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Weizmann-n theory

Another series of composite computational methods, Weizmann-n (Wn), with n = 1-4, have been recently proposed by Martin and co-workers W1 and W2 in 1999 and W3 and W4 in 2004. These models are particularly accurate for thermochemical calculations and they aim at approximating the CBS limit at the CCSD(T) level of theory. In all Wn methods, the core-valence correlations, spin-orbit couplings, and relativistic effects are explicitly included. Note that in G2, for instance, the single-points are performed with the frozen core (FC) approximation, which was discussed in the previous section. In other words, there is no core-valence effect in the G2 theory. Meanwhile, in G3, the corevalence correlation is calculated at the MP2 level with a valence basis set. In the Wn methods, the core-valence correlation is done at the more advanced CCSD(T) level with a specially designed core-valence basis set. [Pg.152]

There are methods that automate some of these steps. They are called composite methods because they combine results from several calculations to estimate the result that would be obtained from a more expensive calculation. The most popular families of composite methods are represented by Gaussian-3 (G3) theory [68,109] and CBS-APNO theory [110,111], where CBS stands for complete basis set. Both families of methods, which are considered reliable, include empirical parameters. The CBS theories incorporate an analytical basis set extrapolation based on perturbation theory, which is in contrast to the phenomenological extrapolation mentioned above. When the Gaussian software is used to perform these calculations, steps 2-, above, are performed automatically, with the result labeled G3 enthalpy (or the Hke) in the output file [20,99]. The user must still choose a reaction (step 1) and manipulate the molecular enthalpies (steps 5 and 6). The most precise composite methods are the Weizmann-n methods, which however are very intensive computationally [112]. [Pg.28]

Shaul Mukamel, who is currently the C. E. Kenneth Mees Professor of Chemistry at the University of Rochester, received his Ph.D. in 1976 from Tel Aviv University, follot by postdoctoral appointments at MIT and the University of California at Berkeley and faculty positions at the Weizmann Institute and at Rice University. He has b n the recipient of the Sloan, Dreyfus, Guggenheim, and Alexander von Humboldt Senior Scientist awards. His research interests in theoretical chemical physics and biophysics include developing a density matrix Liouville-space approach to femtosecond spectroscopy and to many body theory of electronic and vibrational excitations of molecules and semiconductors multidimensional coherent spectroscopies of sbucture and folding dynamics of proteins nonlinear X-ray and single molecule spectroscopy electron transfer and energy ftrnneling in photosynthetic complexes and Dendrimers. He is the author of over 400 publications in scientific journals and of the textbook. Principles of Nonlinear OfMical Spectroscopy (Oxford University Press), 1995. [Pg.2]


See other pages where Weizmann-n theory is mentioned: [Pg.315]    [Pg.324]    [Pg.133]    [Pg.315]    [Pg.324]    [Pg.133]    [Pg.252]    [Pg.8]    [Pg.65]    [Pg.103]   
See also in sourсe #XX -- [ Pg.37 , Pg.38 ]




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