CNDO/2 Calculations

Projected CNDO ihe initial guess at the MCi coefficients is obtained from a CNDO calculation ... 

Practically all CNDO calculations are actually performed using the CNDO/ 2 method, which is an improved parameterization over the original CNDO/1 method. There is a CNDO/S method that is parameterized to reproduce electronic spectra. The CNDO/S method does yield improved prediction of excitation energies, but at the expense of the poorer prediction of molecular geometry. There have also been extensions of the CNDO/2 method to include elements with occupied d orbitals. These techniques have not seen widespread use due to the limited accuracy of results. 

Normally, you would expects all 2p orbitals in a given first row atom to be identical, regardless of their occupancy. This is only true when you perform calculations using Extended Hiickel. The orbitals derived from SCE calculations depend sensitively on their occupation. Eor example, the 2px, 2py, and 2pz orbitals are not degenerate for a CNDO calculation of atomic oxygen. This is especially important when you look at d orbital splittings in transition metals. To see a clear delineation between t2u and eg levels you must use EHT, rather than other semiempirical methods. 

While INDO calculations have more parameters and are somewhat more complex that CNDO calculations, they require essentially no extra computation time and in most situations they are superior to CNDO calculations. 

Dithiaphosphorinanes, 1, 504-506 1,6-Dithia-6aA -selenapentalenes CNDO calculations, 6, 1052 PE spectra, 6, 1057 l,6aA -Dithia-6-selenapentalenes UV spectra, 6, 1056 7,10-Dithiasesquifulvalene-1,6-quinone synthesis, 6, 836... 

CNDO calculations provide estimates of the localization energies. For benzene, naphthalene, and anthracene, these are, respectively, 36.3, 15.4, and 8.3 kcal/mol. ... 

By CNDO calculation BE is an increasing function of cluster size for Ag clusters and for Ni clusters [54]. The calculations for Ni clusters showed that the contribution an atom makes to the total BE is proportional to its coordination number [54]. The orbital energies of Ni follow a smooth function of cluster size. As size increases, LUMO decreases and HOMO increases. This represents a convergence of IP and electron affinity values with increase in size. 

NHO next-highest occupied (orbital) IP ionization potential x) CNDO calculation... 

The CNDO calculation gives a result of the same trend 102>. 

The reason for preferential axial site occupancy by mono-dentate ligands is probably related to results of recent CNDO calculations on [Co CO) ] (15) which show that the axial carbonyls are least involved in back-bonding. Extrapolation to Rh - and Ir -derivatives seems reasonable and finds some support from n.m.r. measurements, which show that the n.m.r. chemical shift of the axial carbonyl is always at higher field than the radial carbonyl in both rhodium (16) and iridium derivatives. (12)... 

Once the preferred conformation of each term of the series has been settled, the basicity (and acidity) scales provided by CNDO calculations on the assumption of standard geometrical models are identical to those obtained from i.c.r. and u.p.s.. Quantum calculations even allowed us to predict the basicity of some Lewis bases which could not be experimentally determined because of side-reactions occurring during the measurements. 

No chelating behavior can be expected, however, from the branching P(III) or As(IIl) atoms, in view of the diverging orientations of their lone electron pairs. The participation of 3d orbitals in bonding in P4O5 has been judged, from an LCAO-SCF-CNDO calculation, to be substantial (54) it may provide a mechanism to even out the relative charges on the P and 0 atoms. 

Complete Neglect of Differential Overlap (CNDO) calculations by Naray-Szabo and Surjan (80MI2), however, were interpreted to favor the lactim form 30a of MOT which is in line with the experimental UV spectra. 

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