Hostname: page-component-cd9895bd7-gxg78 Total loading time: 0 Render date: 2024-12-26T03:10:23.150Z Has data issue: false hasContentIssue false
  • English
  • Français

The RASSCF, RASSI, and CASPT2 Methods Used on Small Molecules of Astrophysical Interest

Published online by Cambridge University Press:  12 April 2016

Per-Åke Malmqvist
Per-Åke Malmqvist*
Affiliation:
Theoretical Chemistry, Chemical Center, P.O. Box 124, 221 00 Lund, Sweden

Extract

Core share and HTML view are not available for this content. However, as you have access to this content, a full PDF is available via the ‘Save PDF’ action button.

To a quantum chemist with no particular background in astrophysics or astronomy, a brief glance at journals and textbooks in these fields shows at least three areas where computational quantum chemistry has had a valuable impact: Interstellar cloud chemistry; stellar atmosphere modelling; and chemistry in extreme conditions, such as at the surface of a neutron star. The first two uses are particularly suitable, since standard methods are directly applicable.

For such problems, good calculations of potential energy as well as expectation values and matrix elements of dipole and other operators appears to be in demand. Many electronic states may be involved, at least a broad range of problems involve fairly small molecules, often radicals, and conformation regions far from equilibrium. Such problems are addressed by three methods originated in our laboratory, and known by the acronyms RASSCF (Restricted Active Space Self-Consistent Field, Malmqvist et al. 1990), RASSI (RAS State Interaction) and CASPT2 (Complete Active Space Perturbation Theory to Second Order-Complete Active Space Perturbation Theory to Second Order, Andersson et al. 1990; Andersson et al. 1992).

Type
Research Article
Information
International Astronomical Union Colloquium , Volume 146: Molecules in the Stellar Environment , 1994 , pp. 338 - 352
Copyright
Copyright © Springer-Verlag 1994

References

Ahlrichs, R., Scharf, P., Ehrhardt, C., 1985, J. Chem. Phys., 82, 890 Google Scholar
Almlöf, J., Taylor, P. R., 1987, J. Chem. Phys., 86, 4070 Google Scholar
Andersson, K., Fülscher, M. P., Lindh, R., Malmqvist, P.-Å., Olsen, J., Roos, B. O., Sadlej, A. S., Widmark, P. O., 1991, MOLCAS version 2. University of Lund, Sweden Google Scholar
Andersson, K., Malmqvist, P.-Å., Roos, B. O., Sadlej, A. S., Wolinski, K., 1990, J. Phys. Chem., 94, 5483 Google Scholar
Andersson, K., Malmqvist, P.-Å., Roos, B. O., 1992, J. Chem. Phys., 96, 1218 CrossRefGoogle Scholar
Chong, D. P., Langhoff, S. R., 1986, J. Chem. Phys., 84, 5606 Google Scholar
Clementi, E., Corongiu, G., Stradella, O. G., 1991, Density Functionals for Molecules, p321 ff in: Modem techniques in computational chemistry: MOTECC-91 (ed. E. Clementi), Leiden 1991.Google Scholar
Gdanitz, R. J., Ahlrichs, R., 1988, Chem. Phys. Letters, 143, 413 CrossRefGoogle Scholar
González-Luque, R., Merchán, M., Roos, B. O., 1992, Molec. Phys., 76, 201 CrossRefGoogle Scholar
Lindh, R., Barnes, L. A., 1993, J. Chem. Phys., (in press).Google Scholar
Lorentzon, J., Malmqvist, P.-Å, Roos B. O., , 1993, J. Chem. Phys., (submitted).Google Scholar
Malmqvist, P.-Å., Rendeli, A. P., Roos, B. O., 1990, J. Phys. Chem., 94, 5477 Google Scholar
Malmqvist, P.-Å., Roos, B. O., 1989, Chem. Phys. Letters, 155, 189 CrossRefGoogle Scholar
Olsen, J., Roos, B. O., Jørgensen, P., Jensen, H. J. Aa., 1988, J. Chem. Phys., 89, 2185 Google Scholar
Roos, B. O., 1980, Int. J. Quantum Chem. Symp., 14, 175 Google Scholar
Roos, B. O., Andersson, K., 1993, Int. J. Quantum Chem., 45, 591 Google Scholar
Roos, B. O., Serrano-Andrés, L., Merchán, M., 1993, Pure Appi. Chem., 65, 1693 Google Scholar
Roos, B. O., Taylor, P. R., Siegbahn, P. E. M., 1980, Chem. Phys., 48, 157 Google Scholar
Rostas, J., Horani, M., Brion, J., Daumont, D., Malicet, J., 1984, Molec. Phys., 52, 1431 Google Scholar
Watts, J. D., Stanton, J. F., Bartlett, R. J., 1991, Chem. Phys. Letters, 178, 471 Google Scholar
Widmark, P. O., Malmqvist, P.-Å., Roos, B. O., 1990, Theor. Chim. Acta, 77, 271 Google Scholar