Quantum B3LYP

Hydroxyfurazans exist solely in the hydroxy form. This is in accord with quantum chemical calculations (Scheme 167). Density functional theoretical studies (B3LYP/6-311- -G(2d,p)) indicate that 3-hydroxyfurazan is more stable than the... 

Quantum-chemical calculations which utilize the density functional theory (DFT) are now perhaps amongst the most frequently performed because of their relatively low cost and high accuracy. Structural results obtained from DFT based methods are often as good as those derived from MP2 calculations. It is well documented that DFT methods, especially those involving hybrid functionals such as B3LYP, B3P86 and B3PW91, yield reliable... 

In the ONIOM(QM MM) scheme as described in Section 2.2, the protein is divided into two subsystems. The QM region (or model system ) contains the active-site selection and is treated by quantum mechanics (here most commonly the density functional B3LYP [31-34]). The MM region (referred to as the real system ) is treated with an empirical force field (here most commonly Amber 96 [35]). The real system contains the surrounding protein (or selected parts of it) and some solvent molecules. To analyze the effects of the protein on the catalytic reactions, we have in general compared the results from ONIOM QM MM models with active-site QM-only calculations. Such comparisons make it possible to isolate catalytic effects originating from e.g. the metal center itself from effects of the surrounding protein matrix. 

A recent ab initio quantum mechanical study (Han et al, 1998) used B3LYP/6-31G density functional theory to examine the relative stabilities of eight conformers of AAMA with four explicit water... 

Figure 2. Jablonski diagram for the photochemical interconversion of la and 3a. The energies (in kcal/mol) of various electronic states were obtained from spectroscopic data or by quantum chemical calculations (in italics) using CISD+Q/6-31 G(d) and B3LYP/6-31 G(d) calculations for Ti -3a.

The quantum-mechanical energy curve was calculated at the B3LYP/6-311++G level of hybrid density-functional theory, as described in Appendix A. However, due to B3LYP convergence failures beyond Ji 3A, the quantities shown in Figs. 2.4—2.8 were calculated at HF/6-311++G" level. 

The unusual position of the C =C+ stretching vibration in the IR spectra of 9b [CBnH6Br6] is in agreement with the results from quantum mechanical calculations. A frequency calculation at the B3LYP/6-3 G(d) level of theory... 

Cl (types of calculations with correlation), we refer to DFT calculations as B3LYP. For a more complete discussion of functions, functionals, and DFT see any recent text on quantum chemistry (e.g., Levine, reading list). 

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