow (1982), Vol. 4, Book 1.Google Scholar
- 9.J. M. Sennesal and J. Schamps, “Electronic states of titanium monohydride. An ab initio study,” Chem. Phys.,114. No. 1, 37–42 (1987).Google Scholar