## Abstract The importance of basis sets and active spaces in the determination of the potential energy curves and relevant energy differences in the O~__h__~βsymmetry model system [Fe(NCH)~6~]^2+^ is analyzed using the Complete Active Space SelfβConsistent Field (CASSCF) method and subsequent seco
A perspective on the CASPT2 method
β Scribed by Peter Pulay
- Publisher
- John Wiley and Sons
- Year
- 2011
- Tongue
- English
- Weight
- 91 KB
- Volume
- 111
- Category
- Article
- ISSN
- 0020-7608
No coin nor oath required. For personal study only.
β¦ Synopsis
Abstract
The CASPT2 method, developed by Roos and coworkers, is reviewed. The rationale for a method that can deal with arbitrary strongly correlated systems at affordable computational cost is presented, and the main milestones in the 20βyear history of CASPT2 are listed. The basic features of the method are summarized. The strengths and weaknesses of CASPT2 are assessed. Its main strength is its ability to deal with arbitrary electronic states at a reasonable computational cost, and giving exact spin states. Its main limitation is that, it is not a black box method, and requires considerable experience to use. Another limitation is that, for accurate results, the active space must be generally larger than the minimum required to describe only the strong (static) correlation. Including dynamical correlation at an earlier stage may resolve some of these issues. Β© 2011 Wiley Periodicals, Inc. Int J Quantum Chem 111:3273β3279, 2011
π SIMILAR VOLUMES
The enthalpies of formation for singlet benzynes were examined at the CASPT2 (second order perturbation theory, based on a complete active space SCF reference function) level of theory. The study employed isodesmic reactions in order to minimize the influence of systematic errors of the method. The
## Abstract Using the complete active space selfβconsistent field method with a large atomic natural orbital basis set, 10, 13, and 9 electronic states of the OClO radical, OClO^+^ cation, and OClO^β^ anion were calculated, respectively. Taking the further correlation effects into account, the seco